gameOfLife.scala

class Cell(alive: Boolean ) {
  var isAlive: Boolean = alive

  override def toString = if (this isAlive) "x" else "-"

  def isDead = !this.isAlive
}

object Grid {
  val width: Int = 10
  val height: Int = 10
  var grid = new Array[Array[Cell]](width, height)

  iterGrid((x, y) => {
    if (x == 0 && y == 0) grid(x)(y) = new Cell(true)
    else if (x == 1 && y == 1) grid(x)(y) = new Cell(true)
    else if (x == 2 && y == 2) grid(x)(y) = new Cell(true)
    else grid(x)(y) = new Cell(false)
  }, Unit => Unit)

  private def iterGrid(inner: (Int, Int) => Unit, outer: Unit => Unit) {
    for (y <- 0 to height - 1) {
      for (x <- 0 to width - 1) {
        inner(x, y)
      }

      outer()
    }
  }

  // TODO fix so that new grid is calculated from old grid, calculating
  // in place leads to side effects
  def goToNextStep = {
    iterGrid((x, y) => {
      val aCell = grid(x)(y)

      val numberOfAliveNeighbors = numberOfAliveNeighborsOfCellAt(x, y)

      if (aCell isAlive) {
        println("Cell (" + x + ", " + y + ") is alive")
        println("Number of alive neighbors: " + numberOfAliveNeighbors)

        if (numberOfAliveNeighbors < 2) kill(aCell)
        else if (numberOfAliveNeighbors > 3) kill(aCell)
      }
      else if (numberOfAliveNeighbors == 3) resurrect(aCell)
    }, Unit => Unit)
  }

  def numberOfAliveNeighborsOfCellAt(x: Int, y: Int): Int = {
    var numberOfAliveNeighbors: Int = 0

    iterNeighbors((x, y) => if (grid(x)(y) isAlive) numberOfAliveNeighbors += 1,
                  x, y)

    return numberOfAliveNeighbors
  }

  def iterNeighbors(f: (Int, Int) => Unit, x: Int, y: Int) = {
    def cellExists(x: Int, y: Int): Boolean = {
      if ((x >= 0 && x <= (width - 1))
        && (y >= 0 && y <= (height - 1))) 
      {
        return true;
      }
      else return false;
    }

    // top left
    if (cellExists(x-1, y-1)) f(x-1,y-1)
    // top center
    if (cellExists(x, y-1)) f(x,y-1)
    // top right
    if (cellExists(x+1, y-1)) f(x+1,y-1)
    // middle left
    if (cellExists(x-1, y)) f(x-1,y)
    // middle right
    if (cellExists(x+1, y)) f(x+1,y)
    // bottom left
    if (cellExists(x-1, y+1)) f(x-1,y+1)
    // bottom center
    if (cellExists(x, y+1)) f(x,y+1)
    // bottom right
    if (cellExists(x+1, y+1)) f(x+1,y+1)
  }

  def kill(aCell: Cell) = aCell isAlive = false
  def resurrect(aCell: Cell) = aCell isAlive = true

  def isNotDead: Boolean = {
    var isDead = true

    iterGrid((x,y) => {
      if (grid(x)(y).isAlive) isDead = false
    }, Unit => Unit)

    return !isDead
  }

  override def toString = {
    var gridStr = ""

    iterGrid((x,y) => {
        gridStr = gridStr + grid(x)(y)
    }, Unit => {gridStr = gridStr + "\n"})

    gridStr
  }
}

object Main {
  def main(args: Array[String]) {
    do
    {
      print(Grid)

      Grid goToNextStep

      readLine("Go to next step? ");
    }
    while (Grid isNotDead)

    print(Grid)
  }
}