let entityWidth = 2;

let buf1 = [];

let buf2 = [];

let PARTITION = 0;

let MERGE = 1;

let state = PARTITION;

let partSize = 0;

let idx = 0;

let startPartition = 0;

let b1idx = 0;

let b2idx = 0;

let wait = 0;

let record = false;

let startRecording = true;

let stopRecording = false;

let fps = 60;

let capturer;

​

​

function setup() {

  createCanvas(400, 400);

  for(let i = 0; i < width/entityWidth;i++)

    entities.push(random(height));  

  frameRate(fps);

  colorMode(HSB, height, 100, 100);

  if (record){

    capturer = new CCapture({

      format: 'png',

      framerate: fps

    });

  }

}

​

function draw() {

  if (record && startRecording){

    capturer.start();

    startRecording = false;

  }  

  if (wait > 0){

    wait -= deltaTime;

    if (record){

      capturer.capture(document.getElementById('defaultCanvas0'));

    }

    return;

  }

  if (record && stopRecording){

    capturer.stop();

    capturer.save();

    noLoop();

  }

  background(20);

  for(let i = 0, x = 0; i < entities.length; x+=entityWidth, i++){

    let c = color(entities[i], 70, 80);

    fill(c);

    stroke(c);

    rect(x, height, entityWidth, -entities[i]);

  }

  let done = true;

  for(let i = 1; i < entities.length; i++){

    if (entities[i-1] > entities[i]){

      done = false;

      break;

    }

  }

  if (done){

    entities = []

    for(let i = 0; i < width/entityWidth;i++)

      entities.push(random(height));  

    state = PARTITION;

    partSize = 0;

    idx = 0;

    startPartition = 0;

    b1idx = 0;

    b2idx = 0;

    wait = 1000;

    buf1 = [];

    buf2 = [];

    stopRecording = true;

  }

  if (b1idx >= buf1.length && b2idx >= buf2.length){

    //idx = 0;

    state = PARTITION;

    if (partSize == 0 || idx >= entities.length){

      if (partSize == 0)

        partSize = 1;

      else

        partSize *= 2;

      idx = 0;

    }

  }

  if (state == PARTITION){

    startPartition = idx;

    buf1 = [];

    buf2 = [];

    b1idx = 0;

    b2idx = 0;

    for(let i = 0; idx < entities.length && i < partSize; i++){

      buf1.push(entities[idx++]);

    }

    for(let i = 0; idx < entities.length && i < partSize; i++){

      buf2.push(entities[idx++]);

    }

    state = MERGE;

    idx = startPartition;

  }

  if (b1idx < buf1.length && b2idx < buf2.length){

    if (buf1[b1idx] < buf2[b2idx]){

      entities[idx++] = buf1[b1idx++];

    }

    else {

      entities[idx++] = buf2[b2idx++];

    }

  }

  else if (b1idx < buf1.length){

    entities[idx++] = buf1[b1idx++];

  }

  else{

    entities[idx++] = buf2[b2idx++];

  }

  if (record){

    capturer.capture(document.getElementById('defaultCanvas0'));

  }

}