package main

import (
	"bytes"
	"context"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"os"
	"os/signal"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/nats-io/nats.go"
	"github.com/vmihailenco/msgpack/v5"

	"git.daviestechlabs.io/daviestechlabs/handler-base/config"
	"git.daviestechlabs.io/daviestechlabs/handler-base/health"
	"git.daviestechlabs.io/daviestechlabs/handler-base/natsutil"
	"git.daviestechlabs.io/daviestechlabs/handler-base/telemetry"
)

// NATS subject prefixes
const (
	requestSubjectPrefix = "ai.voice.tts.request"
	audioSubjectPrefix   = "ai.voice.tts.audio"
	statusSubjectPrefix  = "ai.voice.tts.status"
	voicesListSubject    = "ai.voice.tts.voices.list"
	voicesRefreshSubject = "ai.voice.tts.voices.refresh"
)

// CustomVoice is a trained voice from the coqui-voice-training pipeline.
type CustomVoice struct {
	Name       string `json:"name"`
	ModelPath  string `json:"model_path"`
	ConfigPath string `json:"config_path"`
	CreatedAt  string `json:"created_at"`
	Language   string `json:"language"`
	ModelType  string `json:"model_type"`
}

// VoiceRegistry discovers custom voices from the model store directory.
type VoiceRegistry struct {
	modelStore  string
	mu          sync.RWMutex
	voices      map[string]*CustomVoice
	lastRefresh time.Time
}

func newVoiceRegistry(modelStore string) *VoiceRegistry {
	return &VoiceRegistry{
		modelStore: modelStore,
		voices:     make(map[string]*CustomVoice),
	}
}

func (vr *VoiceRegistry) refresh() int {
	vr.mu.Lock()
	defer vr.mu.Unlock()

	entries, err := os.ReadDir(vr.modelStore)
	if err != nil {
		slog.Warn("voice model store not found", "path", vr.modelStore, "error", err)
		return 0
	}

	discovered := make(map[string]*CustomVoice)
	for _, entry := range entries {
		if !entry.IsDir() {
			continue
		}
		voiceDir := filepath.Join(vr.modelStore, entry.Name())
		infoPath := filepath.Join(voiceDir, "model_info.json")

		infoData, err := os.ReadFile(infoPath)
		if err != nil {
			continue
		}

		var info map[string]string
		if err := json.Unmarshal(infoData, &info); err != nil {
			slog.Error("bad model_info.json", "dir", voiceDir, "error", err)
			continue
		}

		modelPath := filepath.Join(voiceDir, "model.pth")
		if _, err := os.Stat(modelPath); err != nil {
			slog.Warn("model file missing", "voice", entry.Name())
			continue
		}

		configPath := filepath.Join(voiceDir, "config.json")
		if _, err := os.Stat(configPath); err != nil {
			configPath = ""
		}

		name := info["name"]
		if name == "" {
			name = entry.Name()
		}

		discovered[name] = &CustomVoice{
			Name:       name,
			ModelPath:  modelPath,
			ConfigPath: configPath,
			CreatedAt:  info["created_at"],
			Language:   orDefault(info["language"], "en"),
			ModelType:  orDefault(info["type"], "coqui-tts"),
		}
	}

	vr.voices = discovered
	vr.lastRefresh = time.Now()
	slog.Info("voice registry refreshed", "count", len(discovered))
	return len(discovered)
}

func (vr *VoiceRegistry) get(name string) *CustomVoice {
	vr.mu.RLock()
	defer vr.mu.RUnlock()
	return vr.voices[name]
}

func (vr *VoiceRegistry) listVoices() []map[string]any {
	vr.mu.RLock()
	defer vr.mu.RUnlock()
	result := make([]map[string]any, 0, len(vr.voices))
	for _, v := range vr.voices {
		result = append(result, map[string]any{
			"name":       v.Name,
			"language":   v.Language,
			"model_type": v.ModelType,
			"created_at": v.CreatedAt,
		})
	}
	return result
}

func main() {
	slog.SetDefault(slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{Level: slog.LevelInfo})))

	cfg := config.Load()
	cfg.ServiceName = "tts-streaming"

	xttsURL := getEnv("XTTS_URL", "http://xtts-predictor.ai-ml.svc.cluster.local")
	defaultSpeaker := getEnv("TTS_DEFAULT_SPEAKER", "default")
	defaultLanguage := getEnv("TTS_DEFAULT_LANGUAGE", "en")
	audioChunkSize := getEnvInt("TTS_AUDIO_CHUNK_SIZE", 32768)
	sampleRate := getEnvInt("TTS_SAMPLE_RATE", 24000)
	modelStore := getEnv("VOICE_MODEL_STORE", "/models/tts/custom")
	refreshInterval := getEnvInt("VOICE_REGISTRY_REFRESH_SECONDS", 300)

