VideoTools/internal/thumbnail/generator.go

package thumbnail

import (
	"context"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
)

// Config contains configuration for thumbnail generation
type Config struct {
	VideoPath      string
	OutputDir      string
	Count          int     // Number of thumbnails to generate
	Interval       float64 // Interval in seconds between thumbnails (alternative to Count)
	Width          int     // Thumbnail width (0 = auto based on height)
	Height         int     // Thumbnail height (0 = auto based on width)
	Quality        int     // JPEG quality 1-100 (0 = PNG lossless)
	Format         string  // "png" or "jpg"
	StartOffset    float64 // Start generating from this timestamp
	EndOffset      float64 // Stop generating before this timestamp
	ContactSheet   bool    // Generate a single contact sheet instead of individual files
	Columns        int     // Contact sheet columns (if ContactSheet=true)
	Rows           int     // Contact sheet rows (if ContactSheet=true)
	ShowTimestamp  bool    // Overlay timestamp on thumbnails
	ShowMetadata   bool    // Show metadata header on contact sheet
}

// Generator creates thumbnails from videos
type Generator struct {
	FFmpegPath string
}

// NewGenerator creates a new thumbnail generator
func NewGenerator(ffmpegPath string) *Generator {
	return &Generator{
		FFmpegPath: ffmpegPath,
	}
}

// Thumbnail represents a generated thumbnail
type Thumbnail struct {
	Path      string
	Timestamp float64
	Width     int
	Height    int
	Size      int64
}

// GenerateResult contains the results of thumbnail generation
type GenerateResult struct {
	Thumbnails    []Thumbnail
	ContactSheet  string // Path to contact sheet if generated
	TotalDuration float64
	VideoWidth    int
	VideoHeight   int
	VideoFPS      float64
	VideoCodec    string
	AudioCodec    string
	FileSize      int64
	Error         string
}

// Generate creates thumbnails based on the provided configuration
func (g *Generator) Generate(ctx context.Context, config Config) (*GenerateResult, error) {
	result := &GenerateResult{}

	// Validate config
	if config.VideoPath == "" {
		return nil, fmt.Errorf("video path is required")
	}
	if config.OutputDir == "" {
		return nil, fmt.Errorf("output directory is required")
	}

	// Create output directory if it doesn't exist
	if err := os.MkdirAll(config.OutputDir, 0755); err != nil {
		return nil, fmt.Errorf("failed to create output directory: %w", err)
	}

	// Set defaults
	if config.Count == 0 && config.Interval == 0 {
		config.Count = 9 // Default to 9 thumbnails (3x3 grid)
	}
	if config.Format == "" {
		config.Format = "jpg"
	}
	if config.Quality == 0 && config.Format == "jpg" {
		config.Quality = 85
	}
	if config.ContactSheet {
		if config.Columns == 0 {
			config.Columns = 3
		}
		if config.Rows == 0 {
			config.Rows = 3
		}
	}

	// Get video duration and dimensions
	duration, width, height, err := g.getVideoInfo(ctx, config.VideoPath)
	if err != nil {
		return nil, fmt.Errorf("failed to get video info: %w", err)
	}
	result.TotalDuration = duration
	result.VideoWidth = width
	result.VideoHeight = height

	// Calculate thumbnail dimensions
	thumbWidth, thumbHeight := g.calculateDimensions(width, height, config.Width, config.Height)

	if config.ContactSheet {
		// Generate contact sheet
		contactSheetPath, err := g.generateContactSheet(ctx, config, duration, thumbWidth, thumbHeight)
		if err != nil {
			result.Error = err.Error()
			return result, err
		}
		result.ContactSheet = contactSheetPath

		// Get file size
		if fi, err := os.Stat(contactSheetPath); err == nil {
			result.Thumbnails = []Thumbnail{{
				Path:      contactSheetPath,
				Timestamp: 0,
				Width:     thumbWidth * config.Columns,
				Height:    thumbHeight * config.Rows,
				Size:      fi.Size(),
			}}
		}
	} else {
		// Generate individual thumbnails
		thumbnails, err := g.generateIndividual(ctx, config, duration, thumbWidth, thumbHeight)
		if err != nil {
			result.Error = err.Error()
			return result, err
		}
		result.Thumbnails = thumbnails
	}

	return result, nil
}

// getVideoInfo retrieves duration and dimensions from a video file
func (g *Generator) getVideoInfo(ctx context.Context, videoPath string) (duration float64, width, height int, err error) {
	// Use ffprobe to get video information
	cmd := exec.CommandContext(ctx, "ffprobe",
		"-v", "error",
		"-select_streams", "v:0",
		"-show_entries", "stream=width,height,duration",
		"-show_entries", "format=duration",
		"-of", "default=noprint_wrappers=1",
		videoPath,
	)

	output, err := cmd.Output()
	if err != nil {
		return 0, 0, 0, fmt.Errorf("ffprobe failed: %w", err)
	}

	// Parse output
	var w, h int
	var d float64
	_, _ = fmt.Sscanf(string(output), "width=%d\nheight=%d\nduration=%f", &w, &h, &d)

