http.bend

bend-kit-http@0.18.0.0 · 3,307 lines · 0 definitions

1# HTTP/1.1 client and server for http and https, with DNS and TLS. Source: https://github.com/paymog/bend-kit/tree/main/http
2import Base
3# By hash: bend-kit-wire@0.4.0.3, -url@0.4.0.0, -encoding@0.3.0.0, -json@0.5.0.1, -bytes@0.3.0.0, -dns@0.3.2.1, -zlib@0.1.3.0.
4import bend-kit-wire@0.4.0.3/wire.bend as Wire
5import bend-kit-url@0.4.0.0/url.bend as Url
6import bend-kit-encoding@0.3.0.0/encoding.bend as Enc
7import bend-kit-json@0.5.0.1/json.bend as Json
8import bend-kit-bytes@0.3.0.0/bytes.bend as Bytes
9import bend-kit-dns@0.3.2.1/dns.bend as Dns
10import bend-kit-zlib@0.1.3.0/zlib.bend as Zlib
11
12# HTTP/1.1 codec and client (RFC 9112) for http:// and https:// (OpenSSL 3 at run time).
13# parse: start-line → field lines → blank → body length (§6.3); chunked (§7.1).
14# Bodies are Bytes. The String parsers below are the spec: one Char per octet.
15# fetch reads until frame() says the response is whole. It returns Result, not Maybe.
16# Build with -o for big bodies: the `bend file.bend` runner overflows on ~30 KB strings; native binaries do not.
17#   import bend-kit-http@0.15.0.0/http.bend as Http
18
19type Req is Type:
20  Req{method: String, path: String, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes}
21
22type Res is Type:
23  Res{status: U32, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes}
24
25# The body type and its conversions, so a caller needs no bytes import.
26def Body() -> Type:
27  Bytes.Bytes
28
29# A byte string (one Char per octet) to a body, and back.
30def from_string(+s: String) -> Bytes.Bytes:
31  Bytes.from_string(s)
32
33def to_string(b: Bytes.Bytes) -> String:
34  Bytes.to_string(b)
35
36def length(b: Bytes.Bytes) -> Bytes.Bytes & U32:
37  Bytes.length(b)
38
39# Why fetch failed. Wire errors keep the errno and the text the effect already had.
40# ponytail: 60 and 110 are ETIMEDOUT on macOS and Linux. Windows is out of scope.
41type Err is Data:
42  ErrUrl{}
43  ErrDns{}
44  ErrConnect{code: U32, why: String}
45  ErrTls{code: U32, why: String}
46  ErrRead{code: U32, why: String}
47  ErrWrite{code: U32, why: String}
48  ErrTimeout{}
49  ErrRedirect{}
50  ErrBad{}
51
52def err.late(+code: U32) -> Bool:
53  Bool.or(U32.is_eq(code, 60), U32.is_eq(code, 110))
54
55def err.pick(e: Err, late: Bool) -> Err:
56  match late:
57    case True{}:
58      ErrTimeout{}
59    case False{}:
60      e
61
62def err.or_late(code: U32, e: Err) -> Err:
63  err.pick(e, err.late(code))
64
65type Fields is Data:
66  FieldsBad{}
67  FieldsOk{m: Map<&2, List<&2, String>>}
68
69# One list per field name, in arrival order. header() is the first value.
70# Set-Cookie is never joined. Encode writes one line per value.
71def empty() -> Map<&2, List<&2, String>>:
72  Map.new(&2, List<&2, String>)
73
74def fields.of(r: Map<&2, List<&2, String>> & List<&2, String>) -> List<&2, String>:
75  (h, xs) = r
76  xs
77
78def fields(+h: Map<&2, List<&2, String>>, k: String) -> List<&2, String>:
79  fields.of(Map.get(List<&2, String>, Nil{}, h, k))
80
81def header.first(xs: List<&2, String>) -> String:
82  match xs:
83    case Nil{}:
84      ""
85    case Con{v, t}:
86      v
87
88def header(+h: Map<&2, List<&2, String>>, k: String) -> String:
89  header.first(fields(h, k))
90
91def field.last(xs: List<&2, String>) -> String:
92  match xs:
93    case Nil{}:
94      ""
95    case Con{v, Nil{}}:
96      v
97    case Con{v, t}:
98      field.last(t)
99
100# Transfer-Encoding is a list; chunked, when present, is the last coding.
101def header.last(+h: Map<&2, List<&2, String>>, k: String) -> String:
102  field.last(fields(h, k))
103
104def snoc(xs: List<&2, String>, v: String) -> List<&2, String>:
105  match xs:
106    case Nil{}:
107      [v]
108    case Con{h, t}:
109      Con{h, snoc(t, v)}
110
111def set(m: Map<&2, List<&2, String>>, k: String, v: String) -> Map<&2, List<&2, String>>:
112  Map.set(&2, List<&2, String>, m, k, [v])
113
114def add(+m: Map<&2, List<&2, String>>, +k: String, v: String) -> Map<&2, List<&2, String>>:
115  Map.set(&2, List<&2, String>, m, k, snoc(fields(m, k), v))
116
117def sanitize.cons(ch: Char, rest: String, drop: Bool) -> String:
118  match drop:
119    case True{}:
120      rest
121    case False{}:
122      SCon{ch, rest}
123
124def sanitize(s: String) -> String:
125  match s:
126    case SNil{}:
127      SNil{}
128    case SCon{Chr{+c}, t}:
129      sanitize.cons(Chr{c}, sanitize(t), Bool.or(U32.is_eq(c, 13), U32.is_eq(c, 10)))
130
131def drop_cr.last.if(cr: Bool, c: U32) -> String:
132  match cr:
133    case True{}:
134      SNil{}
135    case False{}:
136      SCon{Chr{c}, SNil{}}
137
138def drop_cr.last(+c: U32) -> String:
139  drop_cr.last.if(U32.is_eq(c, 13), c)
140
141# prev is the char before s; it is kept unless it is a final CR.
142def drop_cr.go(s: String, prev: U32) -> String:
143  match s:
144    case SNil{}:
145      drop_cr.last(prev)
146    case SCon{Chr{c}, t}:
147      SCon{Chr{prev}, drop_cr.go(t, c)}
148
149def drop_cr(s: String) -> String:
150  match s:
151    case SNil{}:
152      SNil{}
153    case SCon{Chr{c}, t}:
154      drop_cr.go(t, c)
155
156# w holds the last four octets; a char past 255 clears it.
157def blank_end.go(s: String, w: U32) -> Bool:
158  match s:
159    case SNil{}:
160      U32.is_eq(w, 218762506)
161    case SCon{Chr{+c}, t}:
162      blank_end.go(t, Bool.pick(U32, U32.is_lt(c, 256), (w * 256 + c : U32), 0))
163
164# String.ends_with(s, "\r\n\r\n") in one pass, with no reversed copy.
165def blank_end(s: String) -> Bool:
166  blank_end.go(s, 0)
167
168def trim_end.cons(h: Char, r: String, space: Bool) -> String:
169  match r:
170    case SNil{}:
171      match space:
172        case True{}:
173          SNil{}
174        case False{}:
175          SCon{h, SNil{}}
176    case SCon{a, t}:
177      SCon{h, SCon{a, t}}
178
179# String.trim_end without the two reversed copies.
180def trim_end(s: String) -> String:
181  match s:
182    case SNil{}:
183      SNil{}
184    case SCon{+h, t}:
185      trim_end.cons(h, trim_end(t), Char.is_space(h))
186
187def trim(s: String) -> String:
188  trim_end(String.trim_start(s))
189
190# Bool.pick evaluates both arms; a split that recursed inside it would reverse acc at every byte.
191def take.cut(acc: String, rest: String) -> String & String:
192  (String.reverse(String.drop(acc, 1n)), rest)
193
194# hit: the last char pushed onto acc was the stop char.
195def take_sp.go(s: String, acc: String, hit: Bool) -> String & String:
196  match s:
197    case SNil{}:
198      match hit:
199        case True{}:
200          take.cut(acc, SNil{})
201        case False{}:
202          (String.reverse(acc), SNil{})
203    case SCon{Chr{+c}, t}:
204      match hit:
205        case True{}:
206          take.cut(acc, SCon{Chr{c}, t})
207        case False{}:
208          take_sp.go(t, SCon{Chr{c}, acc}, U32.is_eq(c, 32))
209
210def take_sp(s: String) -> String & String:
211  take_sp.go(s, SNil{}, False{})
212
213def start_line.ver(m: String, pv: String & String) -> String & String & String:
214  (p, v) = pv
215  (m, p, drop_cr(v))
216
217def start_line.rest(mr: String & String) -> String & String & String:
218  (m, r) = mr
219  start_line.ver(m, take_sp(r))
220
221def start_line(s: String) -> String & String & String:
222  start_line.rest(take_sp(s))
223
224def split_at_blank.go(s: String, e: Bool, w: U32, acc: String) -> String & String:
225  match s:
226    case SNil{}:
227      (String.reverse(acc), SNil{})
228    case SCon{Chr{+a}, t}:
229      match e:
230        case True{}:
231          (String.reverse(acc), SCon{Chr{a}, t})
232        case False{}:
233          +w2 = (w * 256 + a : U32)
234          split_at_blank.go(t, U32.is_eq(w2, 218762506), w2, SCon{Chr{a}, acc})
235
236# split_at_blank, plus whether the head ends in the blank line.
237def split_at_blank.flag.go(+raw: String, s: String, off: Nat, w: U32, e: Bool) -> String & String & Bool:
238  match s:
239    case SNil{}:
240      (String.take(raw, off), SNil{}, e)
241    case SCon{Chr{+a}, t}:
242      match e:
243        case True{}:
244          (String.take(raw, off), SCon{Chr{a}, t}, True{})
245        case False{}:
246          +w2 = (w * 256 + a : U32)
247          +off1 = (1n + off : Nat)
248          split_at_blank.flag.go(raw, t, off1, w2, U32.is_eq(w2, 218762506))
249
250def split_at_blank.pair(r: String & String & Bool) -> String & String:
251  (head, rest, whole) = r
252  (head, rest)
253
254def split_at_blank(+s: String) -> String & String:
255  split_at_blank.pair(split_at_blank.flag.go(s, s, 0n, 0, False{}))
256
257def split_colon.go(s: String, acc: String, hit: Bool) -> String & String:
258  match s:
259    case SNil{}:
260      match hit:
261        case True{}:
262          take.cut(acc, SNil{})
263        case False{}:
264          (String.reverse(acc), SNil{})
265    case SCon{Chr{+c}, t}:
266      match hit:
267        case True{}:
268          take.cut(acc, SCon{Chr{c}, t})
269        case False{}:
270          split_colon.go(t, SCon{Char.to_lower(Chr{c}), acc}, U32.is_eq(c, 58))
271
272def split_colon(+s: String) -> String & String:
273  split_colon.go(s, SNil{}, False{})
274
275def has_header.of(r: Map<&2, List<&2, String>> & Bool) -> Bool:
276  (h, b) = r
277  b
278
279def has_header(+h: Map<&2, List<&2, String>>, k: String) -> Bool:
280  has_header.of(Map.has(&2, List<&2, String>, h, k))
281
282def folded(+line: String) -> Bool:
283  Bool.or(String.starts_with(line, " "), String.starts_with(line, "\t"))
284
285def tracked(+k: String) -> Bool:
286  Bool.or(String.eq(k, "host"), String.eq(k, "content-length"))
287
288def fields_put.dup(m: Map<&2, List<&2, String>>, k: String, v: String, bad: Bool) -> Fields:
289  match bad:
290    case True{}:
291      FieldsBad{}
292    case False{}:
293      FieldsOk{add(m, k, v)}
294
295def fields_put.tracked(+m: Map<&2, List<&2, String>>, +k: String, v: String, t: Bool) -> Fields:
296  match t:
297    case True{}:
298      fields_put.dup(m, k, v, has_header(m, k))
299    case False{}:
300      FieldsOk{add(m, k, v)}
301
302def fields_put.key(+m: Map<&2, List<&2, String>>, +k: String, v: String) -> Fields:
303  fields_put.tracked(m, k, v, tracked(k))
304
305def fields_put.kv(m: Map<&2, List<&2, String>>, kv: String & String) -> Fields:
306  (k, v) = kv
307  fields_put.key(m, k, trim(v))
308
309def fields_put.fold(m: Map<&2, List<&2, String>>, line: String, fold: Bool) -> Fields:
310  match fold:
311    case True{}:
312      FieldsBad{}
313    case False{}:
314      fields_put.kv(m, split_colon(line))
315
316def fields_put.empty(m: Map<&2, List<&2, String>>, +line: String, e: Bool) -> Fields:
317  match e:
318    case True{}:
319      FieldsOk{m}
320    case False{}:
321      fields_put.fold(m, line, folded(line))
322
323def fields_put.ok(m: Map<&2, List<&2, String>>, +line: String) -> Fields:
324  fields_put.empty(m, line, String.is_empty(line))
325
326def fields_put(acc: Fields, line: String) -> Fields:
327  match acc:
328    case FieldsBad{}:
329      FieldsBad{}
330    case FieldsOk{m}:
331      fields_put.ok(m, line)
332
333def parse.headers.done(acc: Fields) -> Maybe<&2, Map<&2, List<&2, String>>>:
334  match acc:
335    case FieldsBad{}:
336      None{}
337    case FieldsOk{m}:
338      Some{m}
339
340def parse.headers(xs: List<&2, String>, acc: Fields) -> Maybe<&2, Map<&2, List<&2, String>>>:
341  match xs:
342    case Nil{}:
343      parse.headers.done(acc)
344    case Con{line, rest}:
345      parse.headers(rest, fields_put(acc, drop_cr(line)))
346
347def parse_u32.digit(+c: U32) -> Bool:
348  Bool.and(U32.is_le(48, c), U32.is_le(c, 57))
349
350def parse_u32.add(acc: U32, c: U32) -> U32:
351  (acc * 10 + (c - 48 : U32) : U32)
352
353def parse_u32.done(acc: U32, bad: Bool) -> Maybe<&2, U32>:
354  match bad:
355    case True{}:
356      None{}
357    case False{}:
358      Some{acc}
359
360def parse_u32.go(s: String, acc: U32, bad: Bool) -> Maybe<&2, U32>:
361  match s:
362    case SNil{}:
363      parse_u32.done(acc, bad)
364    case SCon{Chr{+c}, t}:
365      parse_u32.go(t, parse_u32.add(acc, c), Bool.or(bad, Bool.not(parse_u32.digit(c))))
366
367def parse_u32(s: String) -> Maybe<&2, U32>:
368  match s:
369    case SNil{}:
370      None{}
371    case SCon{Chr{+c}, t}:
372      parse_u32.go(t, parse_u32.add(0, c), Bool.not(parse_u32.digit(c)))
373
374# More: a valid prefix. Bad: cannot become a body. Body: a whole chunked body.
375type Hold is Data:
376  HoldMore{}
377  HoldBad{}
378  HoldBody{b: String}
379  HoldUntil{b: String}
380
381def is_hex(+c: U32) -> Bool:
382  Bool.or(parse_u32.digit(c), Bool.or(Bool.and(U32.is_le(97, c), U32.is_le(c, 102)), Bool.and(U32.is_le(65, c), U32.is_le(c, 70))))
383
384def hexv(+c: U32) -> U32:
385  Bool.pick(U32, parse_u32.digit(c), (c - 48 : U32), Bool.pick(U32, U32.is_le(c, 70), (c - 55 : U32), (c - 87 : U32)))
386
387# A chunked body decoder that reads each byte once, so a body fed in pieces
388# costs O(bytes) in total. Tr{j}: j bytes of the closing CRLF CRLF matched.
389type Dc is Data:
390  DcSize{acc: U32, seen: Bool}
391  DcExt{n: U32}
392  DcSizeLf{n: U32}
393  DcData{k: U32}
394  DcDataCr{}
395  DcDataLf{}
396  DcTr{j: U32}
397  DcDone{}
398  DcBad{}
399
400# st: where the decoder is. racc: the body so far, reversed. rest: bytes after a Done body.
401type Dco is Data:
402  Dco{st: Dc, racc: String, rest: String}
403
404def dc.start() -> Dc:
405  DcSize{0, False{}}
406
407def dc.size.semi(+n: U32, semi: Bool) -> Dc:
408  match semi:
409    case True{}:
410      DcExt{n}
411    case False{}:
412      DcBad{}
413
414def dc.size.cr(+n: U32, +c: U32, cr: Bool) -> Dc:
415  match cr:
416    case True{}:
417      DcSizeLf{n}
418    case False{}:
419      dc.size.semi(n, U32.is_eq(c, 59))
420
421def dc.size.end(+n: U32, +c: U32, seen: Bool) -> Dc:
422  match seen:
423    case False{}:
424      DcBad{}
425    case True{}:
426      dc.size.cr(n, c, U32.is_eq(c, 13))
427
428# A size that would overflow 32 bits ends the digits, and size.end then refuses it.
429def dc.size(+acc: U32, seen: Bool, +c: U32, digit: Bool) -> Dc:
430  match digit:
431    case True{}:
432      DcSize{(acc * 16 + hexv(c) : U32), True{}}
433    case False{}:
434      dc.size.end(acc, c, seen)
435
436# RFC 9112 §7.1.1: recipients ignore unknown chunk extensions; a bare LF is not CRLF.
437def dc.ext.lf(+n: U32, lf: Bool) -> Dc:
438  match lf:
439    case True{}:
440      DcBad{}
441    case False{}:
442      DcExt{n}
443
444def dc.ext(+n: U32, +c: U32, cr: Bool) -> Dc:
445  match cr:
446    case True{}:
447      DcSizeLf{n}
448    case False{}:
449      dc.ext.lf(n, U32.is_eq(c, 10))
450
451def dc.sized(+n: U32, zero: Bool) -> Dc:
452  match zero:
453    case True{}:
454      DcTr{2}
455    case False{}:
456      DcData{n}
457
458def dc.size.lf(+n: U32, lf: Bool) -> Dc:
459  match lf:
460    case True{}:
461      dc.sized(n, U32.is_eq(n, 0))
462    case False{}:
463      DcBad{}
464
465# k data bytes are left and m of them were just read.
466def dc.data(+k: U32, +m: U32) -> Dc:
467  Bool.pick(Dc, U32.is_le(k, m), DcDataCr{}, DcData{(k - m : U32)})
468
469def dc.pick(ok: Bool, next: Dc) -> Dc:
470  match ok:
471    case True{}:
472      next
473    case False{}:
474      DcBad{}
475
476# ponytail: trailer fields are dropped unparsed (§7.1.2 allows discarding)
477def dc.tr.hit(+j: U32) -> Dc:
478  Bool.pick(Dc, U32.is_eq(j, 3), DcDone{}, DcTr{(j + 1 : U32)})
479
480def dc.tr(+j: U32, +c: U32, hit: Bool) -> Dc:
481  match hit:
482    case True{}:
483      dc.tr.hit(j)
484    case False{}:
485      Bool.pick(Dc, U32.is_eq(c, 13), DcTr{1}, DcTr{0})
486
487def dc.tr.want(+j: U32) -> U32:
488  Bool.pick(U32, U32.is_eq(U32.mod(j, 2), 0), 13, 10)
489
490def dc.byte(h: Char) -> U32:
491  Chr{c} = h
492  c
493
494# One byte c. Done and Bad never look at it, and a data byte is not inspected.
