// Daniel Shiffman

// http://natureofcode.com

// Wolfram Cellular Automata

​

// CA object prototype

​

function CA(r) {

  this.w = 4;

  this.cols = floor(width/this.w);

  this.rows = floor(height/this.w);

  // An array of 0s and 1s

  this.cells = new Array(this.rows);

  for (let i = 0; i < this.rows; i++) {

    this.cells[i] = new Array(this.cols);

    for (let j = 0; j < this.cols; j++) {

        this.cells[i][j] = 0; 

    }

  }

   // We arbitrarily start with just the middle cell having a state of "1"

  this.cells[this.rows-1][floor(this.cols/2)] = 1;

  this.generation = 0;

​

  // An array to store the ruleset, for example {0,1,1,0,1,1,0,1}

  this.ruleset = r;

​

  // The process of creating the new generation

  this.generate = function() {

    // First we create an empty array filled with 0s for the new values

    var nextgen = [];

    for (let i = 0; i < this.cells.length; i++) {

      nextgen[i] = 0;

    }

    // For every spot, determine new state by examing current state, and neighbor states

    // Ignore edges that only have one neighor

    for (let i = 0; i < this.cols; i++) {

      let left   = this.cells[this.rows-1][(i+this.cols-1)%this.cols];   // Left neighbor state

      let me     = this.cells[this.rows-1][i];     // Current state

      let right  = this.cells[this.rows-1][(i+1)%this.cols];   // Right neighbor state

      nextgen[i] = this.rules(left, me, right); // Compute next generation state based on ruleset

    }

    for (let i = 1; i < this.rows; i++) {

        this.cells[i-1] = this.cells[i];

    }

    // The current generation is the new generation

    this.cells[this.rows-1] = nextgen;

    this.generation++;

  };

​

  // This is the easy part, just draw the cells

  this.display = function() {

    for (let i = 0; i < this.rows; i++) {

      for (let j = 0; j < this.cols; j++) {

        if (this.cells[i][j] == 1) fill(200);

        else                    fill(51);

        noStroke();

        rect(j*this.w, i*this.w, this.w, this.w);

      }

    }

  };

​

  // Implementing the Wolfram rules

  // Could be improved and made more concise, but here we can explicitly see what is going on for each case

  this.rules = function(a, b, c) {

    if (a == 1 && b == 1 && c == 1) return this.ruleset[0];

    if (a == 1 && b == 1 && c === 0) return this.ruleset[1];

    if (a == 1 && b === 0 && c == 1) return this.ruleset[2];

    if (a == 1 && b === 0 && c === 0) return this.ruleset[3];

    if (a === 0 && b == 1 && c == 1) return this.ruleset[4];

    if (a === 0 && b == 1 && c === 0) return this.ruleset[5];

    if (a === 0 && b === 0 && c == 1) return this.ruleset[6];

    if (a === 0 && b === 0 && c === 0) return this.ruleset[7];

    return 0;

  };

}