/*
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/device"
	"bitbucket.org/ausocean/av/filter"
	"bitbucket.org/ausocean/av/revid/config"
	"bitbucket.org/ausocean/iot/pi/netsender"
	"bitbucket.org/ausocean/utils/bitrate"
)

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

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.
	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

	// probe allows us to "probe" frames after being lexed before going off to
	// later encoding stages. This is useful if we wish to perform some processing
	// on frames to derive metrics, for example, we might like to probe frames to
	// derive turbidity levels. This is provided through SetProbe.
	probe io.WriteCloser

	// 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

	// 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.
func (r *Revid) Config() config.Config {
	return r.cfg
}

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

func (r *Revid) Write(p []byte) (int, error) {
	mi, ok := r.input.(*device.ManualInput)
	if !ok {
		return 0, errors.New("cannot write to anything but ManualInput")
	}
	return mi.Write(p)
}

// 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.running {
		r.cfg.Logger.Warning("start called, but revid already running")
		return nil
	}

	r.stop = make(chan struct{})

	r.cfg.Logger.Debug("resetting revid")
	err := r.reset(r.cfg)
	if err != nil {
		r.Stop()
		return err
	}
	r.cfg.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.Debug("starting input processing routine")
	r.wg.Add(1)
	go r.processFrom(d)

	r.running = true
	return nil
}

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

	close(r.stop)

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

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

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

	r.cfg.Logger.Debug("waiting for routines to finish")
	r.wg.Wait()
	r.cfg.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.Debug("starting revid")
	err := r.Start()
	if err != nil {
		return fmt.Errorf("could not start revid: %w", err)
	}
	r.cfg.Logger.Info("revid started")

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

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

	return nil
}

func (r *Revid) Running() bool {
	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.
func (r *Revid) Update(vars map[string]string) error {
	if r.running {
		r.cfg.Logger.Debug("revid running; stopping for re-config")
		r.Stop()
		r.cfg.Logger.Info("revid was running; stopped for re-config")
	}

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

func (r *Revid) SetProbe(p io.WriteCloser) error {
	if r.running {
		return errors.New("cannot set probe when revid is running")
	}
	r.probe = p
	return nil
}