495def dc.step(st: Dc, +c: U32) -> Dc:
496  match st:
497    case DcBad{}:
498      DcBad{}
499    case DcSize{+acc, seen}:
500      dc.size(acc, seen, c, Bool.and(is_hex(c), U32.is_le(acc, 268435455)))
501    case DcExt{+n}:
502      dc.ext(n, c, U32.is_eq(c, 13))
503    case DcSizeLf{+n}:
504      dc.size.lf(n, U32.is_eq(c, 10))
505    case DcDataCr{}:
506      dc.pick(U32.is_eq(c, 13), DcDataLf{})
507    case DcDataLf{}:
508      dc.pick(U32.is_eq(c, 10), dc.start())
509    case DcTr{+j}:
510      dc.tr(j, c, U32.is_eq(c, dc.tr.want(j)))
511    case DcData{+k}:
512      dc.data(k, 1)
513    case DcDone{}:
514      DcDone{}
515
516def dc.live(st: Dc) -> Bool:
517  match st:
518    case DcDone{}:
519      False{}
520    case DcBad{}:
521      False{}
522    case DcSize{a, b}:
523      True{}
524    case DcExt{n}:
525      True{}
526    case DcSizeLf{n}:
527      True{}
528    case DcData{k}:
529      True{}
530    case DcDataCr{}:
531      True{}
532    case DcDataLf{}:
533      True{}
534    case DcTr{j}:
535      True{}
536
537def dc.feed(s: String, st: Dc, racc: String) -> Dco:
538  match s:
539    case SNil{}:
540      Dco{st, racc, ""}
541    case SCon{h, t}:
542      match st:
543        case DcBad{}:
544          Dco{DcBad{}, racc, ""}
545        case DcDone{}:
546          Dco{DcDone{}, racc, SCon{h, t}}
547        case DcData{+k}:
548          dc.feed(t, dc.data(k, 1), SCon{h, racc})
549        case DcSize{+acc, seen}:
550          dc.feed(t, dc.step(DcSize{acc, seen}, dc.byte(h)), racc)
551        case DcExt{+n}:
552          dc.feed(t, dc.step(DcExt{n}, dc.byte(h)), racc)
553        case DcSizeLf{+n}:
554          dc.feed(t, dc.step(DcSizeLf{n}, dc.byte(h)), racc)
555        case DcDataCr{}:
556          dc.feed(t, dc.step(DcDataCr{}, dc.byte(h)), racc)
557        case DcDataLf{}:
558          dc.feed(t, dc.step(DcDataLf{}, dc.byte(h)), racc)
559        case DcTr{+j}:
560          dc.feed(t, dc.step(DcTr{j}, dc.byte(h)), racc)
561
562def chunk.hold(o: Dco) -> Hold:
563  Dco{st, racc, rest} = o
564  match st:
565    case DcDone{}:
566      HoldBody{String.reverse(racc)}
567    case DcBad{}:
568      HoldBad{}
569    case DcSize{a, b}:
570      HoldMore{}
571    case DcExt{n}:
572      HoldMore{}
573    case DcSizeLf{n}:
574      HoldMore{}
575    case DcData{k}:
576      HoldMore{}
577    case DcDataCr{}:
578      HoldMore{}
579    case DcDataLf{}:
580      HoldMore{}
581    case DcTr{j}:
582      HoldMore{}
583
584def chunk.live(s: String) -> Hold:
585  chunk.hold(dc.feed(s, dc.start(), ""))
586
587def chunk.rest(o: Dco) -> Maybe<&2, String>:
588  Dco{st, racc, rest} = o
589  match st:
590    case DcDone{}:
591      Some{rest}
592    case DcBad{}:
593      None{}
594    case DcSize{a, b}:
595      None{}
596    case DcExt{n}:
597      None{}
598    case DcSizeLf{n}:
599      None{}
600    case DcData{k}:
601      None{}
602    case DcDataCr{}:
603      None{}
604    case DcDataLf{}:
605      None{}
606    case DcTr{j}:
607      None{}
608
609def chunk.suffix(s: String) -> Maybe<&2, String>:
610  chunk.rest(dc.feed(s, dc.start(), ""))
611
612def chunk.decode.hold(h: Hold) -> Maybe<&2, String>:
613  match h:
614    case HoldMore{}:
615      None{}
616    case HoldBad{}:
617      None{}
618    case HoldUntil{b}:
619      None{}
620    case HoldBody{b}:
621      Some{b}
622
623def chunk.decode(s: String) -> Maybe<&2, String>:
624  chunk.decode.hold(chunk.live(s))
625
626def bytes.snd(r: Bytes.Bytes & Bytes.Bytes) -> Bytes.Bytes:
627  (a, b) = r
628  b
629
630def found.at(+from: U32, m: Maybe<&2, U32>) -> Maybe<&2, U32>:
631  match m:
632    case None{}:
633      None{}
634    case Some{+j}:
635      Some{(from + j : U32)}
636
637# A chunked body decoded from piece[i..]: a data run is sliced whole, and every other byte steps dc.
638type Cs is Type:
639  Cs{piece: Bytes.Bytes, i: U32, st: Dc, parts: List<&1, Bytes.Bytes>}
640
641# st: where the decoder stopped. parts: the data so far, newest first. rest: the bytes after a Done body.
642type Ck is Type:
643  Ck{st: Dc, parts: List<&1, Bytes.Bytes>, rest: Bytes.Bytes}
644
645def ck.next(+len: U32, +i: U32, +st: Dc, piece: Bytes.Bytes, parts: List<&1, Bytes.Bytes>) -> Bool & Cs:
646  (Bool.and(U32.is_lt(i, len), dc.live(st)), Cs{piece, i, st, parts})
647
648def ck.data(+len: U32, +i: U32, +k: U32, +m: U32, parts: List<&1, Bytes.Bytes>, r: Bytes.Bytes & Bytes.Bytes) -> Bool & Cs:
649  (piece, run) = r
650  ck.next(len, (i + m : U32), dc.data(k, m), piece, Con{run, parts})
651
652def ck.byte(+len: U32, +i: U32, st: Dc, parts: List<&1, Bytes.Bytes>, r: Bytes.Bytes & Maybe<&2, U32>) -> Bool & Cs:
653  (piece, m) = r
654  match m:
655    case None{}:
656      ck.next(len, i, DcBad{}, piece, parts)
657    case Some{+c}:
658      ck.next(len, (i + 1 : U32), dc.step(st, c), piece, parts)
659
660def ck.step(+len: U32, cs: Cs) -> Bool & Cs:
661  Cs{piece, +i, st, parts} = cs
662  match st:
663    case DcData{+k}:
664      +m = U32.min(k, (len - i : U32))
665      ck.data(len, i, k, m, parts, Bytes.slice(piece, i, m))
666    case DcDone{}:
667      (False{}, Cs{piece, i, DcDone{}, parts})
668    case DcBad{}:
669      (False{}, Cs{piece, i, DcBad{}, parts})
670    case DcSize{+acc, seen}:
671      ck.byte(len, i, DcSize{acc, seen}, parts, Bytes.get(piece, i))
672    case DcExt{+n}:
673      ck.byte(len, i, DcExt{n}, parts, Bytes.get(piece, i))
674    case DcSizeLf{+n}:
675      ck.byte(len, i, DcSizeLf{n}, parts, Bytes.get(piece, i))
676    case DcDataCr{}:
677      ck.byte(len, i, DcDataCr{}, parts, Bytes.get(piece, i))
678    case DcDataLf{}:
679      ck.byte(len, i, DcDataLf{}, parts, Bytes.get(piece, i))
680    case DcTr{+j}:
681      ck.byte(len, i, DcTr{j}, parts, Bytes.get(piece, i))
682
683def ck.rest(st: Dc, parts: List<&1, Bytes.Bytes>, r: Bytes.Bytes & Bytes.Bytes) -> Ck:
684  (piece, rest) = r
685  Ck{st, parts, rest}
686
687def ck.end(+len: U32, cs: Cs) -> Ck:
688  Cs{piece, +i, st, parts} = cs
689  ck.rest(st, parts, Bytes.slice(piece, i, (len - i : U32)))
690
691# Each step reads at least one byte, so len steps are enough.
692def ck.feed(f: Nat, +len: U32, r: Bool & Cs) -> Ck:
693  match f:
694    case 0n:
695      (go, cs) = r
696      ck.end(len, cs)
697    case 1n+p:
698      (go, cs) = r
699      match go:
700        case False{}:
701          ck.end(len, cs)
702        case True{}:
703          ck.feed(p, len, ck.step(len, cs))
704
705def ck(piece: Bytes.Bytes, +st: Dc, parts: List<&1, Bytes.Bytes>) -> Ck:
706  Bytes.Bytes{+len, buf} = piece
707  ck.feed(U32.to_nat(len), len, ck.next(len, 0, st, Bytes.Bytes{len, buf}, parts))
708
709def parse.res.cl.have(+rest: String, +k: Nat, short: Bool) -> Hold:
710  match short:
711    case True{}:
712      HoldMore{}
713    case False{}:
714      HoldBody{String.take(rest, k)}
715
716def parse.res.cl.k(+rest: String, +k: Nat) -> Hold:
717  parse.res.cl.have(rest, k, Nat.is_lt(String.length(rest), k))
718
719def parse.res.cl.n(rest: String, n: Maybe<&2, U32>) -> Hold:
720  match n:
721    case None{}:
722      HoldBad{}
723    case Some{k}:
724      parse.res.cl.k(rest, U32.to_nat(k))
725
726def parse.body.cl(+h: Map<&2, List<&2, String>>, rest: String, hascl: Bool) -> Hold:
727  match hascl:
728    case False{}:
729      HoldBody{""}
730    case True{}:
731      parse.res.cl.n(rest, parse_u32(header(h, "content-length")))
732
733# RFC 9112 §6.3 (4): a request coding other than chunked cannot be framed.
734def parse.body.chunked.eq(rest: String, ok: Bool) -> Hold:
735  match ok:
736    case False{}:
737      HoldBad{}
738    case True{}:
739      chunk.live(rest)
740
741def parse.body.chunked.val(te: String, rest: String) -> Hold:
742  parse.body.chunked.eq(rest, String.eq(String.to_lower(te), "chunked"))
743
744def parse.body.chunked(+h: Map<&2, List<&2, String>>, rest: String, hascl: Bool) -> Hold:
745  match hascl:
746    case True{}:
747      HoldBad{}
748    case False{}:
749      parse.body.chunked.val(header.last(h, "transfer-encoding"), rest)
750
751def parse.body.te(+h: Map<&2, List<&2, String>>, rest: String, te: Bool) -> Hold:
752  match te:
753    case True{}:
754      parse.body.chunked(h, rest, has_header(h, "content-length"))
755    case False{}:
756      parse.body.cl(h, rest, has_header(h, "content-length"))
757
758def parse.body(+h: Map<&2, List<&2, String>>, rest: String) -> Hold:
759  parse.body.te(h, rest, has_header(h, "transfer-encoding"))
760
761# Bad: never a request. More: the head is not whole; read on. Head: the head is whole
762# and valid, and the body is still coming (req.body is empty). Req: a whole request.
763type Got is Type:
764  GotBad{}
765  GotMore{}
766  GotHead{req: Req}
767  GotReq{req: Req}
768
769def parse.finish(method: String, path: String, h: Map<&2, List<&2, String>>, body: Hold) -> Got:
770  match body:
771    case HoldBad{}:
772      GotBad{}
773    case HoldMore{}:
774      GotHead{Req{method, path, h, Bytes.new(0)}}
775    case HoldUntil{b}:
776      GotBad{}
777    case HoldBody{b}:
778      GotReq{Req{method, path, h, Bytes.from_string(b)}}
779
780def parse.host(method: String, path: String, +h: Map<&2, List<&2, String>>, rest: String, has: Bool) -> Got:
781  match has:
782    case False{}:
783      GotBad{}
784    case True{}:
785      parse.finish(method, path, h, parse.body(h, rest))
786
787# RFC 9112 §3.2: only HTTP/1.1 requires Host.
788def parse.fields(method: String, path: String, rest: String, v11: Bool, fs: Maybe<&2, Map<&2, List<&2, String>>>) -> Got:
789  match fs:
790    case None{}:
791      GotBad{}
792    case Some{+h}:
793      parse.host(method, path, h, rest, Bool.or(Bool.not(v11), has_header(h, "host")))
794
795def target_ok(+p: String) -> Bool:
796  Bool.or(String.starts_with(p, "/"), Bool.or(String.eq(p, "*"), String.starts_with(p, "http://")))
797
798def parse.target(method: String, +path: String, headers: List<&2, String>, rest: String, v11: Bool, ok: Bool) -> Got:
799  match ok:
800    case False{}:
801      GotBad{}
802    case True{}:
803      parse.fields(method, path, rest, v11, parse.headers(headers, FieldsOk{empty()}))
804
805def parse.ver(method: String, +path: String, +v: String, headers: List<&2, String>, rest: String, ok: Bool) -> Got:
806  match ok:
807    case False{}:
808      GotBad{}
809    case True{}:
810      parse.target(method, path, headers, rest, String.eq(v, "HTTP/1.1"), target_ok(path))
811
812def parse.empty_method(method: String, path: String, +v: String, headers: List<&2, String>, rest: String, empty: Bool) -> Got:
813  match empty:
814    case True{}:
815      GotBad{}
816    case False{}:
817      parse.ver(method, path, v, headers, rest, Bool.or(String.eq(v, "HTTP/1.1"), String.eq(v, "HTTP/1.0")))
818
819def parse.start3(mpv: String & String & String, headers: List<&2, String>, rest: String) -> Got:
820  (+method, path, v) = mpv
821  parse.empty_method(method, path, v, headers, rest, String.is_empty(method))
822
823def parse.lines(xs: List<&2, String>, rest: String) -> Got:
824  match xs:
825    case Nil{}:
826      GotBad{}
827    case Con{line, headers}:
828      parse.start3(start_line(line), headers, rest)
829
830
831def parse.head(+head: String, rest: String, whole: Bool) -> Got:
832  match whole:
833    case False{}:
834      GotMore{}
835    case True{}:
836      parse.lines(String.lines(head), rest)
837
838def parse.of(hb: String & String & Bool) -> Got:
839  (head, rest, whole) = hb
840  parse.head(head, rest, whole)
841
842# serve reads until this is not GotMore.
843def parse.got(+raw: String) -> Got:
844  parse.of(split_at_blank.flag.go(raw, raw, 0n, 0, False{}))
845
846
847def parse.req(g: Got) -> Maybe<&1, Req>:
848  match g:
849    case GotReq{req}:
850      Some{req}
851    case GotBad{}:
852      None{}
853    case GotMore{}:
854      None{}
855    case GotHead{req}:
856      None{}
857
858def parse(raw: String) -> Maybe<&1, Req>:
859  parse.req(parse.got(raw))
860
861def parse.res.cl(+h: Map<&2, List<&2, String>>, rest: String, hascl: Bool) -> Hold:
862  match hascl:
863    case False{}:
864      HoldBody{rest}
865    case True{}:
866      parse.res.cl.n(rest, parse_u32(header(h, "content-length")))
867
868def parse.res.chunked.eq(rest: String, ok: Bool) -> Hold:
869  match ok:
870    case False{}:
871      HoldUntil{rest}
872    case True{}:
873      chunk.live(rest)
874
875def parse.res.chunked.val(te: String, rest: String) -> Hold:
876  parse.res.chunked.eq(rest, String.eq(String.to_lower(te), "chunked"))
877
878def parse.res.chunked(+h: Map<&2, List<&2, String>>, rest: String, hascl: Bool) -> Hold:
879  match hascl:
880    case True{}:
881      HoldBad{}
882    case False{}:
883      parse.res.chunked.val(header.last(h, "transfer-encoding"), rest)
884
885def parse.res.te(+h: Map<&2, List<&2, String>>, rest: String, te: Bool) -> Hold:
886  match te:
887    case True{}:
888      parse.res.chunked(h, rest, has_header(h, "content-length"))
889    case False{}:
890      parse.res.cl(h, rest, has_header(h, "content-length"))
891
892def parse.res.body(+h: Map<&2, List<&2, String>>, rest: String) -> Hold:
893  parse.res.te(h, rest, has_header(h, "transfer-encoding"))
894
895# Bad: never a message. More: a valid prefix; read on. Done: a whole response.
896type Frame is Type:
897  FrameBad{}
898  FrameMore{}
899  FrameDone{res: Res}
900
901# RFC 9112 §8: a message cut short by close is incomplete, not valid.
902def frame.cut(closed: Bool) -> Frame:
903  match closed:
904    case True{}:
905      FrameBad{}
906    case False{}:
907      FrameMore{}
908
909def frame.wait(res: Res, wait: Bool) -> Frame:
910  match wait:
911    case True{}:
912      FrameMore{}
913    case False{}:
914      FrameDone{res}
915
916def frame.done(status: U32, h: Map<&2, List<&2, String>>, body: Hold, +closed: Bool, open: Bool) -> Frame:
917  match body:
918    case HoldBad{}:
919      FrameBad{}
920    case HoldMore{}:
921      frame.cut(closed)
922    case HoldUntil{b}:
923      frame.wait(Res{status, h, Bytes.from_string(b)}, Bool.not(closed))
924    case HoldBody{b}:
925      frame.wait(Res{status, h, Bytes.from_string(b)}, Bool.and(open, Bool.not(closed)))
926
927# RFC 9112 §6.3 (8): no TE and no CL ⇒ the body runs until the server closes.
928def frame.open(+h: Map<&2, List<&2, String>>) -> Bool:
929  Bool.not(Bool.or(has_header(h, "transfer-encoding"), has_header(h, "content-length")))
930
931# RFC 9112 §6.3 (1): HEAD, 1xx, 204 and 304 responses end at the blank line.
932def frame.nobody(+status: U32, head: Bool) -> Bool:
933  Bool.or(head, Bool.or(U32.is_lt(status, 200), Bool.or(U32.is_eq(status, 204), U32.is_eq(status, 304))))
934
935# 101 is the final response. Other 1xx are interim; a final response follows.
936def frame.interim(+status: U32) -> Bool:
937  Bool.and(U32.is_lt(status, 200), Bool.not(U32.is_eq(status, 101)))
938
939def frame.status(status: U32, +h: Map<&2, List<&2, String>>, rest: String, closed: Bool, nobody: Bool) -> Frame:
940  match nobody:
941    case True{}:
942      FrameDone{Res{status, h, Bytes.new(0)}}
943    case False{}:
944      frame.done(status, h, parse.res.body(h, rest), closed, frame.open(h))
945
946def parse.res.fields(+status: U32, rest: String, fs: Maybe<&2, Map<&2, List<&2, String>>>, closed: Bool, head: Bool) -> Frame:
947  match fs:
948    case None{}:
949      FrameBad{}
950    case Some{h}:
951      frame.status(status, h, rest, closed, frame.nobody(status, head))
952
953def parse.res.num(code: Maybe<&2, U32>, headers: List<&2, String>, rest: String, closed: Bool, head: Bool) -> Frame:
954  match code:
955    case None{}:
956      FrameBad{}
957    case Some{n}:
958      parse.res.fields(n, rest, parse.headers(headers, FieldsOk{empty()}), closed, head)
959
960def parse.res.ver(code: String, headers: List<&2, String>, rest: String, closed: Bool, head: Bool, ok: Bool) -> Frame:
961  match ok:
962    case False{}:
963      FrameBad{}
964    case True{}:
965      parse.res.num(parse_u32(code), headers, rest, closed, head)
966
967def parse.res.start3(mpv: String & String & String, headers: List<&2, String>, rest: String, closed: Bool, head: Bool) -> Frame:
968  (+ver, code, reason) = mpv
969  parse.res.ver(code, headers, rest, closed, head, Bool.or(String.eq(ver, "HTTP/1.1"), String.eq(ver, "HTTP/1.0")))
970
971def parse.res.lines(xs: List<&2, String>, rest: String, closed: Bool, head: Bool) -> Frame:
972  match xs:
973    case Nil{}:
974      FrameBad{}
975    case Con{line, headers}:
976      parse.res.start3(start_line(line), headers, rest, closed, head)
977
978def parse.res.blank(hd: String, rest: String, +closed: Bool, head: Bool, ok: Bool) -> Frame:
979  match ok:
980    case False{}:
981      frame.cut(closed)
982    case True{}:
983      parse.res.lines(String.lines(hd), rest, closed, head)
984
985def parse.res.of(hb: String & String, closed: Bool, head: Bool) -> Frame:
986  (+hd, rest) = hb
987  parse.res.blank(hd, rest, closed, head, blank_end(hd))
988
989type Lead is Data:
990  LeadCut{}
991  LeadFinal{}
992  LeadSkip{+rest: String}
993
994def frame.lead.if(rest: String, interim: Bool) -> Lead:
995  match interim:
996    case True{}:
997      LeadSkip{rest}
998    case False{}:
999      LeadFinal{}
1000
1001def frame.lead.num(n: Maybe<&2, U32>, rest: String) -> Lead:
1002  match n:
1003    case None{}:
1004      LeadFinal{}
1005    case Some{s}:
1006      frame.lead.if(rest, frame.interim(s))
1007
1008def frame.lead.code(mpv: String & String & String, rest: String) -> Lead:
1009  (ver, code, reason) = mpv
1010  frame.lead.num(parse_u32(code), rest)
1011
1012def frame.lead.lines(xs: List<&2, String>, rest: String) -> Lead:
1013  match xs:
1014    case Nil{}:
1015      LeadFinal{}
1016    case Con{line, headers}:
1017      frame.lead.code(start_line(line), rest)
1018
1019def frame.lead.blank(+hd: String, rest: String, ok: Bool) -> Lead:
1020  match ok:
1021    case False{}:
1022      LeadCut{}
1023    case True{}:
1024      frame.lead.lines(String.lines(hd), rest)
1025
1026def frame.lead(hb: String & String) -> Lead:
1027  (+hd, rest) = hb
1028  frame.lead.blank(hd, rest, blank_end(hd))
1029
1030def frame.at.cont(+raw: String, lead: Lead) -> String:
1031  match lead:
1032    case LeadCut{}:
1033      raw
1034    case LeadFinal{}:
1035      raw
1036    case LeadSkip{rest}:
1037      rest
1038
1039def frame.at.zero.go(+raw: String, closed: Bool, head: Bool, lead: Lead) -> Frame:
1040  match lead:
1041    case LeadCut{}:
1042      frame.cut(closed)
1043    case LeadFinal{}:
1044      parse.res.of(split_at_blank(raw), closed, head)
1045    case LeadSkip{rest}:
1046      FrameBad{}
1047
1048def frame.at.zero.of(+raw: String, closed: Bool, head: Bool) -> Frame:
1049  frame.at.zero.go(raw, closed, head, frame.lead(split_at_blank(raw)))
1050
1051def frame.at.pos.do(f: Nat, +raw: String, closed: Bool, head: Bool, hb: String & String, lead: Lead) -> Frame:
1052  match f:
1053    case 0n:
1054      match lead:
1055        case LeadCut{}:
1056          frame.cut(closed)
1057        case LeadFinal{}:
1058          parse.res.of(hb, closed, head)
1059        case LeadSkip{+rest}:
1060          frame.at.zero.of(rest, closed, head)
1061    case 1n+g:
1062      match lead:
1063        case LeadCut{}:
1064          frame.cut(closed)
1065        case LeadFinal{}:
1066          parse.res.of(hb, closed, head)
1067        case LeadSkip{+rest}:
1068          frame.at.pos.do(g, rest, closed, head, split_at_blank(rest), frame.lead(split_at_blank(rest)))
1069
1070def frame.at.zero(+raw: String, closed: Bool, head: Bool) -> Frame:
1071  frame.at.zero.of(raw, closed, head)
1072
1073# ponytail: 8 interim responses; raise the fuel if a server sends more
1074def frame.at(fuel: Nat, +raw: String, closed: Bool, head: Bool) -> Frame:
1075  match fuel:
1076    case 0n:
1077      frame.at.zero(raw, closed, head)
1078    case 1n+f:
1079      frame.at.pos.do(f, raw, closed, head, split_at_blank(raw), frame.lead(split_at_blank(raw)))
1080
1081# frame(bytes so far, server closed?, request was HEAD?)
