/*
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 (
	"errors"
	"fmt"
	"io"
	"os"
	"os/exec"
	"strconv"
	"time"

	"bitbucket.org/ausocean/av/encoding"
	"bitbucket.org/ausocean/av/encoding/flv"
	"bitbucket.org/ausocean/av/encoding/mts"
	"bitbucket.org/ausocean/av/parse"
	"bitbucket.org/ausocean/av/rtmp"
	"bitbucket.org/ausocean/iot/pi/netsender"
	"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
	runContinuously         = "0" // -t arg to raspivid
)

// 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
	encoder     encoding.Encoder
	parse       func(dst io.Writer, src io.Reader, delay time.Duration) error
	cmd         *exec.Cmd
	inputReader io.ReadCloser
	ffmpegStdin io.WriteCloser
	outputChan  chan []byte
	setupInput  func() error
	getFrame    func() []byte
	destination loadSender
	rtmpInst    rtmp.Session
	bitrate     int
	ns          *netsender.Sender
}

// New returns a pointer to a new Revid with the desired configuration, and/or
// an error if construction of the new instance was not successful.
func New(c Config, ns *netsender.Sender) (*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)
	r.ns = ns
	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(r.ns, 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.parse = parse.H264
	case Mjpeg:
		r.Log(Info, "Using MJPEG parser!")
		r.parse = parse.MJPEG
	}

	switch r.config.Packetization {
	case None:
		// no packetisation - Revid output chan grabs raw data straight from parser
		r.parse = func(dst io.Writer, src io.Reader, _ time.Duration) error {
			// FIXME(kortschak): Reduce this allocation mess. It exists
			// because we do not know that the dst will not modify the
			// buffer. It shouldn't, but ...
			for {
				var b [4 << 10]byte
				n, rerr := src.Read(b[:])
				_, werr := dst.Write(b[:n])
				if rerr != nil {
					return rerr
				}
				if werr != nil {
					return werr
				}
			}
		}
		r.getFrame = r.getFrameNoPacketization
		return nil
	case Mpegts:
		r.Log(Info, "Using MPEGTS packetisation")
		frameRate, _ := strconv.ParseFloat(r.config.FrameRate, 64)
		r.encoder = mts.NewEncoder(frameRate)
	case Flv:
		r.Log(Info, "Using FLV packetisation")
		frameRate, _ := strconv.Atoi(r.config.FrameRate)
		r.encoder = flv.NewEncoder(true, true, frameRate)
	}
	// We have packetization of some sort, so we want to send data to Generator
	// to perform packetization
	r.getFrame = r.getFramePacketization

	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, "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, "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 encoder with no packetization settings
func (r *Revid) getFrameNoPacketization() []byte {
	return <-r.outputChan
}

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

// TODO(kortschak): Factor this out to an io.Writer type and remove the Stream chans.
// Also add a no-op encoder that handles non-packeted data.
//
// 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.encoder.Stream():
			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", runContinuously,
			"-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", runContinuously,
			"-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 = stdout
	go func() {
		r.Log(Info, "Reading camera data!")
		r.parse(chunkWriter{r.encoder}, r.inputReader, 0)
		r.Log(Info, "Not trying to read from camera anymore!")
	}()
	return nil
}

// 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
	}
	delay := time.Second / time.Duration(fps)

	f, err := os.Open(r.config.InputFileName)
	if err != nil {
		r.Log(Error, err.Error())
		r.Stop()
		return err
	}
	defer f.Close()

	// TODO(kortschak): Maybe we want a context.Context-aware parser that we can stop.
	return r.parse(chunkWriter{r.encoder}, f, delay)
}

// TODO(kortschak): Remove this type and revise the signature of
// the parsers to accept an encoding.Encoder.
//
// chunkWriter is a shim between the new function-based approach
// and the old flow-based approach.
type chunkWriter struct {
	encoding.Encoder
}

func (w chunkWriter) Write(b []byte) (int, error) {
	err := w.Encoder.Encode(b)
	return len(b), err
}