1	import Base
2	import ./ByteManifest.bend as Manifest
3	import ./Fs.bend as Fs
4	import bend-kit-bytes@0.3.2.0/bytes.bend as Bytes
5	
6	# Separates invalid manifest bytes from filesystem failures while opening it.
7	type Error is Data:
8	  Invalid{error: Manifest.Error}
9	  Host{code: U32, message: String}
10	
11	def path.reverse(path: String, reversed: String) -> String:
12	  match path:
13	    case SNil{}: reversed
14	    case SCon{character, rest}: path.reverse(rest, SCon{character, reversed})
15	
16	def path.clone(path: String) -> String:
17	  path.reverse(path.reverse(path, SNil{}), SNil{})
18	
19	def read.result(
20	  result: Result<&1, &1, Manifest.Error, Manifest.ManifestValue>
21	) -> IO(Result<&1, &1, Error, Manifest.ManifestValue>):
22	  match result:
23	    case Fail{error}:
24	      IO.pure(Result<&1, &1, Error, Manifest.ManifestValue>, Fail{Invalid{error}})
25	    case Done{value}:
26	      IO.pure(Result<&1, &1, Error, Manifest.ManifestValue>, Done{value})
27	
28	def read.host(error: U32 & String) -> IO(Result<&1, &1, Error, Manifest.ManifestValue>):
29	  match error:
30	    case (code, message):
31	      IO.pure(Result<&1, &1, Error, Manifest.ManifestValue>, Fail{Host{code, message}})
32	
33	def read.decoded(
34	  pair: File & Result<&1, &1, U32 & String, Bytes.Bytes>
35	) -> IO(Result<&1, &1, Error, Manifest.ManifestValue>):
36	  match pair:
37	    case (file, Fail{error}):
38	      do IO<Result<&1, &1, Error, Manifest.ManifestValue>>:
39	        _closed : Unit <- File.close(file)
40	        read.host(error)
41	    case (file, Done{bytes}):
42	      do IO<Result<&1, &1, Error, Manifest.ManifestValue>>:
43	        _closed : Unit <- File.close(file)
44	        read.result(Manifest.decode(bytes))
45	
46	def read.sized(file: File, size: Nat) -> IO(Result<&1, &1, Error, Manifest.ManifestValue>):
47	  match size:
48	    case 56n:
49	      do IO<Result<&1, &1, Error, Manifest.ManifestValue>>:
50	        pair : File & Result<&1, &1, U32 & String, Bytes.Bytes> <- Fs.read_at(file, 0, 56)
51	        read.decoded(pair)
52	    case 63n:
53	      do IO<Result<&1, &1, Error, Manifest.ManifestValue>>:
54	        pair : File & Result<&1, &1, U32 & String, Bytes.Bytes> <- Fs.read_at(file, 0, 63)
55	        read.decoded(pair)
56	    case 60n:
57	      do IO<Result<&1, &1, Error, Manifest.ManifestValue>>:
58	        pair : File & Result<&1, &1, U32 & String, Bytes.Bytes> <- Fs.read_at(file, 0, 60)
59	        read.decoded(pair)
60	    case _:
61	      do IO<Result<&1, &1, Error, Manifest.ManifestValue>>:
62	        _closed : Unit <- File.close(file)
63	        read.result(Fail{Manifest.Malformed{}})
64	
65	def read.size.result(
66	  file: File,
67	  result: Result<&1, &1, U32 & String, Nat>
68	) -> IO(Result<&1, &1, Error, Manifest.ManifestValue>):
69	  match result:
70	    case Done{size}: read.sized(file, size)
71	    case Fail{error}:
72	      do IO<Result<&1, &1, Error, Manifest.ManifestValue>>:
73	        _closed : Unit <- File.close(file)
74	        read.host(error)
75	
76	def read.path.opened(
77	  path: String,
78	  opened: Result<&1, &1, U32 & String, File>
79	) -> IO(Result<&1, &1, Error, Manifest.ManifestValue>):
80	  match opened:
81	    case Fail{error}:
82	      read.host(error)
83	    case Done{file}:
84	      do IO<Result<&1, &1, Error, Manifest.ManifestValue>>:
85	        size : Result<&1, &1, U32 & String, Nat> <- Fs.file_size(path)
86	        read.size.result(file, size)
87	
88	# Reads and validates one bounded generation-four or generation-five manifest.
