wasm-game-of-life-www/index.js

import { Universe, Cell } from "wasm-game-of-life";
// Import wasm memory
import { memory } from "wasm-game-of-life/wasm_game_of_life_bg";

const CELL_SIZE = 5; // px
const GRID_COLOR = "#444444";
const DEAD_COLOR = "#000000";
const ALIVE_COLOR = "#FFFFFF";

const seed = Math.random();
const universe = ((seed) => {
    if (seed < 1/3) return Universe.new_modulo();
    else if (seed < 2/3) return  Universe.new_random();
    else return Universe.new_space_ship();
})(seed);

const width = universe.width();
const height = universe.height();

const canvas = document.getElementById("game-of-life-canvas");
canvas.height = (CELL_SIZE + 1) * height + 1;
canvas.width = (CELL_SIZE + 1) * width + 1;

const ctx = canvas.getContext('2d');

const PERIODE = 100; // ms
let start;

const renderLoop = (timestamp) => {
  drawGrid();
  drawCells();

  if (start === undefined)
    start = timestamp;
  const elapsed = timestamp - start;

  if (elapsed > PERIODE) {
    universe.tick();
    start = timestamp;
  }

  requestAnimationFrame(renderLoop);
};

const drawGrid = () => {
  ctx.beginPath();
  ctx.strokeStyle = GRID_COLOR;

  for (let i = 0; i <= width; i++) {
    ctx.moveTo(i * (CELL_SIZE + 1) + 1, 0);
    ctx.lineTo(i * (CELL_SIZE + 1) + 1, (CELL_SIZE + 1) * height + 1);
  }

  for (let j = 0; j <= height; j++) {
    ctx.moveTo(0,                           j * (CELL_SIZE + 1) + 1);
    ctx.lineTo((CELL_SIZE + 1) * width + 1, j * (CELL_SIZE + 1) + 1);
  }

  ctx.stroke();
}

const getIndex = (row, column) => {
  return row * width + column;
}

const drawCells = () => {
  const cellsPtr = universe.cells();
  const cells = new Uint8Array(memory.buffer, cellsPtr, width * height / 8);

  ctx.beginPath();

  for (let row = 0; row < height; row++) {
    for (let col = 0; col < width; col++) {
      const i = getIndex(row, col);

      ctx.fillStyle = bitIsSet(i, cells)
        ? ALIVE_COLOR
        : DEAD_COLOR;

      ctx.fillRect(
        col * (CELL_SIZE + 1) + 1,
        row * (CELL_SIZE + 1) + 1,
        CELL_SIZE,
        CELL_SIZE
      );
    }
  }

  ctx.stroke();
}

const bitIsSet = (n, arr) => {
  const byte = Math.floor(n / 8);
  const mask = 1 << (n % 8);
  return (arr[byte] & mask) === mask;
}

requestAnimationFrame(renderLoop);