voicepaste/internal/ws/handler.go

package ws

import (
	"encoding/json"
	"log/slog"
	"sync"

	"github.com/gofiber/contrib/v3/websocket"
	"github.com/gofiber/fiber/v3"
)

// session holds the state for a single WebSocket connection.
type session struct {
	conn        *websocket.Conn
	log         *slog.Logger
	resultCh    chan ServerMsg
	previewMu   sync.Mutex
	previewText string
	sendAudio   func([]byte)
	cleanup     func()
	active      bool
}
// PasteFunc is called when the server should paste text into the focused app.
type PasteFunc func(text string) error

// ASRFactory creates an ASR session. It returns a channel that receives
// partial/final results, and a function to send audio frames.
// The cleanup function must be called when the session ends.
type ASRFactory func(resultCh chan<- ServerMsg) (sendAudio func(pcm []byte), cleanup func(), err error)

// Handler holds dependencies for WebSocket connections.
type Handler struct {
	token      string
	pasteFunc  PasteFunc
	asrFactory ASRFactory
}

// NewHandler creates a WS handler with the given dependencies.
func NewHandler(token string, pasteFn PasteFunc, asrFn ASRFactory) *Handler {
	return &Handler{
		token:      token,
		pasteFunc:  pasteFn,
		asrFactory: asrFn,
	}
}

// Register adds the /ws route to the Fiber app.
func (h *Handler) Register(app *fiber.App) {
  // Token check middleware (before upgrade)
  app.Use("/ws", func(c fiber.Ctx) error {
    if !websocket.IsWebSocketUpgrade(c) {
      return fiber.ErrUpgradeRequired
    }
    if h.token != "" {
      q := c.Query("token")
      if q != h.token {
        return c.Status(fiber.StatusUnauthorized).SendString("invalid token")
      }
    }
    return c.Next()
  })

  app.Get("/ws", websocket.New(h.handleConn))
}

func (h *Handler) handleConn(c *websocket.Conn) {
	sess := &session{
		conn:     c,
		log:      slog.With("remote", c.RemoteAddr().String()),
		resultCh: make(chan ServerMsg, 32),
	}
	sess.log.Info("ws connected")
	defer sess.log.Info("ws disconnected")
	defer close(sess.resultCh)
	defer sess.cleanupASR()
	var wg sync.WaitGroup
	wg.Add(1)
	go sess.writerLoop(&wg)
	defer wg.Wait()
	for {
		mt, data, err := c.ReadMessage()
		if err != nil {
			break
		}
		if mt == websocket.BinaryMessage {
			sess.handleAudioFrame(data)
		} else if mt == websocket.TextMessage {
			h.handleTextMessage(sess, data)
		}
	}
}
func (s *session) writerLoop(wg *sync.WaitGroup) {
	defer wg.Done()
	for msg := range s.resultCh {
		if msg.Type == MsgPartial || msg.Type == MsgFinal {
			s.previewMu.Lock()
			s.previewText = msg.Text
			preview := ServerMsg{Type: msg.Type, Text: s.previewText}
			s.previewMu.Unlock()
			if err := s.conn.WriteMessage(websocket.TextMessage, preview.Bytes()); err != nil {
				s.log.Warn("ws write error", "err", err)
				return
			}
			continue
		}
		if err := s.conn.WriteMessage(websocket.TextMessage, msg.Bytes()); err != nil {
			s.log.Warn("ws write error", "err", err)
			return
		}
	}
}
func (s *session) handleAudioFrame(data []byte) {
	if s.active && s.sendAudio != nil {
		s.sendAudio(data)
	}
}
func (h *Handler) handleTextMessage(s *session, data []byte) {
	var msg ClientMsg
	if err := json.Unmarshal(data, &msg); err != nil {
		s.log.Warn("invalid json", "err", err)
		return
	}
	switch msg.Type {
	case MsgStart:
		h.handleStart(s)
	case MsgStop:
		h.handleStop(s)
	case MsgPaste:
		h.handlePaste(s, msg.Text)
	}
}
func (h *Handler) handleStart(s *session) {
	if s.active {
		return
	}
	s.previewMu.Lock()
	s.previewText = ""
	s.previewMu.Unlock()
	sa, cl, err := h.asrFactory(s.resultCh)
	if err != nil {
		s.log.Error("asr start failed", "err", err)
		s.resultCh <- ServerMsg{Type: MsgError, Message: "ASR start failed"}
		return
	}
	s.sendAudio = sa
	s.cleanup = cl
	s.active = true
	s.log.Info("recording started")
}
func (h *Handler) handleStop(s *session) {
	if !s.active {
		return
	}
	s.cleanupASR()
	s.sendAudio = nil
	s.active = false
	s.previewMu.Lock()
	finalText := s.previewText
	s.previewText = ""
	s.previewMu.Unlock()
	if finalText != "" && h.pasteFunc != nil {
		if err := h.pasteFunc(finalText); err != nil {
			s.log.Error("auto-paste failed", "err", err)
		} else {
			s.resultCh <- ServerMsg{Type: MsgPasted}
		}
	}
	s.log.Info("recording stopped")
}
func (h *Handler) handlePaste(s *session, text string) {
	if text == "" {
		return
	}
	if h.pasteFunc != nil {
		if err := h.pasteFunc(text); err != nil {
			s.log.Error("paste failed", "err", err)
			s.resultCh <- ServerMsg{Type: MsgError, Message: "paste failed"}
		} else {
			s.resultCh <- ServerMsg{Type: MsgPasted}
		}
	}
}
func (s *session) cleanupASR() {
	if s.cleanup != nil {
		s.cleanup()
		s.cleanup = nil
	}
}