local realchess = {}
screwdriver = screwdriver or {}

local function index_to_xy(idx)
	idx = idx - 1
	local x = idx % 8
	local y = (idx - x) / 8
	return x, y
end

local function xy_to_index(x, y)
	return x + y * 8 + 1
end

function realchess.init(pos)
	local meta = minetest.get_meta(pos)
	local inv = meta:get_inventory()
	
	local formspec = [[ size[8,8.6;]
			bgcolor[#080808BB;true]
			background[0,0;8,8;chess_bg.png]
			button[3.1,7.8;2,2;new;New game]
			list[context;board;0,0;8,8;]
			listcolors[#00000000;#00000000;#00000000;#30434C;#FFF] ]]

	meta:set_string("formspec", formspec)
	meta:set_string("infotext", "Chess Board")
	meta:set_string("playerBlack", "")
	meta:set_string("playerWhite", "")
	meta:set_string("lastMove", "")
	meta:set_string("winner", "")

	meta:set_int("lastMoveTime", 0)
	meta:set_int("castlingBlackL", 1)
	meta:set_int("castlingBlackR", 1)
	meta:set_int("castlingWhiteL", 1)
	meta:set_int("castlingWhiteR", 1)

	inv:set_list("board", {
		"realchess:rook_black_1",
		"realchess:knight_black_1",
		"realchess:bishop_black_1",
		"realchess:queen_black",
		"realchess:king_black",
		"realchess:bishop_black_2",
		"realchess:knight_black_2",
		"realchess:rook_black_2",
		"realchess:pawn_black_1",
		"realchess:pawn_black_2",
		"realchess:pawn_black_3",
		"realchess:pawn_black_4",
		"realchess:pawn_black_5",
		"realchess:pawn_black_6",
		"realchess:pawn_black_7",
		"realchess:pawn_black_8",
		'','','','','','','','','','','','','','','','',
		'','','','','','','','','','','','','','','','',
		"realchess:pawn_white_1",
		"realchess:pawn_white_2",
		"realchess:pawn_white_3",
		"realchess:pawn_white_4",
		"realchess:pawn_white_5",
		"realchess:pawn_white_6",
		"realchess:pawn_white_7",
		"realchess:pawn_white_8",
		"realchess:rook_white_1",
		"realchess:knight_white_1",
		"realchess:bishop_white_1",
		"realchess:queen_white",
		"realchess:king_white",
		"realchess:bishop_white_2",
		"realchess:knight_white_2",
		"realchess:rook_white_2"
	})

	inv:set_size("board", 64)
end

function realchess.move(pos, from_list, from_index, to_list, to_index, _, player)
	if from_list ~= "board" and to_list ~= "board" then
		return 0
	end

	local playerName = player:get_player_name()
	local meta = minetest.get_meta(pos)

	if meta:get_string("winner") ~= "" then
		minetest.chat_send_player(playerName, "This game is over.")
		return 0
	end

	local inv = meta:get_inventory()
	local pieceFrom = inv:get_stack(from_list, from_index):get_name()
	local pieceTo = inv:get_stack(to_list, to_index):get_name()
	local lastMove = meta:get_string("lastMove")
	local thisMove -- will replace lastMove when move is legal
	local playerWhite = meta:get_string("playerWhite")
	local playerBlack = meta:get_string("playerBlack")

	if pieceFrom:find("white") then
		if playerWhite ~= "" and playerWhite ~= playerName then
			minetest.chat_send_player(playerName, "Someone else plays white pieces!")
			return 0
		end		
		if lastMove ~= "" and lastMove ~= "black" then
			minetest.chat_send_player(playerName, "It's not your turn, wait for your opponent to play.")
			return 0
		end
		if pieceTo:find("white") then
			-- Don't replace pieces of same color
			return 0
		end
		playerWhite = playerName
		thisMove = "white"
	elseif pieceFrom:find("black") then
		if playerBlack ~= "" and playerBlack ~= playerName then
			minetest.chat_send_player(playerName, "Someone else plays black pieces!")
			return 0
		end
		if lastMove ~= "" and lastMove ~= "white" then
			minetest.chat_send_player(playerName, "It's not your turn, wait for your opponent to play.")
			return 0
		end
		if pieceTo:find("black") then
			-- Don't replace pieces of same color
			return 0
		end
		playerBlack = playerName
		thisMove = "black"
	end

