carttunneler

local tunnelLength = 0
local tunnelDepth = 0
local curIter = 1
local curx = 0
local cury = 0
local curz = 0
local dir = 1 -- 1=Forward, 2=Right, 3=Back & 4=Left
local itemCount = 1

local function toInt(value)
    return math.floor(tonumber(value) or error("Could not cast '" .. tostring(value) .. "' to number.'"))
end

local function forward()
    if turtle.forward() == false then
        if turtle.getFuelLevel() == 0 then
            write("No fuel left, refuel")
            return -1
        else
            write("Blocked")
            return 0
        end
    else
        if dir == 1 then curx = curx + 1 end
        if dir == 2 then cury = cury + 1 end
        if dir == 3 then curx = curx - 1 end
        if dir == 4 then cury = cury - 1 end
    end
    return 1
end

local function back()
    if turtle.back() == false then
        if turtle.getFuelLevel() == 0 then
            write("No fuel left, refuel")
            return -1
        else
            write("Blocked")
            return 0
        end
    else
        if dir == 1 then curx = curx - 1 end
        if dir == 2 then cury = cury - 1 end
        if dir == 3 then curx = curx + 1 end
        if dir == 4 then cury = cury + 1 end
    end
    return 1
end

local function up()
    if turtle.up() == false then
        if turtle.getFuelLevel() == 0 then
            write("No fuel left, refuel")
            return -1
        else
            write("Blocked")
            return 0
        end
    else
        curz = curz + 1
    end
    return 1
end

local function down()
    if turtle.down() == false then
        if turtle.getFuelLevel() == 0 then
            write("No fuel left, refuel")
            return -1
        else
            write("Blocked")
            return 0
        end
    else
        curz = curz - 1
    end
    return 1
end

local function left()
    if turtle.left() == false then
        return 0
    else
        dir = dir - 1
        if dir < 1 then dir = 4 end
        return 1
    end
end

local function right()
    if turtle.right() == false then
        return 0
    else
        dir = dir + 1
        if dir > 4 then dir = 1 end
        return 1
    end
end

local function dig()
    if turtle.dig() == false then
        return 0
    else
        return 1
    end
end

local function digUp()
    if turtle.digUp() == false then
        return 0
    else
        return 1
    end
end

local function digDown()
    if turtle.digDown() == false then
        return 0
    else
        return 1
    end
end

print("Please specify tunnel length:")
tunnelLength = toInt(read())
print("Please specify tunnel depth:")
tunnelDepth = toInt(read())

write("Digging down")
curIter = 1
while curIter <= tunnelDepth do
    digDown()
    down()
    curIter = curIter + 1
end

write("Tunnelling")
curIter = 1
while curIter <= tunnelLength do
    dig()
    forward()
    digDown()
    if itemCount < 6 then
        turtle.select(5)
        turtle.placeDown()
        itemCount = itemCount + 1
    else
        write("Placing powered rail...")
        turtle.select(6)
        turtle.placeDown()
        itemCount = 1
    end
    curIter = curIter + 1
end

write("Digging to surface")
while turtle.detectUp() == true do
    digUp()
    up()
end

write("Going back down")
while curz > (0 - tunnelDepth) do
    down()
end

write("Moving back")
curIter = 1
while curIter <= tunnelLength do
    back()
    curIter = curIter + 1
end

write("Moving up")
curIter = 1
while curIter <= tunnelDepth do
    up()
    curIter = curIter + 1
end

write("Complete")