/*
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

import "fmt"

type RtpToTsConverter interface {
  Convert()
}

type rtpToTsConverter struct {
  TsChan <-chan *MpegTsPacket
  tsChan chan<- *MpegTsPacket
  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
  c.payloadByteChan = make(chan byte, 10000)
  c.currentCC = 0
  return
}

func (c* rtpToTsConverter) Convert(rtpSession *Session) {
  for {
    select{
    default:
    case rtpPacket := <-rtpSession.RtpChan:
      for ii := range rtpPacket.Payload {
        c.payloadByteChan<-rtpPacket.Payload[ii]
      }

      for len(c.payloadByteChan) > 0 {
        lengthOfByteChan := len(c.payloadByteChan)
        c.currentTsPacket = new(MpegTsPacket)
        c.currentTsPacket.SyncByte = 0x47
        c.currentTsPacket.TEI = false
        if lengthOfByteChan == len(rtpPacket.Payload) { // if it's the start of the payload
          c.currentTsPacket.PUSI = true
        } else {
          c.currentTsPacket.PUSI = false
        }
        c.currentTsPacket.Priority = false
        c.currentTsPacket.PID = 256
        c.currentTsPacket.TSC = 0
        c.currentTsPacket.AFC = 3 // adaptationfield followed by payload
        c.currentTsPacket.CC = c.currentCC
        if c.currentCC++; c.currentCC > 15 { c.currentCC = 0 }
        payloadLength := 140
        if lengthOfByteChan < 140 {
          payloadLength = lengthOfByteChan
        }
        stuffingLength := 140-payloadLength
        c.currentTsPacket.AF = make([]byte,2 + stuffingLength) // adaptationfield flag length = 16
        c.currentTsPacket.AF[0] = byte(1 + stuffingLength)
        c.currentTsPacket.AF[1] = 0
        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] = <-c.payloadByteChan
        }
        c.tsChan<-c.currentTsPacket
      }
    }
  }
}