way-of-life/src/js/engine.js

Conway's game of life

'use strict'

class Engine {
  constructor (width, height) {
    this.wasm = false
    this.width = width
    this._width = width + 2
    this.height = height
    this._height = height + 2
    this.module = { calledRun: true }
  }

  init () {
    const buffer = new ArrayBuffer(this._width * this._height)
    this._current = new Uint8Array(buffer)
    const nextBuffer = new ArrayBuffer(this._width * this._height)
    this._next = new Uint8Array(nextBuffer)
    this.module = { calledRun: true }
  }

  index (i, j) {
    return i * this._width + j
  }

  cell (i, j) {
    return this._current[this.index(i, j)]
  }

  cellSafe (i, j) {
    return this._current[(i + 1) * this._width + j + 1]
  }

  next (i, j) {
    return this._next[this.index(i, j)]
  }

  loopCurrentState () {
    for (let j = 1; j < this._width + 1; j++) {
      this._current[this.index(0, j)] = this._current[this.index(this._height - 2, j)]
      this._current[this.index(this._height - 1, j)] = this._current[this.index(1, j)]
    }
    for (let i = 1; i < this._height + 1; i++) {
      this._current[this.index(i, 0)] = this._current[this.index(i, this._width - 2)]
      this._current[this.index(i, this._width - 1)] = this._current[this.index(i, 1)]
    }
    this._current[this.index(0, 0)] = this._current[this.index(this._height - 2, this._width - 2)]
    this._current[this.index(0, this._width - 1)] = this._current[this.index(this._height - 2, 1)]
    this._current[this.index(this._height - 1, 0)] = this._current[this.index(1, this._width - 2)]
    this._current[this.index(this._height - 1, this._width - 1)] = this._current[this.index(1, 1)]
  }

  computeNextState () {
    let neighbors, iM1, iP1, i_, jM1, jP1

    this.loopCurrentState()

    for (let i = 1; i < this._height - 1; i++) {
      iM1 = (i - 1) * this._width
      iP1 = (i + 1) * this._width
      i_ = i * this._width
      for (let j = 1; j < this._width - 1; j++) {
        jM1 = j - 1
        jP1 = j + 1
        neighbors = this._current[iM1 + jM1]
        neighbors += this._current[iM1 + j]
        neighbors += this._current[iM1 + jP1]
        neighbors += this._current[i_ + jM1]
        neighbors += this._current[i_ + jP1]
        neighbors += this._current[iP1 + jM1]
        neighbors += this._current[iP1 + j]
        neighbors += this._current[iP1 + jP1]
        if (neighbors === 3) {
          this._next[i_ + j] = 1
        } else if (neighbors === 2) {
          this._next[i_ + j] = this._current[i_ + j]
        } else {
          this._next[i_ + j] = 0
        }
      }
    }
    this._current.set(this._next)
  }

  set (i, j, value = 1) {
    this._current[this.index(i, j)] = value
  }

  setNext (i, j, value = 1) {
    this._next[this.index(i, j)] = value
  }
}

export { Engine as default }