Kirika/audio/format/guess/guess.go

package guess

import (
	"errors"
	"git.gammaspectra.live/S.O.N.G/Kirika/audio"
	"git.gammaspectra.live/S.O.N.G/Kirika/audio/format"
	"io"
	"path"
	"strings"
)

type NullFormat struct {
	name string
}

func (f NullFormat) Name() string {
	return f.name
}

func (f NullFormat) DecoderDescription() string {
	return "null"
}

func (f NullFormat) EncoderDescription() string {
	return "null"
}

func (f NullFormat) Open(io.ReadSeekCloser) (audio.Source, error) {
	return nil, errors.New("null format")
}

func (f NullFormat) OpenAnalyzer(io.ReadSeekCloser) (audio.Source, format.AnalyzerChannel, error) {
	return nil, nil, errors.New("null format")
}

func (f NullFormat) Encode(audio.Source, io.WriteCloser, map[string]interface{}) error {
	return errors.New("null format")
}

func (f NullFormat) Identify([format.IdentifyPeekBytes]byte, string) bool {
	return false
}

var knownFormats []format.Format

func AddFormat(format format.Format) {
	knownFormats = append(knownFormats, format)
}

func GetFormat(name string) format.Format {
	for _, formatEntry := range knownFormats {
		if formatEntry.Name() == name {
			return formatEntry
		}
	}

	return NullFormat{
		name: name,
	}
}

func GetDecoder(name string) format.Decoder {
	for _, formatEntry := range knownFormats {
		if decoder, ok := formatEntry.(format.Decoder); ok && formatEntry.Name() == name {
			return decoder
		}
	}

	return NullFormat{
		name: name,
	}
}

func GetAnalyzerDecoder(name string) format.AnalyzerDecoder {
	for _, formatEntry := range knownFormats {
		if decoder, ok := formatEntry.(format.AnalyzerDecoder); ok && formatEntry.Name() == name {
			return decoder
		}
	}

	return NullFormat{
		name: name,
	}
}

func GetEncoder(name string) format.Encoder {
	for _, formatEntry := range knownFormats {
		if encoder, ok := formatEntry.(format.Encoder); ok && formatEntry.Name() == name {
			return encoder
		}
	}

	return NullFormat{
		name: name,
	}
}

func GetDecoders(r io.ReadSeekCloser, pathName string) (decoders []format.Decoder, err error) {
	extension := strings.ToLower(strings.TrimPrefix(path.Ext(pathName), "."))

	var startOffset int64
	startOffset, err = r.Seek(0, io.SeekCurrent)
	if err != nil {
		return
	}
	var peek [format.IdentifyPeekBytes]byte
	if _, err = r.Read(peek[:]); err != nil {
		return
	}
	if _, err = r.Seek(startOffset, io.SeekStart); err != nil {
		return
	}

	for _, formatEntry := range knownFormats {
		if decoder, ok := formatEntry.(format.Decoder); ok {
			if decoder.Identify(peek, extension) {
				decoders = append(decoders, decoder)
			}
		}
	}

	if len(decoders) == 0 {
		return nil, errors.New("could not find decoder")
	}

	return
}

func Open(r io.ReadSeekCloser, decoders []format.Decoder) (source audio.Source, err error) {
	var startOffset int64
	startOffset, err = r.Seek(0, io.SeekCurrent)

	for _, decoder := range decoders {
		if _, err = r.Seek(startOffset, io.SeekStart); err != nil {
			return
		}
		source, err = decoder.Open(r)
		if source != nil && err == nil {
			return
		}
	}

	//seek back
	if _, err = r.Seek(startOffset, io.SeekStart); err != nil {
		return
	}
	return nil, errors.New("could not open stream")
}

func OpenAnalyzer(r io.ReadSeekCloser, decoders []format.Decoder) (source audio.Source, analyzerChannel format.AnalyzerChannel, err error) {
	var startOffset int64
	startOffset, err = r.Seek(0, io.SeekCurrent)

	for _, decoder := range decoders {
		if analyzer, ok := decoder.(format.AnalyzerDecoder); ok {
			if _, err = r.Seek(startOffset, io.SeekStart); err != nil {
				return
			}
			source, analyzerChannel, err = analyzer.OpenAnalyzer(r)
			if source != nil && err == nil {
				return
			}
		}
	}

	//seek back
	if _, err = r.Seek(startOffset, io.SeekStart); err != nil {
		return
	}
	return nil, nil, errors.New("could not open stream analyzer")
}