use message dispatcher to process responses and notifications & spread out comments

1 files changed, 287 insertions, 0 deletions

diff --git a/jsonrpc/client/client.go b/jsonrpc/client/client.go
new file mode 100644
index 0000000..a34828a
--- /dev/null
+++ b/jsonrpc/client/client.go
@@ -0,0 +1,287 @@
+package client
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"math/rand"
+	"strconv"
+	"time"
+
+	"github.com/gorilla/websocket"
+	log "github.com/sirupsen/logrus"
+
+	"github.com/karyontech/karyon-go/jsonrpc/message"
+)
+
+const (
+	// JsonRPCVersion Defines the version of the JSON-RPC protocol being used.
+	JsonRPCVersion = "2.0"
+
+	// Default timeout for receiving requests from the server, in milliseconds.
+	DefaultTimeout = 3000
+)
+
+// RPCClientConfig Holds the configuration settings for the RPC client.
+type RPCClientConfig struct {
+	Timeout int    // Timeout for receiving requests from the server, in milliseconds.
+	Addr    string // Address of the RPC server.
+}
+
+// RPCClient RPC Client
+type RPCClient struct {
+	config      RPCClientConfig
+	conn        *websocket.Conn
+	requests    messageDispatcher[message.RequestID, message.Response]
+	subscriber  messageDispatcher[message.SubscriptionID, json.RawMessage]
+	stop_signal chan struct{}
+}
+
+// NewRPCClient Creates a new instance of RPCClient with the provided configuration.
+// It establishes a WebSocket connection to the RPC server.
+func NewRPCClient(config RPCClientConfig) (*RPCClient, error) {
+	conn, _, err := websocket.DefaultDialer.Dial(config.Addr, nil)
+	if err != nil {
+		return nil, err
+	}
+	log.Infof("Successfully connected to the server: %s", config.Addr)
+
+	if config.Timeout == 0 {
+		config.Timeout = DefaultTimeout
+	}
+
+	stop_signal := make(chan struct{}, 2)
+
+	client := &RPCClient{
+		conn:        conn,
+		config:      config,
+		requests:    newMessageDispatcher[message.RequestID, message.Response](1),
+		subscriber:  newMessageDispatcher[message.SubscriptionID, json.RawMessage](10),
+		stop_signal: stop_signal,
+	}
+
+	go func() {
+		if err := client.backgroundReceivingLoop(stop_signal); err != nil {
+			client.Close()
+		}
+	}()
+
+	return client, nil
+}
+
+// Close Closes the underlying websocket connection and stop the receiving loop.
+func (client *RPCClient) Close() {
+	log.Warn("Close the rpc client...")
+	// Send stop signal to the background receiving loop
+	client.stop_signal <- struct{}{}
+
+	// Close the underlying websocket connection
+	err := client.conn.Close()
+	if err != nil {
+		log.WithError(err).Error("Close websocket connection")
+	}
+
+	client.requests.clear()
+	client.subscriber.clear()
+}
+
+// Call Sends an RPC call to the server with the specified method and
+// parameters, and returns the response.
+func (client *RPCClient) Call(method string, params any) (*json.RawMessage, error) {
+	log.Tracef("Call -> method: %s, params: %v", method, params)
+	response, err := client.sendRequest(method, params)
+	if err != nil {
+		return nil, err
+	}
+
+	return response.Result, nil
+}
+
+// Subscribe Sends a subscription request to the server with the specified
+// method and parameters, and it returns the subscription ID and the channel to
+// receive notifications.
+func (client *RPCClient) Subscribe(method string, params any) (message.SubscriptionID, <-chan json.RawMessage, error) {
+	log.Tracef("Sbuscribe ->  method: %s, params: %v", method, params)
+	response, err := client.sendRequest(method, params)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	if response.Result == nil {
+		return 0, nil, fmt.Errorf("Invalid response result")
+	}
+
+	var subID message.SubscriptionID
+	err = json.Unmarshal(*response.Result, &subID)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	// Register a new subscription
+	sub := client.subscriber.register(subID)
+
+	return subID, sub, nil
+}
+
+// Unsubscribe Sends an unsubscription request to the server to cancel the
+// given subscription.
+func (client *RPCClient) Unsubscribe(method string, subID message.SubscriptionID) error {
+	log.Tracef("Unsubscribe -> method: %s, subID: %d", method, subID)
+	_, err := client.sendRequest(method, subID)
+	if err != nil {
+		return err
+	}
+
+	// On success unregister the subscription channel
+	client.subscriber.unregister(subID)
+
+	return nil
+}
+
+// backgroundReceivingLoop Starts reading new messages from the underlying connection.