	// If stream duration not available, try format duration
	if d == 0 {
		_, _ = fmt.Sscanf(string(output), "width=%d\nheight=%d\nwidth=%*d\nheight=%*d\nduration=%f", &w, &h, &d)
	}

	if w == 0 || h == 0 || d == 0 {
		return 0, 0, 0, fmt.Errorf("failed to parse video info")
	}

	return d, w, h, nil
}

// calculateDimensions determines thumbnail dimensions maintaining aspect ratio
func (g *Generator) calculateDimensions(videoWidth, videoHeight, targetWidth, targetHeight int) (width, height int) {
	if targetWidth == 0 && targetHeight == 0 {
		// Default to 320 width
		targetWidth = 320
	}

	aspectRatio := float64(videoWidth) / float64(videoHeight)

	if targetWidth > 0 && targetHeight == 0 {
		// Calculate height from width
		width = targetWidth
		height = int(float64(width) / aspectRatio)
	} else if targetHeight > 0 && targetWidth == 0 {
		// Calculate width from height
		height = targetHeight
		width = int(float64(height) * aspectRatio)
	} else {
		// Both specified, use as-is
		width = targetWidth
		height = targetHeight
	}

	return width, height
}

// generateIndividual creates individual thumbnail files
func (g *Generator) generateIndividual(ctx context.Context, config Config, duration float64, thumbWidth, thumbHeight int) ([]Thumbnail, error) {
	var thumbnails []Thumbnail

	// Calculate timestamps
	timestamps := g.calculateTimestamps(config, duration)

	// Generate each thumbnail
	for i, ts := range timestamps {
		outputPath := filepath.Join(config.OutputDir, fmt.Sprintf("thumb_%04d.%s", i+1, config.Format))

		// Build FFmpeg command
		args := []string{
			"-ss", fmt.Sprintf("%.2f", ts),
			"-i", config.VideoPath,
			"-vf", fmt.Sprintf("scale=%d:%d", thumbWidth, thumbHeight),
			"-frames:v", "1",
			"-y",
		}

		// Add quality settings
		if config.Format == "jpg" {
			args = append(args, "-q:v", fmt.Sprintf("%d", 31-(config.Quality*30/100)))
		}

		// Add timestamp overlay if requested
		if config.ShowTimestamp {
			hours := int(ts) / 3600
			minutes := (int(ts) % 3600) / 60
			seconds := int(ts) % 60
			timeStr := fmt.Sprintf("%02d:%02d:%02d", hours, minutes, seconds)

			drawTextFilter := fmt.Sprintf("scale=%d:%d,drawtext=text='%s':fontcolor=white:fontsize=20:font='DejaVu Sans Mono':box=1:boxcolor=black@0.5:boxborderw=5:x=(w-text_w)/2:y=h-th-10",
				thumbWidth, thumbHeight, timeStr)

			// Replace scale filter with combined filter
			for j, arg := range args {
				if arg == "-vf" && j+1 < len(args) {
					args[j+1] = drawTextFilter
					break
				}
			}
		}

		args = append(args, outputPath)

		cmd := exec.CommandContext(ctx, g.FFmpegPath, args...)
		if err := cmd.Run(); err != nil {
			return nil, fmt.Errorf("failed to generate thumbnail %d: %w", i+1, err)
		}

		// Get file info
		fi, err := os.Stat(outputPath)
		if err != nil {
			return nil, fmt.Errorf("failed to stat thumbnail %d: %w", i+1, err)
		}

		thumbnails = append(thumbnails, Thumbnail{
			Path:      outputPath,
			Timestamp: ts,
			Width:     thumbWidth,
			Height:    thumbHeight,
			Size:      fi.Size(),
		})
	}

	return thumbnails, nil
}

// generateContactSheet creates a single contact sheet with all thumbnails
func (g *Generator) generateContactSheet(ctx context.Context, config Config, duration float64, thumbWidth, thumbHeight int) (string, error) {
	totalThumbs := config.Columns * config.Rows
	if config.Count > 0 && config.Count < totalThumbs {
		totalThumbs = config.Count
	}

	// Calculate timestamps
	tempConfig := config
	tempConfig.Count = totalThumbs
	tempConfig.Interval = 0
	timestamps := g.calculateTimestamps(tempConfig, duration)

	// Build select filter using timestamps (more reliable than frame numbers)
	// Use gte(t,timestamp) approach to select frames closest to target times
	selectFilter := "select='"
	for i, ts := range timestamps {
		if i > 0 {
			selectFilter += "+"
		}
		// Select frame at or after this timestamp, limiting to one frame per timestamp
		selectFilter += fmt.Sprintf("gte(t\\,%.2f)*lt(t\\,%.2f)", ts, ts+0.1)
	}
	selectFilter += "',setpts=N/TB"

	outputPath := filepath.Join(config.OutputDir, fmt.Sprintf("contact_sheet.%s", config.Format))

	// Build tile filter
	tileFilter := fmt.Sprintf("scale=%d:%d,tile=%dx%d", thumbWidth, thumbHeight, config.Columns, config.Rows)

