/*
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"
	"sync"
	"time"

	"bitbucket.org/ausocean/av/codec/lex"
	"bitbucket.org/ausocean/av/container/flv"
	"bitbucket.org/ausocean/av/container/mts"
	"bitbucket.org/ausocean/iot/pi/netsender"
	"bitbucket.org/ausocean/utils/ioext"
	"bitbucket.org/ausocean/utils/logger"
	"bitbucket.org/ausocean/utils/ring"
)

// Ring buffer sizes and read/write timeouts.
const (
	ringBufferSize        = 1000
	ringBufferElementSize = 100000
	writeTimeout          = 10 * time.Millisecond
	readTimeout           = 10 * time.Millisecond
)

// RTMP connection properties.
const (
	rtmpConnectionMaxTries = 5
	rtmpConnectionTimeout  = 10
)

// Duration of video for each clip sent out.
const clipDuration = 1 * time.Second

// Time duration between bitrate checks.
const bitrateTime = 1 * time.Minute

// After a send fail, this is the delay before another send.
const sendFailedDelay = 5 * time.Millisecond

const ffmpegPath = "/usr/local/bin/ffmpeg"

const 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(dest io.Writer, src io.Reader, delay time.Duration) error

	// buffer handles passing frames from the transcoder
	// to the target destination.
	buffer *buffer

	// encoder holds the required encoders, which then write to destinations.
	encoder []io.Writer

	// writeClosers holds the senders that the encoders will write to.
	writeClosers []io.WriteCloser

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

	mu        sync.Mutex
	isRunning bool

	wg sync.WaitGroup

	err chan error
}

// buffer is a wrapper for a ring.Buffer and provides function to write and
// flush in one Write call.
type buffer ring.Buffer

// Write implements the io.Writer interface. It will write to the underlying
// ring.Buffer and then flush to indicate a complete ring.Buffer write.
func (b *buffer) Write(d []byte) (int, error) {
	r := (*ring.Buffer)(b)
	n, err := r.Write(d)
	r.Flush()
	return n, err
}

// 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, err: make(chan error)}
	err := r.reset(c)
	if err != nil {
		return nil, err
	}
	go r.handleErrors()
	return &r, nil
}

// TODO(Saxon): put more thought into error severity.
func (r *Revid) handleErrors() {
	for {
		err := <-r.err
		if err != nil {
			r.config.Logger.Log(logger.Error, pkg+"async error", "error", err.Error())
			r.Stop()
			err = r.Start()
			if err != nil {
				r.config.Logger.Log(logger.Error, pkg+"failed to restart revid", "error", err.Error())
			}
		}
	}
}

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

func (r *Revid) setConfig(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
	return nil
}

// setupPipeline constructs the revid dataPipeline. Inputs, encoders and
// senders are create and linked based on the current revid config.
func (r *Revid) setupPipeline(mtsEnc, flvEnc func(dst io.Writer, rate int) (io.Writer, error), multiWriter func(...io.WriteCloser) io.WriteCloser) error {
	r.buffer = (*buffer)(ring.NewBuffer(ringBufferSize, ringBufferElementSize, writeTimeout))

	r.encoder = r.encoder[:0]

	// mtsSenders will hold the senders the require MPEGTS encoding, and flvSenders
	// will hold senders that require FLV encoding.
	var mtsSenders, flvSenders []io.WriteCloser

