add simple transcription with adapters

internal/transcriber/adapter_openai.go

@@ -0,0 +1,94 @@
+package transcriber
+
+import (
+	"bytes"
+	"context"
+	"encoding/binary"
+	"fmt"
+	"log"
+	"time"
+
+	"github.com/sashabaranov/go-openai"
+)
+
+// OpenAIAdapter implements TranscriptionAdapter for OpenAI Whisper API
+type OpenAIAdapter struct {
+	client *openai.Client
+	config Config
+}
+
+func NewOpenAIAdapter(config Config) *OpenAIAdapter {
+	client := openai.NewClient(config.APIKey)
+	return &OpenAIAdapter{
+		client: client,
+		config: config,
+	}
+}
+
+func (a *OpenAIAdapter) Transcribe(ctx context.Context, audioData []byte) (string, error) {
+	if len(audioData) == 0 {
+		return "", nil
+	}
+
+	// Convert raw PCM to WAV format
+	wavData, err := a.convertToWAV(audioData)
+	if err != nil {
+		return "", fmt.Errorf("convert to WAV: %w", err)
+	}
+
+	// Create transcription request
+	req := openai.AudioRequest{
+		Model:    a.config.Model,
+		Reader:   bytes.NewReader(wavData),
+		FilePath: "audio.wav",
+		Language: a.config.Language,
+	}
+
+	start := time.Now()
+	resp, err := a.client.CreateTranscription(ctx, req)
+	duration := time.Since(start)
+
+	if err != nil {
+		log.Printf("openai-adapter: API call failed after %v: %v", duration, err)
+		return "", fmt.Errorf("openai transcription: %w", err)
+	}
+
+	log.Printf("openai-adapter: transcribed %d bytes in %v: %q", len(audioData), duration, resp.Text)
+	return resp.Text, nil
+}
+
+// convertToWAV converts raw 16-bit PCM audio to WAV format
+func (a *OpenAIAdapter) convertToWAV(rawAudio []byte) ([]byte, error) {
+	var buf bytes.Buffer
+
+	const sampleRate = 16000
+	const channels = 1
+	const bitsPerSample = 16
+	const byteRate = sampleRate * channels * bitsPerSample / 8
+	const blockAlign = channels * bitsPerSample / 8
+
+	dataSize := len(rawAudio)
+	fileSize := 36 + dataSize
+
+	// WAV header
+	buf.WriteString("RIFF")
+	binary.Write(&buf, binary.LittleEndian, uint32(fileSize))
+	buf.WriteString("WAVE")
+
+	// fmt chunk
+	buf.WriteString("fmt ")
+	binary.Write(&buf, binary.LittleEndian, uint32(16))            // fmt chunk size
+	binary.Write(&buf, binary.LittleEndian, uint16(1))             // PCM format
+	binary.Write(&buf, binary.LittleEndian, uint16(channels))      // number of channels
+	binary.Write(&buf, binary.LittleEndian, uint32(sampleRate))    // sample rate
+	binary.Write(&buf, binary.LittleEndian, uint32(byteRate))      // byte rate
+	binary.Write(&buf, binary.LittleEndian, uint16(blockAlign))    // block align
+	binary.Write(&buf, binary.LittleEndian, uint16(bitsPerSample)) // bits per sample
+
+	// data chunk
+	buf.WriteString("data")
+	binary.Write(&buf, binary.LittleEndian, uint32(dataSize))
+	buf.Write(rawAudio)
+
+	return buf.Bytes(), nil
+}