	// Build video filter
	var vfilter string
	if config.ShowMetadata {
		// Add metadata header to contact sheet
		vfilter = g.buildMetadataFilter(config, duration, thumbWidth, thumbHeight, selectFilter, tileFilter)
	} else {
		vfilter = fmt.Sprintf("%s,%s", selectFilter, tileFilter)
	}

	// Build FFmpeg command
	args := []string{
		"-i", config.VideoPath,
		"-vf", vfilter,
		"-frames:v", "1",
		"-y",
	}

	if config.Format == "jpg" {
		args = append(args, "-q:v", fmt.Sprintf("%d", 31-(config.Quality*30/100)))
	}

	args = append(args, outputPath)

	cmd := exec.CommandContext(ctx, g.FFmpegPath, args...)
	if err := cmd.Run(); err != nil {
		return "", fmt.Errorf("failed to generate contact sheet: %w", err)
	}

	return outputPath, nil
}

// buildMetadataFilter creates a filter that adds metadata header to contact sheet
func (g *Generator) buildMetadataFilter(config Config, duration float64, thumbWidth, thumbHeight int, selectFilter, tileFilter string) string {
	// Get file info
	fileInfo, _ := os.Stat(config.VideoPath)
	fileSize := fileInfo.Size()
	fileSizeMB := float64(fileSize) / (1024 * 1024)

	// Get video info (we already have duration, just need dimensions)
	_, videoWidth, videoHeight, _ := g.getVideoInfo(context.Background(), config.VideoPath)

	// Format duration as HH:MM:SS
	hours := int(duration) / 3600
	minutes := (int(duration) % 3600) / 60
	seconds := int(duration) % 60
	durationStr := fmt.Sprintf("%02d\\:%02d\\:%02d", hours, minutes, seconds)

	// Get just the filename without path
	filename := filepath.Base(config.VideoPath)

	// Calculate sheet dimensions
	sheetWidth := thumbWidth * config.Columns
	sheetHeight := thumbHeight * config.Rows
	headerHeight := 80

	// Build metadata text lines
	// Line 1: Filename and file size
	line1 := fmt.Sprintf("%s (%.1f MB)", filename, fileSizeMB)
	// Line 2: Resolution, FPS, Duration
	line2 := fmt.Sprintf("%dx%d | Duration\\: %s", videoWidth, videoHeight, durationStr)

	// Create filter that:
	// 1. Generates contact sheet from selected frames
	// 2. Creates a blank header area with app background color
	// 3. Draws metadata text on header (using monospace font)
	// 4. Stacks header on top of contact sheet
	// App background color: #0B0F1A (dark blue)
	filter := fmt.Sprintf(
		"%s,%s,pad=%d:%d:0:%d:0x0B0F1A,"+
		"drawtext=text='%s':fontcolor=white:fontsize=14:font='DejaVu Sans Mono':x=10:y=10,"+
		"drawtext=text='%s':fontcolor=white:fontsize=12:font='DejaVu Sans Mono':x=10:y=35",
		selectFilter,
		tileFilter,
		sheetWidth,
		sheetHeight+headerHeight,
		headerHeight,
		line1,
		line2,
	)

	return filter
}

// calculateTimestamps generates timestamps for thumbnail extraction
func (g *Generator) calculateTimestamps(config Config, duration float64) []float64 {
	var timestamps []float64

	startTime := config.StartOffset
	endTime := duration - config.EndOffset
	if endTime <= startTime {
		endTime = duration
	}

	availableDuration := endTime - startTime

	if config.Interval > 0 {
		// Use interval mode
		for ts := startTime; ts < endTime; ts += config.Interval {
			timestamps = append(timestamps, ts)
		}
	} else {
		// Use count mode
		if config.Count <= 1 {
			// Single thumbnail at midpoint
			timestamps = append(timestamps, startTime+availableDuration/2)
		} else {
			// Distribute evenly
			step := availableDuration / float64(config.Count+1)
			for i := 1; i <= config.Count; i++ {
				ts := startTime + (step * float64(i))
				timestamps = append(timestamps, ts)
			}
		}
	}

	return timestamps
}

// ExtractFrame extracts a single frame at a specific timestamp
func (g *Generator) ExtractFrame(ctx context.Context, videoPath string, timestamp float64, outputPath string, width, height int) error {
	args := []string{
		"-ss", fmt.Sprintf("%.2f", timestamp),
		"-i", videoPath,
		"-frames:v", "1",
		"-y",
	}

	if width > 0 || height > 0 {
		if width == 0 {
			width = -1 // Auto
		}
		if height == 0 {
			height = -1 // Auto
		}
		args = append(args, "-vf", fmt.Sprintf("scale=%d:%d", width, height))
	}

	args = append(args, outputPath)

	cmd := exec.CommandContext(ctx, g.FFmpegPath, args...)
	if err := cmd.Run(); err != nil {
		return fmt.Errorf("failed to extract frame: %w", err)
	}

	return nil
}

// CleanupThumbnails removes all generated thumbnails
func CleanupThumbnails(outputDir string) error {
	return os.RemoveAll(outputDir)
}