/*
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"
	"strings"
	"time"

	"bitbucket.org/ausocean/av/stream"
	"bitbucket.org/ausocean/av/stream/flv"
	"bitbucket.org/ausocean/av/stream/lex"
	"bitbucket.org/ausocean/av/stream/mts"
	"bitbucket.org/ausocean/iot/pi/netsender"
	"bitbucket.org/ausocean/utils/logger"
	"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          = 10000
	ringBufferElementSize   = 150000
	writeTimeout            = 10 * time.Millisecond
	readTimeout             = 10 * time.Millisecond
	httpTimeout             = 5 * time.Second
	bitrateTime             = 1 * time.Minute
	mjpegParserInChanLen    = 100000
	ffmpegPath              = "/usr/local/bin/ffmpeg"
	rtmpConnectionTimout    = 10
	outputChanSize          = 1000
	cameraRetryPeriod       = 5 * time.Second
	sendFailedDelay         = 5 * time.Millisecond
	maxSendFailedErrorCount = 500
	clipSizeThreshold       = 11
	rtmpConnectionMaxTries  = 5
	raspividNoOfTries       = 3
	sendingWaitTime         = 5 * time.Millisecond
	pkg                     = "revid:"
)

type Logger interface {
	SetLevel(int8)
	Log(level int8, message string, params ...interface{})
}

// 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 {
	// config holds the Revid configuration.
	// For historical reasons it also handles logging.
	// FIXME(kortschak): The relationship of concerns
	// in config/ns is weird.
	config Config
	// ns holds the netsender.Sender responsible for HTTP.
	ns *netsender.Sender

	// setupInput holds the current approach to setting up
	// the input stream.
	setupInput func() error

	// cmd is the exec'd process that may be used to produce
	// the input stream.
	// FIXME(kortschak): This should not exist. Replace this
	// with a context.Context cancellation.
	cmd *exec.Cmd

	// lexTo, encoder and packer handle transcoding the input stream.
	lexTo   func(dst stream.Encoder, src io.Reader, delay time.Duration) error
	encoder stream.Encoder
	packer  packer
	// buffer handles passing frames from the transcoder
	// to the target destination.
	buffer *ring.Buffer
	// destination is the target endpoint.
	destination []loadSender

	// bitrate hold the last send bitrate  calculation result.
	bitrate int

	// isRunning is a loaded and cocked foot-gun.
	isRunning bool
}

// packer takes data segments and packs them into clips
// of the number frames specified in the owners config.
type packer struct {
	owner       *Revid
	lastTime    time.Time
	packetCount uint
}

// Write implements the io.Writer interface.
//
// Unless the ring buffer returns an error, all writes
// are deemed to be successful, although a successful
// write may include a dropped frame.
func (p *packer) Write(frame []byte) (int, error) {
	if len(frame) > ringBufferElementSize {
		p.owner.config.Logger.Log(logger.Warning, pkg+"frame was too big", "frame size", len(frame))
		return len(frame), nil
	}
	n, err := p.owner.buffer.Write(frame)
	if err != nil {
		if err == ring.ErrDropped {
			p.owner.config.Logger.Log(logger.Warning, pkg+"dropped frame", "frame size", len(frame))
			return len(frame), nil
		}
		p.owner.config.Logger.Log(logger.Error, pkg+"unexpected ring buffer write error", "error", err.Error())
		return n, err
	}
	p.packetCount++
	now := time.Now()
	if (p.owner.config.Output1 != Rtmp && now.Sub(p.lastTime) > clipDuration && p.packetCount%7 == 0) || p.owner.config.Output1 == Rtmp {
		p.owner.buffer.Flush()
		p.packetCount = 0
		p.lastTime = now
	}
	return len(frame), nil
}

// 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) {
	r := Revid{ns: ns}
	r.buffer = ring.NewBuffer(ringBufferSize, ringBufferElementSize, writeTimeout)
	r.packer.owner = &r
	err := r.reset(c)
	if err != nil {
		return nil, err
	}
	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

	for _, dest := range r.destination {
		if dest != nil {
			err = dest.close()
			if err != nil {
				return err
			}
		}
	}

	n := 1
	if r.config.Output2 != 0 {
		n = 2
	}
	r.destination = make([]loadSender, n)

