1	# THIS MODULE IS PROJECT-AGNOSTIC. KEEP IT THAT WAY.
2	# A started program that we talk to in lines, over pipes: send lines, then read lines until one
3	# starts with a given text. It knows no protocol.
4	import Base
5	import bend-stdio-pipes@0.1.0.0/impl.bend as Stdio
6	
7	# A running program: its process id, the File that writes its stdin, the File that reads its stdout,
8	# and the most bytes in one of its lines, with its line end.
9	type PipeSession is Type:
10	  PipeSession{pid: U32, input: File, out: File, line_cap: U32}
11	
12	# A line of the program, as PipeSession.ask sorts it.
13	type Heard is Type:
14	  Line{text: String}
15	  Last{text: String}
16	  Ended{}
17	  Failed{error: U32 & String}
18	
19	def PipeSession.pid(session: PipeSession) -> PipeSession & U32:
20	  match session:
21	    case PipeSession{+pid, input, out, line_cap}:
22	      (PipeSession{pid, input, out, line_cap}, pid)
23	
24	def PipeSession.started(
25	  opened: Result<&1, &1, U32 & String, U32 & (File & File)>,
26	  line_cap: U32
27	) -> Result<&1, &1, U32 & String, PipeSession>:
28	  match opened:
29	    case Fail{error}:
30	      Fail{error}
31	    case Done{(pid, (input, out))}:
32	      Done{PipeSession{pid, input, out, line_cap}}
33	
34	# Starts program with args. A longer line of it fails with E2BIG (7).
35	def PipeSession.start(
36	  program: String,
37	  args: List<String>,
38	  line_cap: U32
39	) -> IO(Result<&1, &1, U32 & String, PipeSession>):
40	  do IO<Result<&1, &1, U32 & String, PipeSession>>:
41	    opened: Result<&1, &1, U32 & String, U32 & (File & File)> <- Stdio.open(program, args)
42	    return PipeSession.started(opened, line_cap)
43	
44	# The code of the error that PipeSession.ask gives when the program ended before its answer:
45	# EPIPE.
46	def PipeSession.ended() -> U32:
47	  32
48	
49	def Heard.read(
50	  read: File & Result<&1, &1, U32 & String, Maybe<String>>,
51	  +until: String
52	) -> File
53	  & Heard:
54	  match read:
55	    case (out, Fail{error}):
56	      (out, Failed{error})
57	    case (out, Done{None{}}):
58	      (out, Ended{})
59	    case (out, Done{Some{line}}):
60	      +text = String.trim_end(line)
61	      (out, Bool.pick(Heard, String.starts_with(text, until), Last{text}, Line{text}))
62	
63	# said holds the lines so far, the last first; fuel bounds the lines, far beyond any answer.
64	def PipeSession.ask.go(
65	  fuel: Nat,
66	  at: File & Heard,
67	  +until: String,
68	  +line_cap: U32,
69	  said: List<&2, String>
70	) -> IO(File & Result<&1, &1, U32 & String, List<&2, String>>):
71	  match fuel:
72	    case 0n:
73	      match at:
74	        case (out, _):
75	          IO.pure(
76	            File & Result<&1, &1, U32 & String, List<&2, String>>,
77	            (out, Fail{(5, "the program said too many lines before " ++ until)})
78	          )
79	    case 1n+rest:
80	      match at:
81	        case (out, Failed{error}):
82	          IO.pure(File & Result<&1, &1, U32 & String, List<&2, String>>, (out, Fail{error}))
83	        case (out, Ended{}):
84	          IO.pure(
85	            File & Result<&1, &1, U32 & String, List<&2, String>>,
86	            (out, Fail{(PipeSession.ended(), "the program ended before it said " ++ until)})
87	          )
88	        case (out, Last{text}):
89	          IO.pure(
90	            File & Result<&1, &1, U32 & String, List<&2, String>>,
91	            (out, Done{List.reverse(&2, String, text <> said)})
92	          )
93	        case (out, Line{text}):
94	          do IO<File & Result<&1, &1, U32 & String, List<&2, String>>>:
95	            read: File
96	              & Result<&1, &1, U32 & String, Maybe<String>> <- Stdio.read_line(out, line_cap)
