Added monitor API handler

Co-authored-by: Luca Rinaldi <lucarin@protonmail.com>

Author: cmaglie

go.mod

@@ -31,6 +31,7 @@ require (
 	github.com/goccy/go-yaml v1.18.0
 	github.com/google/go-cmp v0.7.0
 	github.com/google/renameio/v2 v2.0.0
+	github.com/gorilla/websocket v1.5.0
 	github.com/gosimple/slug v1.15.0
 	github.com/jedib0t/go-pretty/v6 v6.6.8
 	github.com/jub0bs/cors v0.7.0
@@ -141,7 +142,6 @@ require (
 	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510 // indirect
 	github.com/google/uuid v1.6.0 // indirect
 	github.com/gorilla/mux v1.8.1 // indirect
-	github.com/gorilla/websocket v1.5.0 // indirect
 	github.com/gosimple/unidecode v1.0.1 // indirect
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.26.1 // indirect
 	github.com/h2non/filetype v1.1.3 // indirect

internal/api/api.go

@@ -70,5 +70,7 @@ func NewHTTPRouter(
 
 	mux.Handle("GET /v1/docs/", http.StripPrefix("/v1/docs/", handlers.DocsServer(docsFS)))
 
+	mux.Handle("GET /v1/monitor/ws", handlers.HandleMonitorWS())
+
 	return mux
 }

internal/api/handlers/monitor.go

@@ -0,0 +1,100 @@
+package handlers
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
+	"net"
+	"net/http"
+	"time"
+
+	"github.com/gorilla/websocket"
+
+	"github.com/arduino/arduino-app-cli/internal/api/models"
+	"github.com/arduino/arduino-app-cli/pkg/render"
+)
+
+var upgrader = websocket.Upgrader{
+	ReadBufferSize:  1024,
+	WriteBufferSize: 1024,
+}
+
+func monitorStream(mon net.Conn, ws *websocket.Conn) {
+	logWebsocketError := func(msg string, err error) {
+		// Do not log simple close or interruption errors
+		if websocket.IsUnexpectedCloseError(err, websocket.CloseNormalClosure, websocket.CloseGoingAway, websocket.CloseNoStatusReceived, websocket.CloseAbnormalClosure) {
+			if e, ok := err.(*websocket.CloseError); ok {
+				slog.Error(msg, slog.String("closecause", fmt.Sprintf("%d: %s", e.Code, err)))
+			} else {
+				slog.Error(msg, slog.String("error", err.Error()))
+			}
+		}
+	}
+	logSocketError := func(msg string, err error) {
+		if !errors.Is(err, net.ErrClosed) && !errors.Is(err, io.EOF) {
+			slog.Error(msg, slog.String("error", err.Error()))
+		}
+	}
+	go func() {
+		defer mon.Close()
+		defer ws.Close()
+		for {
+			// Read from websocket and write to monitor
+			_, msg, err := ws.ReadMessage()
+			if err != nil {
+				logWebsocketError("Error reading from websocket", err)
+				return
+			}
+			if _, err := mon.Write(msg); err != nil {
+				logSocketError("Error writing to monitor", err)
+				return
+			}
+		}
+	}()
+	go func() {
+		defer mon.Close()
+		defer ws.Close()
+		buff := [1024]byte{}
+		for {
+			// Read from monitor and write to websocket
+			n, err := mon.Read(buff[:])
+			if err != nil {
+				logSocketError("Error reading from monitor", err)
+				return
+			}
+
+			if err := ws.WriteMessage(websocket.BinaryMessage, buff[:n]); err != nil {
+				logWebsocketError("Error writing to websocket", err)
+				return
+			}
+		}
+	}()
+}
+
+func HandleMonitorWS() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		// Connect to monitor
+		mon, err := net.DialTimeout("tcp", "127.0.0.1:7500", time.Second)
+		if err != nil {
+			slog.Error("Unable to connect to monitor", slog.String("error", err.Error()))
+			render.EncodeResponse(w, http.StatusServiceUnavailable, models.ErrorResponse{Details: "Unable to connect to monitor: " + err.Error()})
+			return
+		}
+
+		// Upgrade the connection to websocket
+		conn, err := upgrader.Upgrade(w, r, nil)
+		if err != nil {
+			// Remember to close monitor connection if websocket upgrade fails.
+			mon.Close()
+
+			render.EncodeResponse(w, http.StatusInternalServerError, map[string]string{"error": "Failed to upgrade connection"})
+			return
+		}
+
+		// Now the connection is managed by the websocket library, let's move the handlers in the goroutine
+		go monitorStream(mon, conn)
+
+		// and return nothing to the http library
+	}
+}