cart.adb

WITH Text_Io; USE Text_Io;
WITH NT_Console; USE NT_Console;

PACKAGE BODY Cart IS

      task semaphore is
            entry P;			-- Dijkstra’s terminology
            entry V;			-- from the Dutch
	end semaphore;
	task body semaphore is
		begin
		loop
			accept P;	-- won’t accept another P until a caller asks for V
			accept V;
		end loop;
	end semaphore;


      function initCart return cart IS
            C : cart;
      BEGIN
            for I in 0..8 loop
                  C.floorList(I) := initFloor(I);
                  C.buttons(I) := initButton;
            end loop;
            C.operationDelay := clock;
            C.level := C.floorList(0);
            C.max_level := C.level.level;
            C.min_level := C.level.level;
            C.dir := Up;
            RETURN C;
      END;


      procedure driveCart(C : IN OUT cart) IS
      BEGIN

            C.operationDelay := C.operationDelay + 2.0;
            delay until C.operationDelay;

            semaphore.P;

            if C.dir = Up AND
            (isPressed(C.floorList(C.level.level).buttons(Up)) OR
            isPressed(C.buttons(C.level.level)))
            then
                  setFalse(C.floorList(C.level.level).buttons(Up));
                  setFalse(C.buttons(C.level.level));
                  calculateMinMax(C); -- Calculate new min max

                  C.operationDelay := C.operationDelay + 5.0; -- Opens door, could be improved by printing

                  delay until C.operationDelay;

            elsif C.dir = Down AND
            (isPressed(C.floorList(C.level.level).buttons(Down)) OR
            isPressed(C.buttons(C.level.level)))
            then
                  setFalse(C.floorList(C.level.level).buttons(Down));
                  setFalse(C.buttons(C.level.level));
                  calculateMinMax(C); -- Calculate new min max

                  C.operationDelay := C.operationDelay + 5.0; -- Opens door, could be improved by printing
                  delay until C.operationDelay;
            end if;

            if C.level.level < C.max_level AND C.dir = Up then
                  C.level.level := C.level.level + 1;
            elsif C.level.level > C.min_level AND C.dir = Down then
                  C.level.level := C.level.level - 1;
            elsif (C.level.level = C.min_level OR C.level.level < C.min_level)  AND C.dir = Down then
                  C.dir := Up;
            elsif (C.level.level = C.max_level OR C.level.level > C.max_level)  AND C.dir = Up then
                  C.dir := Down;
            end if;
            semaphore.V;
      END;


      procedure pressCartButton(C : IN OUT cart; L : IN integer) IS
      BEGIN

            semaphore.P;

            press(C.buttons(L));
            calculateMinMax(C);
            semaphore.V;

      END;

      procedure pressFloorButton(C : IN OUT cart; L : IN integer; D : IN direction) IS
      BEGIN
            semaphore.P;
            press(C.floorList(L).buttons(D));
            calculateMinMax(C);
            semaphore.V;

      END;

      procedure calculateMinMax(C : IN OUT cart) IS
      -- Calculate new min and max after change in button presses --
      BEGIN
            C.min_level := 8;
            C.max_level := 0;
            for L in 0..8 loop
                  if L < C.min_level AND
                        (isPressed(C.floorList(L).buttons(Up)) OR
                        isPressed(C.floorList(L).buttons(Down)) OR
                        isPressed(C.buttons(L)))
                  then
                        C.min_level := L;
                  end if;
                  if L > C.max_level AND
                        (isPressed(C.floorList(L).buttons(Up)) OR
                        isPressed(C.floorList(L).buttons(Down)) OR
                        isPressed(C.buttons(L)))
                  then
                        C.max_level := L;
                  end if;
            end loop;

            if C.min_level = 8 AND C.max_level = 0 then
                  C.min_level := C.level.level;
                  C.max_level := C.level.level;
            end if;
      END;

      procedure destructCart is
      BEGIN
            abort semaphore;
      END;
End Cart;