/*
NAME
  revid.go

AUTHORS
  Saxon A. Nelson-Milton <saxon@ausocean.org>
  Alan Noble <alan@ausocean.org>
  Dan Kortschak <dan@ausocean.org>
  Trek Hopton <trek@ausocean.org>
  Scott Barnard <scott@ausocean.org>

LICENSE
  revid is Copyright (C) 2017-2020 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
  in gpl.txt.  If not, see http://www.gnu.org/licenses.
*/

// Package revid provides an API for reading, transcoding, and writing audio/video streams and files.
package revid

import (
	"errors"
	"fmt"
	"io"
	"sync"
	"time"

	"bitbucket.org/ausocean/av/codec/codecutil"
	"bitbucket.org/ausocean/av/codec/h264"
	"bitbucket.org/ausocean/av/codec/h265"
	"bitbucket.org/ausocean/av/codec/mjpeg"
	"bitbucket.org/ausocean/av/container/flv"
	"bitbucket.org/ausocean/av/container/mts"
	"bitbucket.org/ausocean/av/device"
	"bitbucket.org/ausocean/av/device/file"
	"bitbucket.org/ausocean/av/device/geovision"
	"bitbucket.org/ausocean/av/device/raspivid"
	"bitbucket.org/ausocean/av/device/webcam"
	"bitbucket.org/ausocean/av/filter"
	"bitbucket.org/ausocean/av/revid/config"
	"bitbucket.org/ausocean/iot/pi/netsender"
	"bitbucket.org/ausocean/utils/bitrate"
	"bitbucket.org/ausocean/utils/ioext"
	"bitbucket.org/ausocean/utils/logger"
	"bitbucket.org/ausocean/utils/ring"
)

// Misc consts.
const (
	rbStartingElementSize  = 10000 // Bytes.
	rtmpConnectionMaxTries = 5
)

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

type encLog struct{ Logger }

func (el *encLog) Debug(msg string, args ...interface{})   { el.Log(logger.Debug, msg, args...) }
func (el *encLog) Info(msg string, args ...interface{})    { el.Log(logger.Info, msg, args...) }
func (el *encLog) Warning(msg string, args ...interface{}) { el.Log(logger.Warning, msg, args...) }
func (el *encLog) Error(msg string, args ...interface{})   { el.Log(logger.Error, msg, args...) }
func (el *encLog) Fatal(msg string, args ...interface{})   { el.Log(logger.Fatal, msg, args...) }

// 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.
	cfg config.Config

	// ns holds the netsender.Sender responsible for HTTP.
	ns *netsender.Sender

	// input will capture audio or video from which we can read data.
	input device.AVDevice

	// closeInput holds the cleanup function return from setupInput and is called
	// in Revid.Stop().
	closeInput func() error

	// lexTo, encoder and packer handle transcoding the input stream.
	lexTo func(dest io.Writer, src io.Reader, delay time.Duration) error

	// filters will hold the filter interface that will write to the chosen filter from the lexer.
	filters []filter.Filter

	// encoders will hold the multiWriteCloser that writes to encoders from the filter.
	encoders io.WriteCloser

	// running is used to keep track of revid's running state between methods.
	running bool

	// mu is used to protect isRunning during concurrent use.
	mu sync.Mutex

	// wg will be used to wait for any processing routines to finish.
	wg sync.WaitGroup

	// err will channel errors from revid routines to the handle errors routine.
	err chan error

	// bitrate is used for bitrate calculations.
	bitrate bitrate.Calculator

	// stop is used to signal stopping when looping an input.
	stop chan struct{}
}

// 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.Config, ns *netsender.Sender) (*Revid, error) {
	r := Revid{ns: ns, err: make(chan error)}
	err := r.setConfig(c)
	if err != nil {
		return nil, fmt.Errorf("could not set config, failed with error: %w", err)
	}
	go r.handleErrors()
	return &r, nil
}

// Config returns a copy of revids current config.
//
// Config is not safe for concurrent use.
func (r *Revid) Config() config.Config {
	return r.cfg
}