	// We will go through our outputs and create the corresponding senders to add
	// to mtsSenders if the output requires MPEGTS encoding, or flvSenders if the
	// output requires FLV encoding.
	var w io.WriteCloser
	for _, out := range r.config.Outputs {
		switch out {
		case Http:
			w = newMtsSender(newHttpSender(r.ns, r.config.Logger.Log), r.config.Logger.Log, ringBufferSize, ringBufferElementSize, writeTimeout)
			mtsSenders = append(mtsSenders, w)
		case Rtp:
			w, err := newRtpSender(r.config.RtpAddress, r.config.Logger.Log, r.config.FrameRate)
			if err != nil {
				r.config.Logger.Log(logger.Warning, pkg+"rtp connect error", "error", err.Error())
			}
			mtsSenders = append(mtsSenders, w)
		case File:
			w, err := newFileSender(r.config.OutputPath)
			if err != nil {
				return err
			}
			mtsSenders = append(mtsSenders, w)
		case Rtmp:
			w, err := newRtmpSender(r.config.RtmpUrl, rtmpConnectionTimeout, rtmpConnectionMaxTries, r.config.Logger.Log)
			if err != nil {
				r.config.Logger.Log(logger.Warning, pkg+"rtmp connect error", "error", err.Error())
			}
			flvSenders = append(flvSenders, w)
		}
	}

	// If we have some senders that require MPEGTS encoding then add an MPEGTS
	// encoder to revid's encoder slice, and give this encoder the mtsSenders
	// as a destination.
	if len(mtsSenders) != 0 {
		mw := multiWriter(mtsSenders...)
		e, _ := mtsEnc(mw, int(r.config.FrameRate))
		r.encoder = append(r.encoder, e)
	}

	// If we have some senders that require FLV encoding then add an FLV
	// encoder to revid's encoder slice, and give this encoder the flvSenders
	// as a destination.
	if len(flvSenders) != 0 {
		mw := multiWriter(flvSenders...)
		e, err := flvEnc(mw, int(r.config.FrameRate))
		if err != nil {
			return err
		}
		r.encoder = append(r.encoder, e)
	}

	switch r.config.Input {
	case Raspivid:
		r.setupInput = r.startRaspivid
	case V4L:
		r.setupInput = r.startV4L
	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
	}
	return nil
}

func newMtsEncoder(dst io.Writer, fps int) (io.Writer, error) {
	e := mts.NewEncoder(dst, float64(fps))
	return e, nil
}

func newFlvEncoder(dst io.Writer, fps int) (io.Writer, error) {
	e, err := flv.NewEncoder(dst, true, true, fps)
	if err != nil {
		return nil, err
	}
	return e, nil
}

// 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 {
	err := r.setConfig(config)
	if err != nil {
		return err
	}

	err = r.setupPipeline(newMtsEncoder, newFlvEncoder, ioext.MultiWriteCloser)
	if err != nil {
		return err
	}

	return nil
}

// IsRunning returns true if revid is running.
func (r *Revid) IsRunning() bool {
	r.mu.Lock()
	ret := r.isRunning
	r.mu.Unlock()
	return ret
}

func (r *Revid) Config() Config {
	r.mu.Lock()
	cfg := r.config
	r.mu.Unlock()
	return cfg
}

// setIsRunning sets r.isRunning using b.
func (r *Revid) setIsRunning(b bool) {
	r.mu.Lock()
	r.isRunning = b
	r.mu.Unlock()
}

// 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() error {
	if r.IsRunning() {
		r.config.Logger.Log(logger.Warning, pkg+"start called, but revid already running")
		return nil
	}
	r.config.Logger.Log(logger.Info, pkg+"starting Revid")
	// TODO: this doesn't need to be here
	r.config.Logger.Log(logger.Debug, pkg+"setting up output")
	r.setIsRunning(true)
	r.config.Logger.Log(logger.Info, pkg+"starting output routine")
	r.wg.Add(1)
	go r.outputClips()
	r.config.Logger.Log(logger.Info, pkg+"setting up input and receiving content")
	err := r.setupInput()
	if err != nil {
		r.Stop()
	}
	return err
}

