/*
NAME
  session.go

DESCRIPTION
  See Readme.md

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 (
	"errors"
)

// Session holds the state for an RTMP session.
type Session struct {
	url                  string
	timeout              uint
	inChunkSize          int32
	outChunkSize         int32
	bwCheckCounter       int32
	nBytesIn             int32
	nBytesInSent         int32
	streamID             int32
	serverBW             int32
	clientBW             int32
	clientBW2            uint8
	isPlaying            bool
	sendEncoding         bool
	numInvokes           int32
	methodCalls          []method
	channelsAllocatedIn  int32
	channelsAllocatedOut int32
	vecChannelsIn        []*packet
	vecChannelsOut       []*packet
	channelTimestamp     []int32
	audioCodecs          float64
	videoCodecs          float64
	encoding             float64
	write                packet
	defered              []byte
	link                 link
}

// NewSession returns a new Session.
func NewSession(url string, connectTimeout uint) *Session {
	return &Session{
		url:     url,
		timeout: connectTimeout,
	}
}

// Open establishes an rtmp connection with the url passed into the constructor.
func (s *Session) Open() error {
	if s.isConnected() {
		return errors.New("rtmp: attempt to start already running session")
	}
	err := s.start()
	if err != nil {
		return err
	}
	return nil
}

// start does the heavylifting for Open().
func (s *Session) start() error {
	s.init()
	err := C_RTMP_SetupURL(s, s.url)
	if err != nil {
		s.close()
		return err
	}

	C_RTMP_EnableWrite(s)
	err = C_RTMP_Connect(s, nil)
	if err != nil {
		s.close()
		return err
	}

	err = C_RTMP_ConnectStream(s, 0)
	if err != nil {
		s.close()
		return err
	}
	return nil
}

// init initializes various RTMP defauls.
// ToDo: define consts for the magic numbers.
func (s *Session) init() {
	s.inChunkSize = RTMP_DEFAULT_CHUNKSIZE
	s.outChunkSize = RTMP_DEFAULT_CHUNKSIZE
	s.clientBW = 2500000
	s.clientBW2 = 2
	s.serverBW = 2500000
	s.audioCodecs = 3191.0
	s.videoCodecs = 252.0
	s.link.timeout = s.timeout
	s.link.swfAge = 30
}

// Close terminates the rtmp connection,
func (s *Session) Close() error {
	if !s.isConnected() {
		return Err(3)
	}
	s.close()
	return nil
}

// close does the heavylifting for Close().
// Any errors are ignored as it is often called in response to an earlier error.
func (s *Session) close() {
	if s.isConnected() {
		if s.streamID > 0 {
			if s.link.protocol&RTMP_FEATURE_WRITE != 0 {
				C_SendFCUnpublish(s)
			}
			C_SendDeleteStream(s, float64(s.streamID))
		}
		s.link.conn.Close()
	}
	s = &Session{}
}

// Write writes a frame (flv tag) to the rtmp connection.
func (s *Session) Write(data []byte) (int, error) {
	if !s.isConnected() {
		return 0, Err(1)
	}
	err := C_RTMP_Write(s, data)
	if err != nil {
		// TODO: propagate err
		return 0, Err(2)
	}
	return len(data), nil
}

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