Game2048Initializer.kt

package games.game2048

import board.Cell
import board.GameBoard
import kotlin.random.Random

interface Game2048Initializer<T> {
    /*
     * Specifies the cell and the value that should be added to this cell.
     */
    fun nextValue(board: GameBoard<T?>): Pair<Cell, T>?
}

object RandomGame2048Initializer : Game2048Initializer<Int> {
    private fun generateRandomStartValue(): Int =
        if (Random.nextInt(10) == 9) 4 else 2

    /*
     * Generate a random value and a random cell among free cells
     * that given value should be added to.
     * The value should be 2 for 90% cases, and 4 for the rest of the cases.
     * Use the 'generateRandomStartValue' function above.
     * If the board is full return null.
     */
   override fun nextValue(board: GameBoard<Int?>): Pair<Cell, Int>? {
        return if (board.all { it != null }) {
            null // no more space available
        } else {
            val c = board.filter { it == null }.random()
            return Pair( c!!, generateRandomStartValue())
        }
    }
}