/*
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) 2017-2018 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.
*/

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

import (
	"bufio"
	"errors"
	"fmt"
	"io"
	"os"
	"os/exec"
	"strconv"
	"time"

	"bitbucket.org/ausocean/av/generator"
	"bitbucket.org/ausocean/av/parser"
	"bitbucket.org/ausocean/av/rtmp"
	"bitbucket.org/ausocean/utils/ring"
)

// Misc constants
const (
	clipDuration            = 1 * time.Second
	mp2tPacketSize          = 188                                    // MPEG-TS packet size
	mp2tMaxPackets          = int(clipDuration * 2016 / time.Second) // # first multiple of 7 and 8 greater than 2000
	ringBufferSize          = 500
	ringBufferElementSize   = 150000
	writeTimeout            = 10 * time.Millisecond
	readTimeout             = 10 * time.Millisecond
	httpTimeout             = 5 * time.Second
	packetsPerFrame         = 7
	bitrateTime             = 1 * time.Minute
	mjpegParserInChanLen    = 100000
	ffmpegPath              = "/usr/local/bin/ffmpeg"
	rtmpConnectionTimout    = 10
	outputChanSize          = 1000
	cameraRetryPeriod       = 5 * time.Second
	sendFailedDelay         = 5
	maxSendFailedErrorCount = 500
	clipSizeThreshold       = 11
	rtmpConnectionMaxTries  = 5
	raspividNoOfTries       = 3
	sendingWaitTime         = 5 * time.Millisecond
)

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

// 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 struct {
	ffmpegPath  string
	tempDir     string
	ringBuffer  *ring.Buffer
	config      Config
	isRunning   bool
	generator   generator.Generator
	parser      parser.Parser
	cmd         *exec.Cmd
	inputReader *bufio.Reader
	ffmpegStdin io.WriteCloser
	outputChan  chan []byte
	setupInput  func() error
	getFrame    func() []byte
	destination loadSender
	rtmpInst    rtmp.Session
	bitrate     int
}

// 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 New(c Config) (*Revid, error) {
	var r Revid
	err := r.reset(c)
	if err != nil {
		return nil, err
	}
	r.ringBuffer = ring.NewBuffer(ringBufferSize, ringBufferElementSize, writeTimeout)
	r.outputChan = make(chan []byte, outputChanSize)
	return &r, nil
}

// Bitrate returns the result of the  most recent bitrate check.
func (r *Revid) Bitrate() int {
	return r.bitrate
}

// Config returns the Revid's config.
func (r *Revid) Config() *Config {
	// FIXME(kortschak): This is a massive footgun and should not exist.
	// Since the config's fields are accessed in running goroutines, any
	// mutation is a data race. With bad luck a data race is possible by
	// reading the returned value since it is possible for the running
	// Ravid to mutate the config it holds.
	return &r.config
}

// reset swaps the current config of a Revid with the passed
// configuration; checking validity and returning errors if not valid.
func (r *Revid) reset(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

	if r.destination != nil {
		err = r.destination.close()
		if err != nil {
			r.Log(Error, err.Error())
		}
	}
	switch r.config.Output {
	case File:
		s, err := newFileSender(config.OutputFileName)
		if err != nil {
			return err
		}
		r.destination = s
	case FfmpegRtmp:
		s, err := newFfmpegSender(config.RtmpUrl, r.config.FrameRate)
		if err != nil {
			return err
		}
		r.destination = s
	case Rtmp:
		s, err := newRtmpSender(config.RtmpUrl, rtmpConnectionTimout, rtmpConnectionMaxTries, r.Log)
		if err != nil {
			return err
		}
		r.destination = s
	case Http:
		r.destination = newHttpSender(config.HttpAddress, httpTimeout, r.Log)
	}

	switch r.config.Input {
	case Raspivid:
		r.setupInput = r.startRaspivid
	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
		return nil
	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.InputChan())

	return nil
}

// SetConfig changes the current configuration of the receiver.
func (r *Revid) SetConfig(c Config) error {
	// FIXME(kortschak): This is reimplemented in cmd/revid-cli/main.go.
	// The implementation in the command is used and this is not.
	// Decide on one or the other.

	r.Stop()
	r, err := New(c)
	if err != nil {
		return err
	}
	r.Start()
	return nil
}

// 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 {
		return
	}
	if r.config.Logger != nil {
		r.config.Logger.Log("revid", logType, m)
		return
	}
	fmt.Println(logType + ": " + m)
}

// IsRunning returns whether the receiver is running.
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() {
	if r.isRunning {
		r.Log(Warning, "Revid.Start() called but revid already running!")
		return
	}
	r.Log(Info, "Starting Revid!")
	r.Log(Debug, "Setting up output!")
	r.isRunning = true
	r.Log(Info, "Starting output routine!")
	go r.outputClips()
	r.Log(Info, "Starting clip packing routine!")
	go r.packClips()
	r.Log(Info, "Starting packetisation generator!")
	r.generator.Start()
	r.Log(Info, "Starting parser!")
	r.parser.Start()
	r.Log(Info, "Setting up input and receiving content!")
	go r.setupInput()
}

