erynwells.me/assets/scripts/nethack/dungeon.js

class Cell {
  character;
  characterColor;
  backgroundColor;

  constructor(char, charColor) {
    this.character = char;
  }
}

class Grid {
  #width;
  #height;
  cells = [];

  constructor(width, height) {
    this.#width = width;
    this.#height = height;

    this.cells = new Array(width * height);
    for (let i = 0; i < this.cells.length; i++) {
      this.cells[i] = new Cell(" ");
    }
  }

  get width() {
    return this.#width;
  }

  get height() {
    return this.#height;
  }

  cellAt(x, y) {
    return this.cells[y * this.#width + x];
  }
}

class Room {
  x = 0;
  y = 0;
  width = 0;
  height = 0;

  constructor(x, y, w, h) {
    this.x = x;
    this.y = y;
    this.width = w;
    this.height = h;
  }

  get maxX() {
    return this.x + this.width;
  }

  get maxY() {
    return this.y + this.height;
  }

  charAt(x, y) {
    const minX = this.x;
    const minY = this.y;
    const maxX = this.maxX
    const maxY = this.maxY;

    if (y == minY && x == minX) { return "┌"; }
    if (y == minY && x == maxX) { return "┐"; }
    if (y == maxY && x == minX) { return "└"; }
    if (y == maxY && x == maxX) { return "┘"; }
    if (y == minY || y == maxY) { return "─"; }
    if (x == minX || x == maxX) { return "│"; }

    if ((x > minX && x < maxX) && (y > minY && y < maxY)) {
      return ".";
    }

    return undefined;
  }
}

class BSPNode {
  static MIN_AREA = 36;
  static MIN_ROOM_DIMENSION = 5;

  x;
  y;
  width;
  height;
  leftChild;
  rightChild;
  room;
  #done = false;

  constructor(x, y, w, h) {
    this.x = x;
    this.y = y;
    this.width = w;
    this.height = h;

    this.leftChild;
    this.rightChild;
    this.room;
  }

  get maxX() {
    return this.x + this.width;
  }

  get maxY() {
    return this.y + this.height;
  }

  get rooms() {
    let rooms = new Array();

    if (this.room) {
      rooms.push(this.room);
      return rooms;
    }

    if (this.leftChild) {
      rooms = rooms.concat(this.leftChild.rooms);
    }

    if (this.rightChild) {
      rooms = rooms.concat(this.rightChild.rooms);
    }

    return rooms;
  }

  divide() {
    if (this.#done) {
      return;
    }

    const area = this.width * this.height;
    if (area < BSPNode.MIN_AREA) {
      if (!this.#done && Math.random() > 0.8) {
        this.#createRoom();
      }
      this.#done = true;
      return;
    }

    if (area < 100 && Math.random() > 0.9) {
      this.#createRoom();
      this.#done = true;
      return;
    }

    let shouldSplitVertically = Math.random() < 0.5;
    console.debug("Should split vertically:", shouldSplitVertically);

    if (shouldSplitVertically) {
      let xCoordinateOfDivision = this.#randomIntBetween(this.x, this.maxX);
      if (xCoordinateOfDivision) {
        this.leftChild = new BSPNode(this.x, this.y, xCoordinateOfDivision - this.x, this.height);
        this.rightChild = new BSPNode(xCoordinateOfDivision, this.y, this.maxX - xCoordinateOfDivision, this.height);
      }
    } else {
      let yCoordinateOfDivision = this.#randomIntBetween(this.y, this.maxY);
      if (yCoordinateOfDivision) {
        this.leftChild = new BSPNode(this.x, this.y, this.width, yCoordinateOfDivision - this.y);
        this.rightChild = new BSPNode(this.x, yCoordinateOfDivision, this.width, this.maxY - yCoordinateOfDivision);
      }
    }

    if (!this.leftChild && !this.rightChild) {
      if (!this.#done && Math.random() > 0.5) {
        this.#createRoom();
      }
      this.#done = true;
    }
  }

  divideRecursively() {
    this.divide();

    if (this.room) {
      return;
    }

    if (this.leftChild) {
      this.leftChild.divideRecursively();
    }
    if (this.rightChild) {
      this.rightChild.divideRecursively();
    }
  }

  #createRoom() {
    this.room = new Room(this.x + 1, this.y + 1, this.width - 2, this.height - 2);
    console.log("Created a room:", this.room);
  }

  #randomIntBetween(lower, upper) {
    const randomMin = lower + BSPNode.MIN_ROOM_DIMENSION;
    const randomMax = upper - BSPNode.MIN_ROOM_DIMENSION;

    console.debug(`Random int between: ${lower} -> ${randomMin} and ${upper} -> ${randomMax}`);

    const result = randomMax > randomMin ? randomMin + Math.floor(Math.random() * (randomMax - randomMin + 1)) : null;
    console.debug("Result:", result);

    return result;
  }
}

let grid;

new p5(p => {
  const CELL_WIDTH = 20;
  const CELL_HEIGHT = Math.floor(CELL_WIDTH * 1.333);

  p.setup = () => {
    const container = document.querySelector('#dungeon-background');
    canvasWidth = parseFloat(getComputedStyle(container).width);
    canvasHeight = parseFloat(getComputedStyle(container).height);

    let canvas = p.createCanvas(canvasWidth, canvasHeight);
    canvas.canvas.removeAttribute('style');
    container.appendChild(canvas.canvas);

    p.pixelDensity(p.displayDensity());
    p.textFont("Courier");

    grid = new Grid(Math.ceil(canvasWidth / CELL_WIDTH), Math.ceil(canvasHeight / CELL_HEIGHT));
    let bsp = new BSPNode(0, 0, grid.width, grid.height);
    bsp.divideRecursively();

    for (let room of bsp.rooms) {
      for (let y = room.y; y <= room.maxY; y++) {
        for (let x = room.x; x <= room.maxX; x++) {
          let charAtXY = room.charAt(x, y);
          if (charAtXY) {
            let cell = grid.cellAt(x, y);
            cell.character = charAtXY;
            cell.characterColor = p.color(255);
          }
        }
      }
    }
  }

  p.draw = () => {
    p.textSize(CELL_HEIGHT);

    for (let y = 0; y < grid.height; y++) {
      for (let x = 0; x < grid.width; x++) {
        let cell = grid.cellAt(x, y);

        let fillColor = cell.characterColor ? cell.characterColor : p.color(255);
        p.fill(fillColor);

        p.textAlign(p.CENTER, p.CENTER);
        p.text(cell.character, x * CELL_WIDTH, y * CELL_HEIGHT, CELL_WIDTH, CELL_HEIGHT);
      }
    }

    p.noLoop();
  };

}, '#dungeon-background');