feat(api): expose process output over websocket

Co-Authored-By: Claude <noreply@anthropic.com>

internal/api/process_handler.go

@@ -1,18 +1,31 @@
 package api
 
 import (
+	"fmt"
 	"net/http"
+	"sync"
+	"time"
 
 	"codespace/internal/model"
+	"codespace/internal/process"
 	"codespace/internal/service"
+	"codespace/internal/util"
 
 	"github.com/gin-gonic/gin"
+	"github.com/gorilla/websocket"
 )
 
 type processHandler struct {
 	svc *service.ProcessService
 }
 
+func exitBanner(exit process.ExitInfo) string {
+	if exit.Signal != "" {
+		return fmt.Sprintf("\r\n[process exited: signal %s]\r\n", exit.Signal)
+	}
+	return fmt.Sprintf("\r\n[process exited with code %d]\r\n", exit.Code)
+}
+
 func (h *processHandler) start(c *gin.Context) {
 	id := c.Param("id")
 	if err := h.svc.Start(id); err != nil {
@@ -53,3 +66,92 @@ func (h *processHandler) status(c *gin.Context) {
 		PID:         status.PID,
 	})
 }
+
+func (h *processHandler) ws(c *gin.Context) {
+	id := c.Param("id")
+
+	stdin, err := h.svc.Input(id)
+	if err != nil {
+		if util.CodeOf(err) == util.CodeNotFound {
+			c.JSON(409, gin.H{"error": "process not running"})
+			return
+		}
+		writeError(c, err)
+		return
+	}
+
+	sub, err := h.svc.Subscribe(id)
+	if err != nil {
+		writeError(c, err)
+		return
+	}
+
+	exit, _ := h.svc.ExitStatus(id)
+
+	upgrader := websocket.Upgrader{
+		CheckOrigin:     func(r *http.Request) bool { return true },
+		ReadBufferSize:  4096,
+		WriteBufferSize: 4096,
+	}
+
+	conn, err := upgrader.Upgrade(c.Writer, c.Request, nil)
+	if err != nil {
+		return
+	}
+
+	done := make(chan struct{})
+	var closeOnce sync.Once
+	closeAll := func() {
+		closeOnce.Do(func() {
+			sub.Close()
+			conn.Close()
+			stdin.Close()
+			close(done)
+		})
+	}
+
+	go func() {
+		ticker := time.NewTicker(30 * time.Second)
+		defer ticker.Stop()
+		for {
+			select {
+			case <-done:
+				return
+			case <-ticker.C:
+				if err := conn.WriteControl(websocket.PingMessage, nil, time.Now().Add(5*time.Second)); err != nil {
+					closeAll()
+					return
+				}
+			case chunk, ok := <-sub.Output():
+				if !ok {
+					banner := exitBanner(exit)
+					conn.WriteMessage(websocket.TextMessage, []byte(banner))
+					conn.WriteMessage(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseNormalClosure, ""))
+					closeAll()
+					return
+				}
+				if err := conn.WriteMessage(websocket.TextMessage, chunk); err != nil {
+					closeAll()
+					return
+				}
+			}
+		}
+	}()
+
+	conn.SetReadLimit(1 << 20)
+	conn.SetReadDeadline(time.Now().Add(60 * time.Second))
+	conn.SetPongHandler(func(string) error {
+		conn.SetReadDeadline(time.Now().Add(60 * time.Second))
+		return nil
+	})
+	for {
+		mt, data, err := conn.ReadMessage()
+		if err != nil {
+			break
+		}
+		if mt == websocket.TextMessage {
+			stdin.Write(data)
+		}
+	}
+	closeAll()
+}