1082def frame(raw: String, closed: Bool, head: Bool) -> Frame:
1083  frame.at(8n, raw, closed, head)
1084
1085def frame.res(f: Frame) -> Maybe<&1, Res>:
1086  match f:
1087    case FrameDone{res}:
1088      Some{res}
1089    case FrameBad{}:
1090      None{}
1091    case FrameMore{}:
1092      None{}
1093
1094def parse_res(raw: String) -> Maybe<&1, Res>:
1095  frame.res(frame(raw, True{}, False{}))
1096
1097def res_fields.res(res: Res, k: String) -> List<&2, String>:
1098  Res{status, headers, body} = res
1099  fields(headers, k)
1100
1101def res_fields(m: Maybe<&1, Res>, k: String) -> List<&2, String>:
1102  match m:
1103    case None{}:
1104      Nil{}
1105    case Some{res}:
1106      res_fields.res(res, k)
1107
1108# The response body as it arrives. Len: bytes left. Chunk: the decoder. Close: until the
1109# server closes. Done: the body is whole. Bad: it cannot become a body.
1110type Rb is Data:
1111  RbLen{left: U32}
1112  RbChunk{st: Dc}
1113  RbClose{}
1114  RbDone{}
1115  RbBad{}
1116
1117def rb.cl(n: Maybe<&2, U32>) -> Maybe<&2, Rb>:
1118  match n:
1119    case None{}:
1120      None{}
1121    case Some{+k}:
1122      Some{Bool.pick(Rb, U32.is_zero(k), RbDone{}, RbLen{k})}
1123
1124def rb.te(+h: Map<&2, List<&2, String>>, cl: Bool) -> Maybe<&2, Rb>:
1125  match cl:
1126    case True{}:
1127      None{}
1128    case False{}:
1129      Some{Bool.pick(Rb, String.eq(String.to_lower(header.last(h, "transfer-encoding")), "chunked"), RbChunk{dc.start()}, RbClose{})}
1130
1131def rb.len(+h: Map<&2, List<&2, String>>, te: Bool) -> Maybe<&2, Rb>:
1132  match te:
1133    case True{}:
1134      rb.te(h, has_header(h, "content-length"))
1135    case False{}:
1136      Bool.pick(Maybe<&2, Rb>, has_header(h, "content-length"), rb.cl(parse_u32(header(h, "content-length"))), Some{RbClose{}})
1137
1138# RFC 9112 §6.3: how the body of this response ends. None: it cannot be framed.
1139def rb.of(+h: Map<&2, List<&2, String>>, nobody: Bool) -> Maybe<&2, Rb>:
1140  match nobody:
1141    case True{}:
1142      Some{RbDone{}}
1143    case False{}:
1144      rb.len(h, has_header(h, "transfer-encoding"))
1145
1146# rb: how the body goes on. parts: body bytes so far, newest first. rest: bytes past a Done body.
1147type Bf is Type:
1148  Bf{rb: Rb, parts: List<&1, Bytes.Bytes>, rest: Bytes.Bytes}
1149
1150def rb.len.cut(parts: List<&1, Bytes.Bytes>, +len: U32, +left: U32, r: Bytes.Bytes & Bytes.Bytes) -> Bf:
1151  (piece, data) = r
1152  Bf{RbDone{}, Con{data, parts}, bytes.snd(Bytes.slice(piece, left, (len - left : U32)))}
1153
1154def rb.len.have(short: Bool, +left: U32, parts: List<&1, Bytes.Bytes>, +len: U32, piece: Bytes.Bytes) -> Bf:
1155  match short:
1156    case True{}:
1157      Bf{RbLen{(left - len : U32)}, Con{piece, parts}, Bytes.new(0)}
1158    case False{}:
1159      rb.len.cut(parts, len, left, Bytes.slice(piece, 0, left))
1160
1161def rb.chunk(c: Ck) -> Bf:
1162  Ck{st, parts, rest} = c
1163  match st:
1164    case DcDone{}:
1165      Bf{RbDone{}, parts, rest}
1166    case DcBad{}:
1167      Bf{RbBad{}, parts, rest}
1168    case DcSize{a, b}:
1169      Bf{RbChunk{DcSize{a, b}}, parts, rest}
1170    case DcExt{x}:
1171      Bf{RbChunk{DcExt{x}}, parts, rest}
1172    case DcSizeLf{x}:
1173      Bf{RbChunk{DcSizeLf{x}}, parts, rest}
1174    case DcData{k}:
1175      Bf{RbChunk{DcData{k}}, parts, rest}
1176    case DcDataCr{}:
1177      Bf{RbChunk{DcDataCr{}}, parts, rest}
1178    case DcDataLf{}:
1179      Bf{RbChunk{DcDataLf{}}, parts, rest}
1180    case DcTr{j}:
1181      Bf{RbChunk{DcTr{j}}, parts, rest}
1182
1183# The body bytes in piece, added to parts.
1184def rb.feed(rb: Rb, parts: List<&1, Bytes.Bytes>, piece: Bytes.Bytes) -> Bf:
1185  match rb:
1186    case RbLen{+left}:
1187      Bytes.Bytes{+len, buf} = piece
1188      rb.len.have(U32.is_lt(len, left), left, parts, len, Bytes.Bytes{len, buf})
1189    case RbChunk{st}:
1190      rb.chunk(ck(piece, st, parts))
1191    case RbClose{}:
1192      Bf{RbClose{}, Con{piece, parts}, Bytes.new(0)}
1193    case RbDone{}:
1194      Bf{RbDone{}, parts, piece}
1195    case RbBad{}:
1196      Bf{RbBad{}, parts, piece}
1197
1198# RFC 9112 §8: only a close-delimited body may end at close.
1199def rb.eof(rb: Rb) -> Bool:
1200  match rb:
1201    case RbClose{}:
1202      True{}
1203    case RbDone{}:
1204      True{}
1205    case RbLen{n}:
1206      False{}
1207    case RbChunk{st}:
1208      False{}
1209    case RbBad{}:
1210      False{}
1211
1212def rb.body(parts: List<&1, Bytes.Bytes>) -> Bytes.Bytes:
1213  Bytes.concat(List.reverse(&1, Bytes.Bytes, parts))
1214
1215# The head scan. Seek: look for the blank line from byte from; k interim heads are behind.
1216# Wait: no blank line yet. Res: the final head, how its body ends, and the bytes after it.
1217type Hs is Type:
1218  HsSeek{buf: Bytes.Bytes, from: U32, k: U32}
1219  HsWait{buf: Bytes.Bytes, k: U32}
1220  HsBad{}
1221  HsRes{res: Res, rb: Rb, rest: Bytes.Bytes}
1222
1223def hs.final(+status: U32, +h: Map<&2, List<&2, String>>, rest: Bytes.Bytes, m: Maybe<&2, Rb>) -> Hs:
1224  match m:
1225    case None{}:
1226      HsBad{}
1227    case Some{rb}:
1228      HsRes{Res{status, h, Bytes.new(0)}, rb, rest}
1229
1230def hs.skip(more: Bool, +k: U32, rest: Bytes.Bytes) -> Hs:
1231  match more:
1232    case True{}:
1233      HsSeek{rest, 0, (k + 1 : U32)}
1234    case False{}:
1235      HsBad{}
1236
1237def hs.pick(interim: Bool, +head: Bool, +k: U32, +status: U32, +h: Map<&2, List<&2, String>>, rest: Bytes.Bytes) -> Hs:
1238  match interim:
1239    case True{}:
1240      hs.skip(U32.is_lt(k, 8), k, rest)
1241    case False{}:
1242      hs.final(status, h, rest, rb.of(h, frame.nobody(status, head)))
1243
1244def hs.res(+head: Bool, +k: U32, rest: Bytes.Bytes, res: Res) -> Hs:
1245  Res{+status, +h, body} = res
1246  hs.pick(frame.interim(status), head, k, status, h, rest)
1247
1248# The head alone, framed as a HEAD response so it stops at the blank line.
1249def hs.parsed(+head: Bool, +k: U32, rest: Bytes.Bytes, f: Frame) -> Hs:
1250  match f:
1251    case FrameDone{res}:
1252      hs.res(head, k, rest, res)
1253    case FrameBad{}:
1254      HsBad{}
1255    case FrameMore{}:
1256      HsBad{}
1257
1258def hs.split(+head: Bool, +k: U32, +hlen: U32, +len: U32, r: Bytes.Bytes & Bytes.Bytes) -> Hs:
1259  (buf, hb) = r
1260  hs.parsed(head, k, bytes.snd(Bytes.slice(buf, hlen, (len - hlen : U32))), parse.res.of(split_at_blank(Bytes.to_string(hb)), False{}, True{}))
1261
1262def hs.hit(+head: Bool, +k: U32, +len: U32, buf: Bytes.Bytes, at: Maybe<&2, U32>) -> Hs:
1263  match at:
1264    case None{}:
1265      HsWait{buf, k}
1266    case Some{+i}:
1267      +hlen = (i + 4 : U32)
1268      hs.split(head, k, hlen, len, Bytes.slice(buf, 0, hlen))
1269
1270def hs.seek.of(+head: Bool, +k: U32, +len: U32, +from: U32, buf: Bytes.Bytes, r: Bytes.Bytes & Maybe<&2, U32>) -> Hs:
1271  (tail, m) = r
1272  hs.hit(head, k, len, buf, found.at(from, m))
1273
1274def hs.seek(+head: Bool, +k: U32, +len: U32, +from: U32, r: Bytes.Bytes & Bytes.Bytes) -> Hs:
1275  (buf, tail) = r
1276  hs.seek.of(head, k, len, from, buf, Bytes.find(tail, "\r\n\r\n"))
1277
1278def hs.step(+head: Bool, st: Hs) -> Hs:
1279  match st:
1280    case HsSeek{buf, +from, +k}:
1281      Bytes.Bytes{+len, b} = buf
1282      hs.seek(head, k, len, from, Bytes.slice(Bytes.Bytes{len, b}, from, (len - from : U32)))
1283    case HsWait{buf, k}:
1284      HsWait{buf, k}
1285    case HsBad{}:
1286      HsBad{}
1287    case HsRes{res, rb, rest}:
1288      HsRes{res, rb, rest}
1289
1290# Each step ends the scan or passes one interim head, and at most 8 interim heads pass.
1291def hs.scan(fuel: Nat, +head: Bool, st: Hs) -> Hs:
1292  match fuel:
1293    case 0n:
1294      match st:
1295        case HsSeek{buf, from, k}:
1296          HsBad{}
1297        case HsWait{buf, k}:
1298          HsWait{buf, k}
1299        case HsBad{}:
1300          HsBad{}
1301        case HsRes{res, rb, rest}:
1302          HsRes{res, rb, rest}
1303    case 1n+f:
1304      hs.scan(f, head, hs.step(head, st))
1305
1306# piece joins buf; only the new bytes, and the 3 before them, can finish the blank line.
1307def hs.more(+head: Bool, +k: U32, buf: Bytes.Bytes, piece: Bytes.Bytes) -> Hs:
1308  Bytes.Bytes{+ol, ob} = buf
1309  hs.scan(10n, head, HsSeek{Bytes.append(Bytes.Bytes{ol, ob}, piece), Bool.pick(U32, U32.is_lt(ol, 3), 0, (ol - 3 : U32)), k})
1310
1311# Untrusted servers must not grow the buffer without bound.
1312def fetch.max() -> Nat:
1313  U32.to_nat(16777216)
1314
1315# A response read in pieces. Head: the head is not whole yet. Body: it is, and parts is the body so far.
1316# Len: a Content-Length body in one buffer of that size, with left bytes still to come.
1317type Rv is Type:
1318  RvHead{buf: Bytes.Bytes, k: U32}
1319  RvBody{res: Res, rb: Rb, parts: List<&1, Bytes.Bytes>}
1320  RvLen{res: Res, left: U32, body: Bytes.Bytes}
1321
1322# More: read on. Done: the response, and the bytes after it when the body is self-delimited.
1323type Rt is Type:
1324  RtMore{rv: Rv}
1325  RtBad{}
1326  RtDone{res: Res, rest: Maybe<&1, Bytes.Bytes>}
1327
1328def rv.start() -> Rv:
1329  RvHead{Bytes.new(0), 0}
1330
1331def rv.whole(res: Res, b: Bytes.Bytes, rest: Maybe<&1, Bytes.Bytes>) -> Rt:
1332  Res{status, headers, body} = res
1333  RtDone{Res{status, headers, b}, rest}
1334
1335def rv.done(res: Res, parts: List<&1, Bytes.Bytes>, rest: Maybe<&1, Bytes.Bytes>) -> Rt:
1336  rv.whole(res, rb.body(parts), rest)
1337
1338def rl.put.of(+total: U32, +len: U32, r: Array<U32> & Array<U32>) -> Bytes.Bytes & Bytes.Bytes:
1339  (src, dst) = r
1340  (Bytes.Bytes{total, dst}, Bytes.Bytes{len, src})
1341
1342# The first m bytes of piece, written into body after the total - left bytes already there.
1343def rl.put(+m: U32, +left: U32, body: Bytes.Bytes, piece: Bytes.Bytes) -> Bytes.Bytes & Bytes.Bytes:
1344  Bytes.Bytes{+total, dst} = body
1345  Bytes.Bytes{+len, src} = piece
1346  rl.put.of(total, len, Bytes.copy(m, src, dst, 0, (total - left : U32)))
1347
1348def rl.fed(short: Bool, res: Res, +left: U32, +len: U32, r: Bytes.Bytes & Bytes.Bytes) -> Rt:
1349  match short:
1350    case True{}:
1351      (body, piece) = r
1352      RtMore{RvLen{res, (left - len : U32), body}}
1353    case False{}:
1354      (body, piece) = r
1355      rv.whole(res, body, Some{bytes.snd(Bytes.slice(piece, left, (len - left : U32)))})
1356
1357def rl.feed(res: Res, +left: U32, body: Bytes.Bytes, piece: Bytes.Bytes) -> Rt:
1358  Bytes.Bytes{+len, buf} = piece
1359  rl.fed(U32.is_lt(len, left), res, left, len, rl.put(U32.min(len, left), left, body, Bytes.Bytes{len, buf}))
1360
1361def rv.fed(res: Res, bf: Bf) -> Rt:
1362  Bf{rb, parts, rest} = bf
1363  match rb:
1364    case RbDone{}:
1365      rv.done(res, parts, Some{rest})
1366    case RbBad{}:
1367      RtBad{}
1368    case RbLen{n}:
1369      RtMore{RvBody{res, RbLen{n}, parts}}
1370    case RbChunk{st}:
1371      RtMore{RvBody{res, RbChunk{st}, parts}}
1372    case RbClose{}:
1373      RtMore{RvBody{res, RbClose{}, parts}}
1374
1375# Some{left}: a Content-Length body small enough to allocate up front. Larger ones fail at the fetch cap.
1376def rb.buf(rb: Rb) -> Maybe<&2, U32>:
1377  match rb:
1378    case RbLen{+left}:
1379      Bool.pick(Maybe<&2, U32>, Nat.is_lt(fetch.max(), U32.to_nat(left)), None{}, Some{left})
1380    case RbChunk{st}:
1381      None{}
1382    case RbClose{}:
1383      None{}
1384    case RbDone{}:
1385      None{}
1386    case RbBad{}:
1387      None{}
1388
1389def rv.body(m: Maybe<&2, U32>, res: Res, rb: Rb, rest: Bytes.Bytes) -> Rt:
1390  match m:
1391    case None{}:
1392      rv.fed(res, rb.feed(rb, Nil{}, rest))
1393    case Some{+left}:
1394      rl.feed(res, left, Bytes.new(left), rest)
1395
1396def rv.head(hs: Hs) -> Rt:
1397  match hs:
1398    case HsWait{buf, k}:
1399      RtMore{RvHead{buf, k}}
1400    case HsBad{}:
1401      RtBad{}
1402    case HsSeek{buf, from, k}:
1403      RtBad{}
1404    case HsRes{res, +rb, rest}:
1405      rv.body(rb.buf(rb), res, rb, rest)
1406
1407def rv.eof(res: Res, parts: List<&1, Bytes.Bytes>, ok: Bool) -> Rt:
1408  match ok:
1409    case True{}:
1410      rv.done(res, parts, None{})
1411    case False{}:
1412      RtBad{}
1413
1414# One read: piece, or the server closed (RFC 9112 §8: a message cut short is not a message).
