const playingField = [' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ']

printInstruction()
nextMove('X')

function printInstruction() {
    process.stdout.write('Cell\'s numbers:\n')
    printRow(1, 2, 3)
    printLine()
    printRow(4, 5, 6)
    printLine()
    printRow(7, 8, 9)
}

function nextMove(player) {

    const nextPlayer = player === 'X' ? 'Y' : 'X'

    process.stdout.write(`You're playing for ${player}. Make a move by choosing a number from 1 to 9\n`)

    process.stdin.once('data', function(data) {

        if (isValidInput(data)) {

            let arrayIndex = data - 1
            playingField[arrayIndex] = player

            if (isEndofGame(arrayIndex)) {
              process.stdout.write('YOU WON!')
            } else {
                printCurrentField()
                nextMove(nextPlayer)
            }
        } else {
            nextMove(player)
        }
    })
}

function printRow(x, y, z) {
    process.stdout.write(`  ${x}  |  ${y}  |  ${z}  \n`)
}

function printLine() {
    process.stdout.write(`- - -|- - -|- - -\n`)
}

function printCurrentField() {
    printRow(...playingField.slice(0, 3))
    printLine()
    printRow(...playingField.slice(3, 6))
    printLine()
    printRow(...playingField.slice(6, 9))
}

function isValidInput(input) {
    if (0 < input && input < 10 ) {
        if (playingField[input - 1] !== ' ') {
            process.stdout.write('The cell is filled already. Try again \n')
            return false
        } else {
              return true
        }
    } else {
            process.stdout.write('This is not a valid number. Try again \n')
        return false
    }
}

function isEndofGame(index) {

    let winningCombinations = [
        [0, 1, 2],
        [3, 4, 5],
        [6, 7, 8],
        [0, 3, 6],
        [1, 4, 7],
        [2, 5, 8],
        [0, 4, 8],
        [2, 4, 6]
    ]

    for (var index = 0; index < winningCombinations.length; index++) {
        if (allEqual(...winningCombinations[index])) {
            return true
        }
    }
}

function allEqual(x, y, z) {
    if (playingField[x] !== ' ' &&
        playingField[x] === playingField[y] &&
        playingField[y] === playingField[z]) {
      return true
    }
    return false
}