// Package voice provides speech-to-text and text-to-speech capabilities.
// TTS providers form a fallback chain: cloud (Bailian/OpenAI-compatible),
// local self-hosted HTTP server, edge-tts CLI, espeak CLI, silent.
// STT uses a Whisper-compatible /audio/transcriptions endpoint
// (cloud or self-hosted, e.g. faster-whisper).
package voice

import (
	"context"
	"net/http"
	"time"
)

// STTProvider converts speech audio to text.
type STTProvider interface {
	// Name returns the provider identifier.
	Name() string // "whisper-api", "silent"

	// Recognize converts audio data to text.
	Recognize(ctx context.Context, audioData []byte) (string, error)
}

// TTSProvider converts text to speech audio.
type TTSProvider interface {
	// Name returns the provider identifier.
	Name() string // "cloud", "local", "edge-tts", "espeak", "silent"

	// Synthesize converts text to audio bytes.
	Synthesize(ctx context.Context, text string, voice string) ([]byte, error)
}

// Service manages STT and TTS providers with fallback chains.
type Service struct {
	sttProvider STTProvider
	ttsProviders []TTSProvider // Ordered by priority (first = preferred)
}

// Config holds voice service configuration.
type Config struct {
	// STT (Whisper-compatible endpoint; works with Bailian compatible mode
	// or a self-hosted faster-whisper server)
	STTApiURL string // e.g. "https://dashscope.aliyuncs.com/compatible-mode/v1"
	STTApiKey string
	STTModel  string // e.g. "whisper-large-v3"

	// TTS fallback chain, e.g. ["cloud", "local", "edge-tts", "silent"]
	TTSProviders []string
	TTSCloudURL   string // OpenAI-compatible base URL for cloud TTS
	TTSCloudKey   string
	TTSCloudModel string // e.g. "cosyvoice-v1" (Bailian) / "tts-1" (OpenAI)
	TTSCloudVoice string // e.g. "longxiaochun"
	TTSLocalURL   string // self-hosted TTS POST endpoint
}

// New creates a new voice service.
func New(cfg Config) *Service {
	svc := &Service{}

	// STT
	if cfg.STTApiURL != "" && cfg.STTApiKey != "" {
		model := cfg.STTModel
		if model == "" {
			model = "whisper-large-v3"
		}
		svc.sttProvider = &whisperSTT{
			baseURL: cfg.STTApiURL, apiKey: cfg.STTApiKey, model: model,
			client: &http.Client{Timeout: 60 * time.Second},
		}
	} else {
		svc.sttProvider = &silentSTT{}
	}

	// TTS: build fallback chain
	for _, name := range cfg.TTSProviders {
		switch name {
		case "cloud":
			if cfg.TTSCloudURL != "" && cfg.TTSCloudKey != "" {
				svc.ttsProviders = append(svc.ttsProviders, &cloudTTS{
					baseURL: cfg.TTSCloudURL, apiKey: cfg.TTSCloudKey,
					model: cfg.TTSCloudModel, defaultVoice: cfg.TTSCloudVoice,
					client: &http.Client{Timeout: 60 * time.Second},
				})
			}
		case "local":
			if cfg.TTSLocalURL != "" {
				svc.ttsProviders = append(svc.ttsProviders, &localTTS{
					url: cfg.TTSLocalURL, client: &http.Client{Timeout: 60 * time.Second},
				})
			}
		case "edge-tts":
			if e := newEdgeTTS(); e.available() {
				svc.ttsProviders = append(svc.ttsProviders, e)
			}
		case "espeak":
			if e := newEspeakTTS(); e.bin != "" {
				svc.ttsProviders = append(svc.ttsProviders, e)
			}
		case "silent":
			svc.ttsProviders = append(svc.ttsProviders, &silentTTS{})
		}
	}
	if len(svc.ttsProviders) == 0 {
		svc.ttsProviders = append(svc.ttsProviders, &silentTTS{})
	}

	return svc
}

// TTSProviderNames returns the active TTS fallback chain.
func (s *Service) TTSProviderNames() []string {
	names := make([]string, len(s.ttsProviders))
	for i, p := range s.ttsProviders {
		names[i] = p.Name()
	}
	return names
}

// Recognize performs speech recognition with the configured STT provider.
func (s *Service) Recognize(ctx context.Context, audioData []byte) (string, error) {
	return s.sttProvider.Recognize(ctx, audioData)
}

// Synthesize performs TTS with automatic fallback through the provider chain.
func (s *Service) Synthesize(ctx context.Context, text string, voice string) ([]byte, error) {
	var lastErr error
	for _, p := range s.ttsProviders {
		audio, err := p.Synthesize(ctx, text, voice)
		if err == nil {
			return audio, nil
		}
		lastErr = err
	}
	return nil, lastErr
}

// --- Silent fallbacks ---

type silentSTT struct{}
func (p *silentSTT) Name() string { return "silent" }
func (p *silentSTT) Recognize(_ context.Context, _ []byte) (string, error) {
	return "", nil
}

type silentTTS struct{}
func (p *silentTTS) Name() string { return "silent" }
func (p *silentTTS) Synthesize(_ context.Context, _ string, _ string) ([]byte, error) {
	return make([]byte, 0), nil
}