89	def read(
90	  +path: String
91	) -> IO(Result<&1, &1, Error, Manifest.ManifestValue>):
92	  do IO<Result<&1, &1, Error, Manifest.ManifestValue>>:
93	    opened : Result<&1, &1, U32 & String, File> <- File.open(path, "r")
94	    read.path.opened(path, opened)
95	
96	def write.directory.synced(
97	  directory: String,
98	  result: Result<&1, &1, U32 & String, Unit>
99	) -> IO(Result<&1, &1, U32 & String, Unit>):
100	  match result:
101	    case Fail{error}: IO.pure(Result<&1, &1, U32 & String, Unit>, Fail{error})
102	    case Done{Unit{}}: Fs.fsync(directory)
103	
104	def write.renamed(
105	  +directory: String,
106	  result: Result<&1, &1, U32 & String, Unit>
107	) -> IO(Result<&1, &1, U32 & String, Unit>):
108	  match result:
109	    case Fail{error}: IO.pure(Result<&1, &1, U32 & String, Unit>, Fail{error})
110	    case Done{Unit{}}:
111	      do IO<Result<&1, &1, U32 & String, Unit>>:
112	        renamed : Result<&1, &1, U32 & String, Unit> <- Fs.rename(directory ++ "/MANIFEST.tmp", directory ++ "/MANIFEST")
113	        write.directory.synced(directory, renamed)
114	
115	def write.closed(
116	  +directory: String,
117	  result: Result<&1, &1, U32 & String, Unit>
118	) -> IO(Result<&1, &1, U32 & String, Unit>):
119	  match result:
120	    case Fail{error}: IO.pure(Result<&1, &1, U32 & String, Unit>, Fail{error})
121	    case Done{Unit{}}:
122	      do IO<Result<&1, &1, U32 & String, Unit>>:
123	        synced : Result<&1, &1, U32 & String, Unit> <- Fs.fsync(directory ++ "/MANIFEST.tmp")
124	        write.renamed(directory, synced)
125	
126	def write.file.synced(
127	  directory: String,
128	  result: File & Result<&1, &1, U32 & String, Unit>
129	) -> IO(Result<&1, &1, U32 & String, Unit>):
130	  match result:
131	    case (file, result):
132	      do IO<Result<&1, &1, U32 & String, Unit>>:
133	        _closed : Unit <- File.close(file)
134	        write.closed(directory, result)
135	
136	def write.bytes(
137	  directory: String,
138	  bytes: Bytes.Bytes,
139	  opened: Result<&1, &1, U32 & String, File>
140	) -> IO(Result<&1, &1, U32 & String, Unit>):
141	  match opened:
142	    case Fail{error}: IO.pure(Result<&1, &1, U32 & String, Unit>, Fail{error})
143	    case Done{file}:
144	      do IO<Result<&1, &1, U32 & String, Unit>>:
145	        result : File & Result<&1, &1, U32 & String, Unit> <- Fs.write_bytes(file, bytes)
146	        write.file.synced(directory, result)
147	
148	# Publishes a manifest through a synced temporary and atomic rename.
149	def write_atomic(
150	  +directory: String,
151	  value: Manifest.ManifestValue
152	) -> IO(Result<&1, &1, U32 & String, Unit>):
153	  do IO<Result<&1, &1, U32 & String, Unit>>:
154	    opened : Result<&1, &1, U32 & String, File> <- File.open(directory ++ "/MANIFEST.tmp", "w")
155	    write.bytes(directory, Manifest.encode(value), opened)