package rtmp

import (
	"bufio"
	"errors"
	"fmt"
	"net"
	"net/url"
	"time"

	"github.com/aler9/gortsplib"
	"github.com/aler9/gortsplib/pkg/aac"
	"github.com/notedit/rtmp/av"
	nhaac "github.com/notedit/rtmp/codec/aac"
	nh264 "github.com/notedit/rtmp/codec/h264"
	"github.com/notedit/rtmp/format/flv/flvio"
	"github.com/notedit/rtmp/format/rtmp"
)

const (
	readBufferSize  = 4096
	writeBufferSize = 4096
	codecH264       = 7
	codecAAC        = 10
)

// Conn is a RTMP connection.
type Conn struct {
	rconn *rtmp.Conn
}

// NewClientConn initializes a client-side connection.
func NewClientConn(nconn net.Conn, u *url.URL) *Conn {
	c := rtmp.NewConn(&bufio.ReadWriter{
		Reader: bufio.NewReaderSize(nconn, readBufferSize),
		Writer: bufio.NewWriterSize(nconn, writeBufferSize),
	})
	c.URL = u

	return &Conn{
		rconn: c,
	}
}

// NewServerConn initializes a server-side connection.
func NewServerConn(nconn net.Conn) *Conn {
	// https://github.com/aler9/rtmp/blob/master/format/rtmp/server.go#L46
	c := rtmp.NewConn(&bufio.ReadWriter{
		Reader: bufio.NewReaderSize(nconn, readBufferSize),
		Writer: bufio.NewWriterSize(nconn, writeBufferSize),
	})
	c.IsServer = true

	return &Conn{
		rconn: c,
	}
}

// ClientHandshake performs the handshake of a client-side connection.
func (c *Conn) ClientHandshake(isPlaying bool) error {
	var flag int
	if isPlaying {
		flag = rtmp.PrepareReading
	} else {
		flag = rtmp.PrepareWriting
	}
	return c.rconn.Prepare(rtmp.StageGotPublishOrPlayCommand, flag)
}

// ServerHandshake performs the handshake of a server-side connection.
func (c *Conn) ServerHandshake() error {
	return c.rconn.Prepare(rtmp.StageGotPublishOrPlayCommand, 0)
}

// IsPublishing returns whether the connection is publishing.
func (c *Conn) IsPublishing() bool {
	return c.rconn.Publishing
}

// URL returns the URL requested by the connection.
func (c *Conn) URL() *url.URL {
	return c.rconn.URL
}

// ReadPacket reads a packet.
func (c *Conn) ReadPacket() (av.Packet, error) {
	return c.rconn.ReadPacket()
}

// WritePacket writes a packet.
func (c *Conn) WritePacket(pkt av.Packet) error {
	err := c.rconn.WritePacket(pkt)
	if err != nil {
		return err
	}
	return c.rconn.FlushWrite()
}

func trackFromH264DecoderConfig(data []byte) (*gortsplib.TrackH264, error) {
	codec, err := nh264.FromDecoderConfig(data)
	if err != nil {
		return nil, err
	}

	return &gortsplib.TrackH264{
		PayloadType: 96,
		SPS:         codec.SPS[0],
		PPS:         codec.PPS[0],
	}, nil
}

func trackFromAACDecoderConfig(data []byte) (*gortsplib.TrackAAC, error) {
	var mpegConf aac.MPEG4AudioConfig
	err := mpegConf.Unmarshal(data)
	if err != nil {
		return nil, err
	}

	return &gortsplib.TrackAAC{
		PayloadType:      97,
		Config:           &mpegConf,
		SizeLength:       13,
		IndexLength:      3,
		IndexDeltaLength: 3,
	}, nil
}

var errEmptyMetadata = errors.New("metadata is empty")

func (c *Conn) readTracksFromMetadata(pkt av.Packet) (*gortsplib.TrackH264, *gortsplib.TrackAAC, error) {
	arr, err := flvio.ParseAMFVals(pkt.Data, false)
	if err != nil {
		return nil, nil, err
	}

	if len(arr) != 1 {
		return nil, nil, fmt.Errorf("invalid metadata")
	}

	md, ok := arr[0].(flvio.AMFMap)
	if !ok {
		return nil, nil, fmt.Errorf("invalid metadata")
	}

	hasVideo, err := func() (bool, error) {
		v, ok := md.GetV("videocodecid")
		if !ok {
			return false, nil
		}

		switch vt := v.(type) {
		case float64:
			switch vt {
			case 0:
				return false, nil

			case codecH264:
				return true, nil
			}

		case string:
			if vt == "avc1" {
				return true, nil
			}
		}

		return false, fmt.Errorf("unsupported video codec %v", v)
	}()
	if err != nil {
		return nil, nil, err
	}

	hasAudio, err := func() (bool, error) {
		v, ok := md.GetV("audiocodecid")
		if !ok {
			return false, nil
		}

		switch vt := v.(type) {
		case float64:
			switch vt {
			case 0:
				return false, nil

			case codecAAC:
				return true, nil
			}

		case string:
			if vt == "mp4a" {
				return true, nil
			}
		}

		return false, fmt.Errorf("unsupported audio codec %v", v)
	}()
	if err != nil {
		return nil, nil, err
	}

	if !hasVideo && !hasAudio {
		return nil, nil, errEmptyMetadata
	}

	var videoTrack *gortsplib.TrackH264
	var audioTrack *gortsplib.TrackAAC

	for {
		var pkt av.Packet
		pkt, err = c.ReadPacket()
		if err != nil {
			return nil, nil, err
		}

