1	# Final application response safety; transport alone owns framing and suppression.
2	import Base
3	
4	def token.extra(c: U32) -> Bool:
5	  match c:
6	    case 33: True{}
7	    case 35: True{}
8	    case 36: True{}
9	    case 37: True{}
10	    case 38: True{}
11	    case 39: True{}
12	    case 42: True{}
13	    case 43: True{}
14	    case 45: True{}
15	    case 46: True{}
16	    case 94: True{}
17	    case 95: True{}
18	    case 96: True{}
19	    case 124: True{}
20	    case 126: True{}
21	    case _: False{}
22	
23	def token(char: Char) -> Bool:
24	  Chr{+c} = char
25	  (U32.is_ge(c, 97) && U32.is_le(c, 122)) || (U32.is_ge(c, 48) && U32.is_le(c, 57)) || token.extra(c)
26	
27	def name.tail(s: String) -> Bool:
28	  match s:
29	    case SNil{}:
30	      True{}
31	    case SCon{c, rest}:
32	      token(c) && name.tail(rest)
33	
34	def name(s: String) -> Bool:
35	  match s:
36	    case SNil{}:
37	      False{}
38	    case SCon{c, rest}:
39	      token(c) && name.tail(rest)
40	
41	def value(s: String) -> Bool:
42	  match s:
43	    case SNil{}:
44	      True{}
45	    case SCon{Chr{+c}, rest}:
46	      (U32.is_eq(c, 9) || (U32.is_ge(c, 32) && U32.is_le(c, 255) && U32.is_ne(c, 127))) && value(rest)
47	
48	def values(xs: List<&2, String>) -> Bool:
49	  match xs:
50	    case Nil{}:
51	      True{}
52	    case item <> rest:
53	      value(item) && values(rest)
54	
55	def connection(xs: List<&2, String>) -> Bool:
56	  match xs:
57	    case Nil{}:
58	      True{}
59	    case item <> rest:
60	      String.eq(item, "close") && connection(rest)
61	
62	def kind(key: String, items: List<&2, String>) -> Bool:
63	  match key:
64	    case "content-length": False{}
65	    case "transfer-encoding": False{}
66	    case "keep-alive": False{}
67	    case "upgrade": False{}
68	    case "te": False{}
69	    case "trailer": False{}
70	    case "proxy-connection": False{}
71	    case "connection": connection(items)
72	    case _: True{}
73	
74	def headers(h: Map<&2, List<&2, String>>) -> Bool:
75	  match h:
76	    case MTip{}:
77	      True{}
78	    case MLeaf{+key, +items}:
79	      name(key) && kind(key, items) && values(items)
80	    case MNode{position, lo, hi}:
81	      headers(lo) && headers(hi)
82	
83	def valid(+status: U32, h: Map<&2, List<&2, String>>) -> Bool:
84	  U32.is_ge(status, 200) && U32.is_le(status, 599) && headers(h)