print "my very first mining program"
print "how far should the square be?"
local size = tonumber(io.read())
print "how deep"
local yLevel = tonumber(io.read())



-- inc X 		/	increase Z 	/	deacrease X	/	decrease Z 	/
-- 0 - front	/ 	1 - right 	/ 	2 - back 	/ 	3 - left 	/
local direction = 0
local traveledX = 0
local traveledY = 0 --
local traveledZ = 0 -- to the right

function CheckFuel()
	--if he needs some, refuelhalf a stack of what's to eat
	if turtle.getFuelLevel() ~= "unlimited" and turtle.getFuelLevel() < math.ceil(turtle.getFuelLimit() / 5) then
		print "I will try refueling"
		for i = 1, 16 do
			turtle.select(i)
			if turtle.refuel(0) then
				print "Fuel level before refueling: " + turtle.getFuelLevel()
				local half = math.ceil(turtle.getItemCount(i)/2)
				turtle.refuel(half)
				print "And after: " + turtle.getFuelLevel()
				return true
			end
		end
		print "I'm out of FUEL  :-("
		return false
	else
		--if turtle.getFuelLevel() < math.ceil(turtle.getFuelLimit() * 0.1) then
		--	print "I'm low on energy, I will return home"
		--	ReturnHome()
		--else
			return true
		--end
	end
end
-- not finished yet
function ReturnHome()
	if traveledY > 0 then
		for i = 0, traveledY do
			MoveUp()
		end
	end
	if traveledX > 0 then
		while direction ~= 2 do
			TurnRight()
		end
		LongForwardMove(traveledX)
	end

	if traveledZ > 0 then
		while direction ~= 3 do
			TurnRight()
		end
		LongForwardMove(traveledZ)
	end
end

function MoveDown()
	if (turtle.detectDown()) then
		turtle.digDown()
	end
	if(turtle.down()) then
   		traveledY = traveledY + 1
   		print "I'm going down"
    	return true
  	end
  	return false
end

function MoveUp()
	if (turtle.detectUp()) then
		turtle.digUp()
	end
	if(turtle.up()) then
		traveledY = traveledY - 1
    	return true
  	end
  	return false

end

function MoveForward()
	if (turtle.detect()) then
		turtle.dig()
	end
	if(turtle.forward()) then
		if direction == 0 then
			traveledX = traveledX + 1
		elseif direction == 1 then
			traveledZ = traveledZ + 1
		elseif direction == 2 then
			traveledX = traveledX - 1
		else
			traveledZ = traveledZ - 1
		end
	end
	return
end

function TurnLeft()
	if direction == 0 then
		direction = 3
	else
		direction = direction - 1
	end
	return

end

function TurnRight()
	if direction == 3 then
		direction = 0
	else
		direction = direction + 1
	end
	return
end

function LongForwardMove(length)
	for i = 1, length do
		CheckFuel()
		MoveForward()
	end

end
function SquareMine()
	LongForwardMove(size-1)
	TurnRight()
	for i = 1, size do
		LongForwardMove(size-2)
		TurnRight()
		MoveForward()
		TurnRight()
	end

	return
end

function Main()

	CheckFuel()
-- goes down to the yLevel and mines the whole square, then he goes up and mines there and so on
	for i = 1, yLevel do
		CheckFuel()
		MoveDown()
	end

	if math.ceil(size % 2) == 0 then
		SquareMine()
	end
	ReturnHome()
end


Main() -- !