/*
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"
	"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/ring"
	"bitbucket.org/ausocean/utils/smartlogger"
)

// 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
	pkg                     = "revid:"
)

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

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 and encoder handle transcoding the input stream.
	lexTo   func(dst stream.Encoder, src io.Reader, delay time.Duration) error
	encoder stream.Encoder
	// ringBuffer handles passing frames from the transcoder
	// to the target destination.
	ringBuffer *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
}

// 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
	r.ns = ns
	err := r.reset(c)
	if err != nil {
		return nil, err
	}
	r.ringBuffer = ring.NewBuffer(ringBufferSize, ringBufferElementSize, writeTimeout)
	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.config.Logger.Log(smartlogger.Error, pkg+"could not close destination", "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.config.Logger.Log)
		if err != nil {
			return err
		}
		r.destination = s
	case Http:
		r.destination = newHttpSender(r.ns, r.config.Logger.Log)
	}

	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(smartlogger.Info, pkg+"using H264 lexer")
		r.lexTo = lex.H264
	case Mjpeg:
		r.config.Logger.Log(smartlogger.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()
	case Mpegts:
		r.config.Logger.Log(smartlogger.Info, pkg+"using MPEGTS packetisation")
		frameRate, _ := strconv.ParseFloat(r.config.FrameRate, 64)
		r.encoder = mts.NewEncoder(frameRate)
	case Flv:
		r.config.Logger.Log(smartlogger.Info, pkg+"using FLV packetisation")
		frameRate, _ := strconv.Atoi(r.config.FrameRate)
		r.encoder = flv.NewEncoder(true, true, frameRate)
	}

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

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

	r.config.Logger.Log(smartlogger.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()
	}
}

// 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.config.Logger.Log(smartlogger.Warning, pkg+"frame was too big", "frame size", lenOfFrame)
				continue
			}
			_, err := r.ringBuffer.Write(frame)
			if err != nil {
				if err == ring.ErrDropped {
					r.config.Logger.Log(smartlogger.Warning, pkg+"dropped frame", "frame size", len(frame))
				} else {
					r.config.Logger.Log(smartlogger.Error, pkg+"unexpected ringbuffer write error",
						"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.config.Logger.Log(smartlogger.Debug, pkg+"about to send")
		err = r.destination.load(chunk)
		if err != nil {
			r.config.Logger.Log(smartlogger.Error, pkg+"failed to load clip")
		}
		err = r.destination.send()
		if err == nil {
			r.config.Logger.Log(smartlogger.Debug, pkg+"sent clip")
		}

		if r.isRunning && err != nil && chunk.Len() > 11 {
			r.config.Logger.Log(smartlogger.Debug, pkg+"send failed, trying again")
			// Try and send again
			err = r.destination.send()
			r.config.Logger.Log(smartlogger.Error, pkg+"destination send error", "error", err.Error())

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

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

				r.config.Logger.Log(smartlogger.Debug, pkg+"trying to send again with new connection")
				err = r.destination.send()
				if err != nil {
					r.config.Logger.Log(smartlogger.Error, pkg+"send failed with error", "error", err.Error())
				}
			}
		}

		r.destination.release()

		r.config.Logger.Log(smartlogger.Debug, pkg+"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.config.Logger.Log(smartlogger.Debug, pkg+"bitrate (bits/s)", "bitrate", r.bitrate)
			r.config.Logger.Log(smartlogger.Debug, pkg+"ring buffer size", "value", r.ringBuffer.Len())
			prevTime = now
			bytes = 0
		}
	}
	r.config.Logger.Log(smartlogger.Info, pkg+"not outputting clips anymore")
	err := r.destination.close()
	if err != nil {
		r.config.Logger.Log(smartlogger.Error, pkg+"failed to close 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(smartlogger.Info, pkg+"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.config.Logger.Log(smartlogger.Info, pkg+"raspivid args", "raspividArgs", strings.Join(args, " "))
		r.cmd = exec.Command("raspivid", args...)

	case Mjpeg:
		// FIXME(saxon): do above in this case too
		r.cmd = exec.Command("raspivid",
			"-cd", "MJPEG",
			"-o", "-",
			"-n",
			"-t", runContinuously,
			"-fps", r.config.FrameRate,
		)
	}
	d, err := strconv.Atoi(r.config.FrameRate)
	if err != nil {
		return err
	}
	delay := time.Second / time.Duration(d)
	stdout, err := r.cmd.StdoutPipe()
	if err != nil {
		return err
	}
	err = r.cmd.Start()
	if err != nil {
		return err
	}

	r.config.Logger.Log(smartlogger.Info, pkg+"reading camera data")
	err = r.lexTo(r.encoder, stdout, delay)
	if err != nil {
		return err
	}
	r.config.Logger.Log(smartlogger.Info, pkg+"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.config.Logger.Log(smartlogger.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)
}