package music

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"

	"jsuse.com/dev/dec-music/decrypt"
	"jsuse.com/dev/dec-music/internal/fileutil"
	"jsuse.com/dev/dec-music/internal/sniff"
	"jsuse.com/dev/dec-music/log"

	_ "jsuse.com/dev/dec-music/decrypt/kgm"
	_ "jsuse.com/dev/dec-music/decrypt/kwm"
	_ "jsuse.com/dev/dec-music/decrypt/ncm"
	_ "jsuse.com/dev/dec-music/decrypt/qmc"
	_ "jsuse.com/dev/dec-music/decrypt/tm"
	_ "jsuse.com/dev/dec-music/decrypt/xiami"
	_ "jsuse.com/dev/dec-music/decrypt/ximalaya"
)

const (
	// ErrNoDecoder is returned when no decoder can handle the file.
	ErrNoDecoder = "no suitable decoder"
)

var defaultLogger = log.New()

// OnProcess is called after each file is processed (err empty on success).
type OnProcess func(src, dst, err string)

// DecryptFile decrypts a single file into outputDir.
func DecryptFile(inputFile, outputDir string, noSubOutput bool, onProcess OnProcess) error {
	inputDir, err := filepath.Abs(filepath.Dir(inputFile))
	if err != nil {
		return err
	}
	outDir, err := filepath.Abs(outputDir)
	if err != nil {
		return err
	}
	return decryptProcessFile(inputFile, outDir, inputDir, noSubOutput, false, false, onProcess)
}

func decryptProcessFile(inputFile, outputDir, inputDir string, noSubOutput, skipNoop, overwrite bool, onProcess OnProcess) error {
	proc := &processor{
		onProcess:       onProcess,
		logger:          defaultLogger,
		inputDir:        inputDir,
		outputDir:       outputDir,
		singleOutput:    noSubOutput,
		skipNoopDecoder: skipNoop,
		overwriteOutput: overwrite,
	}
	return proc.processFile(inputFile)
}

// DecryptProcess decrypts encrypted media under inputDir into outputDir.
// When noSubOutput is false, relative subdirectory structure is preserved.
func DecryptProcess(inputDir, outputDir string, noSubOutput bool, onProcess OnProcess) error {
	return decryptProcessEx(inputDir, outputDir, noSubOutput, false, false, onProcess)
}

// DecryptProcessCLI is like DecryptProcess but accepts skip-noop and overwrite (CLI helper).
func DecryptProcessCLI(inputDir, outputDir string, noSubOutput, skipNoop, overwrite bool) error {
	return decryptProcessEx(inputDir, outputDir, noSubOutput, skipNoop, overwrite, nil)
}

// DecryptFileCLI decrypts one file (CLI helper).
func DecryptFileCLI(inputFile, outputDir string, noSubOutput, skipNoop, overwrite bool) error {
	inputDir, err := filepath.Abs(filepath.Dir(inputFile))
	if err != nil {
		return err
	}
	outDir, err := filepath.Abs(outputDir)
	if err != nil {
		return err
	}
	return decryptProcessFile(inputFile, outDir, inputDir, noSubOutput, skipNoop, overwrite, nil)
}

func decryptProcessEx(inputDir, outputDir string, noSubOutput, skipNoop, overwrite bool, onProcess OnProcess) error {
	proc := &processor{
		onProcess:       onProcess,
		logger:          defaultLogger,
		inputDir:        inputDir,
		outputDir:       outputDir,
		singleOutput:    noSubOutput,
		skipNoopDecoder: skipNoop,
		overwriteOutput: overwrite,
	}
	return proc.processDir(inputDir)
}

type processor struct {
	onProcess       OnProcess
	logger          *log.Logger
	inputDir        string
	outputDir       string
	skipNoopDecoder bool
	overwriteOutput bool
	singleOutput    bool
}

func (p *processor) processDir(inputDir string) error {
	items, err := os.ReadDir(inputDir)
	if err != nil {
		return err
	}

	var lastError error
	for _, item := range items {
		if strings.EqualFold(item.Name(), "temp") {
			continue
		}
		filePath := filepath.Join(inputDir, item.Name())
		if item.IsDir() {
			if err = p.processDir(filePath); err != nil {
				lastError = err
			}
			continue
		}
		if !fileutil.IsMediaFile(item.Name()) {
			continue
		}
		if err = p.processFile(filePath); err != nil {
			lastError = err
			if p.logger != nil {
				p.logger.Error("conversion failed:", item.Name(), err)
			}
		}
	}
	if lastError != nil {
		return fmt.Errorf("last error: %w", lastError)
	}
	return nil
}