97	            PipeSession.ask.go(rest, Heard.read(read, until), until, line_cap, text <> said)
98	
99	def PipeSession.asked(
100	  pid: U32,
101	  input: File,
102	  line_cap: U32,
103	  answer: File & Result<&1, &1, U32 & String, List<&2, String>>
104	) -> IO(PipeSession & Result<&1, &1, U32 & String, List<&2, String>>):
105	  match answer:
106	    case (out, result):
107	      IO.pure(
108	        PipeSession & Result<&1, &1, U32 & String, List<&2, String>>,
109	        (PipeSession{pid, input, out, line_cap}, result)
110	      )
111	
112	def PipeSession.wrote(
113	  pid: U32,
114	  wrote: File & Result<&1, &1, U32 & String, Unit>,
115	  out: File,
116	  +line_cap: U32,
117	  +until: String
118	) -> IO(PipeSession & Result<&1, &1, U32 & String, List<&2, String>>):
119	  match wrote:
120	    case (input, Fail{error}):
121	      IO.pure(
122	        PipeSession & Result<&1, &1, U32 & String, List<&2, String>>,
123	        (PipeSession{pid, input, out, line_cap}, Fail{error})
124	      )
125	    case (input, Done{_}):
126	      do IO<PipeSession & Result<&1, &1, U32 & String, List<&2, String>>>:
127	        read: File & Result<&1, &1, U32 & String, Maybe<String>> <- Stdio.read_line(out, line_cap)
128	        answer: File & Result<&1, &1, U32 & String, List<&2, String>> <-
129	          PipeSession.ask.go(4294967295n, Heard.read(read, until), until, line_cap, [])
130	        PipeSession.asked(pid, input, line_cap, answer)
131	
132	# Sends lines, then answers the program's lines up to the first that starts with until.
133	def PipeSession.ask(
134	  session: PipeSession,
135	  lines: List<String>,
136	  +until: String
137	) -> IO(PipeSession & Result<&1, &1, U32 & String, List<&2, String>>):
138	  match session:
139	    case PipeSession{pid, input, out, line_cap}:
140	      do IO<PipeSession & Result<&1, &1, U32 & String, List<&2, String>>>:
141	        wrote: File & Result<&1, &1, U32 & String, Unit> <- Stdio.write_lines(input, lines)
142	        PipeSession.wrote(pid, wrote, out, line_cap, until)
143	
144	def PipeSession.end.go(
145	  fuel: Nat,
146	  read: File & Result<&1, &1, U32 & String, Maybe<String>>,
147	  +line_cap: U32,
148	  said: List<&2, String>
149	) -> IO(Result<&1, &1, U32 & String, List<&2, String>>):
150	  match fuel read:
151	    case 0n Tuple{out, _}:
152	      do IO<Result<&1, &1, U32 & String, List<&2, String>>>:
153	        File.close(out)
154	        return Fail{(5, "the program said too many lines after its input ended")}
155	    case 1n+rest Tuple{out, Fail{error}}:
156	      do IO<Result<&1, &1, U32 & String, List<&2, String>>>:
157	        File.close(out)
158	        return Fail{error}
159	    case 1n+rest Tuple{out, Done{None{}}}:
160	      do IO<Result<&1, &1, U32 & String, List<&2, String>>>:
161	        File.close(out)
162	        return Done{List.reverse(&2, String, said)}
163	    case 1n+rest Tuple{out, Done{Some{line}}}:
164	      do IO<Result<&1, &1, U32 & String, List<&2, String>>>:
165	        next: File & Result<&1, &1, U32 & String, Maybe<String>> <- Stdio.read_line(out, line_cap)
166	        PipeSession.end.go(rest, next, line_cap, String.trim_end(line) <> said)
167	
168	# Closes the program's stdin, then answers what it said until it ended.
169	def PipeSession.end(session: PipeSession) -> IO(Result<&1, &1, U32 & String, List<&2, String>>):
170	  match session:
171	    case PipeSession{_, input, out, +line_cap}:
172	      do IO<Result<&1, &1, U32 & String, List<&2, String>>>:
173	        File.close(input)
174	        read: File & Result<&1, &1, U32 & String, Maybe<String>> <- Stdio.read_line(out, line_cap)
175	        PipeSession.end.go(4294967295n, read, line_cap, [])