package converter

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

	"sub-cli/internal/format/ass"
	"sub-cli/internal/format/lrc"
	"sub-cli/internal/format/srt"
	"sub-cli/internal/format/txt"
	"sub-cli/internal/format/vtt"
	"sub-cli/internal/model"
)

// ErrUnsupportedFormat is returned when trying to convert to/from an unsupported format
var ErrUnsupportedFormat = errors.New("unsupported format")

// Convert converts a file from one format to another
func Convert(sourceFile, targetFile string) error {
	sourceFmt := strings.TrimPrefix(filepath.Ext(sourceFile), ".")
	targetFmt := strings.TrimPrefix(filepath.Ext(targetFile), ".")

	// TXT only supports being a target format
	if sourceFmt == "txt" {
		return fmt.Errorf("%w: txt is only supported as a target format", ErrUnsupportedFormat)
	}

	// Convert source to intermediate representation
	subtitle, err := convertToIntermediate(sourceFile, sourceFmt)
	if err != nil {
		return err
	}

	// Convert from intermediate representation to target format
	return convertFromIntermediate(subtitle, targetFile, targetFmt)
}

// convertToIntermediate converts a source file to our intermediate Subtitle representation
func convertToIntermediate(sourceFile, sourceFormat string) (model.Subtitle, error) {
	switch sourceFormat {
	case "lrc":
		return lrc.ConvertToSubtitle(sourceFile)
	case "srt":
		return srt.ConvertToSubtitle(sourceFile)
	case "vtt":
		return vtt.ConvertToSubtitle(sourceFile)
	case "ass":
		return ass.ConvertToSubtitle(sourceFile)
	default:
		return model.Subtitle{}, fmt.Errorf("%w: %s", ErrUnsupportedFormat, sourceFormat)
	}
}

// convertFromIntermediate converts our intermediate Subtitle representation to a target format
func convertFromIntermediate(subtitle model.Subtitle, targetFile, targetFormat string) error {
	switch targetFormat {
	case "lrc":
		return lrc.ConvertFromSubtitle(subtitle, targetFile)
	case "srt":
		return srt.ConvertFromSubtitle(subtitle, targetFile)
	case "vtt":
		return vtt.ConvertFromSubtitle(subtitle, targetFile)
	case "ass":
		return ass.ConvertFromSubtitle(subtitle, targetFile)
	case "txt":
		return txt.GenerateFromSubtitle(subtitle, targetFile)
	default:
		return fmt.Errorf("%w: %s", ErrUnsupportedFormat, targetFormat)
	}
}