// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
// SPDX-License-Identifier: MIT

package opus

import "errors"

var (
	errShortPacket          = errors.New("packet is not large enough")
	errNilPacket            = errors.New("invalid nil packet")
	errTooManyPDiff         = errors.New("too many PDiff")
	errTooManySpatialLayers = errors.New("too many spatial layers")
	errUnhandledNALUType    = errors.New("NALU Type is unhandled")

	// AV1 Errors
	errIsKeyframeAndFragment = errors.New("bits Z and N are set. Not possible to have OBU be tail fragment and be keyframe")
)

// audioDepacketizer is a mixin for audio codec depacketizers
type audioDepacketizer struct{}

func (d *audioDepacketizer) IsPartitionTail(_ bool, _ []byte) bool {
	return true
}

func (d *audioDepacketizer) IsPartitionHead(_ []byte) bool {
	return true
}

// Payloader payloads Opus packets
type Payloader struct{}

// Payload fragments an Opus packet across one or more byte arrays
func (p *Payloader) Payload(_ uint16, payload []byte) [][]byte {
	if payload == nil {
		return [][]byte{}
	}

	out := make([]byte, len(payload))
	copy(out, payload)
	return [][]byte{out}
}

// OpusPacket represents the Opus header that is stored in the payload of an RTP Packet
type OpusPacket struct {
	Payload []byte

	audioDepacketizer
}

// Unmarshal parses the passed byte slice and stores the result in the OpusPacket this method is called upon
func (p *OpusPacket) Unmarshal(packet []byte) ([]byte, error) {
	if packet == nil {
		return nil, errNilPacket
	} else if len(packet) == 0 {
		return nil, errShortPacket
	}

	p.Payload = packet
	return packet, nil
}

// OpusPartitionHeadChecker checks Opus partition head.
//
// Deprecated: replaced by OpusPacket.IsPartitionHead()
type OpusPartitionHeadChecker struct{}

// IsPartitionHead checks whether if this is a head of the Opus partition.
//
// Deprecated: replaced by OpusPacket.IsPartitionHead()
func (*OpusPartitionHeadChecker) IsPartitionHead(packet []byte) bool {
	return (&OpusPacket{}).IsPartitionHead(packet)
}