func (p *processor) processFile(filePath string) error {
	factories := decrypt.GetDecoder(filePath, p.skipNoopDecoder)
	if len(factories) == 0 {
		return errors.New("skipping while no suitable decoder")
	}

	if err := p.process(filePath, factories); err != nil {
		if err.Error() == ErrNoDecoder {
			// Fallback: copy as-is when no decoder matches (keeps original extension).
			fallbackDst := filepath.Join(p.outputDir, filepath.Base(filePath))
			copyErr := p.copyFile(filePath, fallbackDst)
			if copyErr == nil {
				p.logResult(filePath, fallbackDst)
			}
			return copyErr
		}
		return err
	}
	return nil
}

func (p *processor) logResult(inputFile, outPath string) {
	inputRelDir, err := filepath.Rel(p.inputDir, filepath.Dir(inputFile))
	dstName := filepath.Base(outPath)
	if !p.singleOutput {
		dstName = filepath.Join(inputRelDir, filepath.Base(outPath))
	}
	srcName := filepath.Join(inputRelDir, filepath.Base(inputFile))
	if err != nil {
		if p.onProcess != nil {
			p.onProcess(srcName, dstName, err.Error())
		}
		return
	}
	if p.onProcess != nil {
		p.onProcess(srcName, dstName, "")
	} else {
		log.PrintSuccess(srcName, dstName)
	}
}

func (p *processor) copyFile(src, dst string) error {
	sourceFile, err := os.Open(src)
	if err != nil {
		return err
	}
	defer sourceFile.Close()

	destFile, err := os.OpenFile(dst, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
	if err != nil {
		return err
	}
	defer destFile.Close()

	_, err = io.Copy(destFile, sourceFile)
	return err
}

func (p *processor) findDecoder(factories []decrypt.Factory, params *decrypt.DecoderParams) (decrypt.Decoder, *decrypt.Factory, error) {
	for i := range factories {
		factory := &factories[i]
		dec := factory.Create(params)
		if err := dec.Validate(); err == nil {
			return dec, factory, nil
		}
	}
	return nil, nil, errors.New("no any decoder can resolve the file")
}

func (p *processor) process(inputFile string, factories []decrypt.Factory) error {
	file, err := os.Open(inputFile)
	if err != nil {
		return err
	}
	defer file.Close()

	params := &decrypt.DecoderParams{
		Reader:    file,
		Extension: filepath.Ext(inputFile),
		FilePath:  inputFile,
		Logger:    p.logger,
	}

	dec, factory, err := p.findDecoder(factories, params)
	if err != nil {
		return errors.New(ErrNoDecoder)
	}

	header := bytes.NewBuffer(nil)
	if _, err = io.CopyN(header, dec, 64); err != nil {
		return fmt.Errorf("read header failed: %w", err)
	}
	audio := io.MultiReader(header, dec)
	audioExt := sniff.AudioExtensionWithFallback(header.Bytes(), ".mp3")

	inputRelDir, err := filepath.Rel(p.inputDir, filepath.Dir(inputFile))
	if err != nil {
		return fmt.Errorf("get relative dir failed: %w", err)
	}

	inFilename := strings.TrimSuffix(filepath.Base(inputFile), factory.Suffix)
	outFolder := p.outputDir
	if !p.singleOutput {
		outFolder = filepath.Join(p.outputDir, inputRelDir)
	}
	if err = os.MkdirAll(outFolder, os.ModePerm); err != nil {
		return err
	}
	outPath := filepath.Join(outFolder, inFilename+audioExt)

	if !p.overwriteOutput {
		if _, err := os.Stat(outPath); err == nil {
			if p.logger != nil {
				p.logger.Info("output already exists, skipped:", outPath)
			}
			return nil
		} else if !errors.Is(err, os.ErrNotExist) {
			return fmt.Errorf("stat output file failed: %w", err)
		}
	}

	outFile, err := os.OpenFile(outPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
	if err != nil {
		return err
	}
	defer outFile.Close()

	if _, err = io.Copy(outFile, audio); err != nil {
		return err
	}

	p.logResult(inputFile, outPath)
	return nil
}