1	# ezhttp/src/step: what the server decides for one connection, kept pure so
2	# a law can state it. server.bend runs the effects and asks this module what
3	# each outcome means; it decides nothing itself.
4	import Base
5	import ./http.bend as Http
6	import ./qs.bend as Qs
7	
8	# what a request asks of the server: answer it now, or call the handler
9	type Step is Data:
10	  Answer{reply: Http.Reply}
11	  Call{req: Http.Request}
12	
13	# an effect's outcome on one connection: the value, or the line to log for
14	# a connection that is lost
15	type Got<-A: Type> is Type:
16	  Kept{value: A}
17	  Lost{line: String}
18	
19	# a request received as octets, as text: its method, target, header names
20	# and values and body each decoded as UTF-8 (SPEC.md HTTP-SRV-2); a bad one
21	# keeps its reason
22	def step.text(req: Http.Request) -> Http.Request:
23	  match req:
24	    case Http.Bad{why}:
25	      Http.Bad{why}
26	    case Http.Request{method, target, headers, body}:
27	      Http.Request{Qs.octets.text(method), Qs.octets.text(target),
28	        Qs.octets.headers(headers), Qs.octets.text(body)}
29	
30	# a bad request is answered 400 with its reason and never reaches the
31	# handler; a good one goes to the handler as it was parsed
32	def step.of(req: Http.Request) -> Step:
33	  match req:
34	    case Http.Bad{why}:
35	      Answer{Http.Reply{400, [], why}}
36	    case Http.Request{method, target, headers, body}:
37	      Call{Http.Request{method, target, headers, body}}
38	
39	# the line logged for a failed effect: `ezhttp: <phase>: <why>`
40	def step.line(phase: String, why: String) -> String:
41	  "ezhttp: " ++ phase ++ ": " ++ why
42	
43	# a failed accept or recv loses the connection instead of ending the server
44	def step.got(
45	  -A: Type,
46	  phase: String,
47	  res: Result<&1, &1, U32 & String, A>
48	) -> Got<A>:
49	  match res:
50	    case Fail{(code, why)}:
51	      Lost{step.line(phase, why)}
52	    case Done{value}:
53	      Kept{value}
54	
55	# a failed send loses the connection too; the bytes it did not send are dropped
56	def step.sent(res: Result<&1, &1, (U32 & String) & List<&2, U32>, Unit>)
57	  -> Got<Unit>:
58	  match res:
59	    case Fail{((code, why), left)}:
60	      Lost{step.line("write", why)}
61	    case Done{value}:
62	      Kept{value}