1415def rv.step(closed: Bool, +head: Bool, rv: Rv, piece: Bytes.Bytes) -> Rt:
1416  match closed:
1417    case True{}:
1418      match rv:
1419        case RvHead{buf, k}:
1420          RtBad{}
1421        case RvBody{res, rb, parts}:
1422          rv.eof(res, parts, rb.eof(rb))
1423        case RvLen{res, left, body}:
1424          RtBad{}
1425    case False{}:
1426      match rv:
1427        case RvHead{buf, +k}:
1428          rv.head(hs.more(head, k, buf, piece))
1429        case RvBody{res, rb, parts}:
1430          rv.fed(res, rb.feed(rb, parts, piece))
1431        case RvLen{res, +left, body}:
1432          rl.feed(res, left, body, piece)
1433
1434def rv.end(closed: Bool, +head: Bool, t: Rt) -> Rt:
1435  match closed:
1436    case False{}:
1437      t
1438    case True{}:
1439      match t:
1440        case RtMore{rv}:
1441          rv.step(True{}, head, rv, Bytes.new(0))
1442        case RtBad{}:
1443          RtBad{}
1444        case RtDone{res, rest}:
1445          RtDone{res, rest}
1446
1447def rv.go(xs: List<&2, String>, closed: Bool, +head: Bool, t: Rt) -> Rt:
1448  match xs:
1449    case Nil{}:
1450      rv.end(closed, head, t)
1451    case Con{+x, rest}:
1452      match t:
1453        case RtMore{rv}:
1454          rv.go(rest, closed, head, rv.step(False{}, head, rv, Bytes.from_string(x)))
1455        case RtBad{}:
1456          RtBad{}
1457        case RtDone{res, r}:
1458          RtDone{res, r}
1459
1460def rt.frame(t: Rt) -> Frame:
1461  match t:
1462    case RtMore{rv}:
1463      FrameMore{}
1464    case RtBad{}:
1465      FrameBad{}
1466    case RtDone{res, rest}:
1467      FrameDone{res}
1468
1469# What the read loop makes of these pieces, then a close when closed is set.
1470def res.frame(xs: List<&2, String>, closed: Bool, +head: Bool) -> Frame:
1471  rt.frame(rv.go(xs, closed, head, RtMore{rv.start()}))
1472
1473def rt.rest(t: Rt) -> Maybe<&1, Bytes.Bytes>:
1474  match t:
1475    case RtMore{rv}:
1476      None{}
1477    case RtBad{}:
1478      None{}
1479    case RtDone{res, rest}:
1480      rest
1481
1482def after.of(m: Maybe<&1, Bytes.Bytes>) -> Maybe<&2, String>:
1483  match m:
1484    case None{}:
1485      None{}
1486    case Some{b}:
1487      Some{Bytes.to_string(b)}
1488
1489# Bytes after a complete self-delimited message. None if it is not one yet.
1490def after(+raw: String, +head: Bool) -> Maybe<&2, String>:
1491  after.of(rt.rest(rv.go([raw], False{}, head, RtMore{rv.start()})))
1492
1493def req.v11.ver(mpv: String & String & String) -> Bool:
1494  (+method, path, v) = mpv
1495  String.eq(v, "HTTP/1.1")
1496
1497def req.v11.line(+line: String) -> Bool:
1498  req.v11.ver(start_line(line))
1499
1500def req.v11.lines(xs: List<&2, String>) -> Bool:
1501  match xs:
1502    case Nil{}:
1503      False{}
1504    case Con{line, headers}:
1505      req.v11.line(line)
1506
1507def req.v11.pick(+head: String, ok: Bool) -> Bool:
1508  match ok:
1509    case False{}:
1510      False{}
1511    case True{}:
1512      req.v11.lines(String.lines(head))
1513
1514def req.v11.of(hb: String & String) -> Bool:
1515  (+head, rest) = hb
1516  req.v11.pick(head, blank_end(head))
1517
1518def req.v11(+raw: String) -> Bool:
1519  req.v11.of(split_at_blank(raw))
1520
1521def req.conn_close(+headers: Map<&2, List<&2, String>>) -> Bool:
1522  String.eq(String.to_lower(header(headers, "connection")), "close")
1523
1524def res.conn_close(+headers: Map<&2, List<&2, String>>) -> Bool:
1525  String.eq(String.to_lower(header(headers, "connection")), "close")
1526
1527def serve.fail_close(+status: U32) -> Bool:
1528  Bool.or(U32.is_eq(status, 400), Bool.or(U32.is_eq(status, 413), U32.is_eq(status, 431)))
1529
1530def serve.keep.ok(fail: Bool, res_close: Bool) -> Bool:
1531  match fail:
1532    case True{}:
1533      False{}
1534    case False{}:
1535      Bool.not(res_close)
1536
1537def serve.keep.v11(v11: Bool, +req_close: Bool, +status: U32, res_close: Bool) -> Bool:
1538  match v11:
1539    case False{}:
1540      False{}
1541    case True{}:
1542      match req_close:
1543        case True{}:
1544          False{}
1545        case False{}:
1546          serve.keep.ok(serve.fail_close(status), res_close)
1547
1548def serve.keep(+headers: Map<&2, List<&2, String>>, v11: Bool, +status: U32, +res: Map<&2, List<&2, String>>) -> Bool:
1549  serve.keep.v11(v11, req.conn_close(headers), status, res.conn_close(res))
1550
1551
1552def again.keep(close: Bool, x: Bytes.Bytes) -> Maybe<&1, Bytes.Bytes>:
1553  match close:
1554    case True{}:
1555      None{}
1556    case False{}:
1557      Some{x}
1558
1559def again.rest(close: Bool, rest: Maybe<&1, Bytes.Bytes>) -> Maybe<&1, Bytes.Bytes>:
1560  match rest:
1561    case None{}:
1562      None{}
1563    case Some{x}:
1564      again.keep(close, x)
1565
1566# The bytes past the response when the socket can take another request: the request did not
1567# ask to close, the response is self-delimited, and the peer did not say close.
1568def again(close: Bool, +h: Map<&2, List<&2, String>>, rest: Maybe<&1, Bytes.Bytes>) -> Maybe<&1, Bytes.Bytes>:
1569  match close:
1570    case True{}:
1571      None{}
1572    case False{}:
1573      again.rest(String.eq(String.to_lower(header(h, "connection")), "close"), rest)
1574
1575def res_body.res(res: Res) -> Bytes.Bytes:
1576  Res{status, headers, body} = res
1577  body
1578
1579def res_body(m: Maybe<&1, Res>) -> Bytes.Bytes:
1580  match m:
1581    case None{}:
1582      Bytes.new(0)
1583    case Some{res}:
1584      res_body.res(res)
1585
1586def text(res: Res) -> String:
1587  Enc.utf8.decode(res_body.res(res))
1588
1589# UTF-8 is checked, not repaired: bad UTF-8 in a string gives None (RFC 8259 §8.1).
1590def json(res: Res) -> Maybe<&1, Json.Val>:
1591  Json.parse.bytes(res_body.res(res))
1592
1593def got_body.req(req: Req) -> Bytes.Bytes:
1594  Req{method, path, headers, body} = req
1595  body
1596
1597def got_body(m: Maybe<&1, Req>) -> Bytes.Bytes:
1598  match m:
1599    case None{}:
1600      Bytes.new(0)
1601    case Some{req}:
1602      got_body.req(req)
1603
1604def body.of(hb: String & String) -> String:
1605  (h, b) = hb
1606  b
1607
1608def body(s: String) -> String:
1609  body.of(split_at_blank.go(s, False{}, 0, SNil{}))
1610
1611def headers_lines(+k: String, vs: List<&2, String>, acc: String) -> String:
1612  match vs:
1613    case Nil{}:
1614      acc
1615    case Con{v, t}:
1616      headers_lines(k, t, acc ++ ("\r\n" ++ sanitize(k) ++ ": " ++ sanitize(v)))
1617
1618def headers_block.go(xs: List<&2, Sigma<&2, &2, String, _ => List<&2, String>>>, acc: String) -> String:
1619  match xs:
1620    case Nil{}:
1621      acc
1622    case (k, vs) <> t:
1623      headers_block.go(t, headers_lines(k, vs, acc))
1624
1625def headers_block(h: Map<&2, List<&2, String>>) -> String:
1626  headers_block.go(Map.to_list(&2, List<&2, String>, h), "")
1627
1628# RFC 9110 §15. An unknown code gets an empty reason, which RFC 9112 §4 allows.
1629type Reason is Data:
1630  Reason{code: U32, text: String}
1631
1632def reasons() -> List<&2, Reason>:
1633  [Reason{100, "Continue"}, Reason{101, "Switching Protocols"}, Reason{103, "Early Hints"},
1634   Reason{200, "OK"}, Reason{201, "Created"}, Reason{202, "Accepted"}, Reason{203, "Non-Authoritative Information"}, Reason{204, "No Content"}, Reason{205, "Reset Content"}, Reason{206, "Partial Content"},
1635   Reason{300, "Multiple Choices"}, Reason{301, "Moved Permanently"}, Reason{302, "Found"}, Reason{303, "See Other"}, Reason{304, "Not Modified"}, Reason{307, "Temporary Redirect"}, Reason{308, "Permanent Redirect"},
1636   Reason{400, "Bad Request"}, Reason{401, "Unauthorized"}, Reason{402, "Payment Required"}, Reason{403, "Forbidden"}, Reason{404, "Not Found"}, Reason{405, "Method Not Allowed"}, Reason{406, "Not Acceptable"}, Reason{407, "Proxy Authentication Required"}, Reason{408, "Request Timeout"}, Reason{409, "Conflict"}, Reason{410, "Gone"}, Reason{411, "Length Required"}, Reason{412, "Precondition Failed"}, Reason{413, "Content Too Large"}, Reason{414, "URI Too Long"}, Reason{415, "Unsupported Media Type"}, Reason{416, "Range Not Satisfiable"}, Reason{417, "Expectation Failed"}, Reason{421, "Misdirected Request"}, Reason{422, "Unprocessable Content"}, Reason{426, "Upgrade Required"}, Reason{428, "Precondition Required"}, Reason{429, "Too Many Requests"}, Reason{431, "Request Header Fields Too Large"},
1637   Reason{500, "Internal Server Error"}, Reason{501, "Not Implemented"}, Reason{502, "Bad Gateway"}, Reason{503, "Service Unavailable"}, Reason{504, "Gateway Timeout"}, Reason{505, "HTTP Version Not Supported"}]
1638
1639def reason.go(xs: List<&2, Reason>, +status: U32) -> String:
1640  match xs:
1641    case Nil{}:
1642      ""
1643    case Con{Reason{k, v}, t}:
1644      Bool.pick(String, U32.is_eq(k, status), v, reason.go(t, status))
1645
1646def reason(+status: U32) -> String:
1647  reason.go(reasons(), status)
1648
1649def response(+status: U32, headers: Map<&2, List<&2, String>>, body: String) -> String:
1650  ("HTTP/1.1 " ++ U32.show(status) ++ " " ++ reason(status) ++ headers_block(headers)) ++ ("\r\n\r\n" ++ body)
1651
1652def encode.body(head: Bool, top: Bytes.Bytes, body: Bytes.Bytes) -> Bytes.Bytes:
1653  match head:
1654    case True{}:
1655      top
1656    case False{}:
1657      Bytes.append(top, body)
1658
1659def encode.len(+status: U32, headers: Map<&2, List<&2, String>>, head: Bool, body: Bytes.Bytes) -> Bytes.Bytes:
1660  Bytes.Bytes{+len, buf} = body
1661  encode.body(head, Bytes.from_string(response(status, set(headers, "content-length", U32.show(len)), "")), Bytes.Bytes{len, buf})
1662
1663# RFC 9110 §6.4.1, §8.6: 1xx, 204 and 304 have no body; HEAD gets the length but no body.
1664def encode.pick(+status: U32, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes, head: Bool, nobody: Bool) -> Bytes.Bytes:
1665  match nobody:
1666    case True{}:
1667      Bytes.from_string(response(status, headers, ""))
1668    case False{}:
1669      encode.len(status, headers, head, body)
1670
1671def encode.on(r: Res, head: Bool) -> Bytes.Bytes:
1672  Res{+status, headers, body} = r
1673  encode.pick(status, headers, body, head, frame.nobody(status, False{}))
1674
1675def encode(r: Res) -> Bytes.Bytes:
1676  encode.on(r, False{})
1677
1678def request(method: String, path: String, headers: Map<&2, List<&2, String>>, body: String) -> String:
1679  (method ++ " " ++ path ++ " HTTP/1.1" ++ headers_block(headers)) ++ ("\r\n\r\n" ++ body)
1680
1681def req.reserved(+k: String) -> Bool:
1682  Bool.or(Bool.or(String.eq(k, "host"), String.eq(k, "connection")), Bool.or(String.eq(k, "content-length"), String.eq(k, "transfer-encoding")))
1683
1684def req.put.one(m: Map<&2, List<&2, String>>, +k: String, vs: List<&2, String>, skip: Bool) -> Map<&2, List<&2, String>>:
1685  match skip:
1686    case True{}:
1687      m
1688    case False{}:
1689      Map.set(&2, List<&2, String>, m, k, vs)
1690
1691def req.put(xs: List<&2, Sigma<&2, &2, String, _ => List<&2, String>>>, m: Map<&2, List<&2, String>>) -> Map<&2, List<&2, String>>:
1692  match xs:
1693    case Nil{}:
1694      m
1695    case (k, vs) <> t:
1696      +lk = String.to_lower(k)
1697      req.put(t, req.put.one(m, lk, vs, req.reserved(lk)))
1698
1699# RFC 9110 §8.6: no Content-Length on a bodiless request whose method gives a body no meaning.
1700def req.cl(+m: Map<&2, List<&2, String>>, +method: String, +len: U32) -> Map<&2, List<&2, String>>:
1701  +bodied = Bool.or(Bool.not(U32.is_zero(len)), Bool.or(String.eq(method, "POST"), Bool.or(String.eq(method, "PUT"), String.eq(method, "PATCH"))))
1702  Bool.pick(Map<&2, List<&2, String>>, bodied, set(m, "content-length", U32.show(len)), m)
1703
1704# Caller headers are lowercased so they cannot duplicate ours; host, connection,
1705# content-length and transfer-encoding are always ours (no smuggling through them).
1706def encode_req.word(close: Bool) -> String:
1707  match close:
1708    case True{}:
1709      "close"
1710    case False{}:
1711      "keep-alive"
1712
1713def encode_req.on(+method: String, target: String, host: String, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes, close: Bool) -> Bytes.Bytes:
1714  Bytes.Bytes{+len, buf} = body
1715  +h = set(set(req.put(Map.to_list(&2, List<&2, String>, headers), empty()), "host", host), "connection", encode_req.word(close))
1716  Bytes.append(Bytes.from_string(request(method, target, req.cl(h, method, len), "")), Bytes.Bytes{len, buf})
1717
1718def encode_req(+method: String, target: String, host: String, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes) -> Bytes.Bytes:
1719  encode_req.on(method, target, host, headers, body, True{})
1720
1721# Redirects (RFC 9110 §15.4, as WHATWG fetch applies them)
1722# --------------------------------------------------------
1723
1724# One request to make: headers are already lowercased (see req.put).
1725type Hop is Type:
1726  Hop{method: String, url: Url.Abs, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes}
1727
1728def redirect.code(+s: U32) -> Bool:
1729  Bool.or(Bool.or(U32.is_eq(s, 301), U32.is_eq(s, 302)), Bool.or(U32.is_eq(s, 303), Bool.or(U32.is_eq(s, 307), U32.is_eq(s, 308))))
1730
1731def redirect.origin(a: Url.Abs) -> String:
1732  Url.Abs{scheme, host, port, target} = a
1733  scheme ++ "://" ++ host ++ ":" ++ U32.show(port)
1734
1735def redirect.del(ks: List<&2, String>, m: Map<&2, List<&2, String>>) -> Map<&2, List<&2, String>>:
1736  match ks:
1737    case Nil{}:
1738      m
1739    case Con{k, t}:
1740      redirect.del(t, Map.del(&2, List<&2, String>, m, k))
1741
1742def redirect.hdrs(+h: Map<&2, List<&2, String>>, drop: Bool, cross: Bool) -> Map<&2, List<&2, String>>:
1743  +h2 = Bool.pick(Map<&2, List<&2, String>>, drop, redirect.del(["content-type", "content-encoding", "content-language", "content-location"], h), h)
1744  Bool.pick(Map<&2, List<&2, String>>, cross, redirect.del(["authorization", "cookie", "proxy-authorization"], h2), h2)
1745
1746# 303 turns any method but HEAD into GET; 301 and 302 turn POST into GET;
1747# 307 and 308 keep method and body. A GET carries no body or body headers.
1748# Credentials do not follow a hop to another origin.
1749def redirect.body(drop: Bool, body: Bytes.Bytes) -> Bytes.Bytes:
1750  match drop:
1751    case True{}:
1752      Bytes.new(0)
1753    case False{}:
1754      body
1755
1756def redirect.to(+status: U32, +method: String, +from: Url.Abs, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes, next: Maybe<&2, Url.Abs>) -> Maybe<&1, Hop>:
1757  match next:
1758    case None{}:
1759      None{}
1760    case Some{+to}:
1761      +drop = Bool.or(Bool.and(U32.is_eq(status, 303), Bool.not(String.eq(method, "HEAD"))), Bool.and(Bool.or(U32.is_eq(status, 301), U32.is_eq(status, 302)), String.eq(method, "POST")))
1762      Some{Hop{Bool.pick(String, drop, "GET", method), to, redirect.hdrs(headers, drop, Bool.not(String.eq(redirect.origin(from), redirect.origin(to)))), redirect.body(drop, body)}}
1763
1764def redirect.hop(status: U32, h: Hop, loc: String) -> Maybe<&1, Hop>:
1765  Hop{method, +url, headers, body} = h
1766  redirect.to(status, method, url, headers, body, Url.resolve(url, loc))
1767
1768def redirect.if(status: U32, h: Hop, loc: String, ok: Bool) -> Maybe<&1, Hop>:
1769  match ok:
1770    case False{}:
1771      None{}
1772    case True{}:
1773      redirect.hop(status, h, loc)
1774
1775# The next request after a response, or None when it is not a redirect we follow.
1776def redirect(+status: U32, +headers: Map<&2, List<&2, String>>, h: Hop) -> Maybe<&1, Hop>:
1777  redirect.if(status, h, header(headers, "location"), Bool.and(redirect.code(status), has_header(headers, "location")))
1778
1779def io.recv.words(tls: Bool, s: Socket, max: U32, ms: U32) -> IO(Socket & Result<&1, &1, U32 & String, U32 & Array<U32>>):
1780  match tls:
1781    case True{}:
1782      Wire.tls.recv.words(s, max, ms)
1783    case False{}:
1784      Wire.recv.words(s, max, ms)
1785
1786def io.send(tls: Bool, s: Socket, data: String) -> IO(Socket & Result<&1, &1, U32 & String, Unit>):
1787  match tls:
1788    case True{}:
1789      Wire.tls.send(s, data)
1790    case False{}:
1791      Wire.send(s, data)
1792
1793def io.send.words(tls: Bool, s: Socket, +len: U32, buf: Array<U32>) -> IO(Socket & Result<&1, &1, U32 & String, Unit>):
1794  match tls:
1795    case True{}:
1796      Wire.tls.send.words(s, len, buf)
1797    case False{}:
1798      Wire.send.words(s, len, buf)
1799
1800def io.send.bytes(tls: Bool, s: Socket, b: Bytes.Bytes) -> IO(Socket & Result<&1, &1, U32 & String, Unit>):
1801  Bytes.Bytes{+len, buf} = b
1802  io.send.words(tls, s, len, buf)
1803
1804def io.close(tls: Bool, s: Socket) -> IO(Unit):
1805  match tls:
1806    case True{}:
1807      Wire.tls.close(s)
1808    case False{}:
1809      Socket.close(s)
1810
1811def fetch.close(tls: Bool, s: Socket, r: Result<&1, &1, Err, Res>) -> IO(Result<&1, &1, Err, Res>):
1812  do IO<Result<&1, &1, Err, Res>>:
1813    io.close(tls, s)
1814    return r
1815
1816# none: no response byte arrived, so an idempotent request may be retried (RFC 9112 §9.3.1).
1817# sock: the socket, when it can take another request.