	-- DETERMINISTIC MOVING

	local from_x, from_y = index_to_xy(from_index)
	local to_x, to_y = index_to_xy(to_index)

	if pieceFrom:sub(11,14) == "pawn" then
		if thisMove == "white" then
			local pawnWhiteMove = inv:get_stack(from_list, xy_to_index(from_x, from_y - 1)):get_name()
			-- white pawns can go up only
			if from_y - 1 == to_y then
				if from_x == to_x then
					if pieceTo ~= "" then
						return 0
					elseif to_index >= 1 and to_index <= 8 then
						inv:set_stack(from_list, from_index, "realchess:queen_white")
					end
				elseif from_x - 1 == to_x or from_x + 1 == to_x then
					if not pieceTo:find("black") then
						return 0
					elseif to_index >= 1 and to_index <= 8 then
						inv:set_stack(from_list, from_index, "realchess:queen_white")
					end
				else
					return 0
				end
			elseif from_y - 2 == to_y then
				if pieceTo ~= "" or from_y < 6 or pawnWhiteMove ~= "" then
					return 0
				end
			else
				return 0
			end
		elseif thisMove == "black" then
			local pawnBlackMove = inv:get_stack(from_list, xy_to_index(from_x, from_y + 1)):get_name()
			-- black pawns can go down only
			if from_y + 1 == to_y then
				if from_x == to_x then
					if pieceTo ~= "" then
						return 0
					elseif to_index >= 57 and to_index <= 64 then
						inv:set_stack(from_list, from_index, "realchess:queen_black")
					end
				elseif from_x - 1 == to_x or from_x + 1 == to_x then
					if not pieceTo:find("white") then
						return 0
					elseif to_index >= 57 and to_index <= 64 then
						inv:set_stack(from_list, from_index, "realchess:queen_black")
					end
				else
					return 0
				end
			elseif from_y + 2 == to_y then
				if pieceTo ~= "" or from_y > 1 or pawnBlackMove ~= "" then
					return 0
				end
			else
				return 0
			end

			-- if x not changed,
			--   ensure that destination cell is empty
			-- elseif x changed one unit left or right
			--   ensure the pawn is killing opponent piece
			-- else
			--   move is not legal - abort

			if from_x == to_x then
				if pieceTo ~= "" then
					return 0
				end
			elseif from_x - 1 == to_x or from_x + 1 == to_x then
				if not pieceTo:find("white") then
					return 0
				end
			else
				return 0
			end
		else
			return 0
		end

	elseif pieceFrom:sub(11,14) == "rook" then
		if from_x == to_x then
			-- moving vertically
			if from_y < to_y then
				-- moving down
				-- ensure that no piece disturbs the way
				for i = from_y + 1, to_y - 1 do
					if inv:get_stack(from_list, xy_to_index(from_x, i)):get_name() ~= "" then
						return 0
					end
				end
			else
				-- mocing up
				-- ensure that no piece disturbs the way
				for i = to_y + 1, from_y - 1 do
					if inv:get_stack(from_list, xy_to_index(from_x, i)):get_name() ~= "" then
						return 0
					end
				end
			end
		elseif from_y == to_y then
			-- mocing horizontally
			if from_x < to_x then
				-- mocing right
				-- ensure that no piece disturbs the way
				for i = from_x + 1, to_x - 1 do
					if inv:get_stack(from_list, xy_to_index(i, from_y)):get_name() ~= "" then
						return 0
					end
				end
			else
				-- mocing left
				-- ensure that no piece disturbs the way
				for i = to_x + 1, from_x - 1 do
					if inv:get_stack(from_list, xy_to_index(i, from_y)):get_name() ~= "" then
						return 0
					end
				end
			end
		else
			-- attempt to move arbitrarily -> abort
			return 0
		end

		if thisMove == "white" or thisMove == "black" then
			if pieceFrom:sub(-1) == "1" then
				meta:set_int("castlingWhiteL", 0)
			elseif pieceFrom:sub(-1) == "2" then
				meta:set_int("castlingWhiteR", 0)
			end
		end

	elseif pieceFrom:sub(11,16) == "knight" then
		-- get relative pos
		local dx = from_x - to_x
		local dy = from_y - to_y

