package workers

import (
	"context"
	"fmt"
	"sync"
	"time"

	"veza-backend-api/internal/models"
	"veza-backend-api/internal/services"

	"github.com/google/uuid"
	"go.uber.org/zap"
	"gorm.io/gorm"
)

// PlaybackAnalyticsWorker gère le traitement par lots des analytics de playback
// T0387: Create Playback Analytics Batch Processing
type PlaybackAnalyticsWorker struct {
	db                *gorm.DB
	analyticsService  *services.PlaybackAnalyticsService
	logger            *zap.Logger
	queue             chan AnalyticsJob
	maxRetries        int
	processingWorkers int
	batchSize         int
	batchTimeout      time.Duration
	stopChan          chan struct{}
	running           bool
	mu                sync.RWMutex
}

// AnalyticsJob représente un job d'analytics à traiter
type AnalyticsJob struct {
	ID        uuid.UUID
	Analytics *models.PlaybackAnalytics
	Retries   int
	CreatedAt time.Time
	Priority  int // 1 = haut, 2 = moyen, 3 = bas
}

// Batch représente un lot d'analytics à traiter
type Batch struct {
	Jobs      []AnalyticsJob
	CreatedAt time.Time
}

// NewPlaybackAnalyticsWorker crée un nouveau worker d'analytics
// T0387: Create Playback Analytics Batch Processing
func NewPlaybackAnalyticsWorker(
	db *gorm.DB,
	analyticsService *services.PlaybackAnalyticsService,
	logger *zap.Logger,
	queueSize int,
	workers int,
	maxRetries int,
	batchSize int,
	batchTimeout time.Duration,
) *PlaybackAnalyticsWorker {
	if logger == nil {
		logger = zap.NewNop()
	}
	if queueSize <= 0 {
		queueSize = 1000 // Taille par défaut de la queue
	}
	if workers <= 0 {
		workers = 3 // Nombre par défaut de workers
	}
	if maxRetries <= 0 {
		maxRetries = 3 // Nombre par défaut de retries
	}
	if batchSize <= 0 {
		batchSize = 100 // Taille par défaut du batch
	}
	if batchTimeout <= 0 {
		batchTimeout = 5 * time.Second // Timeout par défaut pour former un batch
	}

	return &PlaybackAnalyticsWorker{
		db:                db,
		analyticsService:  analyticsService,
		logger:            logger,
		queue:             make(chan AnalyticsJob, queueSize),
		maxRetries:        maxRetries,
		processingWorkers: workers,
		batchSize:         batchSize,
		batchTimeout:      batchTimeout,
		stopChan:          make(chan struct{}),
		running:           false,
	}
}

// Enqueue ajoute un job d'analytics à la queue
// T0387: Create Playback Analytics Batch Processing
func (w *PlaybackAnalyticsWorker) Enqueue(analytics *models.PlaybackAnalytics, priority int) error {
	if analytics == nil {
		return fmt.Errorf("analytics cannot be nil")
	}

	job := AnalyticsJob{
		ID:        uuid.New(),
		Analytics: analytics,
		Retries:   0,
		CreatedAt: time.Now(),
		Priority:  priority,
	}

	select {
	case w.queue <- job:
		w.logger.Debug("Analytics job enqueued",
			zap.String("job_id", job.ID.String()),
			zap.String("track_id", analytics.TrackID.String()),
			zap.String("user_id", analytics.UserID.String()),
			zap.Int("priority", priority))
		return nil
	default:
		w.logger.Warn("Analytics queue full, dropping job",
			zap.String("track_id", analytics.TrackID.String()),
			zap.String("user_id", analytics.UserID.String()))
		return fmt.Errorf("queue is full")
	}
}

// EnqueueBatch ajoute plusieurs analytics à la queue
// T0387: Create Playback Analytics Batch Processing
func (w *PlaybackAnalyticsWorker) EnqueueBatch(analyticsList []*models.PlaybackAnalytics, priority int) error {
	if len(analyticsList) == 0 {
		return fmt.Errorf("analytics list cannot be empty")
	}

	enqueued := 0
	for _, analytics := range analyticsList {
		if err := w.Enqueue(analytics, priority); err != nil {
			w.logger.Warn("Failed to enqueue analytics",
				zap.Error(err),
				zap.String("track_id", analytics.TrackID.String()))
			continue
		}
		enqueued++
	}

	w.logger.Info("Batch enqueued",
		zap.Int("total", len(analyticsList)),
		zap.Int("enqueued", enqueued),
		zap.Int("failed", len(analyticsList)-enqueued))

	return nil
}

// Start démarre le worker
// T0387: Create Playback Analytics Batch Processing
func (w *PlaybackAnalyticsWorker) Start(ctx context.Context) {
	w.mu.Lock()
	if w.running {
		w.mu.Unlock()
		w.logger.Warn("Playback analytics worker is already running")
		return
	}
	w.running = true
	w.mu.Unlock()

	w.logger.Info("Starting playback analytics worker",
		zap.Int("workers", w.processingWorkers),
		zap.Int("batch_size", w.batchSize),
		zap.Duration("batch_timeout", w.batchTimeout))

	for i := 0; i < w.processingWorkers; i++ {
		go w.processWorker(ctx, i)
	}
}

// Stop arrête le worker
// T0387: Create Playback Analytics Batch Processing
func (w *PlaybackAnalyticsWorker) Stop() {
	w.mu.Lock()
	defer w.mu.Unlock()

	if !w.running {
		return
	}

	w.logger.Info("Stopping playback analytics worker")
	close(w.stopChan)
	w.running = false
}

// IsRunning retourne si le worker est en cours d'exécution
func (w *PlaybackAnalyticsWorker) IsRunning() bool {
	w.mu.RLock()
	defer w.mu.RUnlock()
	return w.running
}

