From ff6f7553e62dc67e04b0ace49c6c93ce31b3c2f1 Mon Sep 17 00:00:00 2001
From: Emery Hemingway <ehmry@posteo.net>
Date: Wed, 8 Jun 2022 20:25:45 -0500
Subject: [PATCH] Initial http_protocol utility

---
 .gitignore                        |  1 +
 README.md                         |  7 +++
 http_protocol.prs                 | 20 +++++++
 http_translator.config-example.pr | 21 ++++++++
 src/Tupfile                       |  2 +
 src/http_protocol.nim             | 40 ++++++++++++++
 src/http_translator.nim           | 89 +++++++++++++++++++++++++++++++
 syndicate_utils.nimble            | 13 +++++
 8 files changed, 193 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 README.md
 create mode 100644 http_protocol.prs
 create mode 100644 http_translator.config-example.pr
 create mode 100644 src/Tupfile
 create mode 100644 src/http_protocol.nim
 create mode 100644 src/http_translator.nim
 create mode 100644 syndicate_utils.nimble

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..b26d611
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+http_translator
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..aabc460
--- /dev/null
+++ b/README.md
@@ -0,0 +1,7 @@
+# Syndicate utils
+
+## http_translator
+
+Dispatches HTTP requests to registered handlers.
+
+See [http_translator.config-example.pr](./http_translator.config-example.pr) for an example configuration.
diff --git a/http_protocol.prs b/http_protocol.prs
new file mode 100644
index 0000000..af2e8cf
--- /dev/null
+++ b/http_protocol.prs
@@ -0,0 +1,20 @@
+version 1 .
+
+Method = =GET / =HEAD / =POST / =PUT / =DELETE / =CONNECT / =OPTIONS / =TRACE / =PATCH .
+Methods = #{Method} .
+
+; A URL path split into elements
+Path = [string ...] .
+
+; Register an entity that will handle requests at path prefix.
+; TODO: assert the public base URL of the handler to the entity.
+Handler = <handler @methods Methods @path Path @entity #!any> .
+
+Headers = {string: [string ...] ...:...} .
+
+; A request awaiting a response at handle.
+; TODO: query parameters
+Request = <http @handle int @method Method @headers Headers @path Path @body string> .
+
+; A response to handle.
+Response = <http @handle int @code int @headers Headers @body string> .
diff --git a/http_translator.config-example.pr b/http_translator.config-example.pr
new file mode 100644
index 0000000..09dc41d
--- /dev/null
+++ b/http_translator.config-example.pr
@@ -0,0 +1,21 @@
+<require-service <daemon http_translator>>
+
+<daemon http_translator {
+  argv: "/home/repo/syndicate/syndicate_utils/src/http_translator"
+  protocol: text/syndicate
+}>
+
+let ?other = dataspace
+
+$other [
+  ? <http ?handle GET ?headers ?path ?body> [
+    <http $handle 200 {} "get handler invoked">
+  ]
+]
+
+? <service-object <daemon http_translator> ?cap> [
+  $cap [
+    ; publish GET requests with prefix "/foo/bar" to other dataspace
+    <handler #{GET} ["foo" "bar" ] $other>
+  ]
+]
diff --git a/src/Tupfile b/src/Tupfile
new file mode 100644
index 0000000..e5ee95f
--- /dev/null
+++ b/src/Tupfile
@@ -0,0 +1,2 @@
+include_rules
+: foreach ../*.prs |> !preserves_schema_nim |> %B.nim
diff --git a/src/http_protocol.nim b/src/http_protocol.nim
new file mode 100644
index 0000000..2f9117b
--- /dev/null
+++ b/src/http_protocol.nim
@@ -0,0 +1,40 @@
+
+import
+  std/typetraits, preserves, std/tables, std/sets
+
+type
+  Path* = seq[string]
+  Headers* = TableRef[string, seq[string]]
+  Response* {.preservesRecord: "http".} = object
+    `handle`*: int
+    `code`*: int
+    `headers`*: Headers
+    `body`*: string
+
+  Handler*[E] {.preservesRecord: "handler".} = ref object
+    `methods`*: Methods
+    `path`*: Path
+    `entity`*: Preserve[E]
+
+  `Method`* {.preservesOr, pure.} = enum
+    `GET`, `HEAD`, `POST`, `PUT`, `DELETE`, `CONNECT`, `OPTIONS`, `TRACE`,
+    `PATCH`
+  Request* {.preservesRecord: "http".} = object
+    `handle`*: int
+    `method`*: Method
+    `headers`*: Headers
+    `path`*: Path
+    `body`*: string
+
+  Methods* = HashSet[Method]
+proc `$`*[E](x: Handler[E]): string =
+  `$`(toPreserve(x, E))
+
+proc encode*[E](x: Handler[E]): seq[byte] =
+  encode(toPreserve(x, E))
+
+proc `$`*(x: Path | Headers | Response | Request | Methods): string =
+  `$`(toPreserve(x))
+
+proc encode*(x: Path | Headers | Response | Request | Methods): seq[byte] =
+  encode(toPreserve(x))
diff --git a/src/http_translator.nim b/src/http_translator.nim
new file mode 100644
index 0000000..c6b19cc
--- /dev/null
+++ b/src/http_translator.nim
@@ -0,0 +1,89 @@
+# SPDX-FileCopyrightText: ☭ 2022 Emery Hemingway
+# SPDX-License-Identifier: Unlicense
+
+import std/[asyncdispatch, asynchttpserver, sets, strutils, tables, uri]
+import preserves
+import syndicate, syndicate/actors
+
+import ./http_protocol.nim
+
+func toHttpCore(methods: Methods): set[HttpMethod] =
+  # Convert the schema type to the type in the httpcore module.