		-- get absolute values
		if dx < 0 then dx = -dx end
		if dy < 0 then dy = -dy end

		-- sort x and y
		if dx > dy then dx, dy = dy, dx end

		-- ensure that dx == 1 and dy == 2
		if dx ~= 1 or dy ~= 2 then
			return 0
		end
		-- just ensure that destination cell does not contain friend piece
		-- ^ it was done already thus everything ok

	elseif pieceFrom:sub(11,16) == "bishop" then
		-- get relative pos
		local dx = from_x - to_x
		local dy = from_y - to_y

		-- get absolute values
		if dx < 0 then dx = -dx end
		if dy < 0 then dy = -dy end

		-- ensure dx and dy are equal
		if dx ~= dy then return 0 end

		if from_x < to_x then
			if from_y < to_y then
				-- moving right-down
				-- ensure that no piece disturbs the way
				for i = 1, dx - 1 do
					if inv:get_stack(from_list, xy_to_index(from_x + i, from_y + i)):get_name() ~= "" then
						return 0
					end
				end
			else
				-- moving right-up
				-- ensure that no piece disturbs the way
				for i = 1, dx - 1 do
					if inv:get_stack(from_list, xy_to_index(from_x + i, from_y - i)):get_name() ~= "" then
						return 0
					end
				end
			end
		else
			if from_y < to_y then
				-- moving left-down
				-- ensure that no piece disturbs the way
				for i = 1, dx - 1 do
					if inv:get_stack(from_list, xy_to_index(from_x - i, from_y + i)):get_name() ~= "" then
						return 0
					end
				end
			else
				-- moving left-up
				-- ensure that no piece disturbs the way
				for i = 1, dx - 1 do
					if inv:get_stack(from_list, xy_to_index(from_x - i, from_y - i)):get_name() ~= "" then
						return 0
					end
				end
			end
		end

	elseif pieceFrom:sub(11,15) == "queen" then
		local dx = from_x - to_x
		local dy = from_y - to_y

		-- get absolute values
		if dx < 0 then dx = -dx end
		if dy < 0 then dy = -dy end

		-- ensure valid relative move
		if dx ~= 0 and dy ~= 0 and dx ~= dy then
			return 0
		end

		if from_x == to_x then
			if from_y < to_y then
				-- goes down
				-- ensure that no piece disturbs the way
				for i = 1, dx - 1 do
					if inv:get_stack(from_list, xy_to_index(from_x, from_y + i)):get_name() ~= "" then
						return 0
					end
				end
			else
				-- goes up
				-- ensure that no piece disturbs the way
				for i = 1, dx - 1 do
					if inv:get_stack(from_list, xy_to_index(from_x, from_y - i)):get_name() ~= "" then
						return 0
					end
				end
			end		
		elseif from_x < to_x then
			if from_y == to_y then
				-- goes right
				-- ensure that no piece disturbs the way
				for i = 1, dx - 1 do
					if inv:get_stack(from_list, xy_to_index(from_x + i, from_y)):get_name() ~= "" then
						return 0
					end
				end
			elseif from_y < to_y then
				-- goes right-down
				-- ensure that no piece disturbs the way
				for i = 1, dx - 1 do
					if inv:get_stack(from_list, xy_to_index(from_x + i, from_y + i)):get_name() ~= "" then
						return 0
					end
				end
			else
				-- goes right-up
				-- ensure that no piece disturbs the way
				for i = 1, dx - 1 do
					if inv:get_stack(from_list, xy_to_index(from_x + i, from_y - i)):get_name() ~= "" then
						return 0
					end
				end
			end				
		else
			if from_y == to_y then
				-- goes left
				-- ensure that no piece disturbs the way and destination cell does
				for i = 1, dx - 1 do
					if inv:get_stack(from_list, xy_to_index(from_x - i, from_y)):get_name() ~= "" then
						return 0
					end
				end
			elseif from_y < to_y then
				-- goes left-down
				-- ensure that no piece disturbs the way
				for i = 1, dx - 1 do
					if inv:get_stack(from_list, xy_to_index(from_x - i, from_y + i)):get_name() ~= "" then
						return 0
					end
				end
			else
				-- goes left-up
				-- ensure that no piece disturbs the way
				for i = 1, dx - 1 do
					if inv:get_stack(from_list, xy_to_index(from_x - i, from_y - i)):get_name() ~= "" then
						return 0
					end
				end
			end		
		end