// processWorker traite les jobs de la queue par lots
// T0387: Create Playback Analytics Batch Processing
func (w *PlaybackAnalyticsWorker) processWorker(ctx context.Context, workerID int) {
	logger := w.logger.With(zap.Int("worker_id", workerID))
	logger.Info("Playback analytics worker started")

	for {
		select {
		case <-ctx.Done():
			logger.Info("Playback analytics worker stopping")
			return

		case <-w.stopChan:
			logger.Info("Playback analytics worker stopping (stop requested)")
			return

		default:
			// Collecter les jobs pour former un batch
			batch := w.collectBatch(ctx, workerID)
			if len(batch.Jobs) > 0 {
				w.processBatch(ctx, batch, workerID)
			}
		}
	}
}

// collectBatch collecte les jobs pour former un batch
// T0387: Create Playback Analytics Batch Processing
func (w *PlaybackAnalyticsWorker) collectBatch(ctx context.Context, workerID int) Batch {
	batch := Batch{
		Jobs:      make([]AnalyticsJob, 0, w.batchSize),
		CreatedAt: time.Now(),
	}

	timeout := time.NewTimer(w.batchTimeout)
	defer timeout.Stop()

	for len(batch.Jobs) < w.batchSize {
		select {
		case <-ctx.Done():
			return batch

		case <-w.stopChan:
			return batch

		case <-timeout.C:
			// Timeout atteint, traiter le batch même s'il n'est pas plein
			if len(batch.Jobs) > 0 {
				return batch
			}
			// Réinitialiser le timeout si le batch est vide
			timeout.Reset(w.batchTimeout)

		case job := <-w.queue:
			batch.Jobs = append(batch.Jobs, job)
			// Si le batch est plein, le traiter immédiatement
			if len(batch.Jobs) >= w.batchSize {
				return batch
			}
		}
	}

	return batch
}

// processBatch traite un lot d'analytics
// T0387: Create Playback Analytics Batch Processing
func (w *PlaybackAnalyticsWorker) processBatch(ctx context.Context, batch Batch, workerID int) {
	logger := w.logger.With(
		zap.Int("worker_id", workerID),
		zap.Int("batch_size", len(batch.Jobs)))

	logger.Info("Processing analytics batch")

	// Convertir les jobs en analytics
	analyticsList := make([]*models.PlaybackAnalytics, 0, len(batch.Jobs))
	for _, job := range batch.Jobs {
		analyticsList = append(analyticsList, job.Analytics)
	}

	// Créer un contexte avec timeout pour le traitement du batch
	batchCtx, cancel := context.WithTimeout(ctx, 30*time.Second)
	defer cancel()

	// Traiter le batch
	startTime := time.Now()
	err := w.analyticsService.RecordPlaybackBatch(batchCtx, analyticsList)
	duration := time.Since(startTime)

	if err != nil {
		logger.Error("Batch processing failed",
			zap.Error(err),
			zap.Duration("duration", duration))

		// Retry les jobs individuellement si le batch échoue
		w.retryFailedJobs(ctx, batch.Jobs, err, workerID)
	} else {
		logger.Info("Batch processed successfully",
			zap.Int("count", len(batch.Jobs)),
			zap.Duration("duration", duration))
	}
}

// retryFailedJobs réessaie les jobs qui ont échoué
// T0387: Create Playback Analytics Batch Processing
func (w *PlaybackAnalyticsWorker) retryFailedJobs(ctx context.Context, jobs []AnalyticsJob, batchError error, workerID int) {
	logger := w.logger.With(
		zap.Int("worker_id", workerID),
		zap.Int("failed_jobs", len(jobs)))

	logger.Warn("Retrying failed analytics jobs",
		zap.Error(batchError))

	for _, job := range jobs {
		// Vérifier si on peut encore retry
		if job.Retries >= w.maxRetries {
			logger.Error("Job exceeded max retries, dropping",
				zap.String("job_id", job.ID.String()),
				zap.Int("retries", job.Retries))
			continue
		}

		// Incrémenter le compteur de retries
		job.Retries++

		// Exponential backoff via time.AfterFunc (non-blocking)
		delay := time.Duration(job.Retries) * time.Second
		
		// Capture variable for usage in closure
		jobToRetry := job
		
		time.AfterFunc(delay, func() {
			// Ré-enqueue le job
			select {
			case w.queue <- jobToRetry:
				logger.Debug("Job re-enqueued for retry",
					zap.String("job_id", jobToRetry.ID.String()),
					zap.Int("retries", jobToRetry.Retries))
			default:
				logger.Warn("Queue full, cannot retry job",
					zap.String("job_id", jobToRetry.ID.String()))
			}
		})
	}
}

// GetQueueSize retourne la taille actuelle de la queue
func (w *PlaybackAnalyticsWorker) GetQueueSize() int {
	return len(w.queue)
}

// GetStats retourne les statistiques du worker
type WorkerStats struct {
	Running      bool          `json:"running"`
	QueueSize    int           `json:"queue_size"`
	Workers      int           `json:"workers"`
	MaxRetries   int           `json:"max_retries"`
	BatchSize    int           `json:"batch_size"`
	BatchTimeout time.Duration `json:"batch_timeout"`
}

func (w *PlaybackAnalyticsWorker) GetStats() WorkerStats {
	w.mu.RLock()
	defer w.mu.RUnlock()

	return WorkerStats{
		Running:      w.running,
		QueueSize:    len(w.queue),
		Workers:      w.processingWorkers,
		MaxRetries:   w.maxRetries,
		BatchSize:    w.batchSize,
		BatchTimeout: w.batchTimeout,
	}
}