mine-return-2

-- Globals
local arg = {...}
local SQUARE_SIZE = 3
local DOWN_SQUARE = 0
local UP_SQUARE = 1
local squareType = DOWN_SQUARE
local CONTAINER_SUBSTRINGS = {"chest"}

-- Determines if the block in front of a turtle is a chest
local function isChest()
	local status, data = turtle.inspect()

	if(not status) then
		print("No chest available")
		return false
	end

	local itemName = data["name"]:match(":(.+)"):lower()
	for index, container in pairs(CONTAINER_SUBSTRINGS) do
		if(itemName:find(container)) then
			return true
		end
	end

	return false
end

-- Attempt to refuel the turtle
local function attemptRefuel()
	if(turtle.getFuelLevel() >= 1) then
		return
	end

	local index = 1
	local hasRefueled = false
	while(index <= 16 and not hasRefueled) do
		turtle.select(index)
		if(turtle.refuel(0)) then
			turtle.refuel(1)
			hasRefueled = true
		end
		index = index + 1
	end
end

-- Attempt to dump non-fuel items into a chest in front of the turtle
local function attemptDumpInv()
	if(not isChest()) then
		return
	end

	for index=1, 16 do
		turtle.select(index)
		if(not turtle.refuel(0)) then
			turtle.drop()
		end
	end
end

-- Move in a direction 1 or more times
local function move(direction, distance)
	local distance = tonumber(distance) or 1
	attemptRefuel()

	local result
	if(direction == "up") then
		result = turtle.up()
	elseif(direction == "down") then
		result = turtle.down()
	elseif(direction == "forward") then
		result = turtle.forward()
	elseif(direction == "back") then
		result = turtle.back()
	else
		print("Direction: " .. direction .. " not a valid movement")
		result = false
	end

	if(not result) then
		return result
	end

	if(distance > 1) then
		move(direction, distance - 1)
	end

	return true
end

-- Dig out a block and move into it
local function digMove(direction)
	local result
	if(direction == "up") then
		turtle.digUp()
		result = move("up")
	elseif(direction == "down") then
		turtle.digDown()
		result = move("down")
	elseif(direction == "forward") then
		turtle.dig()
		result = move("forward")
	elseif(direction == "back") then
		turtle.turnLeft()
		turtle.turnLeft()
		turtle.dig()
		turtle.turnLeft()
		turtle.turnLeft()
		result = move("back")
	else
		print("Direction: " .. direction .. " not a valid movement")
		return false
	end

	-- Usually gets stuck on sand/gravel so dig it back out
	if(not result) then
		digMove(direction)
	end

	return true
end

-- Dig out a 3x3 vertical square
local function tunnelSquare()
	-- Dig out adjacent left and right blocks
	local function tunnelAdjacentLR()
		local function verifyDig()
			local status = turtle.inspect()
			while(status) do
				turtle.dig()
				status = turtle.inspect()
			end
		end

		turtle.turnLeft()
		verifyDig()
		turtle.turnLeft()
		turtle.turnLeft()
		verifyDig()
		turtle.turnLeft()
	end

	digMove("forward")	-- Move into next vertical square
	for i=1, SQUARE_SIZE do
		tunnelAdjacentLR()
		if(i < 3) then
			if(DOWN_SQUARE == squareType) then
				digMove("up")
			else
				digMove("down")
			end
		end
	end

	if(DOWN_SQUARE == squareType) then
		squareType = UP_SQUARE
	else
		squareType = DOWN_SQUARE
	end
end

-- Tunnel
local function tunnel(distance, tunnelFunc)
	-- Don't bother with tunnelling negative distances
	if(distance < 1) then
		return
	end

	-- Default to tunnelSquare
	local tunnelFunc = tunnelFunc or tunnelSquare

	-- Tunnel over a distance using specified tunneling function
	for i=1, distance do
		tunnelFunc()
	end
end

-- Display usage info
local function help()
	local name = "<name>"
	if(shell) then
		name = shell.getRunningProgram()
	end

	print("Usage: " .. name .. " <distance to tunnel >= 3> [shaft center spacing (-  left, + right)]\nAlso, if a chest is placed to the turtle's right it'll dump non-fuel items into that")
end

-- Main
local function main(distance, spacing)
	-- Handle args
	local distance = tonumber(distance) or 0
	local spacing = tonumber(spacing) or 0

	if(distance < 3) then
		help()
		return
	end

	-- Initial tunneling distance
	tunnel(distance)

	-- Tunnel over to return shaft
	move("back")
	if(spacing > 0) then
		turtle.turnRight()
		move("forward")
		tunnel(spacing)
		move("back")
		turtle.turnRight()
	elseif(spacing < 0) then
		turtle.turnLeft()
		move("forward")
		tunnel(spacing * -1)
		move("back")
		turtle.turnLeft()
	else
		turtle.turnLeft()
		turtle.turnLeft()
	end

	-- Move to edge of return shaft
	move("forward")

	-- Tunnel/move back to start
	if(spacing == 0) then
		move("forward", distance - 2)
	else
		tunnel(distance - 3)
		move("forward")
	end

	if(UP_SQUARE == squareType) then
		move("down", 2)
	end

	-- Spin back around, dump non-fuel into adjacent chest
	turtle.turnLeft()
	attemptDumpInv()
	turtle.turnLeft()
end

main(arg[1], arg[2])