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	// Telemetry
	tp, shutdown, err := telemetry.Setup(ctx, telemetry.Config{
		ServiceName:      cfg.ServiceName,
		ServiceVersion:   cfg.ServiceVersion,
		ServiceNamespace: cfg.ServiceNamespace,
		DeploymentEnv:    cfg.DeploymentEnv,
		Enabled:          cfg.OTELEnabled,
		Endpoint:         cfg.OTELEndpoint,
	})
	if err != nil {
		slog.Error("telemetry setup failed", "error", err)
	}
	if shutdown != nil {
		defer shutdown(ctx)
	}
	_ = tp // available for future span creation

	// Voice registry
	registry := newVoiceRegistry(modelStore)
	registry.refresh()

	// NATS
	natsOpts := []nats.Option{}
	if cfg.NATSUser != "" && cfg.NATSPassword != "" {
		natsOpts = append(natsOpts, nats.UserInfo(cfg.NATSUser, cfg.NATSPassword))
	}
	nc := natsutil.New(cfg.NATSURL, natsOpts...)
	if err := nc.Connect(); err != nil {
		slog.Error("NATS connect failed", "error", err)
		os.Exit(1)
	}
	defer nc.Close()

	// JetStream stream setup
	js, err := nc.Conn().JetStream()
	if err == nil {
		_, err = js.AddStream(&nats.StreamConfig{
			Name:      "AI_VOICE_TTS",
			Subjects:  []string{"ai.voice.tts.>"},
			Retention: nats.LimitsPolicy,
			MaxAge:    5 * time.Minute,
			Storage:   nats.MemoryStorage,
		})
		if err != nil {
			slog.Info("JetStream stream setup", "msg", err)
		} else {
			slog.Info("created/updated JetStream stream AI_VOICE_TTS")
		}
	}

	httpClient := &http.Client{Timeout: 180 * time.Second}
	running := true

	// Health server
	healthSrv := health.New(cfg.HealthPort, cfg.HealthPath, cfg.ReadyPath, func() bool {
		return running && nc.IsConnected()
	})
	healthSrv.Start()
	defer healthSrv.Stop(ctx)

	// Helper: publish status
	publishStatus := func(sessionID, status, message string) {
		statusMsg := map[string]any{
			"session_id": sessionID,
			"status":     status,
			"message":    message,
			"timestamp":  time.Now().Unix(),
		}
		_ = nc.Publish(fmt.Sprintf("%s.%s", statusSubjectPrefix, sessionID), statusMsg)
	}

	// Helper: synthesize via XTTS HTTP API
	synthesize := func(ctx context.Context, text, speaker, language, speakerWavB64 string) ([]byte, error) {
		payload := map[string]any{
			"text":     text,
			"speaker":  speaker,
			"language": language,
		}

		customVoice := registry.get(speaker)
		if customVoice != nil {
			payload["model_path"] = customVoice.ModelPath
			if customVoice.ConfigPath != "" {
				payload["config_path"] = customVoice.ConfigPath
			}
			payload["language"] = orDefault(language, customVoice.Language)
			slog.Info("using custom voice", "voice", customVoice.Name)
		} else if speakerWavB64 != "" {
			payload["speaker_wav"] = speakerWavB64
		}

		body, _ := json.Marshal(payload)
		req, err := http.NewRequestWithContext(ctx, http.MethodPost, xttsURL+"/v1/audio/speech", bytes.NewReader(body))
		if err != nil {
			return nil, err
		}
		req.Header.Set("Content-Type", "application/json")

		resp, err := httpClient.Do(req)
		if err != nil {
			return nil, fmt.Errorf("xtts request: %w", err)
		}
		defer resp.Body.Close()

		if resp.StatusCode >= 400 {
			respBody, _ := io.ReadAll(resp.Body)
			return nil, fmt.Errorf("xtts %d: %s", resp.StatusCode, string(respBody))
		}

		return io.ReadAll(resp.Body)
	}

	// Helper: stream audio chunks
	streamAudio := func(sessionID string, audioBytes []byte) {
		totalChunks := (len(audioBytes) + audioChunkSize - 1) / audioChunkSize
		for i := 0; i < len(audioBytes); i += audioChunkSize {
			end := i + audioChunkSize
			if end > len(audioBytes) {
				end = len(audioBytes)
			}
			chunk := audioBytes[i:end]
			chunkIndex := i / audioChunkSize
			isLast := end >= len(audioBytes)

			msg := map[string]any{
				"session_id":   sessionID,
				"chunk_index":  chunkIndex,
				"total_chunks": totalChunks,
				"audio_b64":    base64.StdEncoding.EncodeToString(chunk),
				"is_last":      isLast,
				"timestamp":    time.Now().Unix(),
				"sample_rate":  sampleRate,
			}
			_ = nc.Publish(fmt.Sprintf("%s.%s", audioSubjectPrefix, sessionID), msg)
		}
		slog.Info("streamed audio", "session", sessionID, "chunks", totalChunks)
	}