// TODO(Saxon): put more thought into error severity and how to handle these.
func (r *Revid) handleErrors() {
	for {
		err := <-r.err
		if err != nil {
			r.cfg.Logger.Log(logger.Error, "async error", "error", err.Error())
		}
	}
}

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

// reset swaps the current config of a Revid with the passed
// configuration; checking validity and returning errors if not valid. It then
// sets up the data pipeline accordingly to this configuration.
func (r *Revid) reset(c config.Config) error {
	r.cfg.Logger.Log(logger.Debug, "setting config")
	err := r.setConfig(c)
	if err != nil {
		return err
	}
	r.cfg.Logger.Log(logger.Info, "config set")

	r.cfg.Logger.Log(logger.Debug, "setting up revid pipeline")
	err = r.setupPipeline(
		func(dst io.WriteCloser, rate float64) (io.WriteCloser, error) {
			var st int
			var encOptions []func(*mts.Encoder) error

			switch r.cfg.Input {
			case config.InputRaspivid:
				switch r.cfg.InputCodec {
				case codecutil.H264:
					st = mts.EncodeH264
				case codecutil.MJPEG:
					st = mts.EncodeMJPEG
					encOptions = append(encOptions, mts.TimeBasedPSI(time.Duration(r.cfg.PSITime)*time.Second))
					r.cfg.CBR = true
				default:
					panic("unknown input codec for raspivid input")
				}
			case config.InputFile, config.InputV4L:
				switch r.cfg.InputCodec {
				case codecutil.H264:
					st = mts.EncodeH264
				case codecutil.MJPEG:
					st = mts.EncodeMJPEG
					encOptions = append(encOptions, mts.TimeBasedPSI(time.Duration(r.cfg.PSITime)*time.Second))
					r.cfg.CBR = true
				default:
					panic(fmt.Sprintf("unknown input codec %d for v4l or input file input", r.cfg.InputCodec))
				}
			case config.InputRTSP:
				switch r.cfg.InputCodec {
				case codecutil.H265:
					st = mts.EncodeH265
				case codecutil.H264:
					st = mts.EncodeH264
				case codecutil.MJPEG:
					st = mts.EncodeMJPEG
					encOptions = append(encOptions, mts.TimeBasedPSI(time.Duration(r.cfg.PSITime)*time.Second))
					r.cfg.CBR = true
				default:
					panic("unknown input codec for RTSP input")
				}
			case config.InputAudio:
				st = mts.EncodeAudio
				encOptions = append(encOptions, mts.TimeBasedPSI(time.Duration(r.cfg.PSITime)*time.Second))
				rate = 1 / r.cfg.RecPeriod
			default:
				panic("unknown input type")
			}
			encOptions = append(encOptions, mts.MediaType(st), mts.Rate(rate))
			return mts.NewEncoder(dst, &encLog{r.cfg.Logger}, encOptions...)
		},
		func(dst io.WriteCloser, fps int) (io.WriteCloser, error) {
			return flv.NewEncoder(dst, true, true, fps)
		},
		ioext.MultiWriteCloser,
	)
	r.cfg.Logger.Log(logger.Info, "finished setting pipeline")

	if err != nil {
		return err
	}

	return nil
}

// setConfig takes a config, checks it's validity and then replaces the current
// revid config.
func (r *Revid) setConfig(config config.Config) error {
	r.cfg.Logger = config.Logger
	r.cfg.Logger.Log(logger.Debug, "validating config")
	err := config.Validate()
	if err != nil {
		return errors.New("Config struct is bad: " + err.Error())
	}
	r.cfg.Logger.Log(logger.Info, "config validated")
	r.cfg = config
	r.cfg.Logger.SetLevel(r.cfg.LogLevel)
	return nil
}

// setupPipeline constructs the revid dataPipeline. Inputs, encoders and
// senders are created and linked based on the current revid config.
//
// mtsEnc and flvEnc will be called to obtain an mts encoder and flv encoder
// respectively. multiWriter will be used to create an ioext.multiWriteCloser
// so that encoders can write to multiple senders.
func (r *Revid) setupPipeline(mtsEnc func(dst io.WriteCloser, rate float64) (io.WriteCloser, error), flvEnc func(dst io.WriteCloser, rate int) (io.WriteCloser, error), multiWriter func(...io.WriteCloser) io.WriteCloser) error {
	// encoders will hold the encoders that are required for revid's current
	// configuration.
	var encoders []io.WriteCloser