1818type Out is Type:
1819  OutDone{res: Res, sock: Maybe<&1, Socket>, rest: Bytes.Bytes}
1820  OutFail{e: Err, none: Bool}
1821
1822def fetch.boxed(r: Result<&1, &1, Err, Res>, none: Bool) -> Out:
1823  match r:
1824    case Done{res}:
1825      OutDone{res, None{}, Bytes.new(0)}
1826    case Fail{e}:
1827      OutFail{e, none}
1828
1829def fetch.bad(tls: Bool, s: Socket, e: Maybe<&2, Err>) -> IO(Result<&1, &1, Err, Res>):
1830  match e:
1831    case None{}:
1832      fetch.close(tls, s, Fail{ErrBad{}})
1833    case Some{err}:
1834      fetch.close(tls, s, Fail{err})
1835
1836def fetch.shut(tls: Bool, s: Socket, r: Result<&1, &1, Err, Res>, none: Bool) -> IO(Out):
1837  do IO<Out>:
1838    x : Result<&1, &1, Err, Res> <- fetch.close(tls, s, r)
1839    return fetch.boxed(x, none)
1840
1841def fetch.hold.go(tls: Bool, s: Socket, res: Res, left: Maybe<&1, Bytes.Bytes>) -> IO(Out):
1842  match left:
1843    case Some{x}:
1844      IO.pure(Out, OutDone{res, Some{s}, x})
1845    case None{}:
1846      fetch.shut(tls, s, Done{res}, False{})
1847
1848def fetch.hold(tls: Bool, close: Bool, s: Socket, res: Res, left: Maybe<&1, Bytes.Bytes>) -> IO(Out):
1849  Res{status, +headers, body} = res
1850  fetch.hold.go(tls, s, Res{status, headers, body}, again(close, headers, left))
1851
1852def fetch.failout(tls: Bool, s: Socket, e: Maybe<&2, Err>, none: Bool) -> IO(Out):
1853  do IO<Out>:
1854    r : Result<&1, &1, Err, Res> <- fetch.bad(tls, s, e)
1855    return fetch.boxed(r, none)
1856
1857# Read state: the response so far and the bytes read, or how it ended.
1858# none: no byte arrived, so an idempotent request may be retried.
1859type Fl is Type:
1860  FlMore{rv: Rv, n: U32}
1861  FlBad{err: Maybe<&2, Err>, none: Bool}
1862  FlDone{res: Res, rest: Maybe<&1, Bytes.Bytes>}
1863
1864def fetch.rt(+n: U32, t: Rt) -> Fl:
1865  match t:
1866    case RtMore{rv}:
1867      FlMore{rv, n}
1868    case RtBad{}:
1869      FlBad{None{}, U32.is_zero(n)}
1870    case RtDone{res, rest}:
1871      FlDone{res, rest}
1872
1873# 64 KiB of head past the body cap, as serve allows.
1874def fetch.over(+n: U32) -> Bool:
1875  Nat.is_lt(Nat.add(fetch.max(), 65536n), U32.to_nat(n))
1876
1877def fetch.piece.cap(over: Bool, +head: Bool, rv: Rv, +n2: U32, +len: U32, buf: Array<U32>) -> Fl:
1878  match over:
1879    case True{}:
1880      FlBad{None{}, False{}}
1881    case False{}:
1882      fetch.rt(n2, rv.step(U32.is_zero(len), head, rv, Bytes.Bytes{len, buf}))
1883
1884def fetch.piece(+head: Bool, rv: Rv, +n: U32, p: U32 & Array<U32>) -> Fl:
1885  (+len, buf) = p
1886  +n2 = (n + len : U32)
1887  fetch.piece.cap(fetch.over(n2), head, rv, n2, len, buf)
1888
1889def fetch.next(+head: Bool, rv: Rv, +n: U32, m: Socket & Result<&1, &1, U32 & String, U32 & Array<U32>>) -> Socket & Fl:
1890  (s, r) = m
1891  match r:
1892    case Fail{(+code, why)}:
1893      (s, FlBad{Some{err.or_late(code, ErrRead{code, why})}, U32.is_zero(n)})
1894    case Done{p}:
1895      (s, fetch.piece(head, rv, n, p))
1896
1897# Reads until the response is whole or cannot be; an empty read means the server closed.
1898@unsafe
1899def fetch.loop(+close: Bool, +head: Bool, +tls: Bool, +ms: U32, st: Socket & Fl) -> IO(Out):
1900  (s, fl) = st
1901  match fl:
1902    case FlMore{rv, +n}:
1903      do IO<Out>:
1904        m : Socket & Result<&1, &1, U32 & String, U32 & Array<U32>> <- io.recv.words(tls, s, 65536, ms)
1905        fetch.loop(close, head, tls, ms, fetch.next(head, rv, n, m))
1906    case FlBad{err, none}:
1907      fetch.failout(tls, s, err, none)
1908    case FlDone{res, rest}:
1909      fetch.hold(tls, close, s, res, rest)
1910
1911def exchange.sent(+tls: Bool, +ms: U32, +close: Bool, +head: Bool, m: Socket & Result<&1, &1, U32 & String, Unit>) -> IO(Out):
1912  (s, r) = m
1913  match r:
1914    case Fail{(+code, why)}:
1915      fetch.shut(tls, s, Fail{err.or_late(code, ErrWrite{code, why})}, True{})
1916    case Done{u}:
1917      fetch.loop(close, head, tls, ms, (s, FlMore{rv.start(), 0}))
1918
1919def exchange.go(+tls: Bool, +ms: U32, +close: Bool, +head: Bool, s: Socket, wire: Bytes.Bytes) -> IO(Out):
1920  do IO<Out>:
1921    sent : Socket & Result<&1, &1, U32 & String, Unit> <- io.send.bytes(tls, s, wire)
1922    exchange.sent(tls, ms, close, head, sent)
1923
1924def exchange.tup(o: Out) -> Maybe<&1, Socket> & Result<&1, &1, Err, Res> & Bytes.Bytes:
1925  match o:
1926    case OutFail{e, none}:
1927      (None{}, Fail{e}, Bytes.new(0))
1928    case OutDone{res, sock, rest}:
1929      (sock, Done{res}, rest)
1930
1931# One request on an open socket. Some{socket}: it can take another request.
1932def exchange(+tls: Bool, +ms: U32, +close: Bool, +head: Bool, s: Socket, wire: Bytes.Bytes) -> IO(Maybe<&1, Socket> & Result<&1, &1, Err, Res> & Bytes.Bytes):
1933  do IO<Maybe<&1, Socket> & Result<&1, &1, Err, Res> & Bytes.Bytes>:
1934    o : Out <- exchange.go(tls, ms, close, head, s, wire)
1935    return exchange.tup(o)
1936
1937# Connection pool: idle sockets by scheme, host, and port, newest first, at most cap per origin.
1938# fetch uses a fresh pool per call.
1939type Conn is Type:
1940  Conn{tls: Bool, s: Socket}
1941
1942type Pool is Type:
1943  Pool{cap: U32, idle: Map<&1, List<&1, Conn>>}
1944
1945def pool.new.with(+cap: U32) -> Pool:
1946  Pool{cap, Map.new(&1, List<&1, Conn>)}
1947
1948# Up to 8 idle sockets per origin.
1949def pool.new() -> Pool:
1950  pool.new.with(8)
1951
1952def pool.key(+scheme: String, +host: String, +port: U32) -> String:
1953  scheme ++ "://" ++ host ++ ":" ++ U32.show(port)
1954
1955def pool.take.of(+cap: U32, +key: String, r: Map<&1, List<&1, Conn>> & Maybe<&1, List<&1, Conn>>) -> Pool & Maybe<&1, Conn>:
1956  (m, got) = r
1957  match got:
1958    case None{}:
1959      (Pool{cap, m}, None{})
1960    case Some{xs}:
1961      match xs:
1962        case Nil{}:
1963          (Pool{cap, m}, None{})
1964        case Con{c, t}:
1965          (Pool{cap, Map.set(&1, List<&1, Conn>, m, key, t)}, Some{c})
1966
1967# The socket given back last.
1968def pool.take(p: Pool, +key: String) -> Pool & Maybe<&1, Conn>:
1969  Pool{+cap, idle} = p
1970  pool.take.of(cap, key, Map.pop(&1, List<&1, Conn>, idle, key))
1971
1972def conn.close(c: Conn) -> IO(Unit):
1973  Conn{tls, s} = c
1974  io.close(tls, s)
1975
1976# The first n sockets; the rest are closed.
1977def conns.cut(xs: List<&1, Conn>, n: Nat) -> IO(List<&1, Conn>):
1978  match xs:
1979    case Nil{}:
1980      IO.pure(List<&1, Conn>, Nil{})
1981    case Con{c, t}:
1982      match n:
1983        case 0n:
1984          do IO<List<&1, Conn>>:
1985            conn.close(c)
1986            conns.cut(t, 0n)
1987        case 1n+k:
1988          do IO<List<&1, Conn>>:
1989            r : List<&1, Conn> <- conns.cut(t, k)
1990            return c <> r
1991
1992def pool.give.of(+cap: U32, +key: String, c: Conn, r: Map<&1, List<&1, Conn>> & Maybe<&1, List<&1, Conn>>) -> IO(Pool):
1993  (m, old) = r
1994  do IO<Pool>:
1995    xs : List<&1, Conn> <- conns.cut(c <> Maybe.default(&1, List<&1, Conn>, old, Nil{}), U32.to_nat(cap))
1996    return Pool{cap, Map.set(&1, List<&1, Conn>, m, key, xs)}
1997
1998# Past cap, the oldest idle socket of the origin is closed.
1999def pool.give(p: Pool, +key: String, c: Conn) -> IO(Pool):
2000  Pool{+cap, idle} = p
2001  pool.give.of(cap, key, c, Map.pop(&1, List<&1, Conn>, idle, key))
2002
2003def pool.close.go(xs: List<&1, List<&1, Conn>>) -> IO(Unit):
2004  match xs:
2005    case Nil{}:
2006      IO.pure(Unit, Unit{})
2007    case Con{cs, t}:
2008      do IO<Unit>:
2009        none : List<&1, Conn> <- conns.cut(cs, 0n)
2010        pool.close.go(t)
2011
2012def pool.close(p: Pool) -> IO(Unit):
2013  Pool{cap, idle} = p
2014  pool.close.go(Map.values(&1, List<&1, Conn>, idle))
2015
2016# RFC 9110 §9.2.2
2017def pool.idempotent(+method: String) -> Bool:
2018  Bool.or(String.eq(method, "GET"), Bool.or(String.eq(method, "HEAD"), Bool.or(String.eq(method, "OPTIONS"), Bool.or(String.eq(method, "TRACE"), Bool.or(String.eq(method, "PUT"), String.eq(method, "DELETE"))))))
2019
2020def conn.tls(m: Socket & Result<&1, &1, U32 & String, Unit>) -> IO(Result<&1, &1, Err, Conn>):
2021  (s, r) = m
2022  match r:
2023    case Fail{(+code, why)}:
2024      do IO<Result<&1, &1, Err, Conn>>:
2025        Wire.tls.close(s)
2026        return Fail{err.or_late(code, ErrTls{code, why})}
2027    case Done{u}:
2028      IO.pure(Result<&1, &1, Err, Conn>, Done{Conn{True{}, s}})
2029
2030# A failed handshake is an error, never plaintext.
2031def conn.secure(+ms: U32, sni: String, s: Socket, tls: Bool) -> IO(Result<&1, &1, Err, Conn>):
2032  match tls:
2033    case False{}:
2034      IO.pure(Result<&1, &1, Err, Conn>, Done{Conn{False{}, s}})
2035    case True{}:
2036      do IO<Result<&1, &1, Err, Conn>>:
2037        hs : Socket & Result<&1, &1, U32 & String, Unit> <- Wire.tls.connect(s, sni, ms)
2038        conn.tls(hs)
2039
2040def conn.made(+ms: U32, sni: String, tls: Bool, r: Result<&1, &1, U32 & String, Socket>) -> IO(Result<&1, &1, Err, Conn>):
2041  match r:
2042    case Fail{(+code, why)}:
2043      IO.pure(Result<&1, &1, Err, Conn>, Fail{err.or_late(code, ErrConnect{code, why})})
2044    case Done{s}:
2045      conn.secure(ms, sni, s, tls)
2046
2047def conn.open(+tls: Bool, +ms: U32, sni: String, ip: String, port: U32) -> IO(Result<&1, &1, Err, Conn>):
2048  do IO<Result<&1, &1, Err, Conn>>:
2049    c : Result<&1, &1, U32 & String, Socket> <- Wire.connect(ip, port, ms)
2050    conn.made(ms, sni, tls, c)
2051
2052def conn.ex(c: Conn, +ms: U32, +head: Bool, wire: Bytes.Bytes) -> IO(Out):
2053  Conn{+tls, s} = c
2054  exchange.go(tls, ms, False{}, head, s, wire)
2055
2056# A socket with bytes past the response is out of step with the server, so it is closed.
2057def pool.keep.s(p: Pool, +key: String, +tls: Bool, res: Res, s: Socket, clean: Bool) -> IO(Pool & Result<&1, &1, Err, Res>):
2058  match clean:
2059    case True{}:
2060      do IO<Pool & Result<&1, &1, Err, Res>>:
2061        p2 : Pool <- pool.give(p, key, Conn{tls, s})
2062        return (p2, Done{res})
2063    case False{}:
2064      do IO<Pool & Result<&1, &1, Err, Res>>:
2065        io.close(tls, s)
2066        return (p, Done{res})
2067
2068def pool.keep.m(p: Pool, +key: String, +tls: Bool, res: Res, +clean: Bool, sock: Maybe<&1, Socket>) -> IO(Pool & Result<&1, &1, Err, Res>):
2069  match sock:
2070    case None{}:
2071      IO.pure(Pool & Result<&1, &1, Err, Res>, (p, Done{res}))
2072    case Some{s}:
2073      pool.keep.s(p, key, tls, res, s, clean)
2074
2075def pool.keep(p: Pool, +key: String, +tls: Bool, res: Res, sock: Maybe<&1, Socket>, rest: Bytes.Bytes) -> IO(Pool & Result<&1, &1, Err, Res>):
2076  Bytes.Bytes{+len, buf} = rest
2077  pool.keep.m(p, key, tls, res, U32.is_zero(len), sock)
2078
2079def pool.after(p: Pool, +key: String, +tls: Bool, o: Out) -> IO(Pool & Result<&1, &1, Err, Res>):
2080  match o:
2081    case OutFail{e, none}:
2082      IO.pure(Pool & Result<&1, &1, Err, Res>, (p, Fail{e}))
2083    case OutDone{res, sock, rest}:
2084      pool.keep(p, key, tls, res, sock, rest)
2085
2086def pool.fresh.conn(p: Pool, +key: String, +tls: Bool, +ms: U32, +head: Bool, wire: Bytes.Bytes, r: Result<&1, &1, Err, Conn>) -> IO(Pool & Result<&1, &1, Err, Res>):
2087  match r:
2088    case Fail{e}:
2089      IO.pure(Pool & Result<&1, &1, Err, Res>, (p, Fail{e}))
2090    case Done{c}:
2091      do IO<Pool & Result<&1, &1, Err, Res>>:
2092        o : Out <- conn.ex(c, ms, head, wire)
2093        pool.after(p, key, tls, o)
2094
2095def pool.fresh.ip(p: Pool, +key: String, +tls: Bool, +ms: U32, +head: Bool, +host: String, +port: U32, wire: Bytes.Bytes, ip: Maybe<&2, String>) -> IO(Pool & Result<&1, &1, Err, Res>):
2096  match ip:
2097    case None{}:
2098      IO.pure(Pool & Result<&1, &1, Err, Res>, (p, Fail{ErrDns{}}))
2099    case Some{addr}:
2100      do IO<Pool & Result<&1, &1, Err, Res>>:
2101        c : Result<&1, &1, Err, Conn> <- conn.open(tls, ms, host, addr, port)
2102        pool.fresh.conn(p, key, tls, ms, head, wire, c)
2103
2104def pool.fresh(p: Pool, +key: String, +tls: Bool, +ms: U32, +head: Bool, +host: String, +port: U32, wire: Bytes.Bytes) -> IO(Pool & Result<&1, &1, Err, Res>):
2105  do IO<Pool & Result<&1, &1, Err, Res>>:
2106    ip : Maybe<&2, String> <- Dns.resolve(host)
2107    pool.fresh.ip(p, key, tls, ms, head, host, port, wire, ip)
2108
2109# A reused socket the server already closed fails before any response byte.
2110def pool.retry(+none: Bool, +idem: Bool) -> Bool:
2111  Bool.and(none, idem)
2112
2113def pool.stale(p: Pool, +key: String, +tls: Bool, +ms: U32, +head: Bool, +host: String, +port: U32, wire: Bytes.Bytes, e: Err, again: Bool) -> IO(Pool & Result<&1, &1, Err, Res>):
2114  match again:
2115    case True{}:
2116      pool.fresh(p, key, tls, ms, head, host, port, wire)
2117    case False{}:
2118      IO.pure(Pool & Result<&1, &1, Err, Res>, (p, Fail{e}))
2119
2120def pool.reused(p: Pool, +key: String, +tls: Bool, +ms: U32, +head: Bool, +idem: Bool, +host: String, +port: U32, wire: Bytes.Bytes, o: Out) -> IO(Pool & Result<&1, &1, Err, Res>):
2121  match o:
2122    case OutFail{e, +none}:
2123      pool.stale(p, key, tls, ms, head, host, port, wire, e, pool.retry(none, idem))
2124    case OutDone{res, sock, rest}:
2125      pool.keep(p, key, tls, res, sock, rest)
2126
2127# A spare copy of the request, for the retry after a stale socket.
2128def pool.idle.reuse(p: Pool, +key: String, +tls: Bool, +ms: U32, +head: Bool, +idem: Bool, +host: String, +port: U32, c: Conn, r: Bytes.Bytes & Bytes.Bytes) -> IO(Pool & Result<&1, &1, Err, Res>):
2129  (wire, spare) = r
2130  do IO<Pool & Result<&1, &1, Err, Res>>:
2131    o : Out <- conn.ex(c, ms, head, wire)
2132    pool.reused(p, key, tls, ms, head, idem, host, port, spare, o)
2133
2134def pool.idle(taken: Pool & Maybe<&1, Conn>, +key: String, +tls: Bool, +ms: U32, +head: Bool, +idem: Bool, +host: String, +port: U32, wire: Bytes.Bytes) -> IO(Pool & Result<&1, &1, Err, Res>):
2135  (p, m) = taken
2136  match m:
2137    case None{}:
2138      pool.fresh(p, key, tls, ms, head, host, port, wire)
2139    case Some{c}:
2140      pool.idle.reuse(p, key, tls, ms, head, idem, host, port, c, Bytes.slice(wire, 0, 4294967295))
2141
2142def pool.origin(p: Pool, +method: String, +ms: U32, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes, +hf: String, a: Url.Abs, known: Bool) -> IO(Pool & Result<&1, &1, Err, Res>):
2143  Url.Abs{+scheme, +host, +port, target} = a
2144  match known:
2145    case False{}:
2146      IO.pure(Pool & Result<&1, &1, Err, Res>, (p, Fail{ErrUrl{}}))
2147    case True{}:
2148      +key = pool.key(scheme, host, port)
2149      pool.idle(pool.take(p, key), key, String.eq(scheme, "https"), ms, String.eq(method, "HEAD"), pool.idempotent(method), host, port, encode_req.on(method, target, hf, headers, body, False{}))
2150
2151def pool.scheme.ok(a: Url.Abs) -> Bool:
2152  Url.Abs{+scheme, host, port, target} = a
2153  Bool.or(String.eq(scheme, "http"), String.eq(scheme, "https"))
2154
2155def pool.one.back(h: Hop, pr: Pool & Result<&1, &1, Err, Res>) -> Pool & Result<&1, &1, Err, Res> & Hop:
2156  (p, r) = pr
2157  (p, r, h)
2158
2159def pool.one.of(p: Pool, +method: String, +url: Url.Abs, +headers: Map<&2, List<&2, String>>, +ms: U32, r: Bytes.Bytes & Bytes.Bytes) -> IO(Pool & Result<&1, &1, Err, Res> & Hop):
2160  (body, wire) = r
2161  do IO<Pool & Result<&1, &1, Err, Res> & Hop>:
2162    pr : Pool & Result<&1, &1, Err, Res> <- pool.origin(p, method, ms, headers, wire, Url.host_field(url), url, pool.scheme.ok(url))
2163    return pool.one.back(Hop{method, url, headers, body}, pr)
2164
2165# One request, on an idle socket to its origin when the pool has one. The hop comes back for the redirect.
2166def pool.one(p: Pool, h: Hop, +ms: U32) -> IO(Pool & Result<&1, &1, Err, Res> & Hop):
2167  Hop{+method, +url, +headers, body} = h
2168  pool.one.of(p, method, url, headers, ms, Bytes.slice(body, 0, 4294967295))
2169
2170type Next is Type:
2171  NDone{res: Result<&1, &1, Err, Res>}
2172  NStop{}
2173  NGo{left: Nat, hop: Hop}
2174
2175type Mode is Data:
2176  ModeFollow{}
2177  ModeManual{}
2178  ModeError{}
2179
2180# left: redirects still allowed after the request we just finished.
