/*
NAME
  BitrateCalculator.go - is a simple struct with methods to allow for easy
	calculation of bitrate.

DESCRIPTION
  See Readme.md

AUTHOR
  Saxon Nelson-Milton <saxon.milton@gmail.com>

LICENSE
  BitrateCalculator.go is Copyright (C) 2017 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 [GNU licenses](http://www.gnu.org/licenses).
*/

package bitrate

import (
	"fmt"
	"time"
)

// BitrateCalculator provides fields and methods to allow calculation of bitrate
type BitrateCalculator struct {
	outputDelay     int // sec
	now             time.Time
	prev            time.Time
	startedBefore   bool
	elapsedTime     time.Duration
	lastDisplayTime time.Time
}

// Place this at the start of the code segment that you would like to time
func (bc *BitrateCalculator) Start(outputDelay int) {
	if outputDelay >= 0 {
		bc.outputDelay = outputDelay
	} else {
		bc.outputDelay = 0
	}
	bc.prev = time.Now()
	if !bc.startedBefore {
		bc.startedBefore = true
		bc.elapsedTime = time.Duration(0)
		bc.lastDisplayTime = time.Now()
	}
}

// Place this at the end of the code segment that you would like to time
func (bc *BitrateCalculator) Stop(noOfKB float64) (bitrate int64) {
	bc.now = time.Now()
	deltaTime := bc.now.Sub(bc.prev)
	if bc.now.Sub(bc.lastDisplayTime) > time.Duration(bc.outputDelay)*time.Second {
		bitrate = int64(noOfKB / float64(deltaTime/1e9))
		fmt.Printf("Bitrate: %d kbps\n", bitrate)
		bc.elapsedTime = time.Duration(0)
		bc.lastDisplayTime = bc.now
	}
	return
}