	// Subscribe: TTS requests
	handleRequest := func(natMsg *nats.Msg) {
		parts := strings.Split(natMsg.Subject, ".")
		if len(parts) < 5 {
			slog.Warn("invalid subject format", "subject", natMsg.Subject)
			return
		}
		sessionID := parts[4]

		data, err := natsutil.DecodeMsgpackMap(natMsg.Data)
		if err != nil {
			slog.Error("decode error", "error", err)
			return
		}

		text := strVal(data, "text", "")
		speaker := strVal(data, "speaker", defaultSpeaker)
		language := strVal(data, "language", defaultLanguage)
		speakerWavB64 := strVal(data, "speaker_wav_b64", "")
		stream := boolVal(data, "stream", true)

		if text == "" {
			slog.Warn("empty text", "session", sessionID)
			publishStatus(sessionID, "error", "Empty text provided")
			return
		}

		slog.Info("processing TTS request", "session", sessionID, "text_len", len(text))
		publishStatus(sessionID, "processing", fmt.Sprintf("Synthesizing %d characters", len(text)))

		audioBytes, err := synthesize(ctx, text, speaker, language, speakerWavB64)
		if err != nil {
			slog.Error("synthesis failed", "session", sessionID, "error", err)
			publishStatus(sessionID, "error", err.Error())
			return
		}

		if stream {
			streamAudio(sessionID, audioBytes)
		} else {
			msg := map[string]any{
				"session_id":  sessionID,
				"audio_b64":   base64.StdEncoding.EncodeToString(audioBytes),
				"timestamp":   time.Now().Unix(),
				"sample_rate": sampleRate,
			}
			_ = nc.Publish(fmt.Sprintf("%s.%s", audioSubjectPrefix, sessionID), msg)
		}

		publishStatus(sessionID, "completed", fmt.Sprintf("Audio size: %d bytes", len(audioBytes)))
	}

	if _, err := nc.Conn().Subscribe(requestSubjectPrefix+".>", handleRequest); err != nil {
		slog.Error("subscribe request failed", "error", err)
		os.Exit(1)
	}
	slog.Info("subscribed", "subject", requestSubjectPrefix+".>")

	// Subscribe: list voices
	if _, err := nc.Conn().Subscribe(voicesListSubject, func(msg *nats.Msg) {
		resp := map[string]any{
			"default_speaker": defaultSpeaker,
			"custom_voices":   registry.listVoices(),
			"last_refresh":    registry.lastRefresh.Unix(),
			"timestamp":       time.Now().Unix(),
		}
		packed, _ := msgpack.Marshal(resp)
		if msg.Reply != "" {
			msg.Respond(packed)
		}
	}); err != nil {
		slog.Error("subscribe voices list failed", "error", err)
	}

	// Subscribe: refresh voices
	if _, err := nc.Conn().Subscribe(voicesRefreshSubject, func(msg *nats.Msg) {
		count := registry.refresh()
		resp := map[string]any{
			"count":         count,
			"custom_voices": registry.listVoices(),
			"timestamp":     time.Now().Unix(),
		}
		packed, _ := msgpack.Marshal(resp)
		if msg.Reply != "" {
			msg.Respond(packed)
		}
		slog.Info("voice registry refreshed on demand", "count", count)
	}); err != nil {
		slog.Error("subscribe voices refresh failed", "error", err)
	}

	// Periodic voice refresh
	go func() {
		ticker := time.NewTicker(time.Duration(refreshInterval) * time.Second)
		defer ticker.Stop()
		for {
			select {
			case <-ticker.C:
				registry.refresh()
			case <-ctx.Done():
				return
			}
		}
	}()

	slog.Info("tts-streaming ready")

	// Wait for shutdown
	sigCh := make(chan os.Signal, 1)
	signal.Notify(sigCh, syscall.SIGTERM, syscall.SIGINT)
	<-sigCh

	slog.Info("shutting down")
	running = false
	cancel()
	slog.Info("shutdown complete")
}

// Helpers

func strVal(m map[string]any, key, fallback string) string {
	if v, ok := m[key]; ok {
		if s, ok := v.(string); ok {
			return s
		}
	}
	return fallback
}

func boolVal(m map[string]any, key string, fallback bool) bool {
	if v, ok := m[key]; ok {
		if b, ok := v.(bool); ok {
			return b
		}
	}
	return fallback
}

func getEnv(key, fallback string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return fallback
}

func getEnvInt(key string, fallback int) int {
	if v := os.Getenv(key); v != "" {
		if i, err := strconv.Atoi(v); err == nil {
			return i
		}
	}
	return fallback
}

func orDefault(val, def string) string {
	if val == "" {
		return def
	}
	return val
}