+func (client *RPCClient) backgroundReceivingLoop(stop_signal <-chan struct{}) error {
+
+	log.Debug("Background loop started")
+
+	new_msg_ch := make(chan []byte)
+	receive_err_ch := make(chan error)
+
+	// Start listing for new messages
+	go func() {
+		for {
+			_, msg, err := client.conn.ReadMessage()
+			if err != nil {
+				receive_err_ch <- err
+				return
+			}
+			new_msg_ch <- msg
+		}
+	}()
+
+	for {
+		select {
+		case <-stop_signal:
+			log.Warn("Stopping background receiving loop: received stop signal")
+			return nil
+		case msg := <-new_msg_ch:
+			err := client.handleNewMsg(msg)
+			if err != nil {
+				log.WithError(err).Error("Handle a new received msg")
+			}
+		case err := <-receive_err_ch:
+			log.WithError(err).Error("Receive a new msg")
+			return err
+		}
+	}
+}
+
+// handleNewMsg Attempts to decode the received message into either a Response
+// or Notification.
+func (client *RPCClient) handleNewMsg(msg []byte) error {
+	// Check if the received message is of type Response
+	response := message.Response{}
+	decoder := json.NewDecoder(bytes.NewReader(msg))
+	decoder.DisallowUnknownFields()
+	if err := decoder.Decode(&response); err == nil {
+		if response.ID == nil {
+			return fmt.Errorf("Response doesn't have an id")
+		}
+
+		err := client.requests.disptach(*response.ID, response)
+		if err != nil {
+			return fmt.Errorf("Dispatch a response: %w", err)
+		}
+
+		return nil
+	}
+
+	// Check if the received message is of type Notification
+	notification := message.Notification{}
+	if err := json.Unmarshal(msg, &notification); err == nil {
+
+		ntRes := message.NotificationResult{}
+		if err := json.Unmarshal(*notification.Params, &ntRes); err != nil {
+			return fmt.Errorf("Failed to unmarshal notification params: %w", err)
+		}
+
+		// Send the notification to the subscription
+		err := client.subscriber.disptach(ntRes.Subscription, *ntRes.Result)
+		if err != nil {
+			return fmt.Errorf("Dispatch a notification: %w", err)
+		}
+
+		log.Debugf("<-- %s", notification.String())
+
+		return nil
+	}
+
+	return fmt.Errorf("Receive unexpected msg: %s", msg)
+}
+
+// sendRequest Sends a request and wait for the response
+func (client *RPCClient) sendRequest(method string, params any) (message.Response, error) {
+	response := message.Response{}
+
+	params_bytes, err := json.Marshal(params)
+	if err != nil {
+		return response, err
+	}
+
+	params_raw := json.RawMessage(params_bytes)
+
+	// Generate a new id
+	id := strconv.Itoa(rand.Int())
+	req := message.Request{
+		JSONRPC: JsonRPCVersion,
+		ID:      id,
+		Method:  method,
+		Params:  &params_raw,
+	}
+
+	reqJSON, err := json.Marshal(req)
+	if err != nil {
+		return response, err
+	}
+
+	err = client.conn.WriteMessage(websocket.TextMessage, []byte(string(reqJSON)))
+	if err != nil {
+		return response, err
+	}
+
+	log.Debugf("--> %s", req.String())
+
+	rx_ch := client.requests.register(id)
+	defer client.requests.unregister(id)
+
+	// Waits the response, it fails and return error if it exceed the timeout
+	select {
+	case response = <-rx_ch:
+	case <-time.After(time.Duration(client.config.Timeout) * time.Millisecond):
+		return response, fmt.Errorf("Timeout error")
+	}
+
+	err = validateResponse(&response, id)
+	if err != nil {
+		return response, err
+	}
+
+	log.Debugf("<-- %s", response.String())
+
+	return response, nil
+}
+
+// validateResponse Checks the error field and whether the request id is the
+// same as the response id
+func validateResponse(res *message.Response, reqID message.RequestID) error {
+	if res.Error != nil {
+		return fmt.Errorf("Receive An Error: %s", res.Error.String())
+	}
+
+	if res.ID != nil {
+		if *res.ID != reqID {
+			return fmt.Errorf("Invalid response id")
+		}
+	}
+
+	return nil
+}