// Stop halts any processing of video data from a camera or file
func (r *Revid) Stop() {
	if !r.isRunning {
		r.Log(Warning, "Revid.Stop() called but revid not running!")
		return
	}

	r.Log(Info, "Stopping revid!")
	r.isRunning = false

	r.Log(Info, "Stopping generator!")
	if r.generator != nil {
		r.generator.Stop()
	}

	r.Log(Info, "Stopping parser!")
	if r.parser != nil {
		r.parser.Stop()
	}

	r.Log(Info, "Killing input proccess!")
	// 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.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 r.isRunning {
		select {
		// TODO: This is temporary, need to work out how to make this work
		// for cases when there is not packetisation.
		case frame := <-r.generator.OutputChan():
			lenOfFrame := len(frame)
			if lenOfFrame > ringBufferElementSize {
				r.Log(Warning, fmt.Sprintf("Frame was too big: %v bytes, getting another one!", lenOfFrame))
				frame = r.getFrame()
				lenOfFrame = len(frame)
			}
			_, err := r.ringBuffer.Write(frame)
			if err != nil {
				if err == ring.ErrDropped {
					r.Log(Warning, fmt.Sprintf("dropped %d byte frame", len(frame)))
				} else {
					r.Log(Error, err.Error())
				}
			}
			packetCount++
			clipSize += lenOfFrame
			if packetCount >= r.config.FramesPerClip {
				r.ringBuffer.Flush()
				clipSize = 0
				packetCount = 0
				continue
			}
		default:
			time.Sleep(5 * time.Millisecond)
		}
	}
}

// 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.Len() < 2:
			delay++
			time.Sleep(time.Duration(delay) * time.Millisecond)
		case delay > 0:
			delay--
		}
		// If the ringbuffer has something we can read and send off
		chunk, err := r.ringBuffer.Next(readTimeout)
		if err != nil || !r.isRunning {
			if err == io.EOF {
				break
			}
			continue
		}

		bytes += chunk.Len()
		r.Log(Detail, "About to send")
		err = r.destination.load(chunk)
		if err != nil {
			r.Log(Error, "failed to load clip")
		}
		err = r.destination.send()
		if err == nil {
			r.Log(Detail, "sent clip")
		}

		if r.isRunning && err != nil && chunk.Len() > 11 {
			r.Log(Debug, "Send failed! Trying again")
			// Try and send again
			err = r.destination.send()
			r.Log(Error, err.Error())

			// if there's still an error we try and reconnect, unless we're stopping
			for r.isRunning && err != nil {
				r.Log(Debug, "Send failed a again! Trying to reconnect...")
				time.Sleep(time.Duration(sendFailedDelay) * time.Millisecond)
				r.Log(Error, err.Error())

				if rs, ok := r.destination.(restarter); ok {
					r.Log(Debug, fmt.Sprintf("restarting %T session", rs))
					err = rs.restart()
					if err != nil {
						// TODO(kortschak): Make this "Fatal" when that exists.
						r.Log(Error, "failed to restart rtmp session")
						r.isRunning = false
						return
					}
					r.Log(Info, "restarted rtmp session")
				}

				r.Log(Debug, "Trying to send again with new connection...")
				err = r.destination.send()
				if err != nil {
					r.Log(Error, err.Error())
				}
			}
		}

		r.destination.release()

		r.Log(Detail, "Done reading that clip from ringbuffer...")

		// Log some information regarding bitrate and ring buffer size if it's time
		now = time.Now()
		deltaTime := now.Sub(prevTime)
		if deltaTime > bitrateTime {
			// FIXME(kortschak): For subsecond deltaTime, this will give infinite bitrate.
			r.bitrate = int(float64(bytes*8) / float64(deltaTime/time.Second))
			r.Log(Debug, fmt.Sprintf("Bitrate: %v bits/s\n", r.bitrate))
			r.Log(Debug, fmt.Sprintf("Ring buffer size: %v\n", r.ringBuffer.Len()))
			prevTime = now
			bytes = 0
		}
	}
	r.Log(Info, "Not outputting clips anymore!")
	err := r.destination.close()
	if err != nil {
		r.Log(Error, "failed to close destination")
	}
}

// startRaspivid sets up things for input from raspivid i.e. starts
// a raspivid process and pipes it's data output.
func (r *Revid) startRaspivid() error {
	r.Log(Info, "Starting raspivid!")
	switch r.config.InputCodec {
	case H264:
		args := []string{
			"-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,
		}
		if r.config.QuantizationMode == QuantizationOn {
			args = append(args, "-qp", r.config.Quantization)
		}
		if r.config.HorizontalFlip == Yes {
			args = append(args, "-hf")
		}
		if r.config.VerticalFlip == Yes {
			args = append(args, "-vf")
		}

		r.Log(Info, fmt.Sprintf("Starting raspivid with args: %v", args))
		r.cmd = exec.Command("raspivid", args...)

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

// 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 {
		var data [1]byte
		_, err := io.ReadFull(r.inputReader, data[:])
		switch {
		// We know this means we're getting nothing from the cam
		case err != nil && r.isRunning:
			r.Log(Error, "No data from camera!")
			time.Sleep(cameraRetryPeriod)
		default:
			r.parser.InputChan() <- data[0]
		}
	}
	r.Log(Info, "Not trying to read from camera anymore!")
}

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

// readFile reads data from the defined file while the Revid is running.
func (r *Revid) readFile() error {
	f, err := os.Open(r.config.InputFileName)
	if err != nil {
		r.Log(Error, err.Error())
		r.Stop()
		return err
	}
	defer f.Close()
	var buf [1 << 12]byte
	for {
		n, err := f.Read(buf[:])
		for _, b := range buf[:n] {
			r.parser.InputChan() <- b
		}
		if err != nil {
			if err == io.EOF {
				break
			}
			r.Log(Error, err.Error())
			r.Stop()
			return err
		}
	}
	return nil
}