	elseif pieceFrom:sub(11,14) == "king" then
		local dx = from_x - to_x
		local dy = from_y - to_y
		local check = true
		
		if thisMove == "white" then
			if from_y == 7 and to_y == 7 then
				if to_x == 1 then
					local castlingWhiteL = meta:get_int("castlingWhiteL")
					local idx57 = inv:get_stack(from_list, 57):get_name()

					if castlingWhiteL == 1 and idx57 == "realchess:rook_white_1" then
						for i = 58, from_index - 1 do
							if inv:get_stack(from_list, i):get_name() ~= "" then
								return 0
							end
						end
						inv:set_stack(from_list, 57, "")
						inv:set_stack(from_list, 59, "realchess:rook_white_1")
						check = false
					end
				elseif to_x == 6 then
					local castlingWhiteR = meta:get_int("castlingWhiteR")
					local idx64 = inv:get_stack(from_list, 64):get_name()

					if castlingWhiteR == 1 and idx64 == "realchess:rook_white_2" then
						for i = from_index + 1, 63 do
							if inv:get_stack(from_list, i):get_name() ~= "" then
								return 0
							end
						end
						inv:set_stack(from_list, 62, "realchess:rook_white_2")
						inv:set_stack(from_list, 64, "")
						check = false
					end
				end
			end
		elseif thisMove == "black" then
			if from_y == 0 and to_y == 0 then
				if to_x == 1 then
					local castlingBlackL = meta:get_int("castlingBlackL")
					local idx1 = inv:get_stack(from_list, 1):get_name()

					if castlingBlackL == 1 and idx1 == "realchess:rook_black_1" then
						for i = 2, from_index - 1 do
							if inv:get_stack(from_list, i):get_name() ~= "" then
								return 0
							end
						end
						inv:set_stack(from_list, 1, "")
						inv:set_stack(from_list, 3, "realchess:rook_black_1")
						check = false
					end
				elseif to_x == 6 then
					local castlingBlackR = meta:get_int("castlingBlackR")
					local idx8 = inv:get_stack(from_list, 1):get_name()

					if castlingBlackR == 1 and idx8 == "realchess:rook_black_2" then
						for i = from_index + 1, 7 do
							if inv:get_stack(from_list, i):get_name() ~= "" then
								return 0
							end
						end
						inv:set_stack(from_list, 6, "realchess:rook_black_2")
						inv:set_stack(from_list, 8, "")
						check = false
					end
				end
			end
		end

		if check then
			if dx < 0 then dx = -dx end
			if dy < 0 then dy = -dy end
			if dx > 1 or dy > 1 then return 0 end
		end
		
		if thisMove == "white" then
			meta:set_int("castlingWhiteL", 0)
			meta:set_int("castlingWhiteR", 0)
		elseif thisMove == "black" then
			meta:set_int("castlingBlackL", 0)		
			meta:set_int("castlingBlackR", 0)
		end
	end

	meta:set_string("playerWhite", playerWhite)
	meta:set_string("playerBlack", playerBlack)
	lastMove = thisMove
	meta:set_string("lastMove", lastMove)
	meta:set_int("lastMoveTime", minetest.get_gametime())

	if lastMove == "black" then
		minetest.chat_send_player(playerWhite, "["..os.date("%H:%M:%S").."] "..
				playerName.." moved a "..pieceFrom:match(":(%a+)")..", it's now your turn.")
	elseif lastMove == "white" then
		minetest.chat_send_player(playerBlack, "["..os.date("%H:%M:%S").."] "..
				playerName.." moved a "..pieceFrom:match(":(%a+)")..", it's now your turn.")
	end

