// The Coding Train / Daniel Shiffman

// https://thecodingtrain.com/challenges/171-wave-function-collapse

// https://youtu.be/0zac-cDzJwA

​

// Code from Challenge: https://editor.p5js.org/codingtrain/sketches/pLW3_PNDM

// Corrected and Expanded: https://github.com/CodingTrain/Wave-Function-Collapse

​

​

// Function to reverse a string

function reverseString(s) {

  let arr = s.split("");

  arr = arr.reverse();

  return arr.join("");

}

​

// Function to compare two edges

function compareEdge(a, b) {

  return a == reverseString(b);

}

​

// Tile class

class Tile {

  constructor(img, edges) {

    // Image

    this.img = img;

    // Edges

    this.edges = edges;

    // Valid neighbors

    this.up = [];

    this.right = [];

    this.down = [];

    this.left = [];

  }

  // Find the valid neighbors

  analyze(tiles) {

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

      let tile = tiles[i];

      // UP

      if (compareEdge(tile.edges[2], this.edges[0])) {

        this.up.push(i);

      }

      // RIGHT

      if (compareEdge(tile.edges[3], this.edges[1])) {

        this.right.push(i);

      }

      // DOWN

      if (compareEdge(tile.edges[0], this.edges[2])) {

        this.down.push(i);

      }

      // LEFT

      if (compareEdge(tile.edges[1], this.edges[3])) {

        this.left.push(i);

      }

    }

  }

  // Rotate a tile and its edges to create a new one

  rotate(num) {

    // Draw new tile

    const w = this.img.width;

    const h = this.img.height;

    const newImg = createGraphics(w, h);

    newImg.imageMode(CENTER);

    newImg.translate(w / 2, h / 2);

    newImg.rotate(HALF_PI * num);

    newImg.image(this.img, 0, 0);

    // Rotate edges

    const newEdges = [];

    const len = this.edges.length;

    for (let i = 0; i < len; i++) {

      newEdges[i] = this.edges[(i - num + len) % len];

    }

    return new Tile(newImg, newEdges);

  }

}

​