	for outNo, outType := range []uint8{r.config.Output1, r.config.Output2} {
		switch outType {
		case File:
			s, err := newFileSender(config.OutputFileName)
			if err != nil {
				return err
			}
			r.destination[outNo] = s
		case FfmpegRtmp:
			s, err := newFfmpegSender(config.RtmpUrl, fmt.Sprint(r.config.FrameRate))
			if err != nil {
				return err
			}
			r.destination[outNo] = s
		case Rtmp:
			s, err := newRtmpSender(config.RtmpUrl, rtmpConnectionTimout, rtmpConnectionMaxTries, r.config.Logger.Log)
			if err != nil {
				return err
			}
			r.destination[outNo] = s
		case Http:
			r.destination[outNo] = newHttpSender(r.ns, r.config.Logger.Log)
		case Udp:
			s, err := newUdpSender(r.config.RtpAddress, r.config.Logger.Log)
			if err != nil {
				return err
			}
			r.destination[outNo] = s
		case Rtp:
			s, err := newRtpSender(r.config.RtpAddress, r.config.Logger.Log, r.config.FrameRate)
			if err != nil {
				return err
			}
			r.destination[outNo] = s
		}
	}

	switch r.config.Input {
	case Raspivid:
		r.setupInput = r.startRaspivid
	case File:
		r.setupInput = r.setupInputForFile
	}
	switch r.config.InputCodec {
	case H264:
		r.config.Logger.Log(logger.Info, pkg+"using H264 lexer")
		r.lexTo = lex.H264
	case Mjpeg:
		r.config.Logger.Log(logger.Info, pkg+"using MJPEG lexer")
		r.lexTo = lex.MJPEG
	}

	switch r.config.Packetization {
	case None:
		// no packetisation - Revid output chan grabs raw data straight from parser
		r.lexTo = func(dst stream.Encoder, src io.Reader, _ time.Duration) error {
			for {
				var b [4 << 10]byte
				n, rerr := src.Read(b[:])
				werr := dst.Encode(b[:n])
				if rerr != nil {
					return rerr
				}
				if werr != nil {
					return werr
				}
			}
		}
		r.encoder = stream.NopEncoder(&r.packer)
	case Mpegts:
		r.config.Logger.Log(logger.Info, pkg+"using MPEGTS packetisation")
		r.encoder = mts.NewEncoder(&r.packer, float64(r.config.FrameRate))
	case Flv:
		r.config.Logger.Log(logger.Info, pkg+"using FLV packetisation")
		r.encoder, err = flv.NewEncoder(&r.packer, true, true, int(r.config.FrameRate))
		if err != nil {
			r.config.Logger.Log(logger.Fatal, pkg+"failed to open FLV encoder", err.Error())
		}
	}

	return nil
}

// 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.config.Logger.Log(logger.Warning, pkg+"revid.Start() called but revid already running")
		return
	}
	r.config.Logger.Log(logger.Info, pkg+"starting Revid")
	r.config.Logger.Log(logger.Debug, pkg+"setting up output")
	r.isRunning = true
	r.config.Logger.Log(logger.Info, pkg+"starting output routine")
	go r.outputClips()
	r.config.Logger.Log(logger.Info, pkg+"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.config.Logger.Log(logger.Warning, pkg+"revid.Stop() called but revid not running")
		return
	}

	r.config.Logger.Log(logger.Info, pkg+"stopping revid")
	r.isRunning = false

	r.config.Logger.Log(logger.Info, pkg+"killing input proccess")
	// If a cmd process is running, we kill!
	if r.cmd != nil && r.cmd.Process != nil {
		r.cmd.Process.Kill()
	}
}

// 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() {
	lastTime := time.Now()
	var count int
loop:
	for r.isRunning {
		// If the ring buffer has something we can read and send off
		chunk, err := r.buffer.Next(readTimeout)
		switch err {
		case nil:
			// Do nothing.
		case ring.ErrTimeout:
			r.config.Logger.Log(logger.Warning, pkg+"ring buffer read timeout")
			continue
		default:
			r.config.Logger.Log(logger.Error, pkg+"unexpected error", "error", err.Error())
			fallthrough
		case io.EOF:
			break loop
		}

		count += chunk.Len()
		r.config.Logger.Log(logger.Debug, pkg+"about to send")
		for i, dest := range r.destination {
			err = dest.load(chunk)
			if err != nil {
				r.config.Logger.Log(logger.Error, pkg+"failed to load clip to output"+strconv.Itoa(i))
			}
		}

