1	import Base
2	import ./lex.bend as Lex
3	
4	def hexd(+n: U32) -> Char:
5	  Chr{Lex.sel(U32.is_lt(n, 10), (n + 48 : U32), (n + 87 : U32))}
6	
7	# \uXXXX, lowercase hex as Python writes it.
8	def uesc(+n: U32) -> String:
9	  "\\u" ++ SCon{hexd(((n >> 12n) .&. 15 : U32)), SCon{hexd(((n >> 8n) .&. 15 : U32)), SCon{hexd(((n >> 4n) .&. 15 : U32)), SCon{hexd((n .&. 15 : U32)), SNil{}}}}}
10	
11	def uesc.pair(+c: U32) -> String:
12	  uesc((55296 + ((c - 65536) >> 10n) : U32)) ++ uesc((56320 + ((c - 65536) .&. 1023) : U32))
13	
14	def esc.high(ascii: Bool, +c: U32) -> String:
15	  match ascii:
16	    case False{}:
17	      SCon{Chr{c}, SNil{}}
18	    case True{}:
19	      Lex.sel.s(U32.is_lt(c, 65536), uesc(c), uesc.pair(c))
20	
21	def esc.rest(ascii: Bool, +c: U32) -> String:
22	  Lex.sel.s(U32.is_lt(c, 32), uesc(c),
23	  Lex.sel.s(U32.is_lt(c, 127), SCon{Chr{c}, SNil{}}, esc.high(ascii, c)))
24	
25	# One char as Python's encoder writes it inside quotes. ensure_ascii escapes
26	# everything above `~` (U+007F included); otherwise only controls.
27	def esc.char(+ascii: Bool, +c: U32) -> String:
28	  Lex.sel.s(U32.is_eq(c, 34), "\\\"",
29	  Lex.sel.s(U32.is_eq(c, 92), "\\\\",
30	  Lex.sel.s(U32.is_eq(c, 10), "\\n",
31	  Lex.sel.s(U32.is_eq(c, 13), "\\r",
32	  Lex.sel.s(U32.is_eq(c, 9), "\\t",
33	  Lex.sel.s(U32.is_eq(c, 8), "\\b",
34	  Lex.sel.s(U32.is_eq(c, 12), "\\f",
35	  Lex.sel.s(U32.is_eq(c, 127), Lex.sel.s(ascii, uesc(127), SCon{Chr{127}, SNil{}}), esc.rest(ascii, c)))))))))
36	
37	def quote.body(s: String, +ascii: Bool) -> String:
38	  match s:
39	    case SNil{}:
40	      SNil{}
41	    case SCon{Chr{c}, t}:
42	      esc.char(ascii, c) ++ quote.body(t, ascii)
43	
44	# `"text"` with escapes.
45	def quote(s: String, ascii: Bool) -> String:
46	  "\"" ++ quote.body(s, ascii) ++ "\""
47	
48	# style 0: compact `,` `:`; 1: Python's default `, ` `: `; 2: indent=2.
49	def indent(d: Nat) -> String:
50	  String.repeat("  ", d)
51	
52	def nl(style: U32, d: Nat) -> String:
53	  Lex.sel.s(U32.is_eq(style, 2), "\n" ++ indent(d), "")
54	
55	def sep(+style: U32, d: Nat) -> String:
56	  Lex.sel.s(U32.is_eq(style, 0), ",", Lex.sel.s(U32.is_eq(style, 1), ", ", ",\n" ++ indent(d)))
57	
58	def colon(+style: U32) -> String:
59	  Lex.sel.s(U32.is_eq(style, 0), ":", ": ")
60	
61	# Separator between a chain cell and the next: nothing at the end.