/*
NAME
  Revid.go

DESCRIPTION
  See Readme.md

AUTHORS
	Saxon A. Nelson-Milton <saxon@ausocean.org>
	Alan Noble <alan@ausocean.org>

LICENSE
  revid 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).
*/

// revid is a testbed for re-muxing and re-directing video streams as MPEG-TS over various protocols.
package revid

import (
	"bufio"
	"bytes"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"os"
	"os/exec"
	"strconv"
	"sync"
	"time"

	"bitbucket.org/ausocean/av/generator"
	"bitbucket.org/ausocean/av/parser"
	"bitbucket.org/ausocean/av/ringbuffer"
	"bitbucket.org/ausocean/av/rtmp"
	/*
		"../generator"
		"../parser"
		"../ringbuffer"
		"../rtmp"
	*/)

// Misc constants
const (
	clipDuration          = 1                   // s
	mp2tPacketSize        = 188                 // MPEG-TS packet size
	mp2tMaxPackets        = 2016 * clipDuration // # first multiple of 7 and 8 greater than 2000
	ringBufferSize        = 1000
	ringBufferElementSize = 100000
	maxClipSize           = 10000
	httpTimeOut           = 5 // s
	packetsPerFrame       = 7
	h264BufferSize        = 1000000
	bitrateTime           = 10 // s
	mjpegParserInChanLen  = 100000
	ffmpegPath            = "/usr/local/bin/ffmpeg"
	rtmpConnectionTimout  = 10
	outputChanSize        = 10000
	cameraRetryPeriod     = 5 * time.Second
	sendFailedDelay       = 5
	maxSendFailedErrorCount = 500
	clipSizeThreshold = 11
)

// Log Types
const (
	Error   = "Error"
	Warning = "Warning"
	Info    = "Info"
	Debug   = "Debug"
)


// Revid provides methods to control a revid session; providing methods
// to start, stop and change the state of an instance using the Config struct.
type Revid interface {
	Start()
	Stop()
	changeState(newconfig Config) error
	GetConfigRef() *Config
	Log(logType, m string)
	IsRunning() bool
}

// The revid struct provides fields to describe the state of a Revid.
type revid struct {
	ffmpegPath  string
	tempDir     string
	ringBuffer  ringbuffer.RingBuffer
	config      Config
	isRunning   bool
	outputFile  *os.File
	inputFile   *os.File
	generator   generator.Generator
	parser      parser.Parser
	cmd         *exec.Cmd
	ffmpegCmd   *exec.Cmd
	inputReader *bufio.Reader
	ffmpegStdin io.WriteCloser
	outputChan  chan []byte
	setupInput  func() error
	setupOutput func() error
	getFrame    func() []byte
	sendClip    func(clip []byte) error
	rtmpInst    rtmp.RTMPSession
	mutex       sync.Mutex
	currentBitrate int64
}

// NewRevid returns a pointer to a new revid with the desired
// configuration, and/or an error if construction of the new instant was not
// successful.
func NewRevid(config Config) (r *revid, err error) {
	r = new(revid)
	r.mutex = sync.Mutex{}
	r.ringBuffer = ringbuffer.NewRingBuffer(ringBufferSize, ringBufferElementSize)
	err = r.changeState(config)
	if err != nil {
		r = nil
		return
	}
	r.outputChan = make(chan []byte, outputChanSize)
	r.parser.Start()
	go r.packClips()
	return
}

// Returns the currently saved bitrate from the most recent bitrate check
// check bitrate output delay in consts for this period
func (r *revid) GetBitrate() int64 {
	return r.currentBitrate
}

// GetConfigRef returns a pointer to the revidInst's Config struct object
func (r *revid) GetConfigRef() *Config {
	return &r.config
}

// changeState swaps the current config of a revid with the passed
// configuration; checking validity and returning errors if not valid.
func (r *revid) changeState(config Config) error {
	r.config.Logger = config.Logger
	err := config.Validate(r)
	if err != nil {
		return errors.New("Config struct is bad!: " + err.Error())
	}
	r.config = config

	switch r.config.Output {
	case File:
		r.sendClip = r.sendClipToFile
		r.setupOutput = r.setupOutputForFile
	case FfmpegRtmp:
		r.setupOutput = r.setupOutputForFfmpegRtmp
		r.sendClip = r.sendClipToFfmpegRtmp
	case NativeRtmp:
		r.setupOutput = r.setupOutputForLibRtmp
		r.sendClip = r.sendClipToLibRtmp
	case Http:
		r.sendClip = r.sendClipToHTTP
	}

