package workers

import (
	"context"
	"time"

	"veza-backend-api/internal/core/education"
	"veza-backend-api/internal/services"

	"go.uber.org/zap"
	"gorm.io/gorm"
)

// VideoTranscodeWorker processes video transcoding jobs for course lessons
type VideoTranscodeWorker struct {
	db               *gorm.DB
	transcodeService *services.VideoTranscodeService
	educationService *education.Service
	logger           *zap.Logger
	pollInterval     time.Duration
	stopChan         chan struct{}
}

// NewVideoTranscodeWorker creates a new video transcoding worker
func NewVideoTranscodeWorker(
	db *gorm.DB,
	transcodeService *services.VideoTranscodeService,
	educationService *education.Service,
	logger *zap.Logger,
	pollInterval time.Duration,
) *VideoTranscodeWorker {
	if logger == nil {
		logger = zap.NewNop()
	}
	if pollInterval == 0 {
		pollInterval = 10 * time.Second
	}

	return &VideoTranscodeWorker{
		db:               db,
		transcodeService: transcodeService,
		educationService: educationService,
		logger:           logger,
		pollInterval:     pollInterval,
		stopChan:         make(chan struct{}),
	}
}

// Start begins polling for pending video transcoding jobs
func (w *VideoTranscodeWorker) Start(ctx context.Context) {
	w.logger.Info("Starting video transcode worker", zap.Duration("poll_interval", w.pollInterval))
	go w.processLoop(ctx)
}

// Stop stops the worker
func (w *VideoTranscodeWorker) Stop() {
	w.logger.Info("Stopping video transcode worker")
	close(w.stopChan)
}

func (w *VideoTranscodeWorker) processLoop(ctx context.Context) {
	ticker := time.NewTicker(w.pollInterval)
	defer ticker.Stop()

	for {
		select {
		case <-ctx.Done():
			return
		case <-w.stopChan:
			return
		case <-ticker.C:
			w.processNext(ctx)
		}
	}
}

func (w *VideoTranscodeWorker) processNext(ctx context.Context) {
	// Find a lesson with pending transcoding and a video file
	var lesson education.Lesson
	err := w.db.WithContext(ctx).
		Where("transcoding_status = ? AND video_file_path != ''", string(education.TranscodingPending)).
		Order("created_at ASC").
		First(&lesson).Error
	if err != nil {
		return // no pending jobs or error
	}

	w.logger.Info("Processing video transcoding",
		zap.String("lesson_id", lesson.ID.String()),
		zap.String("video_path", lesson.VideoFilePath),
	)

	// Mark as processing
	if err := w.educationService.UpdateLessonTranscoding(ctx, lesson.ID, education.TranscodingProcessing, "", 0); err != nil {
		w.logger.Error("Failed to mark lesson as processing", zap.Error(err))
		return
	}

	// Transcode
	result, err := w.transcodeService.TranscodeVideo(ctx, lesson.ID, lesson.VideoFilePath)
	if err != nil {
		w.logger.Error("Video transcoding failed",
			zap.String("lesson_id", lesson.ID.String()),
			zap.Error(err),
		)
		if updateErr := w.educationService.UpdateLessonTranscoding(ctx, lesson.ID, education.TranscodingFailed, "", 0); updateErr != nil {
			w.logger.Error("Failed to mark lesson as failed", zap.Error(updateErr))
		}
		return
	}

	// Mark as complete
	if err := w.educationService.UpdateLessonTranscoding(ctx, lesson.ID, education.TranscodingComplete, result.MasterPlaylistURL, result.DurationSeconds); err != nil {
		w.logger.Error("Failed to mark lesson as complete", zap.Error(err))
		return
	}

	w.logger.Info("Video transcoding completed",
		zap.String("lesson_id", lesson.ID.String()),
		zap.String("hls_url", result.MasterPlaylistURL),
		zap.Int("duration_seconds", result.DurationSeconds),
	)
}