Stip Mine

--Startup
tArgs = {...}
sides = {"right","left","bottom","top","front"}
location = true

for i = 1,#sides do
	if peripheral.getType(sides[i]) == "modem" then
		modem = true
		rednet.open(sides[i])
		break
	else
		modem = false
	end
end

if not modem then
	print("Could not find a modem")
	error()
end

if not tArgs[1] or not tonumber(tArgs[1]) then
	print("Usage: shaft <length>")
	error(
else
	length = tonumber(tArgs[1])
end

x,y,z = gps.locate()
if y ~= nil then
	backupy = y
	path = y - 14
	print("Current Y is "..y..". Going "..path.." blocks down")
else
	print("Could not determine y cord")
	error()
end

--Functions
function dig()
	if turtle.detect() then
		while not turtle.dig() do
			turtle.attack()
		end
	end
end

function digUp()
	if turtle.detectUp() then
		while not turtle.digUp() do
			turtle.attackUp()
		end
	end
end

function digDown()
	if turtle.detectDown() then
		while not turtle.digDown() do
			turtle.attackDown()
		end
	end
end


function forward()
	while not turtle.forward() do
		turtle.dig()
		turtle.attack()
	end
end

function up()
	while not turtle.up() do
		turtle.digUp()
		turtle.attackUp()
	end
end

function down()
	while not turtle.down() do
		turtle.digDown()
		turtle.attackDown()
	end
end

function right()
	turtle.turnRight()
end

function left()
	turtle.turnLeft()
end

function back()
	while not turtle.back() do
		turtle.turnRight()
		turtle.turnRight()
		repeat until not turtle.dig() and not turtle.attack()
		turtle.turnLeft()
		turtle.turnLeft()
	end
end

function checkInv()
	if turtle.getItemCount(16) then
		return true
	end
end

function dig()
	if turtle.detect() then
		while not turtle.dig() do
			turtle.attack()
		end
	end
end

function getPos()
	x,y,z = nil
	x,y,z = gps.locate()
	if y == nil then
		return false
	else
		return y
	end
end

function stair()
	time = 0
	repeat
		for i = 1,4 do
			if location then
				y = getPos()
				if not y then
					print("Could not determine location. Relying on backup y")
					y = backupy
					location = false
				else
					location = true
				end
			else
				y = backupy
			end

			turtle.digDown()
			turtle.down()
			backupy = backupy - 1
			dig()
			forward()
			digDown()
			digUp()
			right()
			dig()
			forward()
			digDown()
			digUp()
			back()
			if time == 4 then
				turtle.select(1)
				turtle.place()
				left()
				time = 0
			else
				left()
				time = time + 1
			end
			if y < 16 then
				break
			end
		end
	until y < 16
end

function shaft()
	for i = 1,length do
		for i = 1,2 do
			dig()
			forward()
			digUp()
			right()
			dig()
			forward()
			digUp()
			back()
			left()
		end
  		dig()
		forward()
		digUp()
		right()
		dig()
		forward()
		digUp()
		for i = 1,3 do
			dig()
			forward()
			digUp()
		end

		for i = 1,4 do
			back()
		end
		left()
		left()
		for i = 1,3 do
			dig()
			forward()
			digUp()
		end

		for i = 1,3 do
			back()
		end
		right()
	end
end

stair()
shaft()