		for i, dest := range r.destination {
			err = dest.send()
			if err == nil {
				r.config.Logger.Log(logger.Debug, pkg+"sent clip to output "+strconv.Itoa(i))
			} else if r.config.SendRetry == false {
				r.config.Logger.Log(logger.Warning, pkg+"send to output "+strconv.Itoa(i)+"failed", "error", err.Error())
			} else {
				r.config.Logger.Log(logger.Error, pkg+"send to output "+strconv.Itoa(i)+
					"failed, trying again", "error", err.Error())
				err = dest.send()
				if err != nil && chunk.Len() > 11 {
					r.config.Logger.Log(logger.Error, pkg+"second send attempted failed, restarting connection", "error", err.Error())
					for err != nil {
						time.Sleep(sendFailedDelay)
						if rs, ok := dest.(restarter); ok {
							r.config.Logger.Log(logger.Debug, pkg+"restarting session", "session", rs)
							err = rs.restart()
							if err != nil {
								r.config.Logger.Log(logger.Error, pkg+"failed to restart rtmp session", "error", err.Error())
								r.isRunning = false
								return
							}

							r.config.Logger.Log(logger.Info, pkg+"restarted rtmp session")
						}

						err = dest.send()
						if err != nil {
							r.config.Logger.Log(logger.Error, pkg+"send failed again, with error", "error", err.Error())
						}
					}
				}
			}
		}

		// Release the chunk back to the ring buffer for use
		for _, dest := range r.destination {
			dest.release()
		}
		r.config.Logger.Log(logger.Debug, pkg+"done reading that clip from ring buffer")

		// Log some information regarding bitrate and ring buffer size if it's time
		now := time.Now()
		deltaTime := now.Sub(lastTime)
		if deltaTime > bitrateTime {
			// FIXME(kortschak): For subsecond deltaTime, this will give infinite bitrate.
			r.bitrate = int(float64(count*8) / float64(deltaTime/time.Second))
			r.config.Logger.Log(logger.Debug, pkg+"bitrate (bits/s)", "bitrate", r.bitrate)
			r.config.Logger.Log(logger.Debug, pkg+"ring buffer size", "value", r.buffer.Len())
			lastTime = now
			count = 0
		}
	}
	r.config.Logger.Log(logger.Info, pkg+"not outputting clips anymore")
	for i, dest := range r.destination {
		err := dest.close()
		if err != nil {
			r.config.Logger.Log(logger.Error, pkg+"failed to close output"+strconv.Itoa(i)+" destination", "error", err.Error())
		}
	}
}

// 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.config.Logger.Log(logger.Info, pkg+"starting raspivid")

	const disabled = "0"
	args := []string{
		"--output", "-",
		"--nopreview",
		"--timeout", disabled,
		"--width", fmt.Sprint(r.config.Width),
		"--height", fmt.Sprint(r.config.Height),
		"--bitrate", fmt.Sprint(r.config.Bitrate),
		"--framerate", fmt.Sprint(r.config.FrameRate),
	}
	if r.config.FlipHorizontal {
		args = append(args, "--hflip")
	}
	if r.config.FlipVertical {
		args = append(args, "--vflip")
	}
	switch r.config.InputCodec {
	default:
		return fmt.Errorf("revid: invalid input codec: %v", r.config.InputCodec)
	case H264:
		args = append(args,
			"--codec", "H264",
			"--inline",
			"--intra", fmt.Sprint(r.config.IntraRefreshPeriod),
		)
		if r.config.Quantize {
			args = append(args, "-qp", fmt.Sprint(r.config.Quantization))
		}
	case Mjpeg:
		args = append(args, "--codec", "MJPEG")
	}
	r.config.Logger.Log(logger.Info, pkg+"raspivid args", "raspividArgs", strings.Join(args, " "))
	r.cmd = exec.Command("raspivid", args...)

	stdout, err := r.cmd.StdoutPipe()
	if err != nil {
		return err
	}
	err = r.cmd.Start()
	if err != nil {
		r.config.Logger.Log(logger.Fatal, pkg+"cannot start raspivid", "error", err.Error())
	}

	r.config.Logger.Log(logger.Info, pkg+"reading camera data")
	delay := time.Second / time.Duration(r.config.FrameRate)
	err = r.lexTo(r.encoder, stdout, delay)
	r.config.Logger.Log(logger.Info, pkg+"finished reading camera data")
	return err
}

// setupInputForFile sets things up for getting input from a file
func (r *Revid) setupInputForFile() error {
	delay := time.Second / time.Duration(r.config.FrameRate)
	f, err := os.Open(r.config.InputFileName)
	if err != nil {
		r.config.Logger.Log(logger.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.lexTo(r.encoder, f, delay)
}