// 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+"stop called but revid isn't running")
		return
	}

	for _, w := range r.writeClosers {
		err := w.Close()
		if err != nil {
			r.config.Logger.Log(logger.Error, pkg+"could not close all writeClosers, cannot stop", "error", err.Error())
			return
		}
	}
	r.config.Logger.Log(logger.Info, pkg+"stopping revid")
	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()
	}
	r.wg.Wait()
	r.setIsRunning(false)
}

func (r *Revid) Update(vars map[string]string) error {
	if r.IsRunning() {
		r.Stop()
	}
	//look through the vars and update revid where needed
	for key, value := range vars {
		switch key {
		case "Saturation":
			s, err := strconv.ParseInt(value, 10, 0)
			if err != nil {
				r.config.Logger.Log(logger.Warning, pkg+"invalid saturation param", "value", value)
			}
			r.config.Saturation = int(s)
		case "Brightness":
			b, err := strconv.ParseUint(value, 10, 0)
			if err != nil {
				r.config.Logger.Log(logger.Warning, pkg+"invalid brightness param", "value", value)
			}
			r.config.Brightness = uint(b)
		case "Exposure":
			r.config.Exposure = value
		case "AutoWhiteBalance":
			r.config.AutoWhiteBalance = value
		case "Output":
			outputs := strings.Split(value, ",")
			r.config.Outputs = make([]uint8, len(outputs))

			for i, output := range outputs {
				switch output {
				case "File":
					r.config.Outputs[i] = File
				case "Http":
					r.config.Outputs[i] = Http
				case "Rtmp":
					r.config.Outputs[i] = Rtmp
				case "Rtp":
					r.config.Outputs[i] = Rtp
				default:
					r.config.Logger.Log(logger.Warning, pkg+"invalid output param", "value", value)
					continue
				}
			}

		case "RtmpUrl":
			r.config.RtmpUrl = value
		case "RtpAddress":
			r.config.RtpAddress = value
		case "Bitrate":
			v, err := strconv.ParseUint(value, 10, 0)
			if err != nil {
				r.config.Logger.Log(logger.Warning, pkg+"invalid framerate param", "value", value)
				break
			}
			r.config.Bitrate = uint(v)
		case "OutputPath":
			r.config.OutputPath = value
		case "InputPath":
			r.config.InputPath = value
		case "Height":
			h, err := strconv.ParseUint(value, 10, 0)
			if err != nil {
				r.config.Logger.Log(logger.Warning, pkg+"invalid height param", "value", value)
				break
			}
			r.config.Height = uint(h)
		case "Width":
			w, err := strconv.ParseUint(value, 10, 0)
			if err != nil {
				r.config.Logger.Log(logger.Warning, pkg+"invalid width param", "value", value)
				break
			}
			r.config.Width = uint(w)
		case "FrameRate":
			v, err := strconv.ParseUint(value, 10, 0)
			if err != nil {
				r.config.Logger.Log(logger.Warning, pkg+"invalid framerate param", "value", value)
				break
			}
			r.config.FrameRate = uint(v)
		case "Rotation":
			v, err := strconv.ParseUint(value, 10, 0)
			if err != nil || v > 359 {
				r.config.Logger.Log(logger.Warning, pkg+"invalid rotation param", "value", value)
				break
			}
			r.config.Rotation = uint(v)
		case "HttpAddress":
			r.config.HttpAddress = value
		case "Quantization":
			q, err := strconv.ParseUint(value, 10, 0)
			if err != nil {
				r.config.Logger.Log(logger.Warning, pkg+"invalid quantization param", "value", value)
				break
			}
			r.config.Quantization = uint(q)
		case "IntraRefreshPeriod":
			p, err := strconv.ParseUint(value, 10, 0)
			if err != nil {
				r.config.Logger.Log(logger.Warning, pkg+"invalid intrarefreshperiod param", "value", value)
				break
			}
			r.config.IntraRefreshPeriod = uint(p)

		case "HorizontalFlip":
			switch strings.ToLower(value) {
			case "true":
				r.config.FlipHorizontal = true
			case "false":
				r.config.FlipHorizontal = false
			default:
				r.config.Logger.Log(logger.Warning, pkg+"invalid HorizontalFlip param", "value", value)
			}
		case "VerticalFlip":
			switch strings.ToLower(value) {
			case "true":
				r.config.FlipVertical = true
			case "false":
				r.config.FlipVertical = false
			default:
				r.config.Logger.Log(logger.Warning, pkg+"invalid VerticalFlip param", "value", value)
			}
		case "BurstPeriod":
			v, err := strconv.ParseUint(value, 10, 0)
			if err != nil {
				r.config.Logger.Log(logger.Warning, pkg+"invalid BurstPeriod param", "value", value)
				break
			}
			r.config.BurstPeriod = uint(v)
		}
	}
	r.config.Logger.Log(logger.Info, pkg+"revid config changed", "config", fmt.Sprintf("%+v", r.config))
	return r.reset(r.config)
}