	if pieceTo:sub(11,14) == "king" then
		minetest.chat_send_player(playerBlack, playerName.." won the game.")
		minetest.chat_send_player(playerWhite, playerName.." won the game.")
		meta:set_string("winner", thisMove)
	end

	return 1
end

local function timeout_format(timeout_limit)
	local time_remaining = timeout_limit - minetest.get_gametime()
	local minutes = math.floor(time_remaining / 60)
	local seconds = time_remaining % 60

	if minutes == 0 then return seconds.." sec." end
	return minutes.." min. "..seconds.." sec."
end

function realchess.fields(pos, _, fields, sender)
	local playerName = sender:get_player_name()
	local meta = minetest.get_meta(pos)
	local timeout_limit = meta:get_int("lastMoveTime") + 300
	local playerWhite = meta:get_string("playerWhite")
	local playerBlack = meta:get_string("playerBlack")
	local lastMoveTime = meta:get_int("lastMoveTime")
	if fields.quit then return end

	-- timeout is 5 min. by default for resetting the game (non-players only)
	if fields.new and (playerWhite == playerName or playerBlack == playerName) then
		realchess.init(pos)
	elseif fields.new and lastMoveTime ~= 0 and minetest.get_gametime() >= timeout_limit and
			(playerWhite ~= playerName or playerBlack ~= playerName) then
		realchess.init(pos)
	else
		minetest.chat_send_player(playerName, "[!] You can't reset the chessboard, a game has been started.\n"..
				"If you are not a current player, try again in "..timeout_format(timeout_limit))
	end
end

function realchess.dig(pos, player)
	if not player then
		return false
	end
	local meta = minetest.get_meta(pos)
	local playerName = player:get_player_name()
	local timeout_limit = meta:get_int("lastMoveTime") + 300
	local lastMoveTime = meta:get_int("lastMoveTime")

	-- timeout is 5 min. by default for digging the chessboard (non-players only)
	return (lastMoveTime == 0 and minetest.get_gametime() > timeout_limit) or
		minetest.chat_send_player(playerName, "[!] You can't dig the chessboard, a game has been started.\n"..
				"Reset it first if you're a current player, or dig again in "..timeout_format(timeout_limit))
end

function realchess.on_move(pos, from_list, from_index)
	local inv = minetest.get_meta(pos):get_inventory()
	inv:set_stack(from_list, from_index, '')
	return false
end

minetest.register_node(":realchess:chessboard", {
	description = "Chess Board",
	drawtype = "nodebox",
	paramtype = "light",
	paramtype2 = "facedir",
	inventory_image = "chessboard_top.png",
	wield_image = "chessboard_top.png",
	tiles = {"chessboard_top.png", "chessboard_top.png", "chessboard_sides.png"},
	groups = {choppy=3, oddly_breakable_by_hand=2, flammable=3},
	sounds = default.node_sound_wood_defaults(),
	node_box = {type = "fixed", fixed = {-.375, -.5, -.375, .375, -.4375, .375}},
	sunlight_propagates = true,
	on_rotate = screwdriver.rotate_simple,
	can_dig = realchess.dig,
	on_construct = realchess.init,
	on_receive_fields = realchess.fields,
	allow_metadata_inventory_move = realchess.move,
	on_metadata_inventory_move = realchess.on_move,
	allow_metadata_inventory_take = function() return 0 end
})

local function register_piece(name, count)
	for _, color in pairs({"black", "white"}) do
	if not count then
		minetest.register_craftitem(":realchess:"..name.."_"..color, {
			description = color:gsub("^%l", string.upper).." "..name:gsub("^%l", string.upper),
			inventory_image = name.."_"..color..".png",
			stack_max = 1,
			groups = {not_in_creative_inventory=1}
		})
	else
		for i = 1, count do
			minetest.register_craftitem(":realchess:"..name.."_"..color.."_"..i, {
				description = color:gsub("^%l", string.upper).." "..name:gsub("^%l", string.upper),
				inventory_image = name.."_"..color..".png",
				stack_max = 1,
				groups = {not_in_creative_inventory=1}
			})
		end
	end
	end
end

register_piece("pawn", 8)
register_piece("rook", 2)
register_piece("knight", 2)
register_piece("bishop", 2)
register_piece("queen")
register_piece("king")