import Foundation

let rows = 10
let cols = 10

func printBoard(_ board: [[Int]]) {
    board.forEach { row in
        row.forEach { cell in
            print(cell == 1 ? "@" : ".", terminator: "")
        }
        print()
    }
    print("\n")
}

func countLiveNeighbors(_ board: [[Int]], x: Int, y: Int) -> Int {
    let directions = [(-1, -1), (-1, 0), (-1, 1), (0, -1), (0, 1), (1, -1), (1, 0), (1, 1)]
    return directions.reduce(0) { count, dir in
        let newX = x + dir.0
        let newY = y + dir.1
        if newX >= 0 && newX < rows && newY >= 0 && newY < cols {
            return count + board[newX][newY]
        }
        return count
    }
}

func nextGeneration(_ currentBoard: [[Int]]) -> [[Int]] {
    return currentBoard.enumerated().map { (x, row) in
        return row.enumerated().map { (y, cell) in
            let liveNeighbors = countLiveNeighbors(currentBoard, x: x, y: y)
            if cell == 1 && (liveNeighbors < 2 || liveNeighbors > 3) {
                return 0
            } else if cell == 0 && liveNeighbors == 3 {
                return 1
            }
            return cell
        }
    }
}

func simulate(board: [[Int]], generations: Int) {
    var currentBoard = board
    for _ in 0..<generations {
        printBoard(currentBoard)
        currentBoard = nextGeneration(currentBoard)
        sleep(1) // FIXME: figure out how to sleep for periods shorter than a full second
    }
}

var glider = Array(repeating: Array(repeating: 0, count: cols), count: rows)
glider[1][2] = 1
glider[2][3] = 1
glider[3][1] = 1
glider[3][2] = 1
glider[3][3] = 1
simulate(board: glider, generations: 10)

var flasher = Array(repeating: Array(repeating: 0, count: cols), count: rows)
flasher[4][5] = 1
flasher[5][5] = 1
flasher[6][5] = 1
simulate(board: flasher, generations: 4)

var beacon = Array(repeating: Array(repeating: 0, count: cols), count: rows)
beacon[2][2] = 1
beacon[2][3] = 1
beacon[3][2] = 1
beacon[4][5] = 1
beacon[5][4] = 1
beacon[5][5] = 1
simulate(board: beacon, generations: 4)

var toad = Array(repeating: Array(repeating: 0, count: cols), count: rows)
toad[3][4] = 1
toad[3][5] = 1
toad[3][6] = 1
toad[4][3] = 1
toad[4][4] = 1
toad[4][5] = 1
simulate(board: toad, generations: 5)