2181def fetch.hop(left: Nat, h: Hop) -> Next:
2182  match left:
2183    case 0n:
2184      NStop{}
2185    case 1n+p:
2186      NGo{p, h}
2187
2188def fetch.decide.r(left: Nat, r: Res, next: Maybe<&1, Hop>) -> Next:
2189  match next:
2190    case None{}:
2191      NDone{Done{r}}
2192    case Some{h}:
2193      fetch.hop(left, h)
2194
2195def fetch.decide.res(left: Nat, h: Hop, r: Res) -> Next:
2196  Res{+status, +headers, body} = r
2197  fetch.decide.r(left, Res{status, headers, body}, redirect(status, headers, h))
2198
2199def fetch.decide(left: Nat, h: Hop, m: Result<&1, &1, Err, Res>) -> Next:
2200  match m:
2201    case Fail{e}:
2202      NDone{Fail{e}}
2203    case Done{r}:
2204      fetch.decide.res(left, h, r)
2205
2206def fetch.error.res(r: Res, bad: Bool) -> Next:
2207  match bad:
2208    case True{}:
2209      NDone{Fail{ErrRedirect{}}}
2210    case False{}:
2211      NDone{Done{r}}
2212
2213def fetch.error(h: Hop, m: Result<&1, &1, Err, Res>) -> Next:
2214  match m:
2215    case Fail{e}:
2216      NDone{Fail{e}}
2217    case Done{r}:
2218      Res{+status, +headers, body} = r
2219      fetch.error.res(Res{status, headers, body}, Bool.and(redirect.code(status), has_header(headers, "location")))
2220
2221def fetch.policy(mode: Mode, left: Nat, h: Hop, m: Result<&1, &1, Err, Res>) -> Next:
2222  match mode:
2223    case ModeFollow{}:
2224      fetch.decide(left, h, m)
2225    case ModeManual{}:
2226      NDone{m}
2227    case ModeError{}:
2228      fetch.error(h, m)
2229
2230# A caller's own Accept-Encoding wins; enc is the codings fetch can undo.
2231def accept.enc(+h: Map<&2, List<&2, String>>, +enc: String) -> Map<&2, List<&2, String>>:
2232  Bool.pick(Map<&2, List<&2, String>>, has_header(h, "accept-encoding"), h, set(h, "accept-encoding", enc))
2233
2234def fetch.start(method: String, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes, u: Maybe<&2, Url.Abs>, +enc: String) -> Next:
2235  match u:
2236    case None{}:
2237      NDone{Fail{ErrUrl{}}}
2238    case Some{a}:
2239      NGo{20n, Hop{method, a, accept.enc(req.put(Map.to_list(&2, List<&2, String>, headers), empty()), enc), body}}
2240
2241def pool.next(+mode: Mode, left: Nat, x: Pool & Result<&1, &1, Err, Res> & Hop) -> Pool & Next:
2242  (p, m, h) = x
2243  (p, fetch.policy(mode, left, h, m))
2244
2245# NGo.left is how many redirects may follow this request. 20 is WHATWG's limit.
2246@unsafe
2247def pool.hops(+mode: Mode, +ms: U32, st: Pool & Next) -> IO(Pool & Result<&1, &1, Err, Res>):
2248  (p, n) = st
2249  match n:
2250    case NDone{m}:
2251      IO.pure(Pool & Result<&1, &1, Err, Res>, (p, m))
2252    case NStop{}:
2253      IO.pure(Pool & Result<&1, &1, Err, Res>, (p, Fail{ErrRedirect{}}))
2254    case NGo{+left, h}:
2255      do IO<Pool & Result<&1, &1, Err, Res>>:
2256        x : Pool & Result<&1, &1, Err, Res> & Hop <- pool.one(p, h, ms)
2257        pool.hops(mode, ms, pool.next(mode, left, x))
2258
2259# Content-Encoding (RFC 9110 §8.4): each value, trimmed and lowercased, in the order applied.
2260def ce.keep(+w: String, +rest: List<&2, String>) -> List<&2, String>:
2261  Bool.pick(List<&2, String>, String.is_empty(w), rest, Con{w, rest})
2262
2263def ce.norm(xs: List<&2, String>) -> List<&2, String>:
2264  match xs:
2265    case Nil{}:
2266      Nil{}
2267    case Con{v, t}:
2268      ce.keep(String.to_lower(trim(v)), ce.norm(t))
2269
2270def ce.split(xs: List<&2, String>) -> List<&2, String>:
2271  match xs:
2272    case Nil{}:
2273      Nil{}
2274    case Con{v, t}:
2275      List.append(&2, String, ce.norm(String.split(v, ',')), ce.split(t))
2276
2277# Ok: decoded so far. Bad: a coding failed. Skip: a coding we cannot decode, so the body stays as sent.
2278type Dec is Data:
2279  DecOk{b: String}
2280  DecBad{}
2281  DecSkip{}
2282
2283def ce.of(m: Maybe<&2, String>) -> Dec:
2284  match m:
2285    case None{}:
2286      DecBad{}
2287    case Some{b}:
2288      DecOk{b}
2289
2290# Servers send deflate both with and without the zlib wrapper.
2291def ce.deflate(+b: String, m: Maybe<&2, String>) -> Dec:
2292  match m:
2293    case Some{out}:
2294      DecOk{out}
2295    case None{}:
2296      ce.of(Zlib.inflate(b))
2297
2298def ce.apply(+c: String, +b: String) -> Dec:
2299  Bool.pick(Dec, Bool.or(String.eq(c, "gzip"), String.eq(c, "x-gzip")), ce.of(Zlib.gunzip(b)),
2300    Bool.pick(Dec, String.eq(c, "deflate"), ce.deflate(b, Zlib.unzlib(b)),
2301      Bool.pick(Dec, String.eq(c, "identity"), DecOk{b}, DecSkip{})))
2302
2303def ce.go(cs: List<&2, String>, d: Dec) -> Dec:
2304  match cs:
2305    case Nil{}:
2306      d
2307    case Con{+c, t}:
2308      match d:
2309        case DecOk{+b}:
2310          ce.go(t, ce.apply(c, b))
2311        case DecBad{}:
2312          DecBad{}
2313        case DecSkip{}:
2314          DecSkip{}
2315
2316def decoded.pick(d: Dec, +status: U32, headers: Map<&2, List<&2, String>>, body: String) -> Result<&1, &1, Err, Res>:
2317  match d:
2318    case DecOk{b}:
2319      Done{Res{status, headers, Bytes.from_string(b)}}
2320    case DecBad{}:
2321      Fail{ErrBad{}}
2322    case DecSkip{}:
2323      Done{Res{status, headers, Bytes.from_string(body)}}
2324
2325# ponytail: the codings run on a String copy of the body; give zlib a Bytes input if gzip bodies get big.
2326def decoded.cs(+status: U32, +headers: Map<&2, List<&2, String>>, body: Bytes.Bytes, cs: List<&2, String>) -> Result<&1, &1, Err, Res>:
2327  match cs:
2328    case Nil{}:
2329      Done{Res{status, headers, body}}
2330    case Con{c, t}:
2331      +s = Bytes.to_string(body)
2332      decoded.pick(ce.go(Con{c, t}, DecOk{s}), status, headers, s)
2333
2334def decoded.go(empty: Bool, +status: U32, +headers: Map<&2, List<&2, String>>, body: Bytes.Bytes) -> Result<&1, &1, Err, Res>:
2335  match empty:
2336    case True{}:
2337      Done{Res{status, headers, body}}
2338    case False{}:
2339      decoded.cs(status, headers, body, List.reverse(&2, String, ce.split(fields(headers, "content-encoding"))))
2340
2341# The body decoded per Content-Encoding; the headers stay as sent. A corrupt body is ErrBad.
2342def decoded(res: Res) -> Result<&1, &1, Err, Res>:
2343  Res{+status, +headers, body} = res
2344  Bytes.Bytes{+len, buf} = body
2345  decoded.go(U32.is_zero(len), status, headers, Bytes.Bytes{len, buf})
2346
2347def decoded.m(r: Result<&1, &1, Err, Res>) -> Maybe<&1, Res>:
2348  match r:
2349    case Done{x}:
2350      Some{x}
2351    case Fail{e}:
2352      None{}
2353
2354def decoded.some(res: Res) -> Maybe<&1, Res>:
2355  decoded.m(decoded(res))
2356
2357def ce.words(r: Result<&1, &1, U32 & String, U32 & Array<U32>>) -> Maybe<&1, Bytes.Bytes>:
2358  match r:
2359    case Fail{e}:
2360      None{}
2361    case Done{(+len, buf)}:
2362      Some{Bytes.Bytes{len, buf}}
2363
2364# A decoded body stops at 16 MiB, like a received one.
2365def ce.eff(~eff: U32 -> U32 -> Array<U32> -> IO(Result<&1, &1, U32 & String, U32 & Array<U32>>), b: Bytes.Bytes) -> IO(Maybe<&1, Bytes.Bytes>):
2366  Bytes.Bytes{+len, buf} = b
2367  do IO<Maybe<&1, Bytes.Bytes>>:
2368    r : Result<&1, &1, U32 & String, U32 & Array<U32>> <- eff(16777216, len, buf)
2369    return ce.words(r)
2370
2371def ce.dec(d: Dec) -> Maybe<&1, Bytes.Bytes>:
2372  match d:
2373    case DecOk{b}:
2374      Some{Bytes.from_string(b)}
2375    case DecBad{}:
2376      None{}
2377    case DecSkip{}:
2378      None{}
2379
2380# ponytail: deflate runs on the pure decoder, which also takes raw DEFLATE; servers rarely send it.
2381def ce.io.deflate(on: Bool, b: Bytes.Bytes) -> IO(Maybe<&1, Bytes.Bytes>):
2382  match on:
2383    case True{}:
2384      +s = Bytes.to_string(b)
2385      IO.pure(Maybe<&1, Bytes.Bytes>, ce.dec(ce.deflate(s, Zlib.unzlib(s))))
2386    case False{}:
2387      IO.pure(Maybe<&1, Bytes.Bytes>, Some{b})
2388
2389def ce.io.zstd(on: Bool, +c: String, b: Bytes.Bytes) -> IO(Maybe<&1, Bytes.Bytes>):
2390  match on:
2391    case True{}:
2392      ce.eff(~Zlib.zstd.words, b)
2393    case False{}:
2394      ce.io.deflate(String.eq(c, "deflate"), b)
2395
2396def ce.io.br(on: Bool, +c: String, b: Bytes.Bytes) -> IO(Maybe<&1, Bytes.Bytes>):
2397  match on:
2398    case True{}:
2399      ce.eff(~Zlib.brotli.words, b)
2400    case False{}:
2401      ce.io.zstd(String.eq(c, "zstd"), c, b)
2402
2403# One known coding undone: gzip, x-gzip, br, zstd, deflate, or identity.
2404def ce.io.gz(on: Bool, +c: String, b: Bytes.Bytes) -> IO(Maybe<&1, Bytes.Bytes>):
2405  match on:
2406    case True{}:
2407      ce.eff(~Zlib.inflate.words, b)
2408    case False{}:
2409      ce.io.br(String.eq(c, "br"), c, b)
2410
2411def ce.io.go(cs: List<&2, String>, m: Maybe<&1, Bytes.Bytes>) -> IO(Maybe<&1, Bytes.Bytes>):
2412  match cs:
2413    case Nil{}:
2414      match m:
2415        case None{}:
2416          IO.pure(Maybe<&1, Bytes.Bytes>, None{})
2417        case Some{b}:
2418          IO.pure(Maybe<&1, Bytes.Bytes>, Some{b})
2419    case Con{+c, t}:
2420      match m:
2421        case None{}:
2422          IO.pure(Maybe<&1, Bytes.Bytes>, None{})
2423        case Some{b}:
2424          do IO<Maybe<&1, Bytes.Bytes>>:
2425            n : Maybe<&1, Bytes.Bytes> <- ce.io.gz(Bool.or(String.eq(c, "gzip"), String.eq(c, "x-gzip")), c, b)
2426            ce.io.go(t, n)
2427
2428def ce.has(xs: List<&2, String>, +c: String) -> Bool:
2429  match xs:
2430    case Nil{}:
2431      False{}
2432    case Con{x, t}:
2433      Bool.or(String.eq(c, x), ce.has(t, c))
2434
2435def ce.known(cs: List<&2, String>, +ok: List<&2, String>) -> Bool:
2436  match cs:
2437    case Nil{}:
2438      True{}
2439    case Con{c, t}:
2440      Bool.and(ce.has(ok, c), ce.known(t, ok))
2441
2442def decoded.io.pick(m: Maybe<&1, Bytes.Bytes>, +status: U32, headers: Map<&2, List<&2, String>>) -> Result<&1, &1, Err, Res>:
2443  match m:
2444    case Some{b}:
2445      Done{Res{status, headers, b}}
2446    case None{}:
2447      Fail{ErrBad{}}
2448
2449def decoded.io.run(known: Bool, +status: U32, +headers: Map<&2, List<&2, String>>, body: Bytes.Bytes, cs: List<&2, String>) -> IO(Result<&1, &1, Err, Res>):
2450  match known:
2451    case True{}:
2452      do IO<Result<&1, &1, Err, Res>>:
2453        m : Maybe<&1, Bytes.Bytes> <- ce.io.go(cs, Some{body})
2454        return decoded.io.pick(m, status, headers)
2455    case False{}:
2456      IO.pure(Result<&1, &1, Err, Res>, Done{Res{status, headers, body}})
2457
2458def decoded.io.go(empty: Bool, +enc: String, +status: U32, +headers: Map<&2, List<&2, String>>, body: Bytes.Bytes) -> IO(Result<&1, &1, Err, Res>):
2459  match empty:
2460    case True{}:
2461      IO.pure(Result<&1, &1, Err, Res>, Done{Res{status, headers, body}})
2462    case False{}:
2463      +cs = List.reverse(&2, String, ce.split(fields(headers, "content-encoding")))
2464      decoded.io.run(ce.known(cs, Con{"identity", Con{"x-gzip", ce.split(Con{enc, Nil{}})}}), status, headers, body, cs)
2465
2466# decoded through the C libraries, for the codings in enc. A body with any other coding stays as sent.
2467def decoded.io(+enc: String, res: Res) -> IO(Result<&1, &1, Err, Res>):
2468  Res{+status, +headers, body} = res
2469  Bytes.Bytes{+len, buf} = body
2470  decoded.io.go(U32.is_zero(len), enc, status, headers, Bytes.Bytes{len, buf})
2471
2472# An effect on empty input fails with ENOENT only when its library does not load.
2473def codings.ok(r: Result<&1, &1, U32 & String, U32 & Array<U32>>) -> Bool:
2474  match r:
2475    case Fail{(+c, why)}:
2476      Bool.not(U32.is_eq(c, 2))
2477    case Done{p}:
2478      True{}
2479
2480def codings.has(~eff: U32 -> U32 -> Array<U32> -> IO(Result<&1, &1, U32 & String, U32 & Array<U32>>), b: Bytes.Bytes) -> IO(Bool):
2481  Bytes.Bytes{+len, buf} = b
2482  do IO<Bool>:
2483    r : Result<&1, &1, U32 & String, U32 & Array<U32>> <- eff(0, len, buf)
2484    return codings.ok(r)
2485
2486def codings.add(has: Bool, +enc: String, +c: String) -> String:
2487  Bool.pick(String, has, enc ++ ", " ++ c, enc)
2488
2489# gzip and deflate, then br and zstd when their C library loads.
2490def codings() -> IO(String):
2491  do IO<String>:
2492    b : Bool <- codings.has(~Zlib.brotli.words, Bytes.new(0))
2493    z : Bool <- codings.has(~Zlib.zstd.words, Bytes.new(0))
2494    return codings.add(z, codings.add(b, "gzip, deflate", "br"), "zstd")
2495
2496# The final response of a fetch, after redirects.
2497def fetch.final(+enc: String, r: Result<&1, &1, Err, Res>) -> IO(Result<&1, &1, Err, Res>):
2498  match r:
2499    case Done{res}:
2500      decoded.io(enc, res)
2501    case Fail{e}:
2502      IO.pure(Result<&1, &1, Err, Res>, Fail{e})
2503
2504def pool.final(+enc: String, pr: Pool & Result<&1, &1, Err, Res>) -> IO(Pool & Result<&1, &1, Err, Res>):
2505  (p, r) = pr
2506  do IO<Pool & Result<&1, &1, Err, Res>>:
2507    d : Result<&1, &1, Err, Res> <- fetch.final(enc, r)
2508    return (p, d)
2509
2510def pool.how.enc(+enc: String, p: Pool, method: String, url: String, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes, ms: U32, mode: Mode) -> IO(Pool & Result<&1, &1, Err, Res>):
2511  do IO<Pool & Result<&1, &1, Err, Res>>:
2512    pr : Pool & Result<&1, &1, Err, Res> <- pool.hops(mode, ms, (p, fetch.start(method, headers, body, Url.absolute(url), enc)))
2513    pool.final(enc, pr)
2514
2515# pool.how(p, "GET", "https://example.com/x?y=1", headers, body, ms, mode) follows redirects
2516# on p's idle sockets. Fail is a bad URL, a failed lookup, connect, handshake, send, read,
2517# a malformed response, more than 20 redirects, or a step past ms. Bodies are bytes.
2518def pool.how(p: Pool, method: String, url: String, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes, ms: U32, mode: Mode) -> IO(Pool & Result<&1, &1, Err, Res>):
2519  do IO<Pool & Result<&1, &1, Err, Res>>:
2520    enc : String <- codings()
2521    pool.how.enc(enc, p, method, url, headers, body, ms, mode)
2522
2523def pool.fetch.with(p: Pool, method: String, url: String, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes, ms: U32) -> IO(Pool & Result<&1, &1, Err, Res>):
2524  pool.how(p, method, url, headers, body, ms, ModeFollow{})
2525
2526def pool.fetch(p: Pool, method: String, url: String, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes) -> IO(Pool & Result<&1, &1, Err, Res>):
2527  pool.fetch.with(p, method, url, headers, body, 30000)
2528
2529def fetch.end(pr: Pool & Result<&1, &1, Err, Res>) -> IO(Result<&1, &1, Err, Res>):
2530  (p, r) = pr
2531  do IO<Result<&1, &1, Err, Res>>:
2532    pool.close(p)
2533    return r
2534
2535# fetch is pool.how on a fresh pool that closes afterwards.
2536def fetch.how(method: String, url: String, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes, ms: U32, mode: Mode) -> IO(Result<&1, &1, Err, Res>):
2537  do IO<Result<&1, &1, Err, Res>>:
2538    pr : Pool & Result<&1, &1, Err, Res> <- pool.how(pool.new(), method, url, headers, body, ms, mode)
2539    fetch.end(pr)
2540
2541def fetch.with(method: String, url: String, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes, ms: U32) -> IO(Result<&1, &1, Err, Res>):
2542  fetch.how(method, url, headers, body, ms, ModeFollow{})
2543
2544# fetch.with and a 30 s step timeout.
2545def fetch(method: String, url: String, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes) -> IO(Result<&1, &1, Err, Res>):
2546  fetch.with(method, url, headers, body, 30000)
2547
2548def get(url: String) -> IO(Result<&1, &1, Err, Res>):
2549  fetch("GET", url, empty(), Bytes.new(0))
2550
2551# Streaming (a body read or sent in pieces). Stream bodies are never content-decoded.
2552# What the next read returns: read more, a piece, the end, or an error.
2553type Po is Type:
2554  PoNone{}
2555  PoPiece{b: Bytes.Bytes}
2556  PoEnd{}
2557  PoBad{e: Err}
2558
2559type Stream is Type:
2560  Stream{tls: Bool, s: Socket, ms: U32, res: Res, rb: Rb, out: Po}
2561
2562type Pc is Type:
2563  Pc{rb: Rb, out: Po}
2564
2565# A body piece, or none when empty: more reads the next piece, and not more is the end.
