fun checkPosValid((i,j):int*int, n:int) =
	if (i < 0 orelse i > n-1 orelse j < 0 orelse j > n-1) then
		false
	else
		true
;


fun isSquareRevealed(Revealed(_)) = true
|	isSquareRevealed(_) = false
;



fun updateRow(row:Square list, j:int) =
	let
		val square = List.nth(row, j)
		val newRow = List.take(row, j)
	in
		case (square) of
			Concealed(Mine) => newRow@[Revealed(Mine)]@List.drop(row, j+1)
		|	Concealed(Blank) => newRow@[Revealed(Blank)]@List.drop(row, j+1)
		|	Concealed(Digit(x)) => newRow@[Revealed(Digit(x))]@List.drop(row, j+1)
		|	_ => raise IllegalArgumentException
	end
;


fun updateGrid(grid:Square list list, (i,j):int*int) =
	List.take(grid, i)@[updateRow(List.nth(grid, i), j)]@List.drop(grid, i+1)
;


fun revealSquare(mss:MineSweeperState, pos: int*int):MineSweeperState =
	if (checkPosValid(pos, length(#1(mss))) = false) then
		raise IllegalArgumentException
	else
		let
			val grid = updateGrid(#1(mss), pos)
			val n = length(grid)
			val status = #2(mss)
			val square = List.nth(List.nth(grid, #1(pos)), #2(pos))

			fun revealProjections(grid:Square list list, (i,j):int*int, index:int) =
				case (index) of
					(*Right*)
					1 => if (j < n-1  andalso not(isSquareRevealed(List.nth(List.nth(grid, i), j+1)))) then
							revealProjections(#1(revealSquare((grid,OnGoing),(i,j+1))), (i,j), index+1)
						else
							revealProjections(grid, (i,j), index+1)
					(*RightDown*)
				|	2 => if (i < n-1 andalso j < n-1  andalso not(isSquareRevealed(List.nth(List.nth(grid, i+1), j+1)))) then
							revealProjections(#1(revealSquare((grid,OnGoing),(i+1,j+1))), (i,j), index+1)
						else
							revealProjections(grid, (i,j), index+1)
					(*Down*)
				|	3 => if (i < n-1 andalso not(isSquareRevealed(List.nth(List.nth(grid, i+1), j)))) then
							revealProjections(#1(revealSquare((grid,OnGoing),(i+1,j))), (i,j), index+1)
						else
							revealProjections(grid, (i,j), index+1)
					(*LeftDown*)
				|	4 => if (i < n-1 andalso j > 0 andalso not(isSquareRevealed(List.nth(List.nth(grid, i+1), j-1)))) then
							revealProjections(#1(revealSquare((grid,OnGoing),(i+1,j-1))), (i,j), index+1)
						else
							revealProjections(grid, (i,j), index+1)
					(*Left*)
				|	5 => if (j > 0 andalso not(isSquareRevealed(List.nth(List.nth(grid, i), j-1)))) then
							revealProjections(#1(revealSquare((grid,OnGoing),(i,j-1))), (i,j), index+1)
						else
							revealProjections(grid, (i,j), index+1)
					(*LeftUp*)
				|	6 => if (i > 0 andalso j > 0 andalso not(isSquareRevealed(List.nth(List.nth(grid, i-1), j-1)))) then
							revealProjections(#1(revealSquare((grid,OnGoing),(i-1,j-1))), (i,j), index+1)
						else
							revealProjections(grid, (i,j), index+1)
					(*Up*)
				|	7 => if (i > 0 andalso not(isSquareRevealed(List.nth(List.nth(grid, i-1), j)))) then
							revealProjections(#1(revealSquare((grid,OnGoing),(i-1,j))), (i,j), index+1)
						else
							revealProjections(grid, (i,j), index+1)
					(*RightUp*)
				|	8 => if (i > 0 andalso j < n-1 andalso not(isSquareRevealed(List.nth(List.nth(grid, i-1), j+1)))) then
							(#1(revealSquare((grid,OnGoing),(i-1,j+1))))
						else
							(grid)
				|	_	=> grid
		in
			case (square) of
				Revealed(Mine) => (grid, Failure)
			|	Revealed(Blank) => 	let
										val newGrid = revealProjections(grid, pos, 1)
									in
										if determineStatusOf(newGrid) then
											(newGrid, Success)
										else
											(newGrid, OnGoing)
									end
			|	_ => if (determineStatusOf(grid)) then
						(grid, Success)
					else
						(grid, OnGoing)
		end
;