function GpsPos()
		local x, y, z = gps.locate()
		return {x, y, z}
end

local args = { ... }

if (#args ~= 2) then
		print("Gib depth then gib width plsss")
		error()
end

nb_blocks = 2
movement = 1
base_forward_movement = tonumber(args[1]) - 1
forward_movement_left = base_forward_movement
lateral_movement_left = tonumber(args[2])

function Sign(p_int)
		if (p_int < 0) then
				return -1
		end
		return 1
end

function Abs(p_int)
		return p_int * Sign(p_int)
end

function UpdateMovement()
		--[[ Determine if we have gone far enough --]]
		if (forward_movement_left == 0) then
				print("Bounds detected")
				forward_movement_left = base_forward_movement

				lateral_movement_left = lateral_movement_left - 1

				if (lateral_movement_left == 0) then
						return
				end

				--[[ Lateral movement --]]
				if (movement == 1) then
					turtle.turnRight()
					turtle.forward()
					turtle.turnRight()
				else
					turtle.turnLeft()
					turtle.forward()
					turtle.turnLeft()
				end

				UpdateBlocks(GpsPos())

				--[[ Reverse current direction --]]
				movement = -movement
		end

		turtle.forward()
		forward_movement_left = forward_movement_left - 1
end

function Distance(xA, zA, xB, zB)
		return Abs(xB - xA) + Abs(zB - zA)
end

function GetBlockId(p_pos)
		if (Distance(0, 0, p_pos[1], p_pos[3]) == 10) then
				return 1
		end
		if (Distance(10, 10, p_pos[1], p_pos[3]) == 5) then
				return 1
		end
		if (Distance(-10, 10, p_pos[1], p_pos[3]) == 5) then
				return 1
		end
		if (Distance(10, -10, p_pos[1], p_pos[3]) == 5) then
				return 1
		end
		if (Distance(-10, -10, p_pos[1], p_pos[3]) == 5) then
				return 1
		end
		return 2
end

function UpdateBlocks(p_pos)
		Reload()

		--[[ Determine what to place below --]]
		print("Position is " .. p_pos[1] .. " " .. p_pos[3])

		turtle.select(GetBlockId(p_pos))

		--[[ Check if below is already the block we want to place --]]
		if (not turtle.compareDown()) then
			if (turtle.detectDown()) then
				turtle.digDown()
			end
			turtle.placeDown()
		end
end

function GetBlockFromNextSlot(slot_id)
		local slot_to_take_from = slot_id + nb_blocks
 print("Checking number of blocks of slot " .. slot_id)

		--[[ If the slot we want to take blocks from doesn't have them, ask them to fetch them --]]
		if (turtle.getItemCount(slot_to_take_from) < 32) then
				GetBlockFromNextSlot(slot_to_take_from)
		end
		turtle.select(slot_to_take_from)
		turtle.transferTo(slot_id, 32)
end

function Reload()
		local i = 1
		while (i < nb_blocks + 1) do
  print("We have " .. turtle.getItemCount(i) .. " items in slot")
				if (turtle.getItemCount(i) == 0) then
						GetBlockFromNextSlot(i)
				end
				i = i + 1
		end
end

function Update()
		UpdateBlocks(GpsPos())
		UpdateMovement()
end

function GoForwardFor(fwd)
	while (fwd > 0) do
		fwd = fwd - 1
		turtle.forward()
	end
end

while(lateral_movement_left > 0) do
		Update()
end

print("Let's go back home")

if (args[2] % 2 == 0) then
	turtle.turnRight()

	GoForwardFor(tonumber(args[2]) - 1)

	turtle.turnRight()
else
	turtle.turnLeft()

	GoForwardFor(tonumber(args[2]) - 1)

	turtle.turnLeft()

	GoForwardFor(tonumber(args[1]) - 1)

	turtle.turnLeft()
	turtle.turnLeft()
end

print("Job's done!")