/*
NAME
  RtpToTsConverter.go - provides utilities for the conversion of Rtp packets
  to equivalent MpegTs packets.

DESCRIPTION
  See Readme.md

AUTHOR
  Saxon Nelson-Milton <saxon.milton@gmail.com>

LICENSE
  RtpToTsConverter.go is Copyright (C) 2017 the Australian Ocean Lab (AusOcean)

  It is free software: you can redistribute it and/or modify them
  under the terms of the GNU General Public License as published by the
  Free Software Foundation, either version 3 of the License, or (at your
  option) any later version.

  It is distributed in the hope that it will be useful, but WITHOUT
  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
 for more details.

  You should have received a copy of the GNU General Public License
  along with revid in gpl.txt.  If not, see [GNU licenses](http://www.gnu.org/licenses).
*/

package packets

type RtpToTsConverter interface {
  Convert()
}

type rtpToTsConverter struct {
  TsChan <-chan *MpegTsPacket
  tsChan chan<- *MpegTsPacket
  InputChan chan<- *RtpPacket
  inputChan <-chan *RtpPacket
  currentTsPacket *MpegTsPacket
  payloadByteChan chan byte
  currentCC byte
}

func NewRtpToTsConverter() (c *rtpToTsConverter) {
  c = new(rtpToTsConverter)
  tsChan := make(chan *MpegTsPacket,100)
  c.TsChan = tsChan
  c.tsChan = tsChan
  inputChan := make(chan *RtpPacket,100)
  c.InputChan = inputChan
  c.inputChan = inputChan
  c.currentCC = 0
  return
}

func (c* rtpToTsConverter) Convert() {
  nalUnitChan := make(chan NALUnit, 1000)
  pesPktChan := make(chan []byte, 1000)
  pesDataChan := make(chan byte, 1000)
  payloadByteChan := make(chan byte, 10000)
  // Get nal units from incoming rtp
  for {
    select {
    default:
    case rtpPacket := <-c.inputChan:
      if GetNalType( rtpPacket.Payload ) == 28 {
        nalUnitChan<-ParseNALFragment(rtpPacket.Payload)
      } else {
        nalUnitChan<-ParseNALSpsPps(rtpPacket.Payload)
      }
    case nalUnit := <-nalUnitChan:
      nalUnitByteSlice := nalUnit.ToByteSlice()
      for ii := range nalUnitByteSlice {
        pesDataChan<-nalUnitByteSlice[ii]
      }
      if nalFragment, isNALFragment := nalUnit.(*NALFragment);
          (isNALFragment && nalFragment.End) || !isNALFragment {
        pesDataChanLen := len(pesDataChan)
        pesPkt := new(PESPacket)
        pesPkt.StreamID = 0xE0
        pesPkt.Length = uint16( 3 + pesDataChanLen )
        pesPkt.ScramblingControl = 0
        pesPkt.Priority = true
        pesPkt.DAI = false
        pesPkt.Copyright = false
        pesPkt.Original = true
        pesPkt.PDI = 0
        pesPkt.ESCR = false
        pesPkt.ESRate = false
        pesPkt.DSMTrickMode = false
        pesPkt.ACI = false
        pesPkt.CRC = false
        pesPkt.Ext = false
        pesPkt.HeaderLength = 0
        pesPkt.Data = make([]byte,pesDataChanLen)
        for ii:=0; ii<pesDataChanLen; ii++ {
          pesPkt.Data[ii] = <-pesDataChan
        }
        pesPktChan<-pesPkt.ToByteSlice()
      }

    case pesPkt := <-pesPktChan:
      for ii:=range pesPkt {
        payloadByteChan<-pesPkt[ii]
      }
      firstPacket:=true
      for len(payloadByteChan) > 0 {
        lengthOfByteChan := len(payloadByteChan)
        c.currentTsPacket = new(MpegTsPacket)
        c.currentTsPacket.SyncByte = 0x47
        c.currentTsPacket.TEI = false
        c.currentTsPacket.PUSI = false
        if firstPacket  { // if it's the start of the payload
          c.currentTsPacket.PUSI = true
          firstPacket = false
        }
        c.currentTsPacket.Priority = false
        c.currentTsPacket.PID = 256
        c.currentTsPacket.TSC = 0
        c.currentTsPacket.CC = c.currentCC
        if c.currentCC++; c.currentCC > 15 { c.currentCC = 0 }
        payloadLength := 182
        if lengthOfByteChan < 182 {
          payloadLength = lengthOfByteChan
        }
        c.currentTsPacket.AFC = 3
        stuffingLength := 182-payloadLength
        c.currentTsPacket.AF = make([]byte,2 + stuffingLength) // adaptationfield flag length = 16
        c.currentTsPacket.AF[0] = byte(1 + stuffingLength)
        c.currentTsPacket.AF[1] = 0
        if c.currentTsPacket.PUSI {
          c.currentTsPacket.AF[1] = 0x00
        }
        for ii := 0; ii < stuffingLength; ii++ {
          c.currentTsPacket.AF[2+ii] = 0xFF
        }
        c.currentTsPacket.Payload = make([]byte, payloadLength)
        for ii:=0; ii < payloadLength; ii++ {
          c.currentTsPacket.Payload[ii] = <-payloadByteChan
        }
        c.tsChan<-c.currentTsPacket
      }
    }
  }
}