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

	// Calculate no. of ring buffer elements based on starting element size
	// const and config directed max ring buffer size, then create buffer.
	// This is only used if the selected output uses a ring buffer.
	nElements := r.cfg.RBCapacity / rbStartingElementSize
	writeTimeout := time.Duration(r.cfg.RBWriteTimeout) * time.Second

	// 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.cfg.Outputs {
		switch out {
		case config.OutputHTTP:
			r.cfg.Logger.Log(logger.Debug, "using HTTP output")
			rb := ring.NewBuffer(rbStartingElementSize, int(nElements), writeTimeout)
			hs := newHTTPSender(r.ns, r.cfg.Logger.Log, r.bitrate.Report)
			w = newMTSSender(hs, r.cfg.Logger.Log, rb, r.cfg.ClipDuration)
			mtsSenders = append(mtsSenders, w)

		case config.OutputRTP:
			r.cfg.Logger.Log(logger.Debug, "using RTP output")
			w, err := newRtpSender(r.cfg.RTPAddress, r.cfg.Logger.Log, r.cfg.FrameRate, r.bitrate.Report)
			if err != nil {
				r.cfg.Logger.Log(logger.Warning, "rtp connect error", "error", err.Error())
			}
			mtsSenders = append(mtsSenders, w)
		case config.OutputFile:
			r.cfg.Logger.Log(logger.Debug, "using File output")
			w, err := newFileSender(r.cfg.OutputPath)
			if err != nil {
				return err
			}
			mtsSenders = append(mtsSenders, w)
		case config.OutputRTMP:
			r.cfg.Logger.Log(logger.Debug, "using RTMP output")
			rb := ring.NewBuffer(rbStartingElementSize, int(nElements), writeTimeout)
			w, err := newRtmpSender(r.cfg.RTMPURL, rtmpConnectionMaxTries, rb, r.cfg.Logger.Log, r.bitrate.Report)
			if err != nil {
				r.cfg.Logger.Log(logger.Warning, "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, float64(r.cfg.FrameRate))
		encoders = append(encoders, 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.cfg.FrameRate))
		if err != nil {
			return err
		}
		encoders = append(encoders, e)
	}

	r.encoders = multiWriter(encoders...)

	l := len(r.cfg.Filters)
	r.filters = []filter.Filter{filter.NewNoOp(r.encoders)}
	if l != 0 {
		r.cfg.Logger.Log(logger.Debug, "setting up filters", "filters", r.cfg.Filters)
		r.filters = make([]filter.Filter, l)
		dst := r.encoders

		for i := l - 1; i >= 0; i-- {
			switch r.cfg.Filters[i] {
			case config.FilterNoOp:
				r.cfg.Logger.Log(logger.Debug, "using NoOp filter")
				r.filters[i] = filter.NewNoOp(dst)
			case config.FilterMOG:
				r.cfg.Logger.Log(logger.Debug, "using MOG filter")
				r.filters[i] = filter.NewMOG(dst, r.cfg)
			case config.FilterVariableFPS:
				r.cfg.Logger.Log(logger.Debug, "using Variable FPS MOG filter")
				r.filters[i] = filter.NewVariableFPS(dst, r.cfg.MinFPS, filter.NewMOG(dst, r.cfg))
			case config.FilterKNN:
				r.cfg.Logger.Log(logger.Debug, "using KNN filter")
				r.filters[i] = filter.NewKNN(dst, r.cfg)
			case config.FilterDiff:
				r.cfg.Logger.Log(logger.Debug, "using gocv difference filter")
				r.filters[i] = filter.NewDiff(dst, r.cfg)
			case config.FilterBasic:
				r.cfg.Logger.Log(logger.Debug, "using go difference filter")
				r.filters[i] = filter.NewBasic(dst, r.cfg)
			default:
				panic("Undefined Filter")
			}
			dst = r.filters[i]
		}
		r.cfg.Logger.Log(logger.Info, "filters set up")
	}

