#################################
###      Sudoku Generator     ###
#################################
#                               #
# Generates a 9x9 Sudoku puzzle.#
#                               #
#################################

class Board
    def initialize()
        @grid = Array.new(81) { 0 }
    end

    # coordinates is a list [x,y]
    def toBoard(value,coordinates)
        index = (coordinates[0]*9)+(coordinates[1])
        @grid[index] = value
    end

    # get value at [x,y] coordinates
    def getVal(coordinates)
        index = (coordinates[0]*9)+(coordinates[1])
        return @grid[index]
    end

    # print full board
    def show
        (0..80).step(9) do |i|
            print @grid[i..i+8].to_s+"\n"
        end
    end

    # check for conflicts in grid
    def check
    end
end

# test if number at coordinate valid
def validNumber(sudoku, num, coordinates)
    # create list of numbers in same column
    colNums = []
    (0..8).each do |i|
        colNums[i] = sudoku.getVal([i,coordinates[1]])
    end

    # create list of numbers in same row
    rowNums = []
    (0..8).each do |i|
        rowNums[i] = sudoku.getVal([coordinates[0],i])
    end

    if ! colNums.include?(num) and ! rowNums.include?(num)
        return true
    else
        return false
    end
end

# get random valid number
def getNumber(sudoku, coordinates)
    numPool = [1,2,3,4,5,6,7,8,9]
    num = numPool.sample

    while true do
        if validNumber(sudoku, num, coordinates) == true
            return num
        else
            numPool.delete!(num)
            num = numPool.sample
        end
    end
end

def indexToCoord(index)
    y = index % 9
    x = (index - y)/9

    coordinates = [x,y]
    return coordinates
end


sudoku = Board.new()

@grid.each_with_index do |cell, index|
    sudoku.toBoard(getNumber(sudoku,indexToCoord(index)))
end

print sudoku