MeteorLight/listener/icy/icy.go

package icy

import (
	"fmt"
	"git.gammaspectra.live/S.O.N.G/Kirika/audio/packetizer"
	"git.gammaspectra.live/S.O.N.G/MeteorLight/listener"
	"git.gammaspectra.live/S.O.N.G/MeteorLight/queue/metadata"
	"strconv"
	"sync/atomic"
)

// icyInterval weird clients might not support other numbers than this
const icyInterval = 8192

type Listener struct {
	information         listener.Information
	started             atomic.Bool
	streamStartOffset   int64
	streamSamplesBuffer int64

	counter int

	writer      listener.WriterFunc
	waiter      chan struct{}
	offsetStart bool

	pendingMetadata map[string]string
}

func NewListener(info listener.Information, writer listener.WriterFunc, samplesToBuffer int64, offsetStart bool) (*Listener, map[string]string) {
	headers := make(map[string]string)
	headers["icy-metaint"] = strconv.Itoa(icyInterval)

	return &Listener{
		information:         info,
		writer:              writer,
		offsetStart:         offsetStart,
		streamSamplesBuffer: samplesToBuffer,
		streamStartOffset:   -1,
		pendingMetadata:     make(map[string]string),
		waiter:              make(chan struct{}),
	}, headers
}

func (l *Listener) Wait() {
	<-l.waiter
}

func (l *Listener) Identifier() string {
	return l.information.Identifier
}

func (l *Listener) Information() *listener.Information {
	return &l.information
}

func (l *Listener) HasStarted() bool {
	return l.started.Load()
}

func (l *Listener) Start(packets []packetizer.Packet) error {
	if l.started.Swap(true) {
		return nil
	}

	if len(packets) > 0 {
		sampleBufferMin := packets[len(packets)-1].GetStartSampleNumber() - l.streamSamplesBuffer
		for _, p := range packets {
			if p.KeepMode() != packetizer.Discard || p.GetEndSampleNumber() >= sampleBufferMin {
				if err := l.Write(p); err != nil {
					return err
				}
			}
		}
	}
	return nil
}

func (l *Listener) writeIcy() []byte {
	packetContent := make([]byte, 1, 16*255+1)
	for k, v := range l.pendingMetadata {
		packetContent = append(packetContent, []byte(fmt.Sprintf("%s='%s';", k, v))...)
		delete(l.pendingMetadata, k)

		//shouldn't send multiple properties in same packet if we want working single quotes, wait until next ICY frame
		break
	}

	contentLength := len(packetContent) - 1
	if contentLength > 16*255 {
		//cannot send long titles
		return make([]byte, 1)
	}

	if (contentLength % 16) == 0 { //already padded
		packetContent[0] = byte(contentLength / 16)
	} else {
		packetContent[0] = byte(contentLength/16) + 1
		packetContent = append(packetContent, make([]byte, 16-(contentLength%16))...)
	}

	return packetContent
}

func (l *Listener) Write(packet packetizer.Packet) error {

	if metadataPacket, ok := packet.(*metadata.Packet); ok {
		if len(metadataPacket.TrackEntry.Artist()) > 0 {
			l.pendingMetadata["StreamTitle"] = fmt.Sprintf("%s - %s", metadataPacket.TrackEntry.Artist(), metadataPacket.TrackEntry.Title())
		} else {
			l.pendingMetadata["StreamTitle"] = metadataPacket.TrackEntry.Title()
		}
		if len(metadataPacket.TrackEntry.Metadata.Art) > 0 {
			l.pendingMetadata["StreamURL"] = metadataPacket.TrackEntry.Metadata.Art
		}
		return nil
	}

	var p []byte
	if offsetable, ok := packet.(packetizer.OffsetablePacket); l.offsetStart && ok {
		if l.streamStartOffset <= -1 {
			if offsetable.KeepMode() != packetizer.Keep {
				l.streamStartOffset = offsetable.GetStartSampleNumber()
				p = offsetable.GetDataOffset(l.streamStartOffset)
			} else {
				p = packet.GetData()
			}
		} else {
			p = offsetable.GetDataOffset(l.streamStartOffset)
		}
	} else {
		p = packet.GetData()
	}

	var data []byte
	for len(p) > 0 {
		length := icyInterval - l.counter
		if length <= len(p) {
			data = append(data, p[:length]...)
			data = append(data, l.writeIcy()...)
			l.counter = 0
			p = p[length:]
		} else {
			data = append(data, p...)
			l.counter += len(p)
			p = p[:0]
		}
	}

	return l.writer(data)
}

func (l *Listener) Close() {
	_ = l.writer(nil)
	close(l.waiter)
}