	switch r.config.Input {
	case Raspivid:
		r.setupInput = r.setupInputForRaspivid
	case File:
		r.setupInput = r.setupInputForFile
	}
	switch r.config.InputCodec {
	case H264:
		r.Log(Info, "Using H264 parser!")
		r.parser = parser.NewH264Parser()
	case Mjpeg:
		r.Log(Info, "Using MJPEG parser!")
		r.parser = parser.NewMJPEGParser(mjpegParserInChanLen)
	}

	switch r.config.Packetization {
	case None:
		// no packetisation - Revid output chan grabs raw data straight from parser
		r.parser.SetOutputChan(r.outputChan)
		r.getFrame = r.getFrameNoPacketization
		goto noPacketizationSetup
	case Mpegts:
		r.Log(Info, "Using MPEGTS packetisation!")
		frameRateAsInt, _ := strconv.Atoi(r.config.FrameRate)
		r.generator = generator.NewTsGenerator(uint(frameRateAsInt))
	case Flv:
		r.Log(Info, "Using FLV packetisation!")
		frameRateAsInt, _ := strconv.Atoi(r.config.FrameRate)
		r.generator = generator.NewFlvGenerator(true, true, uint(frameRateAsInt))
	}
	// We have packetization of some sort, so we want to send data to Generator
	// to perform packetization
	r.getFrame = r.getFramePacketization
	r.parser.SetOutputChan(r.generator.GetInputChan())
	r.generator.Start()
noPacketizationSetup:

	return nil
}

// ChangeConfig changes the current configuration of the revid instance.
func (r *revid) ChangeConfig(config Config) (err error) {
	r.Stop()
	r, err = NewRevid(config)
	if err != nil {
		return
	}
	r.Start()
	return
}

// Log takes a logtype and message and tries to send this information to the
// logger provided in the revid config - if there is one, otherwise the message
// is sent to stdout
func (r *revid) Log(logType, m string) {
	if r.config.Verbosity == Yes {
		if r.config.Logger != nil {
			r.config.Logger.Log(logType, m)
			return
		}
		fmt.Println(logType + ": " + m)
	}
}

// IsRunning returns true if the revid is currently running and false otherwise
func (r *revid) IsRunning() bool {
	return r.isRunning
}

// Start invokes a revid to start processing video from a defined input
// and packetising (if theres packetization) to a defined output.
func (r *revid) Start() {
	r.mutex.Lock()
	defer r.mutex.Unlock()
	if r.isRunning {
		r.Log(Warning, "revid.Start() called but revid already running!")
		return
	}
	r.Log(Info, "Starting Revid!")
	if r.setupOutput != nil {
		err := r.setupOutput()
		if err != nil {
			r.Log(Error, "Output setup didn't work!")
			return
		}
	}
	go r.setupInput()
	go r.outputClips()
	r.isRunning = true
}

// Stop halts any processing of video data from a camera or file
func (r *revid) Stop() {
	r.mutex.Lock()
	defer r.mutex.Unlock()
	if !r.isRunning {
		r.Log(Warning, "revid.Stop() called but revid not running!")
		return
	}
	r.Log(Info, "Stopping revid!")
	r.isRunning = false
	// If a cmd process is running, we kill!
	if r.cmd != nil && r.cmd.Process != nil {
		r.cmd.Process.Kill()
	}
}

// getFrameNoPacketization gets a frame directly from the revid output chan
// as we don't need to go through the generator with no packetization settings
func (r *revid) getFrameNoPacketization() []byte {
	return <-r.outputChan
}

// getFramePacketization gets a frame from the generators output chan - the
// the generator being an mpegts or flv generator depending on the config
func (r *revid) getFramePacketization() []byte {
	return <-(r.generator.GetOutputChan())
}

// flushDataPacketization removes data from the revid inst's coutput chan
func (r *revid) flushData() {
	for len(r.outputChan) > 0 {
		<-(r.outputChan)
	}
}

// packClips takes data segments; whether that be tsPackets or mjpeg frames and
// packs them into clips consisting of the amount frames specified in the config
func (r *revid) packClips() {
	clipSize := 0
	packetCount := 0
	for {
		// Get some memory from the ring buffer for out clip
		var clip []byte
		var err error
		if clip, err = r.ringBuffer.Get(); err != nil {
			r.Log(Error, err.Error())
			r.Log(Warning, "Clearing output chan!")
			// Keep clearing output chan until out buffer has some space
			for clip, err = r.ringBuffer.Get(); err != nil; {
				r.flushData()
			}
			continue
		}
		for {
			frame := r.getFrame()
			lenOfFrame := len(frame)
			upperBound := clipSize + lenOfFrame
			copy(clip[clipSize:upperBound], frame)
			packetCount++
			clipSize += lenOfFrame
			fpcAsInt,_ := strconv.Atoi(r.config.FramesPerClip)
			if packetCount >= fpcAsInt {
				if err := r.ringBuffer.DoneWriting(clipSize); err != nil {
					r.Log(Error, err.Error())
					r.Log(Warning, "Dropping clip!")
				}
				clipSize = 0
				packetCount = 0
				break
			}
		}
	}
}

func (r* revid)reboot() {
	cmd := exec.Command("sudo", "reboot")
	err := cmd.Run()
	r.Log(Error, err.Error())
	r.Log(Info, "Rebooting!")
}