// 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() {
	defer r.wg.Done()
	lastTime := time.Now()
	var count int
loop:
	for r.IsRunning() {
		// If the ring buffer has something we can read and send off
		chunk, err := (*ring.Buffer)(r.buffer).Next(readTimeout)
		switch err {
		case nil:
			// Do nothing.
		case ring.ErrTimeout:
			r.config.Logger.Log(logger.Debug, 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
		}

		// Loop over encoders and hand bytes over to each one.
		for _, e := range r.encoder {
			_, err := chunk.WriteTo(e)
			if err != nil {
				r.err <- err
			}
		}

		// Release the chunk back to the ring buffer.
		chunk.Close()

		// FIXME(saxon): this doesn't work anymore.
		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", (*ring.Buffer)(r.buffer).Len())
			lastTime = now
			count = 0
		}
	}
	r.config.Logger.Log(logger.Info, pkg+"not outputting clips anymore")
}

// 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),
		"--rotation", fmt.Sprint(r.config.Rotation),
		"--brightness", fmt.Sprint(r.config.Brightness),
		"--saturation", fmt.Sprint(r.config.Saturation),
		"--exposure", fmt.Sprint(r.config.Exposure),
		"--awb", fmt.Sprint(r.config.AutoWhiteBalance),
	}

	if r.config.FlipHorizontal {
		args = append(args, "--hflip")
	}

	if r.config.FlipVertical {
		args = append(args, "--vflip")
	}
	if r.config.FlipHorizontal {
		args = append(args, "--hflip")
	}

	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.wg.Add(1)
	go r.processFrom(stdout, 0)
	return nil
}

func (r *Revid) startV4L() error {
	const defaultVideo = "/dev/video0"

	r.config.Logger.Log(logger.Info, pkg+"starting webcam")
	if r.config.InputPath == "" {
		r.config.Logger.Log(logger.Info, pkg+"using default video device", "device", defaultVideo)
		r.config.InputPath = defaultVideo
	}

	args := []string{
		"-i", r.config.InputPath,
		"-f", "h264",
		"-r", fmt.Sprint(r.config.FrameRate),
	}

	args = append(args,
		"-b:v", fmt.Sprint(r.config.Bitrate),
		"-maxrate", fmt.Sprint(r.config.Bitrate),
		"-bufsize", fmt.Sprint(r.config.Bitrate/2),
		"-s", fmt.Sprintf("%dx%d", r.config.Width, r.config.Height),
		"-",
	)

	r.config.Logger.Log(logger.Info, pkg+"ffmpeg args", "args", strings.Join(args, " "))
	r.cmd = exec.Command("ffmpeg", 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 webcam", "error", err.Error())
		return err
	}

	r.wg.Add(1)
	go r.processFrom(stdout, time.Duration(0))
	return nil
}

// setupInputForFile sets things up for getting input from a file
func (r *Revid) setupInputForFile() error {
	f, err := os.Open(r.config.InputPath)
	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.
	r.wg.Add(1)
	go r.processFrom(f, time.Second/time.Duration(r.config.FrameRate))
	return nil
}

func (r *Revid) processFrom(read io.Reader, delay time.Duration) {
	r.config.Logger.Log(logger.Info, pkg+"reading input data")
	r.err <- r.lexTo(r.buffer, read, delay)
	r.config.Logger.Log(logger.Info, pkg+"finished reading input data")
	r.wg.Done()
}