package sync

import (
	"fmt"
	"path/filepath"
	"strings"

	"sub-cli/internal/format/lrc"
	"sub-cli/internal/model"
)

// SyncLyrics synchronizes the timeline of a source lyrics file with a target lyrics file
func SyncLyrics(sourceFile, targetFile string) error {
	sourceFmt := strings.TrimPrefix(filepath.Ext(sourceFile), ".")
	targetFmt := strings.TrimPrefix(filepath.Ext(targetFile), ".")
	
	// Currently only supports LRC files
	if sourceFmt != "lrc" || targetFmt != "lrc" {
		return fmt.Errorf("sync only supports LRC files currently")
	}
	
	source, err := lrc.Parse(sourceFile)
	if err != nil {
		return fmt.Errorf("error parsing source file: %w", err)
	}
	
	target, err := lrc.Parse(targetFile)
	if err != nil {
		return fmt.Errorf("error parsing target file: %w", err)
	}
	
	// Apply timeline from source to target
	syncedLyrics := syncTimeline(source, target)
	
	// Write the synced lyrics to the target file
	return lrc.Generate(syncedLyrics, targetFile)
}

// syncTimeline applies the timeline from the source lyrics to the target lyrics
func syncTimeline(source, target model.Lyrics) model.Lyrics {
	result := model.Lyrics{
		Metadata: target.Metadata,
		Content:  target.Content,
	}
	
	// Use source timeline if available and lengths match
	if len(source.Timeline) > 0 && len(source.Timeline) == len(target.Content) {
		result.Timeline = source.Timeline
	} else if len(source.Timeline) > 0 {
		// If lengths don't match, scale timeline
		result.Timeline = scaleTimeline(source.Timeline, len(target.Content))
	}
	
	return result
}

// scaleTimeline scales a timeline to match a different number of entries
func scaleTimeline(timeline []model.Timestamp, targetCount int) []model.Timestamp {
	if targetCount <= 0 || len(timeline) == 0 {
		return []model.Timestamp{}
	}
	
	result := make([]model.Timestamp, targetCount)
	
	if targetCount == 1 {
		result[0] = timeline[0]
		return result
	}
	
	sourceLength := len(timeline)
	
	for i := 0; i < targetCount; i++ {
		// Scale index to match source timeline
		sourceIndex := i * (sourceLength - 1) / (targetCount - 1)
		result[i] = timeline[sourceIndex]
	}
	
	return result
}