// outputClips takes the clips produced in the packClips method and outputs them
// to the desired output defined in the revid config
func (r *revid) outputClips() {
	now := time.Now()
	prevTime := now
	bytes := 0
	delay := 0
	for r.isRunning {
		// Here we slow things down as much as we can to decrease cpu usage
		switch {
		case r.ringBuffer.GetNoOfElements() < 2:
			delay++
			time.Sleep(time.Duration(delay) * time.Millisecond)
		case delay > 0:
			delay--
		}

		// If the ringbuffer has something we can read and send off
		if clip, err := r.ringBuffer.Read(); err == nil {
			bytes += len(clip)
			errorCount := 0
			err := r.sendClip(clip)
			for ; err != nil; errorCount++ {
				r.Log(Warning, "Send failed trying again!")
				// If the clip size is not bigger than the threshold then we classify
				// it as junk and we don't try to send it off again.
				if len(clip) >= clipSizeThreshold {
					err = r.sendClip(clip)
				} else {
					break
				}
				// So that we don't fill up the log, once we reach the maxSendFailedErrorCount
				// we will add some delay to slow things down until we have a connection again
				if errorCount > maxSendFailedErrorCount {
					time.Sleep(time.Duration(sendFailedDelay) * time.Second)
				}
				r.Log(Error, err.Error())
				if r.config.Output == NativeRtmp && errorCount > 5 {
					r.reboot()
				}
			}
			// let the ringbuffer know that we're done with the memory we grabbed when
			// we call ringBuffer.Get()
			if err := r.ringBuffer.DoneReading(); err != nil {
				r.Log(Error, err.Error())
			}
			// Log some information regarding bitrate and ring buffer size if it's time
			now = time.Now()
			deltaTime := now.Sub(prevTime)
			if deltaTime > time.Duration(bitrateTime)*time.Second {
				r.currentBitrate = int64(float64(bytes*8)/float64(deltaTime/1e9))
				r.Log(Info, fmt.Sprintf("Bitrate: %v bits/s\n", r.currentBitrate ))
				r.Log(Info, fmt.Sprintf("Ring buffer size: %v\n", r.ringBuffer.GetNoOfElements()))
				prevTime = now
				bytes = 0
			}
		}
	}
	r.Log(Info, "Not outputting clips anymore!")
}

// senClipToFile writes the passed clip to a file
func (r *revid) sendClipToFile(clip []byte) error {
	_, err := r.outputFile.Write(clip)
	if err != nil {
		return err
	}
	return nil
}

// sendClipToHTTP takes a clip and an output url and posts through http.
func (r *revid) sendClipToHTTP(clip []byte) error {
	timeout := time.Duration(httpTimeOut * time.Second)
	client := http.Client{Timeout: timeout}
	url := r.config.HttpAddress + strconv.Itoa(len(clip))
	r.Log(Debug, fmt.Sprintf("Posting %s (%d bytes)\n", url, len(clip)))
	resp, err := client.Post(url, "video/mp2t", bytes.NewReader(clip))
	if err != nil {
		return fmt.Errorf("Error posting to %s: %s", url, err)
	}
	defer resp.Body.Close()
	body, err := ioutil.ReadAll(resp.Body)
	if err == nil {
		r.Log(Debug, fmt.Sprintf("%s\n", body))
	} else {
		r.Log(Error, err.Error())
	}
	return nil
}

// sendClipToFfmpegRtmp sends the clip over the current rtmp connection using
// an ffmpeg process.
func (r *revid) sendClipToFfmpegRtmp(clip []byte) (err error) {
	_, err = r.ffmpegStdin.Write(clip)
	return
}

// sendClipToLibRtmp send the clip over the current rtmp connection using the
// c based librtmp library
func (r *revid) sendClipToLibRtmp(clip []byte) (err error) {
	err = r.rtmpInst.WriteFrame(clip, uint(len(clip)))
	return
}

// setupOutputForFfmpegRtmp sets up output to rtmp using an ffmpeg process
func (r *revid) setupOutputForFfmpegRtmp() error {
	r.ffmpegCmd = exec.Command(ffmpegPath,
		"-f", "h264",
		"-r", r.config.FrameRate,
		"-i", "-",
		"-f", "lavfi",
		"-i", "aevalsrc=0",
		"-fflags", "nobuffer",
		"-vcodec", "copy",
		"-acodec", "aac",
		"-map", "0:0",
		"-map", "1:0",
		"-strict", "experimental",
		"-f", "flv",
		r.config.RtmpUrl,
	)
	var err error
	r.ffmpegStdin, err = r.ffmpegCmd.StdinPipe()
	if err != nil {
		r.Log(Error, err.Error())
		r.Stop()
		return err
	}
	err = r.ffmpegCmd.Start()
	if err != nil {
		r.Log(Error, err.Error())
		r.Stop()
		return err
	}
	return nil
}

