Facilitate http code response on authentication failure (#134)

json_rpc/servers/websocketserver.nim

@@ -10,18 +10,51 @@ logScope:
   topics = "JSONRPC-WS-SERVER"
 
 type
+  RpcWebSocketServerAuth* = ##\
+    ## Authenticator function. On error, the resulting `HttpCode` is sent back\
+    ## to the client and the `string` argument will be used in an exception,\
+    ## following.
+    proc(req: HttpTable): Result[void,(HttpCode,string)]
+      {.gcsafe, raises: [Defect].}
+
   RpcWebSocketServer* = ref object of RpcServer
-    authHook: seq[Hook]
+    authHook: Option[RpcWebSocketServerAuth] ## Authorization call back handler
     server: StreamServer
     wsserver: WSServer
 
+  HookEx = ref object of Hook
+    handler: RpcWebSocketServerAuth ## from `RpcWebSocketServer`
+    request: HttpRequest            ## current request needed for error response
+
+proc authWithHtCodeResponse(ctx: Hook, headers: HttpTable):
+            Future[Result[void, string]] {.async, gcsafe, raises: [Defect].} =
+  ## Wrapper around authorization handler which is stored in the
+  ## extended `Hook` object.
+  let
+    cty = ctx.HookEx
+    rc = cty.handler(headers)
+  if rc.isErr:
+    await cty.request.stream.writer.sendError(rc.error[0])
+    return err(rc.error[1])
+  return ok()
+
 proc handleRequest(rpc: RpcWebSocketServer, request: HttpRequest) {.async.} =
   trace "Handling request:", uri = request.uri.path
   trace "Initiating web socket connection."
 
+  # Authorization handler constructor (if enabled)
+  var hooks: seq[Hook]
+  if rpc.authHook.isSome:
+    let hookEx = HookEx(
+      append: nil,
+      request: request,
+      handler: rpc.authHook.get,
+      verify: authWithHtCodeResponse)
+    hooks = @[hookEx.Hook]
+
   try:
     let server = rpc.wsserver
-    let ws = await server.handleRequest(request, hooks = rpc.authHook)
+    let ws = await server.handleRequest(request, hooks = hooks)
     if ws.readyState != ReadyState.Open:
       error "Failed to open websocket connection"
       return
@@ -60,8 +93,8 @@ proc handleRequest(rpc: RpcWebSocketServer, request: HttpRequest) {.async.} =
   except WebSocketError as exc:
     error "WebSocket error:", exception = exc.msg
 
-proc initWebsocket(rpc: RpcWebSocketServer,
-                   compression: bool, authHandler: seq[Hook]) =
+proc initWebsocket(rpc: RpcWebSocketServer, compression: bool,
+                   authHandler: Option[RpcWebSocketServerAuth]) =
   if compression:
     let deflateFactory = deflateFactory()
     rpc.wsserver = WSServer.new(factories = [deflateFactory])
@@ -73,7 +106,7 @@ proc newRpcWebSocketServer*(
   address: TransportAddress,
   compression: bool = false,
   flags: set[ServerFlags] = {ServerFlags.TcpNoDelay,ServerFlags.ReuseAddr},
-  authHandler: seq[Hook] = @[]): RpcWebSocketServer =
+  authHandler = none(RpcWebSocketServerAuth)): RpcWebSocketServer =
 
   var server = new(RpcWebSocketServer)
   proc processCallback(request: HttpRequest): Future[void] =
@@ -93,7 +126,7 @@ proc newRpcWebSocketServer*(
   port: Port,
   compression: bool = false,
   flags: set[ServerFlags] = {ServerFlags.TcpNoDelay, ServerFlags.ReuseAddr},
-  authHandler: seq[Hook] = @[]): RpcWebSocketServer =
+  authHandler = none(RpcWebSocketServerAuth)): RpcWebSocketServer =
 
   newRpcWebSocketServer(
     initTAddress(host, port),
@@ -112,7 +145,7 @@ proc newRpcWebSocketServer*(
   tlsFlags: set[TLSFlags] = {},
   tlsMinVersion = TLSVersion.TLS12,
   tlsMaxVersion = TLSVersion.TLS12,
-  authHandler: seq[Hook] = @[]): RpcWebSocketServer =
+  authHandler = none(RpcWebSocketServerAuth)): RpcWebSocketServer =
 
   var server = new(RpcWebSocketServer)
   proc processCallback(request: HttpRequest): Future[void] =
@@ -143,7 +176,7 @@ proc newRpcWebSocketServer*(
   tlsFlags: set[TLSFlags] = {},
   tlsMinVersion = TLSVersion.TLS12,
   tlsMaxVersion = TLSVersion.TLS12,
-  authHandler: seq[Hook] = @[]): RpcWebSocketServer =
+  authHandler = none(RpcWebSocketServerAuth)): RpcWebSocketServer =
 
   newRpcWebSocketServer(
     initTAddress(host, port),