1	# rule space: trailing whitespace, a tab, or a line over 120 characters. The
2	# width counts a string literal as two characters: a long message or a test
3	# fixture does not make a line hard to read, code does. A comment counts at
4	# its full width. Expectation trailers (`#|` lines) are data and exempt from
5	# the width only: trailing whitespace on a `#|` line is still reported. A tab
6	# is reported wherever it sits, inside a string literal included. A line
7	# with both trailing whitespace and a tab is reported once, for the
8	# whitespace.
9	import Base
10	import ../../src.bend as Src
11	import ../../finding.bend as F
12	import ../../syntax/lex.bend as Lex
13	import ../../lazy/lazy.bend as Lazy
14	
15	# is there a tab among the chars?
16	def has_tab(cs: List<&2, Char>) -> Bool:
17	  match cs:
18	    case Nil{}:
19	      False{}
20	    case Con{c, t}:
21	      Lazy.or_else(Char.is_eq(c, '\t'), _u => has_tab(t))
22	
23	# does the line end in whitespace?
24	def trailing(cs: List<&2, Char>) -> Bool:
25	  match cs:
26	    case Nil{}:
27	      False{}
28	    case Con{c, Nil{}}:
29	      Char.is_space(c)
30	    case Con{c, t}:
31	      trailing(t)
32	
33	# a token's share of its line's width; a `#|` trailer line counts nothing
34	def width_of(kk: Lex.TokKind, +tt: String) -> U32:
35	  match kk:
36	    case Lex.TStr{}:
37	      2
38	    case Lex.TNewline{}:
39	      0
40	    case Lex.TComment{}:
41	      Bool.pick(U32, String.starts_with(tt, "#|"), 0, U32.from_nat(String.length(tt)))
42	    case other:
43	      U32.from_nat(String.length(tt))
44	
45	# a finding when the width is over 120
46	def too_wide(+width: U32, +path: String, +nn: U32, +more: List<&2, F.Finding>) -> List<&2, F.Finding>:
47	  Bool.pick(List<&2, F.Finding>, U32.is_gt(width, 120),
48	    F.Finding{path, nn, 120, 0, "space", "Line is longer than 120 characters."} <> more, more)
49	
50	# one pass over the tokens: a newline closes a line's width
51	def widths(toks: List<&2, Lex.Tok>, +path: String, +nn: U32, +acc: U32) -> List<&2, F.Finding>:
52	  match toks:
53	    case Nil{}:
54	      too_wide(acc, path, nn, [])
55	    case Con{Lex.Tok{Lex.TNewline{}, t, l, c}, rest}:
56	      too_wide(acc, path, nn, widths(rest, path, (nn + 1 : U32), 0))
57	    case Con{Lex.Tok{k, t, l, c}, rest}:
58	      +w = width_of(k, t)
59	      widths(rest, path, nn, (acc + w : U32))
60	
61	def check.line(+path: String, +nn: U32, +cs: List<&2, Char>, +more: List<&2, F.Finding>) -> List<&2, F.Finding>:
62	  +len = U32.from_nat(List.length(&2, Char, cs))
63	  Bool.pick(List<&2, F.Finding>, trailing(cs),
64	    F.Finding{path, nn, (len - 1 : U32), 1, "space", "Line has trailing whitespace."} <> more,
65	    Bool.pick(List<&2, F.Finding>, has_tab(cs),
66	      F.Finding{path, nn, 0, 1, "space", "Line contains a tab; indent with spaces."} <> more, more))
67	
68	def check.go(lines: List<&2, String>, +path: String, +nn: U32) -> List<&2, F.Finding>:
69	  match lines:
70	    case Nil{}:
71	      Nil{}
72	    case Con{line, rest}:
73	      check.line(path, nn, String.to_list(line), check.go(rest, path, (nn + 1 : U32)))
74	
75	# the rule
76	def check(ss: Src.Src) -> List<&2, F.Finding>:
77	  Src.Src{+path, text, toks, tree, bound, items} = ss
78	  List.append(&2, F.Finding, check.go(String.lines(text), path, 0), widths(toks, path, 0, 0))