	switch r.cfg.Input {
	case config.InputRaspivid:
		r.cfg.Logger.Log(logger.Debug, "using raspivid input")
		r.input = raspivid.New(r.cfg.Logger)
		r.setLexer(r.cfg.InputCodec, false)

	case config.InputV4L:
		r.cfg.Logger.Log(logger.Debug, "using V4L input")
		r.input = webcam.New(r.cfg.Logger)
		r.setLexer(r.cfg.InputCodec, false)

	case config.InputFile:
		r.cfg.Logger.Log(logger.Debug, "using file input")
		r.input = file.New()
		r.setLexer(r.cfg.InputCodec, false)

	case config.InputRTSP:
		r.cfg.Logger.Log(logger.Debug, "using RTSP input")
		r.input = geovision.New(r.cfg.Logger)
		r.setLexer(r.cfg.InputCodec, true)

	case config.InputAudio:
		r.cfg.Logger.Log(logger.Debug, "using audio input")
		err := r.setupAudio()
		if err != nil {
			return err
		}
	}

	// Configure the input device. We know that defaults are set, so no need to
	// return error, but we should log.
	r.cfg.Logger.Log(logger.Debug, "configuring input device")
	err := r.input.Set(r.cfg)
	if err != nil {
		r.cfg.Logger.Log(logger.Warning, "errors from configuring input device", "errors", err)
	}
	r.cfg.Logger.Log(logger.Info, "input device configured")

	return nil
}

// setLexer sets the revid input lexer based on input codec and whether input
// is RTSP or not, in which case an RTP/<codec> extractor is used.
func (r *Revid) setLexer(c uint8, isRTSP bool) {
	switch c {
	case codecutil.H264:
		r.cfg.Logger.Log(logger.Debug, "using H.264 codec")
		r.lexTo = h264.Lex
		if isRTSP {
			r.lexTo = h264.NewExtractor().Extract
		}
	case codecutil.H265:
		r.cfg.Logger.Log(logger.Debug, "using H.265 codec")
		r.lexTo = h265.NewExtractor(false).Extract
		if !isRTSP {
			panic("byte stream H.265 lexing not implemented")
		}
	case codecutil.MJPEG:
		r.cfg.Logger.Log(logger.Debug, "using MJPEG codec")
		r.lexTo = mjpeg.Lex
		if isRTSP {
			r.lexTo = mjpeg.NewExtractor().Extract
		}
	default:
		panic("unrecognised codec")
	}
}

// Start invokes a Revid to start processing video from a defined input
// and packetising (if theres packetization) to a defined output.
//
// Start is safe for concurrent use.
func (r *Revid) Start() error {
	if r.IsRunning() {
		r.cfg.Logger.Log(logger.Warning, "start called, but revid already running")
		return nil
	}

	r.mu.Lock()
	defer r.mu.Unlock()

	r.stop = make(chan struct{})

	r.cfg.Logger.Log(logger.Debug, "resetting revid")
	err := r.reset(r.cfg)
	if err != nil {
		r.Stop()
		return err
	}
	r.cfg.Logger.Log(logger.Info, "revid reset")

	// Calculate delay between frames based on FileFPS for video or
	// between recording periods for audio.
	d := time.Duration(0)
	if r.cfg.Input == config.InputAudio {
		d = time.Duration(r.cfg.RecPeriod * float64(time.Second))
	} else if r.cfg.FileFPS != 0 {
		d = time.Duration(1000/r.cfg.FileFPS) * time.Millisecond
	}

	r.cfg.Logger.Log(logger.Debug, "starting input processing routine")
	r.wg.Add(1)
	go r.processFrom(r.input, d)

	r.running = true
	return nil
}

// Stop closes down the pipeline. This closes encoders and sender output routines,
// connections, and/or files.
//
// Stop is safe for concurrent use.
func (r *Revid) Stop() {
	if !r.IsRunning() {
		r.cfg.Logger.Log(logger.Warning, "stop called but revid isn't running")
		return
	}

	r.mu.Lock()
	defer r.mu.Unlock()

	close(r.stop)

