A lua script for the ComputerCraft Minecraft mod. Makes a branch mine. Usage: branchMine <length>

branchMine.lua

-- This work is licensed under a CC BY-NC-SA 3.0 license.
-- http://creativecommons.org/licenses/by-nc-sa/3.0/
-- 
-- by the Forlorn Hedgehog
--
-- Usage: branchMine <length>
-- Fuel goes in slot 1. Torches go in slot 2. Floor blocks (usually cobblestone) go in slot 3.
-- Mines a trunk <length> blocks long, with an 8 block long branch, on each side, every 3 blocks, starting 2 blocks in (n=3n-1)

-- If fuel level is less than 10, refuel
function fuel()
	if turtle.getFuelLevel() < 10 then
		turtle.select(1)
		if turtle.refuel(1) then
			return true
		end
		print("Refuelling failed.")
		return false
	end
end

-- Place floor block, if there is not already one.
function placeFloorBlock()
	if not turtle.detectDown() then
		turtle.select(3)
		if turtle.placeDown() then
			return true
		end
		print("Placing floor block failed.")
		return false
	end
end

-- Digs and moves into a 1x2x1 (xyz) area.
function basicDigAndMove()
	while not turtle.forward() do
		if not turtle.dig() then
			turtle.attack()
		end
	end
	while turtle.detectUp() do
		turtle.digUp()
		sleep(0.5)
	end
	placeFloorBlock()
end

-- Turn turtle 180 degrees
function turnAround()
	turtle.turnLeft()
	turtle.turnLeft()
end

-- Place torch on floor, in front of the turtle
function placeTorch()
	turtle.select(2)
	if turtle.place() then
		return true
	end
	print("Placing torch failed.")
	return false
end

-- This function mines a 1x2x8 (xyz) tunnel directly infront of the turtle, placing a torch near the end, and returning to start point (but in opposite orientation)
function branch()
	local blocksMovedSideways = 0
	while blocksMovedSideways < 8 do
		fuel()
		basicDigAndMove()
		blocksMovedSideways = blocksMovedSideways + 1

		if blocksMovedSideways == 8 then
			turnAround()
			placeTorch()
		end
	end
	
	-- Back to start point (goes up to avoid the torch on floor)
	turtle.up()
	for i=1,8 do
		turtle.forward()
		blocksMovedSideways = blocksMovedSideways - 1
	end
	turtle.down()
end

-- Arguments
local tArgs = {...}
if #tArgs ~= 1 or tonumber(tArgs[1]) == nil or math.floor(tonumber(tArgs[1])) ~= tonumber(tArgs[1]) or tonumber(tArgs[1]) < 1 then
	print("Usage: branchMine <length>")
	return
end

local length = tonumber(tArgs[1])

local blocksMovedForward = 0
while blocksMovedForward < length do
	fuel()
	basicDigAndMove()
	blocksMovedForward = blocksMovedForward + 1

	-- Add torch (on floor) every 8 blocks
	if (blocksMovedForward % 8) == 0 then
		turnAround()
		placeTorch()
		turnAround()
	end

	-- n=3n-1
	if ((blocksMovedForward + 1) % 3) == 0 then
		turtle.turnLeft()
		branch()
		branch()
		turtle.turnRight()
	end
end