+  for m in methods:
+    result.incl(
+      case m
+      of Method.GET: HttpGET
+      of Method.HEAD: HttpHEAD
+      of Method.POST: HttpPOST
+      of Method.PUT: HttpPUT
+      of Method.DELETE: HttpDELETE
+      of Method.CONNECT: HttpCONNECT
+      of Method.OPTIONS: HttpOPTIONS
+      of Method.TRACE: HttpTRACE
+      of Method.PATCH: HttpPATCH)
+
+proc splitPath(u: Uri): Path =
+  u.path.strip(chars = {'/'}).split("/")
+
+proc hitch(a, b: Future[void]) =
+  a.addCallback do (f: Future[void]):
+    if f.failed: fail(b, f.error)
+    else: complete(b)
+
+bootDataspace("main") do (ds: Ref; turn: var Turn):
+  connectStdio(ds, turn)
+  var
+    handlers: Table[seq[string], (Ref, set[HttpMethod])]
+    pathPrefixMaxLen = 0
+    requestIdSource = 0
+
+  during(turn, ds, ?Handler[Ref]) do (methods: Methods; path: seq[string]; entity: Ref):
+    handlers[path] = (entity, methods.toHttpCore)
+    pathPrefixMaxLen = max(pathPrefixMaxLen, path.len)
+  do:
+    handlers.del(path)
+    pathPrefixMaxLen = 0
+    for path in handlers.keys:
+      pathPrefixMaxLen = max(pathPrefixMaxLen, path.len)
+
+  var parentFacet = turn.facet
+  proc handleRequest(req: asynchttpserver.Request): Future[void] =
+    # TODO: use pattern matching
+    var
+      entity: Ref
+      methods: set[HttpMethod]
+      path = req.url.splitPath()
+    block:
+      var prefix = path[0..min(pathPrefixMaxLen.succ, path.high)]
+      while entity.isNil:
+        (entity, methods) = handlers.getOrDefault(prefix)
+        if prefix.len == 0: break
+        else: discard prefix.pop()
+    if entity.isNil:
+      result = req.respond(Http503, "no handler registered for this path")
+    else:
+      var parentFut = newFuture[void]("handleRequest")
+      result = parentFut
+      if req.reqMethod notin methods:
+        result = req.respond(Http405, "method not valid for this handler")
+      else:
+        run(parentFacet) do (turn: var Turn):
+          inc requestIdSource
+          let
+            rId = requestIdSource
+          let rHandle = publish(turn, entity, http_protocol.Request(
+            handle: rId,
+            `method`: Method.GET,
+            headers: req.headers.table,
+            path: path,
+            body: req.body))
+
+          onPublish(turn, entity, Response ? { 0: ?rId, 1: ?int, 3: ?string }) do (code: HttpCode, body: string):
+            req.respond(code, body).addCallback do (fut: Future[void]):
+              run(parentFacet) do (turn: var Turn): retract(turn, rHandle)
+              hitch(fut, parentFut)
+
+  var http = newAsyncHttpServer()
+  asyncCheck serve(http, Port 8888, handleRequest)
+
+runForever()
diff --git a/syndicate_utils.nimble b/syndicate_utils.nimble
new file mode 100644
index 0000000..30e79ce
--- /dev/null
+++ b/syndicate_utils.nimble
@@ -0,0 +1,13 @@
+# Package
+
+version       = "0.1.0"
+author        = "Emery Hemingway"
+description   = "Utilites for Syndicated Actors and Synit"
+license       = "unlicense"
+srcDir        = "src"
+bin           = @["http_translator"]
+
+
+# Dependencies
+
+requires "nim >= 1.6.6", "syndicate >= 0.3.1"