2566def pc.po(more: Bool, empty: Bool, b: Bytes.Bytes) -> Po:
2567  match empty:
2568    case True{}:
2569      Bool.pick(Po, more, PoNone{}, PoEnd{})
2570    case False{}:
2571      PoPiece{b}
2572
2573def pc.piece(more: Bool, +rb: Rb, b: Bytes.Bytes) -> Pc:
2574  Bytes.Bytes{+len, buf} = b
2575  Pc{rb, pc.po(more, U32.is_zero(len), Bytes.Bytes{len, buf})}
2576
2577def pc.fed.of(b: Bytes.Bytes, st: Rb) -> Pc:
2578  match st:
2579    case RbDone{}:
2580      pc.piece(False{}, RbDone{}, b)
2581    case RbBad{}:
2582      Pc{RbDone{}, PoBad{ErrBad{}}}
2583    case RbLen{n}:
2584      pc.piece(True{}, RbLen{n}, b)
2585    case RbChunk{st}:
2586      pc.piece(True{}, RbChunk{st}, b)
2587    case RbClose{}:
2588      pc.piece(True{}, RbClose{}, b)
2589
2590def pc.fed(bf: Bf) -> Pc:
2591  Bf{st, parts, rest} = bf
2592  pc.fed.of(rb.body(parts), st)
2593
2594# The body bytes that just arrived: what they add to the body, and how it ends.
2595def pc.of(rb: Rb, piece: Bytes.Bytes) -> Pc:
2596  pc.fed(rb.feed(rb, Nil{}, piece))
2597
2598# The server closed. Only a close-delimited body may end this way (RFC 9112 §8).
2599def pc.end(ok: Bool) -> Pc:
2600  match ok:
2601    case True{}:
2602      Pc{RbDone{}, PoEnd{}}
2603    case False{}:
2604      Pc{RbDone{}, PoBad{ErrBad{}}}
2605
2606def pc.eof(st: Rb) -> Pc:
2607  pc.end(rb.eof(st))
2608
2609def stream.mk(+tls: Bool, s: Socket, +ms: U32, res: Res, pc: Pc) -> Stream:
2610  Pc{rb, out} = pc
2611  Stream{tls, s, ms, res, rb, out}
2612
2613def stream.got.piece(+tls: Bool, s: Socket, +ms: U32, res: Res, +rb: Rb, p: U32 & Array<U32>) -> Stream:
2614  (+len, buf) = p
2615  stream.mk(tls, s, ms, res, Bool.pick(Pc, U32.is_zero(len), pc.eof(rb), pc.of(rb, Bytes.Bytes{len, buf})))
2616
2617def stream.got(+tls: Bool, +ms: U32, res: Res, +rb: Rb, m: Socket & Result<&1, &1, U32 & String, U32 & Array<U32>>) -> Stream:
2618  (s, r) = m
2619  match r:
2620    case Fail{(+code, why)}:
2621      Stream{tls, s, ms, res, RbDone{}, PoBad{err.or_late(code, ErrRead{code, why})}}
2622    case Done{p}:
2623      stream.got.piece(tls, s, ms, res, rb, p)
2624
2625def stream.after(+rb: Rb) -> Po:
2626  match rb:
2627    case RbDone{}:
2628      PoEnd{}
2629    case RbBad{}:
2630      PoEnd{}
2631    case RbLen{n}:
2632      PoNone{}
2633    case RbChunk{st}:
2634      PoNone{}
2635    case RbClose{}:
2636      PoNone{}
2637
2638# The next piece of the body; None at the end. A piece is never empty.
2639@unsafe
2640def stream.read(st: Stream) -> IO(Stream & Result<&1, &1, Err, Maybe<&1, Bytes.Bytes>>):
2641  Stream{+tls, s, +ms, res, +rb, out} = st
2642  match out:
2643    case PoPiece{b}:
2644      IO.pure(Stream & Result<&1, &1, Err, Maybe<&1, Bytes.Bytes>>, (Stream{tls, s, ms, res, rb, stream.after(rb)}, Done{Some{b}}))
2645    case PoEnd{}:
2646      IO.pure(Stream & Result<&1, &1, Err, Maybe<&1, Bytes.Bytes>>, (Stream{tls, s, ms, res, rb, PoEnd{}}, Done{None{}}))
2647    case PoBad{+e}:
2648      IO.pure(Stream & Result<&1, &1, Err, Maybe<&1, Bytes.Bytes>>, (Stream{tls, s, ms, res, rb, PoBad{e}}, Fail{e}))
2649    case PoNone{}:
2650      do IO<Stream & Result<&1, &1, Err, Maybe<&1, Bytes.Bytes>>>:
2651        m : Socket & Result<&1, &1, U32 & String, U32 & Array<U32>> <- io.recv.words(tls, s, 65536, ms)
2652        stream.read(stream.got(tls, ms, res, rb, m))
2653
2654# Status and headers. Its body is empty: read the body with stream.read.
2655def stream.res(st: Stream) -> Stream & Res:
2656  Stream{tls, s, ms, res, rb, out} = st
2657  Res{+status, +headers, body} = res
2658  (Stream{tls, s, ms, Res{status, headers, body}, rb, out}, Res{status, headers, Bytes.new(0)})
2659
2660def stream.close(st: Stream) -> IO(Unit):
2661  Stream{tls, s, ms, res, rb, out} = st
2662  io.close(tls, s)
2663
2664# Head read state: still scanning, cut short or bad, or the head with the bytes after it.
2665type Sh is Type:
2666  ShMore{buf: Bytes.Bytes, k: U32}
2667  ShBad{err: Maybe<&2, Err>}
2668  ShRes{res: Res, rb: Rb, rest: Bytes.Bytes}
2669
2670def sh.of(hs: Hs) -> Sh:
2671  match hs:
2672    case HsWait{buf, k}:
2673      ShMore{buf, k}
2674    case HsBad{}:
2675      ShBad{None{}}
2676    case HsSeek{buf, from, k}:
2677      ShBad{None{}}
2678    case HsRes{res, rb, rest}:
2679      ShRes{res, rb, rest}
2680
2681def sh.piece(+head: Bool, buf: Bytes.Bytes, +k: U32, p: U32 & Array<U32>) -> Sh:
2682  (+len, b) = p
2683  Bool.pick(Sh, U32.is_zero(len), ShBad{None{}}, sh.of(hs.more(head, k, buf, Bytes.Bytes{len, b})))
2684
2685def sh.next(+head: Bool, buf: Bytes.Bytes, +k: U32, m: Socket & Result<&1, &1, U32 & String, U32 & Array<U32>>) -> Socket & Sh:
2686  (s, r) = m
2687  match r:
2688    case Fail{(+code, why)}:
2689      (s, ShBad{Some{err.or_late(code, ErrRead{code, why})}})
2690    case Done{p}:
2691      (s, sh.piece(head, buf, k, p))
2692
2693def fetch.fail.of(r: Result<&1, &1, Err, Res>) -> Result<&1, &1, Err, Stream>:
2694  match r:
2695    case Fail{e}:
2696      Fail{e}
2697    case Done{res}:
2698      Fail{ErrBad{}}
2699
2700# Reads until the final head is in; the body bytes that came with it are the first piece.
2701@unsafe
2702def stream.head(+tls: Bool, +ms: U32, +head: Bool, st: Socket & Sh) -> IO(Result<&1, &1, Err, Stream>):
2703  (s, sh) = st
2704  match sh:
2705    case ShMore{buf, +k}:
2706      do IO<Result<&1, &1, Err, Stream>>:
2707        m : Socket & Result<&1, &1, U32 & String, U32 & Array<U32>> <- io.recv.words(tls, s, 65536, ms)
2708        stream.head(tls, ms, head, sh.next(head, buf, k, m))
2709    case ShBad{err}:
2710      do IO<Result<&1, &1, Err, Stream>>:
2711        r : Result<&1, &1, Err, Res> <- fetch.bad(tls, s, err)
2712        return fetch.fail.of(r)
2713    case ShRes{res, rb, rest}:
2714      IO.pure(Result<&1, &1, Err, Stream>, Done{stream.mk(tls, s, ms, res, pc.of(rb, rest))})
2715
2716def stream.sent(+tls: Bool, +ms: U32, +head: Bool, m: Socket & Result<&1, &1, U32 & String, Unit>) -> IO(Result<&1, &1, Err, Stream>):
2717  (s, r) = m
2718  match r:
2719    case Fail{(+code, why)}:
2720      do IO<Result<&1, &1, Err, Stream>>:
2721        io.close(tls, s)
2722        return Fail{err.or_late(code, ErrWrite{code, why})}
2723    case Done{u}:
2724      stream.head(tls, ms, head, (s, ShMore{Bytes.new(0), 0}))
2725
2726def stream.conn(r: Result<&1, &1, Err, Conn>, +ms: U32, +head: Bool, wire: Bytes.Bytes) -> IO(Result<&1, &1, Err, Stream>):
2727  match r:
2728    case Fail{e}:
2729      IO.pure(Result<&1, &1, Err, Stream>, Fail{e})
2730    case Done{c}:
2731      Conn{+tls, s} = c
2732      do IO<Result<&1, &1, Err, Stream>>:
2733        sent : Socket & Result<&1, &1, U32 & String, Unit> <- io.send.bytes(tls, s, wire)
2734        stream.sent(tls, ms, head, sent)
2735
2736def stream.ip(+tls: Bool, +ms: U32, +head: Bool, +host: String, +port: U32, wire: Bytes.Bytes, ip: Maybe<&2, String>) -> IO(Result<&1, &1, Err, Stream>):
2737  match ip:
2738    case None{}:
2739      IO.pure(Result<&1, &1, Err, Stream>, Fail{ErrDns{}})
2740    case Some{addr}:
2741      do IO<Result<&1, &1, Err, Stream>>:
2742        c : Result<&1, &1, Err, Conn> <- conn.open(tls, ms, host, addr, port)
2743        stream.conn(c, ms, head, wire)
2744
2745# One connection per stream; the request says close.
2746def stream.origin(+ms: U32, +head: Bool, wire: Bytes.Bytes, a: Url.Abs, known: Bool) -> IO(Result<&1, &1, Err, Stream>):
2747  Url.Abs{+scheme, +host, +port, target} = a
2748  match known:
2749    case False{}:
2750      IO.pure(Result<&1, &1, Err, Stream>, Fail{ErrUrl{}})
2751    case True{}:
2752      do IO<Result<&1, &1, Err, Stream>>:
2753        ip : Maybe<&2, String> <- Dns.resolve(host)
2754        stream.ip(String.eq(scheme, "https"), ms, head, host, port, wire, ip)
2755
2756def stream.one.of(+method: String, +url: Url.Abs, +headers: Map<&2, List<&2, String>>, +ms: U32, r: Bytes.Bytes & Bytes.Bytes) -> IO(Hop & Result<&1, &1, Err, Stream>):
2757  Url.Abs{scheme, host, port, +target} = url
2758  (body, wire) = r
2759  do IO<Hop & Result<&1, &1, Err, Stream>>:
2760    got : Result<&1, &1, Err, Stream> <- stream.origin(ms, String.eq(method, "HEAD"), encode_req.on(method, target, Url.host_field(url), headers, wire, True{}), url, pool.scheme.ok(url))
2761    return (Hop{method, url, headers, body}, got)
2762
2763# One request on its own connection. The hop comes back for the redirect.
2764def stream.one(h: Hop, +ms: U32) -> IO(Hop & Result<&1, &1, Err, Stream>):
2765  Hop{+method, +url, +headers, body} = h
2766  stream.one.of(method, url, headers, ms, Bytes.slice(body, 0, 4294967295))
2767
2768# Go: the next request. Drop: close this stream, then go on. Done: the answer.
2769type Sn is Type:
2770  SnGo{left: Nat, hop: Hop}
2771  SnDrop{st: Stream, next: Next}
2772  SnDone{r: Result<&1, &1, Err, Stream>}
2773
2774def sn.of(n: Next) -> Sn:
2775  match n:
2776    case NGo{l, h}:
2777      SnGo{l, h}
2778    case NStop{}:
2779      SnDone{Fail{ErrRedirect{}}}
2780    case NDone{m}:
2781      match m:
2782        case Fail{e}:
2783          SnDone{Fail{e}}
2784        case Done{r}:
2785          SnDone{Fail{ErrBad{}}}
2786
2787def stream.decide.n(st: Stream, n: Next) -> Sn:
2788  match n:
2789    case NDone{m}:
2790      SnDone{Done{st}}
2791    case NGo{l, h}:
2792      SnDrop{st, NGo{l, h}}
2793    case NStop{}:
2794      SnDrop{st, NStop{}}
2795
2796def stream.decide.of(+left: Nat, hop: Hop, sr: Stream & Res) -> Sn:
2797  (st, res) = sr
2798  stream.decide.n(st, fetch.decide(left, hop, Done{res}))
2799
2800def stream.decide(+left: Nat, x: Hop & Result<&1, &1, Err, Stream>) -> Sn:
2801  (hop, r) = x
2802  match r:
2803    case Fail{e}:
2804      SnDone{Fail{e}}
2805    case Done{st}:
2806      stream.decide.of(left, hop, stream.res(st))
2807
2808@unsafe
2809def stream.hops(+ms: U32, sn: Sn) -> IO(Result<&1, &1, Err, Stream>):
2810  match sn:
2811    case SnDone{r}:
2812      IO.pure(Result<&1, &1, Err, Stream>, r)
2813    case SnGo{+left, hop}:
2814      do IO<Result<&1, &1, Err, Stream>>:
2815        x : Hop & Result<&1, &1, Err, Stream> <- stream.one(hop, ms)
2816        stream.hops(ms, stream.decide(left, x))
2817    case SnDrop{st, next}:
2818      do IO<Result<&1, &1, Err, Stream>>:
2819        stream.close(st)
2820        stream.hops(ms, sn.of(next))
2821
2822def stream.start(method: String, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes, u: Maybe<&2, Url.Abs>) -> Sn:
2823  match u:
2824    case None{}:
2825      SnDone{Fail{ErrUrl{}}}
2826    case Some{a}:
2827      SnGo{20n, Hop{method, a, req.put(Map.to_list(&2, List<&2, String>, headers), empty()), body}}
2828
2829# Http.open(method, url, headers, body) follows redirects like fetch and returns once the head is in.
2830# Read the body with stream.read. Stream bodies are sent and returned as is: no Accept-Encoding, no decoding.
2831def open.with(method: String, url: String, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes, +ms: U32) -> IO(Result<&1, &1, Err, Stream>):
2832  stream.hops(ms, stream.start(method, headers, body, Url.absolute(url)))
2833
2834def open(method: String, url: String, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes) -> IO(Result<&1, &1, Err, Stream>):
2835  open.with(method, url, headers, body, 30000)
2836
2837# Upload: the request body sent in chunks (RFC 9112 §7.1). err: the first failed write.
2838type Up is Type:
2839  Up{tls: Bool, s: Socket, ms: U32, head: Bool, err: Maybe<&2, Err>}
2840
2841def hex.digit(+n: U32) -> Char:
2842  Chr{Bool.pick(U32, U32.is_lt(n, 10), (48 + n : U32), (87 + n : U32))}
2843
2844def hex.go(k: Nat, +n: U32, acc: String) -> String:
2845  match k:
2846    case 0n:
2847      acc
2848    case 1n+p:
2849      hex.go(p, U32.shrn(n, 4n), SCon{hex.digit(U32.and(n, 15)), acc})
2850
2851def hex.trim(+s: String) -> String:
2852  match s:
2853    case SNil{}:
2854      SNil{}
2855    case SCon{Chr{+c}, +t}:
2856      Bool.pick(String, Bool.and(U32.is_eq(c, 48), Bool.not(String.is_empty(t))), hex.trim(t), SCon{Chr{c}, t})
2857
2858def hex(+n: U32) -> String:
2859  hex.trim(hex.go(8n, n, ""))
2860
2861def up.sent(+tls: Bool, +ms: U32, +head: Bool, m: Socket & Result<&1, &1, U32 & String, Unit>) -> Up:
2862  (s, r) = m
2863  match r:
2864    case Fail{(+code, why)}:
2865      Up{tls, s, ms, head, Some{err.or_late(code, ErrWrite{code, why})}}
2866    case Done{u}:
2867      Up{tls, s, ms, head, None{}}
2868
2869def up.conn(r: Result<&1, &1, Err, Conn>, +ms: U32, +head: Bool, wire: String) -> IO(Result<&1, &1, Err, Up>):
2870  match r:
2871    case Fail{e}:
2872      IO.pure(Result<&1, &1, Err, Up>, Fail{e})
2873    case Done{c}:
2874      Conn{+tls, s} = c
2875      do IO<Result<&1, &1, Err, Up>>:
2876        sent : Socket & Result<&1, &1, U32 & String, Unit> <- io.send(tls, s, wire)
2877        return Done{up.sent(tls, ms, head, sent)}
2878
2879def up.ip(+tls: Bool, +ms: U32, +head: Bool, +host: String, +port: U32, wire: String, ip: Maybe<&2, String>) -> IO(Result<&1, &1, Err, Up>):
2880  match ip:
2881    case None{}:
2882      IO.pure(Result<&1, &1, Err, Up>, Fail{ErrDns{}})
2883    case Some{addr}:
2884      do IO<Result<&1, &1, Err, Up>>:
2885        c : Result<&1, &1, Err, Conn> <- conn.open(tls, ms, host, addr, port)
2886        up.conn(c, ms, head, wire)
2887
2888def up.head(+method: String, +target: String, +hf: String, +headers: Map<&2, List<&2, String>>) -> String:
2889  request(method, target, set(set(set(req.put(Map.to_list(&2, List<&2, String>, headers), empty()), "host", hf), "connection", "close"), "transfer-encoding", "chunked"), "")
2890
2891def up.origin(+method: String, +ms: U32, headers: Map<&2, List<&2, String>>, a: Url.Abs, known: Bool) -> IO(Result<&1, &1, Err, Up>):
2892  Url.Abs{+scheme, +host, +port, +target} = a
2893  match known:
2894    case False{}:
2895      IO.pure(Result<&1, &1, Err, Up>, Fail{ErrUrl{}})
2896    case True{}:
2897      do IO<Result<&1, &1, Err, Up>>:
2898        ip : Maybe<&2, String> <- Dns.resolve(host)
2899        up.ip(String.eq(scheme, "https"), ms, String.eq(method, "HEAD"), host, port, up.head(method, target, Url.host_field(a), headers), ip)
2900
2901def up.url(+method: String, +ms: U32, headers: Map<&2, List<&2, String>>, u: Maybe<&2, Url.Abs>) -> IO(Result<&1, &1, Err, Up>):
2902  match u:
2903    case None{}:
2904      IO.pure(Result<&1, &1, Err, Up>, Fail{ErrUrl{}})
2905    case Some{+a}:
2906      up.origin(method, ms, headers, a, pool.scheme.ok(a))
2907
2908# Http.upload(method, url, headers) sends the head. A streamed body cannot be replayed, so redirects are not followed.
2909def upload.with(+method: String, url: String, headers: Map<&2, List<&2, String>>, +ms: U32) -> IO(Result<&1, &1, Err, Up>):
2910  up.url(method, ms, headers, Url.absolute(url))
2911
2912def upload(+method: String, url: String, headers: Map<&2, List<&2, String>>) -> IO(Result<&1, &1, Err, Up>):
2913  upload.with(method, url, headers, 30000)
2914
2915def up.wrote(+tls: Bool, +ms: U32, +head: Bool, m: Socket & Result<&1, &1, U32 & String, Unit>) -> Up & Result<&2, &2, Err, Unit>:
2916  (s, r) = m
2917  match r:
2918    case Fail{(+code, why)}:
2919      +e = err.or_late(code, ErrWrite{code, why})
2920      (Up{tls, s, ms, head, Some{e}}, Fail{e})
2921    case Done{u}:
2922      (Up{tls, s, ms, head, None{}}, Done{Unit{}})
2923
2924# One write per chunk, so the size line and the data do not wait on each other (Nagle).