// setupOutputForLibRtmp sets up rtmp output using the wrapper for the c based
// librtmp library - makes connection and starts comms etc.
func (r *revid) setupOutputForLibRtmp() (err error) {
	r.rtmpInst = rtmp.NewRTMPSession(r.config.RtmpUrl, rtmpConnectionTimout)
	err = r.rtmpInst.StartSession()
	// go r.testRtmp(5000)
	return
}

// setupOutputForFile sets up an output file to output data to
func (r *revid) setupOutputForFile() (err error) {
	r.outputFile, err = os.Create(r.config.OutputFileName)
	return
}

// setupInputForRaspivid sets up things for input from raspivid i.e. starts
// a raspivid process and pipes it's data output.
func (r *revid) setupInputForRaspivid() error {
	r.Log(Info, "Starting raspivid!")
	switch r.config.InputCodec {
	case H264:
		switch r.config.QuantizationMode {
		case QuantizationOn:
			r.cmd = exec.Command("raspivid",
				"-cd", "H264",
				"-o", "-",
				"-n",
				"-t", r.config.Timeout,
				"-b", "0",
				"-qp", r.config.Quantization,
				"-w", r.config.Width,
				"-h", r.config.Height,
				"-fps", r.config.FrameRate,
				"-ih",
				"-g", r.config.IntraRefreshPeriod,
			)
		case QuantizationOff:
			r.cmd = exec.Command("raspivid",
				"-cd", "H264",
				"-o", "-",
				"-n",
				"-t", r.config.Timeout,
				"-b", r.config.Bitrate,
				"-w", r.config.Width,
				"-h", r.config.Height,
				"-fps", r.config.FrameRate,
				"-ih",
				"-g", r.config.IntraRefreshPeriod,
			)
		}

	case Mjpeg:
		r.cmd = exec.Command("raspivid",
			"-cd", "MJPEG",
			"-o", "-",
			"-n",
			"-t", r.config.Timeout,
			"-fps", r.config.FrameRate,
		)
	}
	stdout, _ := r.cmd.StdoutPipe()
	err := r.cmd.Start()
	r.inputReader = bufio.NewReader(stdout)
	if err != nil {
		r.Log(Error, err.Error())
		return err
	}
	go r.readCamera()
	return nil
}

// setupInputForFile sets things up for getting input from a file
func (r *revid) setupInputForFile() error {
	fps, _ := strconv.Atoi(r.config.FrameRate)
	r.parser.SetDelay(uint(float64(1000) / float64(fps)))
	r.readFile()
	return nil
}

// testRtmp is useful to check robustness of connections. Intended to be run as
// goroutine. After every 'delayTime' the rtmp connection is ended and then
// restarted
func (r *revid) testRtmp(delayTime uint) {
	for {
		time.Sleep(time.Duration(delayTime) * time.Millisecond)
		r.rtmpInst.EndSession()
		r.rtmpInst.StartSession()
	}
}

// readCamera reads data from the defined camera while the revid is running.
// TODO: use ringbuffer here instead of allocating mem every time!
func (r *revid) readCamera() {
	r.Log(Info, "Reading camera data!")
	for r.isRunning {
		data := make([]byte, 1)
		_, err := io.ReadFull(r.inputReader, data)
		switch {
		// We know this means we're getting nothing from the cam
	case ( err != nil && err.Error() == "EOF" && r.isRunning ) || ( err != nil && r.isRunning):
			r.Log(Error, "No data from camera!")
			time.Sleep(cameraRetryPeriod)
		default:
			r.parser.GetInputChan() <- data[0]
		}
	}
	r.Log(Info, "Not trying to read from camera anymore!")
}

// readFile reads data from the defined file while the revid is running.
func (r *revid) readFile() error {
	var err error
	r.inputFile, err = os.Open(r.config.InputFileName)
	if err != nil {
		r.Log(Error, err.Error())
		r.Stop()
		return err
	}
	stats, err := r.inputFile.Stat()
	if err != nil {
		r.Log(Error, "Could not get input file stats!")
		r.Stop()
		return err
	}
	data := make([]byte, stats.Size())
	_, err = r.inputFile.Read(data)
	if err != nil {
		r.Log(Error, err.Error())
		r.Stop()
		return err
	}
	for i := range data {
		r.parser.GetInputChan() <- data[i]
	}
	r.inputFile.Close()
	return nil
}