1	# walk/disk: an effect (CPU event loop only): the names directly in a
2	# directory, whether a path is a directory, and the working directory
3	# relative paths are named from. A name that is itself a directory ends in
4	# "/"; "." and ".." are never in the list, and a directory that cannot be
5	# opened lists as empty. Order is the file system's; the lint planner
6	# (src/lint/plan.bend) sorts what it keeps.
7	#
8	# It is the real file system, through a foreign effect (dir.c, dir.js) that
9	# lists one directory: its names, one a line, a directory's name ending in
10	# "/"; one (cwd.c, cwd.js) that names the working directory; and Base's
11	# File, which tells a directory from a file.
12	import Base
13	
14	# every name directly in the directory, one a line
15	def walkdir.entries(dir: String) -> IO(String):
16	  import "./dir.c"
17	  import "./dir.js"
18	
19	# the named lines: the text ends in a newline, so the last line is empty
20	def named(ls: List<&2, String>) -> List<&2, String>:
21	  match ls:
22	    case Nil{}:
23	      Nil{}
24	    case Con{+l, t}:
25	      +more = named(t)
26	      Bool.pick(List<&2, String>, String.is_empty(l), more, l <> more)
27	
28	# a directory's entries, a directory marked by a `/`
29	def entries(dir: String) -> IO(List<&2, String>):  # noqa: L001 disk effect
30	  do IO<List<&2, String>>:
31	    text : String <- walkdir.entries(dir)
32	    return named(String.lines(text))
33	
34	# whether a first read failed as a directory's does (EISDIR, 21, in C and
35	# in node alike)
36	def is_dir.code(rr: Result<&1, &1, U32 & String, List<&2, U32>>) -> Bool:
37	  match rr:
38	    case Fail{e}:
39	      (code, _msg) = e
40	      U32.is_eq(code, 21)
41	    case Done{_bytes}:
42	      False{}
43	
44	# the file closed, and what its first read said
45	def is_dir.got(got: File & Result<&1, &1, U32 & String, List<&2, U32>>) -> IO(Bool):
46	  (file, rr) = got
47	  do IO<Bool>:
48	    File.close(file)
49	    return is_dir.code(rr)
50	
51	# a path that opened: read one byte and see; one that did not is no directory
52	def is_dir.opened(rr: Result<&1, &1, U32 & String, File>) -> IO(Bool):
53	  match rr:
54	    case Fail{_e}:
55	      IO.pure(Bool, False{})
56	    case Done{file}:
57	      do IO<Bool>:
58	        got : File & Result<&1, &1, U32 & String, List<&2, U32>> <- File.read_bytes(file, 1)
59	        is_dir.got(got)
60	
61	# whether a path is a directory: it opens, and reading it fails as a
62	# directory's read does. Base's File has no stat, and a directory opens for
63	# reading on both lanes.
64	def is_dir(path: String) -> IO(Bool):  # noqa: L001 disk effect
65	  do IO<Bool>:
66	    r : Result<&1, &1, U32 & String, File> <- File.open(path, "r")
67	    is_dir.opened(r)
68	
69	# the working directory, from the root; "" when it cannot be named
70	def walkdir.cwd() -> IO(String):
71	  import "./cwd.c"
72	  import "./cwd.js"
73	
74	# the working directory, from the root ("" when it cannot be named)
75	def cwd() -> IO(String):  # noqa: L001 disk effect
76	  walkdir.cwd()