-- Turtle inventory should be 4 by 4
-- A chest or an inventory should be present at the left of the starting position
-- The block layer at the turtle's level should be clear, fully digged for the defined mining zone
-- Fuel should be on the lower right slot
-- Any well-sealing block should be on slot 15, left of the fuel
-- Blocks not to be mined should be on the first line

-- Define the mining zone here
MaxForward = 16
MaxRight = 16
-- Number of holes to skip (beginning)
SkipHoles = 0

local pos = {0, 0, 0}
local facing = 0
local curMessage = ''

function tWrite(txt)
	term.clear()
	term.setCursorPos(1, 1)
	if txt then term.write(txt)
	else term.write(curMessage)
	end
end

function turnRight(n)
	n = n or 1
	
	while n > 0 do
		n = n - 1
		facing = (facing + 1) % 4
		turtle.turnRight()
	end
end

function turnLeft(n)
	n = n or 1
	
	while n > 0 do
		n = n - 1
		facing = (facing - 1) % 4
		turtle.turnLeft()
	end
end

function right(n)
	n = n or 1
	checkFuel(n)

	if facing == 0 then
		turnRight()
		while n > 0 do
			if turtle.forward() then
				n = n - 1
				pos[1] = pos[1] + 1
			end
		end
	elseif facing == 1 then
		while n > 0 do
			if turtle.forward() then
				n = n - 1
				pos[1] = pos[1] + 1
			end
		end
	elseif facing == 2 then
		turnLeft()
		while n > 0 do
			if turtle.forward() then
				n = n - 1
				pos[1] = pos[1] + 1
			end
		end
	else
		while n > 0 do
			if turtle.back() then
				n = n - 1
				pos[1] = pos[1] + 1
			end
		end
	end
end

function left(n)
	n = n or 1
	checkFuel(n)
	
	if facing == 0 then
		turnLeft()
		while n > 0 do
			if turtle.forward() then
				n = n - 1
				pos[1] = pos[1] - 1
			end
		end
	elseif facing == 1 then
		while n > 0 do
			if turtle.back() then
				n = n - 1
				pos[1] = pos[1] - 1
			end
		end
	elseif facing == 2 then
		turnRight()
		while n > 0 do
			if turtle.forward() then
				n = n - 1
				pos[1] = pos[1] - 1
			end
		end
	else
		while n > 0 do
			if turtle.forward() then
				n = n - 1
				pos[1] = pos[1] - 1
			end
		end
	end
end

function forward(n)
	n = n or 1
	checkFuel(n)

	if facing == 0 then
		while n > 0 do
			if turtle.forward() then
				n = n - 1
				pos[2] = pos[2] + 1
			end
		end
	elseif facing == 1 then
		turnLeft()
		while n > 0 do
			if turtle.forward() then
				n = n - 1
				pos[2] = pos[2] + 1
			end
		end
	elseif facing == 2 then
		while n > 0 do
			if turtle.back() then
				n = n - 1
				pos[2] = pos[2] + 1
			end
		end
	else
		turnRight()
		while n > 0 do
			if turtle.forward() then
				n = n - 1
				pos[2] = pos[2] + 1
			end
		end
	end
end

function backward(n)
	n = n or 1
	checkFuel(n)

	if facing == 0 then
		while n > 0 do
			if turtle.back() then
				n = n - 1
				pos[2] = pos[2] - 1
			end
		end
	elseif facing == 1 then
		turnRight()
		while n > 0 do
			if turtle.forward() then
				n = n - 1
				pos[2] = pos[2] - 1
			end
		end
	elseif facing == 2 then
		while n > 0 do
			if turtle.forward() then
				n = n - 1
				pos[2] = pos[2] - 1
			end
		end
	else
		turnLeft()
		while n > 0 do
			if turtle.forward() then
				n = n - 1
				pos[2] = pos[2] - 1
			end
		end
	end
end

function up(n)
	n = n or 1
	checkFuel(n)
	
	while n > 0 do
		if turtle.up() then
			n = n - 1
			pos[3] = pos[3] + 1
		end
	end
end

function down(n)
	n = n or 1
	checkFuel(n)
	
	while n > 0 do
		if turtle.down() then
			n = n - 1
			pos[3] = pos[3] - 1
		end
	end
end
 
function getTo(nPos)
	if not nPos[1] then nPos[1] = pos[1] end
	if not nPos[2] then nPos[2] = pos[2] end
	if not nPos[3] then nPos[3] = pos[3] end
	diff = {nPos[1] - pos[1], nPos[2] - pos[2], nPos[3] - pos[3]}

	-- Right / left
	if diff[1] > 0 then right(diff[1])
	elseif diff[1] < 0 then left(-diff[1])
	end
  
	-- Forward / backward
	if diff[2] > 0 then forward(diff[2])
	elseif diff[2] < 0 then backward(-diff[2])
	end
	
	-- Up / down
	if diff[3] > 0 then up(diff[3])
	elseif diff[3] < 0 then down(-diff[3])
	end
end

function checkFuel(n)
	if turtle.getFuelLevel() < n then
		tWrite('Refueling...')
		
		turtle.select(16)
		while turtle.getFuelLevel() < n do
			turtle.refuel(1)
		end
		
		tWrite()
	end
end

function startingPoint(row)
	return (2 * (row-1)) % 5 + 1
end

function ascend()
	curMessage = 'Ascending...'
	tWrite()
		
	while pos[3] < 0 do
		if turtle.detectUp() then turtle.digUp() end
		up()
	end
	
	turtle.select(15)
	turtle.placeDown()
	
	tWrite()
end

function drillSides()
	for i = 0, 3, 1 do
		local canDig = true
		
		for j = 1, 4, 1 do
			turtle.select(j)
			if turtle.compare() then canDig = false end
		end
		
		if canDig then turtle.dig() end
		if i ~=3 then turnLeft() end
	end
end

function drill()
	curMessage = 'Drilling...'
	tWrite()
		
	while (not turtle.detectDown()) or (turtle.detectDown() and turtle.digDown()) do
		down()
		drillSides()
	end
	
	ascend()
	
	tWrite()
end

function drillRow(row)
	getTo({row, startingPoint(row)})
	
	local willMove = 0
	
	while (pos[2] + willMove) <= (MaxForward - 2) do
		emptyInventory()
		
		if willMove == 0 then willMove = 5
		else forward(willMove)
		end
		
		if SkipHoles == 0 then drill()
		else SkipHoles = SkipHoles - 1
		end
	end
end

function emptyInventory()
	curMessage = 'Emptying inventory...'
	tWrite()
	
	local curPos = {pos[1], pos[2]}
	getTo({0,0})
	
	while facing ~= 3 do
		turnRight()
	end
	
	for i = 5, 14, 1 do
		turtle.select(i)
		turtle.drop()
	end
	
	getTo(curPos)
	
	tWrite()
end

tWrite('Initializing...')

for i = 1, MaxRight - 2, 1 do
	drillRow(i)
end

tWrite('Ended')