/*
NAME
  session.go

DESCRIPTION
  RTMP session functionality.

AUTHORS
  Saxon Nelson-Milton <saxon@ausocean.org>
  Dan Kortschak <dan@ausocean.org>
  Alan Noble <alan@ausocean.org>

LICENSE
  session.go is Copyright (C) 2017-2019 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 http://www.gnu.org/licenses.

	Derived from librtmp under the GNU Lesser General Public License 2.1
	Copyright (C) 2005-2008 Team XBMC http://www.xbmc.org
	Copyright (C) 2008-2009 Andrej Stepanchuk
	Copyright (C) 2009-2010 Howard Chu
*/
package rtmp

import (
	"io"
	"net"
	"time"

	"bitbucket.org/ausocean/av/rtmp/amf"
)

// Session holds the state for an RTMP session.
type Session struct {
	url                  string
	inChunkSize          int32
	outChunkSize         int32
	checkCounter         int32
	nBytesIn             int32
	nBytesInSent         int32
	streamID             int32
	serverBW             int32
	clientBW             int32
	clientBW2            uint8
	isPlaying            bool
	numInvokes           int32
	methodCalls          []method
	channelsAllocatedIn  int32
	channelsAllocatedOut int32
	channelsIn           []*packet
	channelsOut          []*packet
	channelTimestamp     []int32
	audioCodecs          float64
	videoCodecs          float64
	deferred             []byte
	link                 link
	log                  Log
}

// link represents RTMP URL and connection information.
type link struct {
	host     string
	playpath string
	url      string
	app      string
	auth     string
	token    string
	flags    int32
	protocol int32
	timeout  uint
	port     uint16
	conn     *net.TCPConn
}

// method represents an RTMP method.
type method struct {
	name string
	num  int32
}

// Log defines the RTMP logging function.
type Log func(level int8, message string, params ...interface{})

// Log levels used by Log.
const (
	DebugLevel int8 = -1
	InfoLevel  int8 = 0
	WarnLevel  int8 = 1
	ErrorLevel int8 = 2
	FatalLevel int8 = 5
)

// flvTagheaderSize is the FLV header size we expect.
// NB: We don't accept extended headers.
const flvTagheaderSize = 11

// NewSession returns a new Session.
func NewSession(url string, timeout uint, log Log) *Session {
	return &Session{
		url:          url,
		inChunkSize:  128,
		outChunkSize: 128,
		clientBW:     2500000,
		clientBW2:    2,
		serverBW:     2500000,
		audioCodecs:  3191.0,
		videoCodecs:  252.0,
		log:          log,
		link: link{
			timeout: timeout,
		},
	}
}

// Open establishes an rtmp connection with the url passed into the constructor.
func (s *Session) Open() error {
	s.log(DebugLevel, pkg+"Session.Open")
	if s.isConnected() {
		return errConnected
	}
	err := s.init()
	if err != nil {
		return err
	}
	err = connect(s)
	if err != nil {
		s.Close()
		return err
	}

	err = connectStream(s)
	if err != nil {
		s.Close()
		return err
	}
	return nil
}

// Close terminates the rtmp connection.
// NB: Close is idempotent and the session value is cleared completely.
func (s *Session) Close() error {
	s.log(DebugLevel, pkg+"Session.Close")
	if !s.isConnected() {
		return errNotConnected
	}
	if s.streamID > 0 {
		if s.link.protocol&featureWrite != 0 {
			sendFCUnpublish(s)
		}
		sendDeleteStream(s, float64(s.streamID))
	}
	s.link.conn.Close()
	*s = Session{}
	return nil
}

// Write writes a frame (flv tag) to the rtmp connection.
func (s *Session) Write(data []byte) (int, error) {
	if !s.isConnected() {
		return 0, errNotConnected
	}
	if len(data) < flvTagheaderSize {
		return 0, errInvalidFlvTag
	}
	if data[0] == packetTypeInfo || (data[0] == 'F' && data[1] == 'L' && data[2] == 'V') {
		return 0, errUnimplemented
	}

	pkt := packet{
		packetType: data[0],
		bodySize:   amf.DecodeInt24(data[1:4]),
		timestamp:  amf.DecodeInt24(data[4:7]) | uint32(data[7])<<24,
		channel:    chanSource,
		info:       s.streamID,
	}

	pkt.resize(pkt.bodySize, headerSizeAuto)
	copy(pkt.body, data[flvTagheaderSize:flvTagheaderSize+pkt.bodySize])
	err := pkt.write(s, false)
	if err != nil {
		return 0, err
	}
	return len(data), nil
}

// I/O functions

// read from an RTMP connection. Sends a bytes received message if the
// number of bytes received (nBytesIn) is greater than the number sent
// (nBytesInSent) by 10% of the bandwidth.
func (s *Session) read(buf []byte) (int, error) {
	err := s.link.conn.SetReadDeadline(time.Now().Add(time.Second * time.Duration(s.link.timeout)))
	if err != nil {
		return 0, err
	}
	n, err := io.ReadFull(s.link.conn, buf)
	if err != nil {
		s.log(DebugLevel, pkg+"read failed", "error", err.Error())
		return 0, err
	}
	s.nBytesIn += int32(n)
	if s.nBytesIn > (s.nBytesInSent + s.clientBW/10) {
		err := sendBytesReceived(s)
		if err != nil {
			return n, err // NB: we still read n bytes, even though send bytes failed
		}
	}
	return n, nil
}

// write to an RTMP connection.
func (s *Session) write(buf []byte) (int, error) {
	//ToDo: consider using a different timeout for writes than for reads
	err := s.link.conn.SetWriteDeadline(time.Now().Add(time.Second * time.Duration(s.link.timeout)))
	if err != nil {
		return 0, err
	}
	n, err := s.link.conn.Write(buf)
	if err != nil {
		s.log(WarnLevel, pkg+"write failed", "error", err.Error())
		return 0, err
	}
	return n, nil
}

// isConnected returns true if the RTMP connection is up.
func (s *Session) isConnected() bool {
	return s.link.conn != nil
}