		switch pkt.Type {
		case av.H264DecoderConfig:
			if !hasVideo {
				return nil, nil, fmt.Errorf("unexpected video packet")
			}

			if videoTrack != nil {
				return nil, nil, fmt.Errorf("video track setupped twice")
			}

			videoTrack, err = trackFromH264DecoderConfig(pkt.Data)
			if err != nil {
				return nil, nil, err
			}

		case av.AACDecoderConfig:
			if !hasAudio {
				return nil, nil, fmt.Errorf("unexpected audio packet")
			}

			if audioTrack != nil {
				return nil, nil, fmt.Errorf("audio track setupped twice")
			}

			audioTrack, err = trackFromAACDecoderConfig(pkt.Data)
			if err != nil {
				return nil, nil, err
			}
		}

		if (!hasVideo || videoTrack != nil) &&
			(!hasAudio || audioTrack != nil) {
			return videoTrack, audioTrack, nil
		}
	}
}

func (c *Conn) readTracksFromPackets(pkt av.Packet) (*gortsplib.TrackH264, *gortsplib.TrackAAC, error) {
	startTime := pkt.Time
	var videoTrack *gortsplib.TrackH264
	var audioTrack *gortsplib.TrackAAC

	// analyze 1 second of packets
	for {
		switch pkt.Type {
		case av.H264DecoderConfig:
			if videoTrack == nil {
				var err error
				videoTrack, err = trackFromH264DecoderConfig(pkt.Data)
				if err != nil {
					return nil, nil, err
				}

				// stop the analysis if both tracks are found
				if videoTrack != nil && audioTrack != nil {
					return videoTrack, audioTrack, nil
				}
			}

		case av.AACDecoderConfig:
			if audioTrack == nil {
				var err error
				audioTrack, err = trackFromAACDecoderConfig(pkt.Data)
				if err != nil {
					return nil, nil, err
				}

				// stop the analysis if both tracks are found
				if videoTrack != nil && audioTrack != nil {
					return videoTrack, audioTrack, nil
				}
			}
		}

		if (pkt.Time - startTime) >= 1*time.Second {
			break
		}

		var err error
		pkt, err = c.ReadPacket()
		if err != nil {
			return nil, nil, err
		}
	}

	if videoTrack == nil && audioTrack == nil {
		return nil, nil, fmt.Errorf("no tracks found")
	}

	return videoTrack, audioTrack, nil
}

// ReadTracks reads track informations.
func (c *Conn) ReadTracks() (*gortsplib.TrackH264, *gortsplib.TrackAAC, error) {
	pkt, err := c.ReadPacket()
	if err != nil {
		return nil, nil, err
	}

	if pkt.Type == av.Metadata {
		videoTrack, audioTrack, err := c.readTracksFromMetadata(pkt)
		if err != nil {
			if err == errEmptyMetadata {
				pkt, err := c.ReadPacket()
				if err != nil {
					return nil, nil, err
				}

				videoTrack, audioTrack, err := c.readTracksFromPackets(pkt)
				if err != nil {
					return nil, nil, err
				}

				return videoTrack, audioTrack, nil
			}

			return nil, nil, err
		}

		return videoTrack, audioTrack, nil
	}

	videoTrack, audioTrack, err := c.readTracksFromPackets(pkt)
	if err != nil {
		return nil, nil, err
	}

	return videoTrack, audioTrack, nil
}

// WriteTracks writes track informations.
func (c *Conn) WriteTracks(videoTrack *gortsplib.TrackH264, audioTrack *gortsplib.TrackAAC) error {
	err := c.WritePacket(av.Packet{
		Type: av.Metadata,
		Data: flvio.FillAMF0ValMalloc(flvio.AMFMap{
			{
				K: "videodatarate",
				V: float64(0),
			},
			{
				K: "videocodecid",
				V: func() float64 {
					if videoTrack != nil {
						return codecH264
					}
					return 0
				}(),
			},
			{
				K: "audiodatarate",
				V: float64(0),
			},
			{
				K: "audiocodecid",
				V: func() float64 {
					if audioTrack != nil {
						return codecAAC
					}
					return 0
				}(),
			},
		}),
	})
	if err != nil {
		return err
	}

	// write decoder config only if SPS and PPS are available.
	// if they're not available yet, they're sent later as H264 NALUs.
	if videoTrack != nil && videoTrack.SafeSPS() != nil && videoTrack.SafePPS() != nil {
		codec := nh264.Codec{
			SPS: map[int][]byte{
				0: videoTrack.SafeSPS(),
			},
			PPS: map[int][]byte{
				0: videoTrack.SafePPS(),
			},
		}
		b := make([]byte, 128)
		var n int
		codec.ToConfig(b, &n)
		b = b[:n]

		err = c.WritePacket(av.Packet{
			Type: av.H264DecoderConfig,
			Data: b,
		})
		if err != nil {
			return err
		}
	}

	if audioTrack != nil {
		enc, err := audioTrack.Config.Marshal()
		if err != nil {
			return err
		}

		err = c.WritePacket(av.Packet{
			Type: av.AACDecoderConfig,
			AAC: &nhaac.Codec{
				Config: nhaac.MPEG4AudioConfig{
					ChannelLayout: nhaac.CH_STEREO,
				},
			},
			Data: enc,
		})
		if err != nil {
			return err
		}
	}

	return nil
}