window.php

<?php
/* USAGE EXAMPLE:
 * $data = [
 *   'key1' => [1, 1, 1, 1],
 *   'key2' => [1, 1],
 * ];
 * 
 * $win = new Window(2);
 * foreach($data as $key => $points)
 * {
 *   foreach($points as $point)
 *     $win->push($key, $point);
 * }
 *
 * print_r($win->getKeys());
 * print_r($win->getValues());
 *
 * OUTPUT:
 * Array
 * (
 *     [0] => key1
 *     [2] => key2
 * )
 * Array
 * (
 *     [0] => 2
 *     [1] => 2
 *     [2] => 2
 * )
 */

class Window
{
  private $size = 0;
  private $outIndex = 0;
  private $winIndex = 0;
  private $keys = [];
  private $lastKey = null;
  private $values = [];
  private $buffer = [];
  private $tick = 0;
  private $sumFunc = null;
  private $enableInterpolation = false;

  function __construct($size, $interpolate = false)
  {
    $this->size = max(1, $size);
    $this->enableInterpolation = $interpolate;

    $this->sumFunc = function($a, $b) { return $a + $b; };
  }

  function setSumFunction(callable $f) { $this->sumFunc = $f; }

  function push($key, $value)
  {
    if($this->winIndex < $this->size)
      $this->winIndex++;
    else if($this->tick > 0) {
      $this->wrapUp();
      $this->outIndex++;
    }

    $index = $this->makeIndex($this->outIndex);

    if($key != $this->lastKey && !isset($this->keys[$index])) {
      $this->keys[$index] = $key;
      $this->lastKey = $key;
    }

    $this->buffer[] = $value;
    $this->tick++;
  }

  private function wrapUp()
  {
    end($this->values);
    $lastIndex = key($this->values);

    $index = $this->makeIndex($this->outIndex);
    $this->values[$index] = array_reduce($this->buffer, $this->sumFunc);

    if($lastIndex !== null && $this->enableInterpolation)
      $this->interpolate($lastIndex, $index);

    $this->winIndex = 1;
    $this->buffer = [];
  }

  private function interpolate($from, $to)
  {
    $fromValue = $this->values[$from];
    $toValue = $this->values[$to];

    for($i = $from + 1; $i < $to; $i++) {
      $value = (($i - $from) * ($toValue - $fromValue))
        / ($to - $from) + $fromValue;

      $this->values[$i] = $value;
    }

    ksort($this->values);
  }

  private function makeIndex($index)
  {
    return $this->enableInterpolation ? $index * $this->size : $index;
  }

  function getBuffer()
  {
    return $this->buffer;
  }

  function getKeys()
  {
    return $this->keys;
  }

  function getValues()
  {
    if(!empty($this->buffer))
      $this->wrapUp();

    return $this->values;
  }

  function getSize()
  {
    return $this->size;
  }
}