package wav

import (
    "bytes"
    "encoding/binary"
    "fmt"
    "io"

    "rtp-app/pkg/riff"
)

var (
    markerIART    = [4]byte{'I', 'A', 'R', 'T'}
    markerISFT    = [4]byte{'I', 'S', 'F', 'T'}
    markerICRD    = [4]byte{'I', 'C', 'R', 'D'}
    markerICOP    = [4]byte{'I', 'C', 'O', 'P'}
    markerIARL    = [4]byte{'I', 'A', 'R', 'L'}
    markerINAM    = [4]byte{'I', 'N', 'A', 'M'}
    markerIENG    = [4]byte{'I', 'E', 'N', 'G'}
    markerIGNR    = [4]byte{'I', 'G', 'N', 'R'}
    markerIPRD    = [4]byte{'I', 'P', 'R', 'D'}
    markerISRC    = [4]byte{'I', 'S', 'R', 'C'}
    markerISBJ    = [4]byte{'I', 'S', 'B', 'J'}
    markerICMT    = [4]byte{'I', 'C', 'M', 'T'}
    markerITRK    = [4]byte{'I', 'T', 'R', 'K'}
    markerITRKBug = [4]byte{'i', 't', 'r', 'k'}
    markerITCH    = [4]byte{'I', 'T', 'C', 'H'}
    markerIKEY    = [4]byte{'I', 'K', 'E', 'Y'}
    markerIMED    = [4]byte{'I', 'M', 'E', 'D'}
)

func DecodeListChunk(d *Decoder, ch *riff.Chunk) error {
    if ch == nil {
        return fmt.Errorf("can't decode a nil chunk")
    }
    if d == nil {
        return fmt.Errorf("nil decoder")
    }
    if ch.ID == CIDList {
        buf := make([]byte, ch.Size)
        var err error
        if _, err = ch.Read(buf); err != nil {
            return fmt.Errorf("failed to read the LIST chunk - %v", err)
        }
        r := bytes.NewReader(buf)
        scratch := make([]byte, 4)
        if _, err = r.Read(scratch); err != nil {
            return fmt.Errorf("failed to read the INFO subchunk - %v", err)
        }
        if !bytes.Equal(scratch, CIDInfo[:]) {
            ch.Drain()
            return nil
        }
        if d.Metadata == nil {
            d.Metadata = &Metadata{}
        }
        var (
            id   [4]byte
            size uint32
        )
        readSubHeader := func() error {
            if err := binary.Read(r, binary.BigEndian, &id); err != nil {
                return err
            }
            return binary.Read(r, binary.LittleEndian, &size)
        }
        for err == nil {
            err = readSubHeader()
            if err != nil {
                break
            }
            scratch = make([]byte, size)
            r.Read(scratch)
            switch id {
                case markerIARL:
                    d.Metadata.Location = nullTermStr(scratch)
                case markerIART:
                    d.Metadata.Artist = nullTermStr(scratch)
                case markerISFT:
                    d.Metadata.Software = nullTermStr(scratch)
                case markerICRD:
                    d.Metadata.CreationDate = nullTermStr(scratch)
                case markerICOP:
                    d.Metadata.Copyright = nullTermStr(scratch)
                case markerINAM:
                    d.Metadata.Title = nullTermStr(scratch)
                case markerIENG:
                    d.Metadata.Engineer = nullTermStr(scratch)
                case markerIGNR:
                    d.Metadata.Genre = nullTermStr(scratch)
                case markerIPRD:
                    d.Metadata.Product = nullTermStr(scratch)
                case markerISRC:
                    d.Metadata.Source = nullTermStr(scratch)
                case markerISBJ:
                    d.Metadata.Subject = nullTermStr(scratch)
                case markerICMT:
                    d.Metadata.Comments = nullTermStr(scratch)
                case markerITRK, markerITRKBug:
                    d.Metadata.TrackNbr = nullTermStr(scratch)
                case markerITCH:
                    d.Metadata.Technician = nullTermStr(scratch)
                case markerIKEY:
                    d.Metadata.Keywords = nullTermStr(scratch)
                case markerIMED:
                    d.Metadata.Medium = nullTermStr(scratch)
            }

            if size%2 == 1 {
                r.Seek(1, io.SeekCurrent)
            }
        }
    }
    ch.Drain()
    return nil
}

func encodeInfoChunk(e *Encoder) []byte {
    if e == nil || e.Metadata == nil {
        return nil
    }
    buf := bytes.NewBuffer(nil)
    writeSection := func(id [4]byte, val string) {
        buf.Write(id[:])
        binary.Write(buf, binary.LittleEndian, uint32(len(val)+1))
        buf.Write(append([]byte(val), 0x00))
    }
    if e.Metadata.Artist != "" {
        writeSection(markerIART, e.Metadata.Artist)
    }
    if e.Metadata.Comments != "" {
        writeSection(markerICMT, e.Metadata.Comments)
    }
    if e.Metadata.Copyright != "" {
        writeSection(markerICOP, e.Metadata.Copyright)
    }
    if e.Metadata.CreationDate != "" {
        writeSection(markerICRD, e.Metadata.CreationDate)
    }
    if e.Metadata.Engineer != "" {
        writeSection(markerIENG, e.Metadata.Engineer)
    }
    if e.Metadata.Technician != "" {
        writeSection(markerITCH, e.Metadata.Technician)
    }
    if e.Metadata.Genre != "" {
        writeSection(markerIGNR, e.Metadata.Genre)
    }
    if e.Metadata.Keywords != "" {
        writeSection(markerIKEY, e.Metadata.Keywords)
    }
    if e.Metadata.Medium != "" {
        writeSection(markerIMED, e.Metadata.Medium)
    }
    if e.Metadata.Title != "" {
        writeSection(markerINAM, e.Metadata.Title)
    }
    if e.Metadata.Product != "" {
        writeSection(markerIPRD, e.Metadata.Product)
    }
    if e.Metadata.Subject != "" {
        writeSection(markerISBJ, e.Metadata.Subject)
    }
    if e.Metadata.Software != "" {
        writeSection(markerISFT, e.Metadata.Software)
    }
    if e.Metadata.Source != "" {
        writeSection(markerISRC, e.Metadata.Source)
    }
    if e.Metadata.Location != "" {
        writeSection(markerIARL, e.Metadata.Location)
    }
    if e.Metadata.TrackNbr != "" {
        writeSection(markerITRK, e.Metadata.TrackNbr)
    }
    return append(CIDInfo, buf.Bytes()...)
}