voicepaste/internal/asr/client.go

package asr

import (
	"fmt"
	"log/slog"
	"net/http"
	"sync"
	"time"

	"github.com/fasthttp/websocket"
	"github.com/google/uuid"
	wsMsg "github.com/imbytecat/voicepaste/internal/ws"
)

const (
	doubaoEndpoint = "wss://openspeech.bytedance.com/api/v3/sauc/bigmodel_async"
	writeTimeout   = 10 * time.Second
	readTimeout    = 30 * time.Second
)

// Config holds Doubao ASR connection parameters.
type Config struct {
	AppID       string
	AccessToken string
	ResourceID string
}

// Client manages a single ASR session with Doubao.
type Client struct {
	cfg     Config
	conn    *websocket.Conn
	mu      sync.Mutex
	closed  bool
	closeCh chan struct{}
	log     *slog.Logger
}
// Dial connects to Doubao ASR and sends the initial FullClientRequest.
// resultCh receives partial/final results. Caller must call Close() when done.
func Dial(cfg Config, resultCh chan<- wsMsg.ServerMsg) (*Client, error) {
	connID := uuid.New().String()
	headers := http.Header{
		"X-Api-App-Key":    {cfg.AppID},
		"X-Api-Access-Key": {cfg.AccessToken},
		"X-Api-Resource-Id": {cfg.ResourceID},
		"X-Api-Connect-Id": {connID},
	}
	dialer := websocket.Dialer{
		HandshakeTimeout: 10 * time.Second,
	}
	conn, _, err := dialer.Dial(doubaoEndpoint, headers)
	if err != nil {
		return nil, fmt.Errorf("dial doubao: %w", err)
	}
	c := &Client{
		cfg:     cfg,
		conn:    conn,
		closeCh: make(chan struct{}),
		log:     slog.With("conn_id", connID),
	}
	// Send FullClientRequest
	req := &FullClientRequest{
		User: UserMeta{UID: connID},
		Audio: AudioMeta{
			Format:  "pcm",
			Codec:   "raw",
			Rate:    16000,
			Bits:    16,
			Channel: 1,
		},
		Request: RequestMeta{
			ModelName:         "seedasr-2.0",
			EnableITN:         true,
			EnablePUNC:        true,
			EnableDDC:         true,
			ShowUtterances:    true,
			ResultType:        "full",
			EnableNonstream:   true,
			EndWindowSize:     800,
		},
	}
	data, err := EncodeFullClientRequest(req)
	if err != nil {
		conn.Close()
		return nil, fmt.Errorf("encode full request: %w", err)
	}
	_ = conn.SetWriteDeadline(time.Now().Add(writeTimeout))
	if err := conn.WriteMessage(websocket.BinaryMessage, data); err != nil {
		conn.Close()
		return nil, fmt.Errorf("send full request: %w", err)
	}
	// Start read loop
	go c.readLoop(resultCh)
	return c, nil
}

// SendAudio sends a PCM audio frame to Doubao.
func (c *Client) SendAudio(pcm []byte, last bool) error {
	c.mu.Lock()
	defer c.mu.Unlock()
	if c.closed {
		return fmt.Errorf("client closed")
	}
	data, err := EncodeAudioFrame(pcm, last)
	if err != nil {
		return fmt.Errorf("encode audio: %w", err)
	}
	_ = c.conn.SetWriteDeadline(time.Now().Add(writeTimeout))
	return c.conn.WriteMessage(websocket.BinaryMessage, data)
}
// readLoop reads server responses and forwards them to resultCh.
func (c *Client) readLoop(resultCh chan<- wsMsg.ServerMsg) {
	defer func() {
		c.conn.Close()
		c.mu.Lock()
		c.closed = true
		c.mu.Unlock()
		close(c.closeCh)
	}()
	for {
		_ = c.conn.SetReadDeadline(time.Now().Add(readTimeout))
		_, data, err := c.conn.ReadMessage()
		if err != nil {
			c.log.Debug("asr read done", "err", err)
			return
		}
		resp, err := ParseResponse(data)
		if err != nil {
			c.log.Warn("parse asr response", "err", err)
			continue
		}
		if resp.Code != 0 {
			c.log.Error("asr error", "code", resp.Code, "msg", resp.ErrMsg)
			resultCh <- wsMsg.ServerMsg{Type: wsMsg.MsgError, Message: resp.ErrMsg}
			return
		}
		// bigmodel_async with enable_nonstream: returns both streaming (partial) and definite (final) results
		text := resp.Text
		if text != "" {
			if resp.IsLast {
				resultCh <- wsMsg.ServerMsg{Type: wsMsg.MsgFinal, Text: text}
			} else {
				// Intermediate streaming result (first pass) — preview only
				resultCh <- wsMsg.ServerMsg{Type: wsMsg.MsgPartial, Text: text}
			}
		}
		if resp.IsLast {
			return
		}
	}
}
// Finish sends the last audio frame and waits for ASR to return final results.
func (c *Client) Finish() {
	c.mu.Lock()
	if c.closed {
		c.mu.Unlock()
		return
	}
	c.mu.Unlock()
	_ = c.SendAudio(nil, true)
	<-c.closeCh
}

// Close forcefully shuts down the ASR connection.
func (c *Client) Close() {
	c.mu.Lock()
	if c.closed {
		c.mu.Unlock()
		return
	}
	c.conn.Close()
	c.mu.Unlock()
	<-c.closeCh
}