const pr = t => process.stdout.write(t)

class GameOfLife {
  constructor(){
    this.width = process.stdout.columns - 2
    this.height = process.stdout.rows - 4
    this.cells = Array.from({length: this.width * this.height}, () => Math.round(Math.random()))
  }

  printBoard() {
    console.clear()
    pr('╔' + '═'.repeat(this.width) + '╗')
    pr('║' + ' '.repeat(Math.floor((this.width - 12) / 2)) + 'GAME OF LIFE' + ' '.repeat(Math.ceil((this.width - 12) / 2)) + '║')
    pr('╠' + '═'.repeat(this.width) + '╣')
    for (let l=0; l<this.height; l++) {
      pr('║' + this.cells.slice(l*this.width, (l+1)*this.width).map((c, i) => (
        c === 1
          ? this.prevCells && this.prevCells[l*this.width+i] === 1
            ? '#'
            : '\x1b[32m#\x1b[0m'
          : this.prevCells && this.prevCells[l*this.width+i] === 1
            ? '\x1b[31m#\x1b[0m'
            : ' '
      )).join('') + '║')
    }
    pr('╚' + '═'.repeat(this.width) + '╝')
  }

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

  computeCellNextState(x, y){
    const st = (x, y) => {
      if (x >= 0 && x < this.width && y >= 0 && y < this.height) {
        return this.findCell(x, y)
      } else {
        return 0;
      }
    }

    const total = st(x-1, y-1) + st(x, y-1) + st(x+1, y-1) + st(x-1, y) + st(x+1, y) + st(x-1, y+1) + st(x, y+1) + st(x+1, y+1)

    if (st(x, y) === 1) {
      if (total < 2) {
        return 0
      } else if (total >= 2 && total <= 3) {
        return 1
      } else {
        return 0
      }
    } else if (total === 3) {
      return 1
    } else {
      return 0
    }
  }

  printNextGeneration(){
    const nextState = []

    for (let y = 0; y < this.height; y++) {
      for (let x = 0; x < this.width; x++) {
        nextState.push(this.computeCellNextState(x, y))
      }
    }

    this.prevCells = this.cells
    this.cells = nextState
    this.printBoard()
  }
}

let game = new GameOfLife()

pr('\u001B[?25l')
let animation = setInterval(() => game.printNextGeneration(), 250)

process.on('SIGINT', function() {
  clearInterval(animation)
  pr('\u001B[?25h')
  console.clear()
  process.exit()
});

process.stdout.on('resize', () => {
  clearInterval(animation)
  game = new GameOfLife()
  animation = setInterval(() => game.printNextGeneration(), 250)
})