	r.cfg.Logger.Log(logger.Debug, "stopping input")
	err := r.input.Stop()
	if err != nil {
		r.cfg.Logger.Log(logger.Error, "could not stop input", "error", err.Error())
	} else {
		r.cfg.Logger.Log(logger.Info, "input stopped")
	}

	r.cfg.Logger.Log(logger.Debug, "closing pipeline")
	err = r.encoders.Close()
	if err != nil {
		r.cfg.Logger.Log(logger.Error, "failed to close pipeline", "error", err.Error())
	} else {
		r.cfg.Logger.Log(logger.Info, "pipeline closed")
	}

	for _, filter := range r.filters {
		err = filter.Close()
		if err != nil {
			r.cfg.Logger.Log(logger.Error, "failed to close filters", "error", err.Error())
		} else {
			r.cfg.Logger.Log(logger.Info, "filters closed")
		}
	}

	r.cfg.Logger.Log(logger.Debug, "waiting for routines to finish")
	r.wg.Wait()
	r.cfg.Logger.Log(logger.Info, "routines finished")

	r.running = false
}

// Burst starts revid, waits for time specified, and then stops revid.
func (r *Revid) Burst() error {
	r.cfg.Logger.Log(logger.Debug, "starting revid")
	err := r.Start()
	if err != nil {
		return fmt.Errorf("could not start revid: %w", err)
	}
	r.cfg.Logger.Log(logger.Info, "revid started")

	dur := time.Duration(r.cfg.BurstPeriod) * time.Second
	time.Sleep(dur)

	r.cfg.Logger.Log(logger.Debug, "stopping revid")
	r.Stop()
	r.cfg.Logger.Log(logger.Info, "revid stopped")

	return nil
}

func (r *Revid) IsRunning() bool {
	r.mu.Lock()
	defer r.mu.Unlock()
	return r.running
}

// Update takes a map of variables and their values and edits the current config
// if the variables are recognised as valid parameters.
//
// Update is safe for concurrent use.
func (r *Revid) Update(vars map[string]string) error {
	if r.IsRunning() {
		r.cfg.Logger.Log(logger.Debug, "revid running; stopping for re-config")
		r.Stop()
		r.cfg.Logger.Log(logger.Info, "revid was running; stopped for re-config")
	}

	r.mu.Lock()
	defer r.mu.Unlock()
	//look through the vars and update revid where needed
	r.cfg.Logger.Log(logger.Debug, "checking vars from server", "vars", vars)
	r.cfg.Update(vars)
	r.cfg.Logger.Log(logger.Info, "finished reconfig")
	r.cfg.Logger.Log(logger.Debug, "config changed", "config", r.cfg)
	return nil
}

// processFrom is run as a routine to read from a input data source, lex and
// then send individual access units to revid's encoders.
func (r *Revid) processFrom(in device.AVDevice, delay time.Duration) {
	defer r.wg.Done()

	for l := true; l; l = r.cfg.Loop {
		err := in.Start()
		if err != nil {
			r.err <- fmt.Errorf("could not start input device: %w", err)
			return
		}

		// Lex data from input device, in, until finished or an error is encountered.
		// For a continuous source e.g. a camera or microphone, we should remain
		// in this call indefinitely unless in.Stop() is called and an io.EOF is forced.
		r.cfg.Logger.Log(logger.Debug, "lexing")
		err = r.lexTo(r.filters[0], in, delay)
		switch err {
		case nil, io.EOF:
			r.cfg.Logger.Log(logger.Info, "end of file")
		case io.ErrUnexpectedEOF:
			r.cfg.Logger.Log(logger.Info, "unexpected EOF from input")
		default:
			r.err <- err
		}
		r.cfg.Logger.Log(logger.Info, "finished reading input")

		r.cfg.Logger.Log(logger.Debug, "stopping input")
		err = in.Stop()
		if err != nil {
			r.err <- fmt.Errorf("could not stop input source: %w", err)
		} else {
			r.cfg.Logger.Log(logger.Info, "input stopped")
		}

		// If we're looping and we get a stop signal we return.
		select {
		case <-r.stop:
			return
		default:
		}
	}
}