2925def up.put(+tls: Bool, s: Socket, +ms: U32, +head: Bool, +len: U32, piece: Bytes.Bytes, skip: Bool) -> IO(Up & Result<&2, &2, Err, Unit>):
2926  match skip:
2927    case True{}:
2928      IO.pure(Up & Result<&2, &2, Err, Unit>, (Up{tls, s, ms, head, None{}}, Done{Unit{}}))
2929    case False{}:
2930      do IO<Up & Result<&2, &2, Err, Unit>>:
2931        sent : Socket & Result<&1, &1, U32 & String, Unit> <- io.send.bytes(tls, s, Bytes.concat(Con{Bytes.from_string(hex(len) ++ "\r\n"), Con{piece, Con{Bytes.from_string("\r\n"), Nil{}}}}))
2932        return up.wrote(tls, ms, head, sent)
2933
2934def up.chunk(+tls: Bool, s: Socket, +ms: U32, +head: Bool, piece: Bytes.Bytes) -> IO(Up & Result<&2, &2, Err, Unit>):
2935  Bytes.Bytes{+len, buf} = piece
2936  up.put(tls, s, ms, head, len, Bytes.Bytes{len, buf}, U32.is_zero(len))
2937
2938# One chunk. An empty piece sends nothing, since an empty chunk would end the body.
2939def upload.write(up: Up, piece: Bytes.Bytes) -> IO(Up & Result<&2, &2, Err, Unit>):
2940  Up{+tls, s, +ms, +head, err} = up
2941  match err:
2942    case Some{+e}:
2943      IO.pure(Up & Result<&2, &2, Err, Unit>, (Up{tls, s, ms, head, Some{e}}, Fail{e}))
2944    case None{}:
2945      up.chunk(tls, s, ms, head, piece)
2946
2947# Ends the body and returns the response as a stream.
2948def upload.finish(up: Up) -> IO(Result<&1, &1, Err, Stream>):
2949  Up{+tls, s, +ms, +head, err} = up
2950  match err:
2951    case Some{e}:
2952      do IO<Result<&1, &1, Err, Stream>>:
2953        io.close(tls, s)
2954        return Fail{e}
2955    case None{}:
2956      do IO<Result<&1, &1, Err, Stream>>:
2957        sent : Socket & Result<&1, &1, U32 & String, Unit> <- io.send(tls, s, "0\r\n\r\n")
2958        stream.sent(tls, ms, head, sent)
2959
2960def reply.bytes(res: Res, head: Bool, close: Bool) -> Bytes.Bytes:
2961  Res{+status, +headers, body} = res
2962  encode.on(Res{status, Bool.pick(Map<&2, List<&2, String>>, close, set(headers, "connection", "close"), headers), body}, head)
2963
2964def reply.fail.bytes(+status: U32) -> Res:
2965  Res{status, empty(), Bytes.from_string(reason(status))}
2966
2967def reply.sent.close(m: Socket & Result<&1, &1, U32 & String, Unit>) -> IO(Unit):
2968  (s, r) = m
2969  Socket.close(s)
2970
2971def reply_fail(s: Socket, +status: U32) -> IO(Unit):
2972  do IO<Unit>:
2973    sent : Socket & Result<&1, &1, U32 & String, Unit> <- io.send.bytes(False{}, s, encode(reply.fail.bytes(status)))
2974    reply.sent.close(sent)
2975
2976
2977# The head is parsed once, when it is whole. Body pieces are kept as they come and joined once.
2978type Sv is Type:
2979  SvHead{buf: Bytes.Bytes}
2980  SvLen{req: Req, v11: Bool, left: U32, parts: List<&1, Bytes.Bytes>}
2981  SvChunk{req: Req, v11: Bool, n: U32, st: Dc, parts: List<&1, Bytes.Bytes>}
2982
2983# More: read on, first answering 100 Continue when cont is set.
2984type Turn is Type:
2985  TurnClose{}
2986  TurnFail{status: U32}
2987  TurnReq{req: Req, rest: Bytes.Bytes, v11: Bool}
2988  TurnMore{sv: Sv, cont: Bool}
2989
2990def serve.max() -> Nat:
2991  fetch.max()
2992
2993def sv.none() -> Sv:
2994  SvHead{Bytes.new(0)}
2995
2996def sv.body(req: Req, +v11: Bool, parts: List<&1, Bytes.Bytes>, rest: Bytes.Bytes) -> Turn:
2997  Req{method, path, headers, body} = req
2998  TurnReq{Req{method, path, headers, rb.body(parts)}, rest, v11}
2999
3000def sv.len.cut(req: Req, +v11: Bool, parts: List<&1, Bytes.Bytes>, +len: U32, +left: U32, r: Bytes.Bytes & Bytes.Bytes) -> Turn:
3001  (piece, last) = r
3002  sv.body(req, v11, Con{last, parts}, bytes.snd(Bytes.slice(piece, left, (len - left : U32))))
3003
3004def sv.len.have(short: Bool, req: Req, +v11: Bool, +left: U32, parts: List<&1, Bytes.Bytes>, +len: U32, piece: Bytes.Bytes) -> Turn:
3005  match short:
3006    case True{}:
3007      TurnMore{SvLen{req, v11, (left - len : U32), Con{piece, parts}}, False{}}
3008    case False{}:
3009      sv.len.cut(req, v11, parts, len, left, Bytes.slice(piece, 0, left))
3010
3011def sv.len(req: Req, +v11: Bool, +left: U32, parts: List<&1, Bytes.Bytes>, piece: Bytes.Bytes) -> Turn:
3012  Bytes.Bytes{+len, buf} = piece
3013  sv.len.have(U32.is_lt(len, left), req, v11, left, parts, len, Bytes.Bytes{len, buf})
3014
3015def sv.chunk.of(req: Req, +v11: Bool, +n: U32, c: Ck) -> Turn:
3016  Ck{st, parts, rest} = c
3017  match st:
3018    case DcDone{}:
3019      sv.body(req, v11, parts, rest)
3020    case DcBad{}:
3021      TurnFail{400}
3022    case DcSize{a, b}:
3023      TurnMore{SvChunk{req, v11, n, DcSize{a, b}, parts}, False{}}
3024    case DcExt{x}:
3025      TurnMore{SvChunk{req, v11, n, DcExt{x}, parts}, False{}}
3026    case DcSizeLf{x}:
3027      TurnMore{SvChunk{req, v11, n, DcSizeLf{x}, parts}, False{}}
3028    case DcData{k}:
3029      TurnMore{SvChunk{req, v11, n, DcData{k}, parts}, False{}}
3030    case DcDataCr{}:
3031      TurnMore{SvChunk{req, v11, n, DcDataCr{}, parts}, False{}}
3032    case DcDataLf{}:
3033      TurnMore{SvChunk{req, v11, n, DcDataLf{}, parts}, False{}}
3034    case DcTr{j}:
3035      TurnMore{SvChunk{req, v11, n, DcTr{j}, parts}, False{}}
3036
3037def sv.chunk.cap(big: Bool, req: Req, +v11: Bool, +n: U32, st: Dc, parts: List<&1, Bytes.Bytes>, piece: Bytes.Bytes) -> Turn:
3038  match big:
3039    case True{}:
3040      TurnFail{413}
3041    case False{}:
3042      sv.chunk.of(req, v11, n, ck(piece, st, parts))
3043
3044def sv.chunk(+max: Nat, req: Req, +v11: Bool, +n: U32, st: Dc, parts: List<&1, Bytes.Bytes>, piece: Bytes.Bytes) -> Turn:
3045  Bytes.Bytes{+len, buf} = piece
3046  +n2 = (n + len : U32)
3047  sv.chunk.cap(Bool.or(U32.is_lt(n2, n), Nat.is_lt(max, U32.to_nat(n2))), req, v11, n2, st, parts, Bytes.Bytes{len, buf})
3048
3049# RFC 9110 §10.1.1: answer 100 Continue only when the body is still to come.
3050def sv.cont(want: Bool, t: Turn) -> Turn:
3051  match t:
3052    case TurnMore{sv, c}:
3053      TurnMore{sv, want}
3054    case TurnClose{}:
3055      TurnClose{}
3056    case TurnFail{s}:
3057      TurnFail{s}
3058    case TurnReq{req, rest, v11}:
3059      TurnReq{req, rest, v11}
3060
3061def sv.cl.k(big: Bool, req: Req, +v11: Bool, +k: U32, rest: Bytes.Bytes) -> Turn:
3062  match big:
3063    case True{}:
3064      TurnFail{413}
3065    case False{}:
3066      sv.len(req, v11, k, Nil{}, rest)
3067
3068def sv.cl(+max: Nat, req: Req, +v11: Bool, rest: Bytes.Bytes, n: Maybe<&2, U32>) -> Turn:
3069  match n:
3070    case None{}:
3071      TurnFail{400}
3072    case Some{+k}:
3073      sv.cl.k(Nat.is_lt(max, U32.to_nat(k)), req, v11, k, rest)
3074
3075def sv.frame(+max: Nat, req: Req, +v11: Bool, rest: Bytes.Bytes, te: Bool) -> Turn:
3076  Req{method, path, +headers, body} = req
3077  match te:
3078    case True{}:
3079      sv.chunk(max, Req{method, path, headers, body}, v11, 0, dc.start(), Nil{}, rest)
3080    case False{}:
3081      sv.cl(max, Req{method, path, headers, body}, v11, rest, parse_u32(header(headers, "content-length")))
3082
3083def sv.expects(+v11: Bool, +headers: Map<&2, List<&2, String>>) -> Bool:
3084  Bool.and(v11, String.eq(String.to_lower(header(headers, "expect")), "100-continue"))
3085
3086def sv.got.head(+max: Nat, +v11: Bool, rest: Bytes.Bytes, req: Req) -> Turn:
3087  Req{method, path, +headers, body} = req
3088  sv.cont(sv.expects(v11, headers), sv.frame(max, Req{method, path, headers, body}, v11, rest, has_header(headers, "transfer-encoding")))
3089
3090def sv.parsed(+max: Nat, +v11: Bool, rest: Bytes.Bytes, g: Got) -> Turn:
3091  match g:
3092    case GotBad{}:
3093      TurnFail{400}
3094    case GotMore{}:
3095      TurnFail{400}
3096    case GotReq{req}:
3097      TurnReq{req, rest, v11}
3098    case GotHead{req}:
3099      sv.got.head(max, v11, rest, req)
3100
3101def sv.split(+max: Nat, +hlen: U32, +len: U32, r: Bytes.Bytes & Bytes.Bytes) -> Turn:
3102  (buf, hb) = r
3103  +head = Bytes.to_string(hb)
3104  sv.parsed(max, req.v11(head), bytes.snd(Bytes.slice(buf, hlen, (len - hlen : U32))), parse.got(head))
3105
3106def sv.hit.none(big: Bool, buf: Bytes.Bytes) -> Turn:
3107  match big:
3108    case True{}:
3109      TurnFail{431}
3110    case False{}:
3111      TurnMore{SvHead{buf}, False{}}
3112
3113def sv.hit.some(big: Bool, +max: Nat, +hlen: U32, +len: U32, buf: Bytes.Bytes) -> Turn:
3114  match big:
3115    case True{}:
3116      TurnFail{431}
3117    case False{}:
3118      sv.split(max, hlen, len, Bytes.slice(buf, 0, hlen))
3119
3120# RFC 6585 §5: a head over 64 KiB is refused.
3121def sv.hit(+max: Nat, +len: U32, buf: Bytes.Bytes, at: Maybe<&2, U32>) -> Turn:
3122  match at:
3123    case None{}:
3124      sv.hit.none(U32.is_lt(65536, len), buf)
3125    case Some{+i}:
3126      +hlen = (i + 4 : U32)
3127      sv.hit.some(U32.is_lt(65536, hlen), max, hlen, len, buf)
3128
3129def sv.seek.of(+max: Nat, +len: U32, +from: U32, buf: Bytes.Bytes, r: Bytes.Bytes & Maybe<&2, U32>) -> Turn:
3130  (tail, m) = r
3131  sv.hit(max, len, buf, found.at(from, m))
3132
3133def sv.seek(+max: Nat, +len: U32, +from: U32, r: Bytes.Bytes & Bytes.Bytes) -> Turn:
3134  (buf, tail) = r
3135  sv.seek.of(max, len, from, buf, Bytes.find(tail, "\r\n\r\n"))
3136
3137# Only the new bytes, and the 3 before them, can finish the blank line.
3138def sv.head.at(+max: Nat, +from: U32, buf: Bytes.Bytes) -> Turn:
3139  Bytes.Bytes{+len, b} = buf
3140  sv.seek(max, len, from, Bytes.slice(Bytes.Bytes{len, b}, from, (len - from : U32)))
3141
3142def sv.head(+max: Nat, buf: Bytes.Bytes, piece: Bytes.Bytes) -> Turn:
3143  Bytes.Bytes{+ol, ob} = buf
3144  sv.head.at(max, Bool.pick(U32, U32.is_lt(ol, 3), 0, (ol - 3 : U32)), Bytes.append(Bytes.Bytes{ol, ob}, piece))
3145
3146def sv.closed.pick(empty: Bool) -> Turn:
3147  match empty:
3148    case True{}:
3149      TurnClose{}
3150    case False{}:
3151      TurnFail{400}
3152
3153def sv.closed.head(buf: Bytes.Bytes) -> Turn:
3154  Bytes.Bytes{+len, b} = buf
3155  sv.closed.pick(U32.is_eq(len, 0))
3156
3157# A close mid-request is a request cut short (RFC 9112 §8).
3158def sv.step(closed: Bool, +max: Nat, sv: Sv, piece: Bytes.Bytes) -> Turn:
3159  match closed:
3160    case True{}:
3161      match sv:
3162        case SvHead{buf}:
3163          sv.closed.head(buf)
3164        case SvLen{req, v11, left, parts}:
3165          TurnFail{400}
3166        case SvChunk{req, v11, n, st, parts}:
3167          TurnFail{400}
3168    case False{}:
3169      match sv:
3170        case SvHead{buf}:
3171          sv.head(max, buf, piece)
3172        case SvLen{req, +v11, +left, parts}:
3173          sv.len(req, v11, left, parts, piece)
3174        case SvChunk{req, +v11, +n, st, parts}:
3175          sv.chunk(max, req, v11, n, st, parts, piece)
3176
3177def sv.frame.req(t: Turn) -> Maybe<&1, String & String>:
3178  match t:
3179    case TurnReq{req, rest, v11}:
3180      Req{method, path, headers, body} = req
3181      Some{(Bytes.to_string(body), Bytes.to_string(rest))}
3182    case TurnMore{sv, c}:
3183      None{}
3184    case TurnFail{s}:
3185      None{}
3186    case TurnClose{}:
3187      None{}
3188
3189def sv.frame.go(xs: List<&2, String>, t: Turn) -> Maybe<&1, String & String>:
3190  match xs:
3191    case Nil{}:
3192      sv.frame.req(t)
3193    case Con{+x, rest}:
3194      match t:
3195        case TurnMore{sv, c}:
3196          sv.frame.go(rest, sv.step(False{}, serve.max(), sv, Bytes.from_string(x)))
3197        case TurnReq{req, r, v11}:
3198          sv.frame.req(TurnReq{req, r, v11})
3199        case TurnFail{s}:
3200          None{}
3201        case TurnClose{}:
3202          None{}
3203
3204# The body and the bytes after it, once the pieces make a whole request; None otherwise.
3205def serve.frame(xs: List<&2, String>) -> Maybe<&1, String & String>:
3206  sv.frame.go(xs, TurnMore{sv.none(), False{}})
3207
3208def talk.piece(+max: Nat, sv: Sv, p: U32 & Array<U32>) -> Turn:
3209  (+len, buf) = p
3210  sv.step(U32.is_eq(len, 0), max, sv, Bytes.Bytes{len, buf})
3211
3212def talk.next(+max: Nat, sv: Sv, m: Socket & Result<&1, &1, U32 & String, U32 & Array<U32>>) -> Socket & Turn:
3213  (s, r) = m
3214  match r:
3215    case Fail{e}:
3216      (s, TurnClose{})
3217    case Done{p}:
3218      (s, talk.piece(max, sv, p))
3219
3220def talk.after.pick(empty: Bool, +max: Nat, rest: Bytes.Bytes) -> Turn:
3221  match empty:
3222    case True{}:
3223      TurnMore{sv.none(), False{}}
3224    case False{}:
3225      sv.step(False{}, max, sv.none(), rest)
3226
3227def talk.after.rest(+max: Nat, rest: Bytes.Bytes, s: Socket) -> Socket & Turn:
3228  Bytes.Bytes{+len, buf} = rest
3229  (s, talk.after.pick(U32.is_eq(len, 0), max, Bytes.Bytes{len, buf}))
3230
3231def talk.after.keep(keep: Bool, +max: Nat, rest: Bytes.Bytes, s: Socket) -> Socket & Turn:
3232  match keep:
3233    case False{}:
3234      (s, TurnClose{})
3235    case True{}:
3236      talk.after.rest(max, rest, s)
3237
3238def talk.after(+max: Nat, keep: Bool, rest: Bytes.Bytes, m: Socket & Result<&1, &1, U32 & String, Unit>) -> Socket & Turn:
3239  (s, r) = m
3240  match r:
3241    case Fail{e}:
3242      (s, TurnClose{})
3243    case Done{u}:
3244      talk.after.keep(keep, max, rest, s)
3245
3246def talk.send(+max: Nat, s: Socket, rest: Bytes.Bytes, +headers: Map<&2, List<&2, String>>, v11: Bool, +head: Bool, res: Res) -> IO(Socket & Turn):
3247  Res{+status, +rh, body} = res
3248  +keep = serve.keep(headers, v11, status, rh)
3249  do IO<Socket & Turn>:
3250    sent : Socket & Result<&1, &1, U32 & String, Unit> <- io.send.bytes(False{}, s, reply.bytes(Res{status, rh, body}, head, Bool.not(keep)))
3251    return talk.after(max, keep, rest, sent)
3252
3253def talk.cont.sent(m: Socket & Result<&1, &1, U32 & String, Unit>) -> Socket:
3254  (s, r) = m
3255  s
3256
3257def talk.cont(cont: Bool, s: Socket) -> IO(Socket):
3258  match cont:
3259    case False{}:
3260      IO.pure(Socket, s)
3261    case True{}:
3262      do IO<Socket>:
3263        sent : Socket & Result<&1, &1, U32 & String, Unit> <- Wire.send(s, "HTTP/1.1 100 Continue\r\n\r\n")
3264        return talk.cont.sent(sent)
3265
3266@unsafe
3267def talk(~h: Req -> IO(Res), +max: Nat, st: Socket & Turn) -> IO(Unit):
3268  (s, t) = st
3269  match t:
3270    case TurnMore{sv, cont}:
3271      do IO<Unit>:
3272        s2 : Socket <- talk.cont(cont, s)
3273        m : Socket & Result<&1, &1, U32 & String, U32 & Array<U32>> <- Wire.recv.words(s2, 65536, 30000)
3274        talk(~h, max, talk.next(max, sv, m))
3275    case TurnReq{req, rest, v11}:
3276      Req{+method, path, +headers, body} = req
3277      do IO<Unit>:
3278        res : Res <- h(Req{method, path, headers, body})
3279        next : Socket & Turn <- talk.send(max, s, rest, headers, v11, String.eq(method, "HEAD"), res)
3280        talk(~h, max, next)
3281    case TurnFail{status}:
3282      reply_fail(s, status)
3283    case TurnClose{}:
3284      Socket.close(s)
3285
3286def conn(~h: Req -> IO(Res), +max: Nat, m: Listener & Result<&1, &1, U32 & String, Socket>) -> IO(Listener):
3287  (l, r) = m
3288  do IO<Listener>:
3289    s : Socket <- IO.pass(Socket, r)
3290    IO.spawn(Unit, talk(~h, max, (s, TurnMore{sv.none(), False{}})))
3291    return l
3292
3293@unsafe
3294def loop(~h: Req -> IO(Res), +max: Nat, l: Listener) -> IO(Unit):
3295  do IO<Unit>:
3296    m  : Listener & Result<&1, &1, U32 & String, Socket> <- TCP.accept(l)
3297    l2 : Listener <- conn(~h, max, m)
3298    loop(~h, max, l2)
3299
3300def serve.with(~h: Req -> IO(Res), +port: U32, +max: Nat) -> IO(Unit):
3301  do IO<Unit>:
3302    l : Listener <- IO.try(Listener, TCP.listen(port))
3303    IO.print("http://127.0.0.1:" ++ U32.show(port))
3304    loop(~h, max, l)
3305
3306def serve(~h: Req -> IO(Res), +port: U32) -> IO(Unit):
3307  serve.with(~h, port, serve.max())