implement json rpc websocket server

- both ws and wss mode

fixes #76

json_rpc/rpcserver.nim

@@ -1,3 +1,3 @@
 import server
-import servers/[socketserver, httpserver]
-export server, socketserver, httpserver
+import servers/[socketserver, httpserver, websocketserver]
+export server, socketserver, httpserver, websocketserver

json_rpc/servers/websocketserver.nim

@@ -0,0 +1,150 @@
+import
+  chronicles, httputils, chronos, ws/ws,
+  ".."/[errors, server]
+
+export server
+
+logScope:
+  topics = "JSONRPC-WS-SERVER"
+
+type
+  RpcWebSocketServer* = ref object of RpcServer
+    server: StreamServer
+    wsserver: WSServer
+
+proc handleRequest(rpc: RpcWebSocketServer, request: HttpRequest) {.async.} =
+  trace "Handling request:", uri = request.uri.path
+  trace "Initiating web socket connection."
+  try:
+    let server = rpc.wsserver
+    let ws = await server.handleRequest(request)
+    if ws.readyState != Open:
+      error "Failed to open websocket connection"
+      return
+
+    trace "Websocket handshake completed"
+    while ws.readyState != ReadyState.Closed:
+      let recvData = await ws.recv()
+      trace "Client message: ", size = recvData.len, binary = ws.binary
+
+      if ws.readyState == ReadyState.Closed:
+        # if session already terminated by peer,
+        # no need to send response
+        break
+
+      if recvData.len == 0:
+        await ws.close(
+          reason = "cannot process zero length message"
+        )
+        break
+
+      let future = rpc.route(cast[string](recvData))
+      yield future
+      if future.failed:
+        debug "Internal error, while processing RPC call",
+              address = $request.uri
+        await ws.close(
+          reason = "Internal error, while processing RPC call"
+        )
+        break
+
+      var data = future.read()
+      trace "RPC result has been sent", address = $request.uri
+
+      await ws.send(data)
+
+  except WebSocketError as exc:
+    error "WebSocket error:", exception = exc.msg
+
+proc newRpcWebSocketServer*(
+  address: TransportAddress,
+  flags: set[ServerFlags] = {ServerFlags.TcpNoDelay,
+    ServerFlags.ReuseAddr}): RpcWebSocketServer =
+
+  var server = new(RpcWebSocketServer)
+  proc processCallback(request: HttpRequest): Future[void] =
+    handleRequest(server, request)
+
+  server.wsserver = WSServer.new()
+  server.server = HttpServer.create(
+    address,
+    processCallback,
+    flags
+  )
+
+  server
+
+proc newRpcWebSocketServer*(
+  host: string,
+  port: Port,
+  flags: set[ServerFlags] = {ServerFlags.TcpNoDelay,
+    ServerFlags.ReuseAddr}): RpcWebSocketServer =
+
+  newRpcWebSocketServer(initTAddress(host, port), flags)
+
+proc newRpcWebSocketServer*(
+  address: TransportAddress,
+  tlsPrivateKey: TLSPrivateKey,
+  tlsCertificate: TLSCertificate,
+  flags: set[ServerFlags] = {ServerFlags.TcpNoDelay,
+    ServerFlags.ReuseAddr},
+  tlsFlags: set[TLSFlags] = {},
+  tlsMinVersion = TLSVersion.TLS12,
+  tlsMaxVersion = TLSVersion.TLS12): RpcWebSocketServer =
+
+  var server = new(RpcWebSocketServer)
+  proc processCallback(request: HttpRequest): Future[void] =
+    handleRequest(server, request)
+
+  server.wsserver = WSServer.new()
+  server.server = TlsHttpServer.create(
+    address,
+    tlsPrivateKey,
+    tlsCertificate,
+    processCallback,
+    flags,
+    tlsFlags,
+    tlsMinVersion,
+    tlsMaxVersion
+  )
+
+  server
+
+proc newRpcWebSocketServer*(
+  host: string,
+  port: Port,
+  tlsPrivateKey: TLSPrivateKey,
+  tlsCertificate: TLSCertificate,
+  flags: set[ServerFlags] = {ServerFlags.TcpNoDelay,
+    ServerFlags.ReuseAddr},
+  tlsFlags: set[TLSFlags] = {},
+  tlsMinVersion = TLSVersion.TLS12,
+  tlsMaxVersion = TLSVersion.TLS12): RpcWebSocketServer =
+
+  newRpcWebSocketServer(
+    initTAddress(host, port),
+    tlsPrivateKey,
+    tlsCertificate,
+    flags,
+    tlsFlags,
+    tlsMinVersion,
+    tlsMaxVersion
+  )
+
+proc start*(server: RpcWebSocketServer) =
+  ## Start the RPC server.
+  notice "WS RPC server started", address = server.server.local
+  server.server.start()
+
+proc stop*(server: RpcWebSocketServer) =
+  ## Stop the RPC server.
+  notice "WS RPC server stopped", address = server.server.local
+  server.server.stop()
+
+proc close*(server: RpcWebSocketServer) =
+  ## Cleanup resources of RPC server.
+  server.server.close()
+
+proc closeWait*(server: RpcWebSocketServer) {.async.} =
+  ## Cleanup resources of RPC server.
+  await server.server.closeWait()