General Turtle Movement

--[[
        X+(0)
          ^
    Z-(3) < Turtle > Z+(1)
          v
        X-(2)

]]--

x = 0
y = 0
z = 0
dir = 0
autoFuel = false --refuels using picked up fuel items (eg. coal + wood)
allowDrain = false --allow turtle to take directions even if there is not enough fuel
hardFuelLimit = false --dont allow turtle to refuel if the next fuel item exceeds limit (will stop using items after cap is reached regardless of this option, allow autofuel + allowDrain for trips exceeding fuel limit)

--[[ END OF VARIABLES ]]--

fuel = turtle.getFuelLevel()
needsFuel = true
if (fuel == "unlimited") then
    needsFuel = false
    autoFuel = false
    allowDrain = true
else
    fuelLim = turtle.getFuelLimit()
end

function align(toward)
    for i=1, math.abs(toward - dir) do
        if (toward < dir) then
            turtle.turnLeft()
            dir = (dir + 3) % 4
        else
            turtle.turnRight()
            dir = (dir + 1) % 4
        end
    end
end

function distTo(destX, destY, destZ)
    return math.abs(destX - x) + math.abs(destY - y) + math.abs(destZ - z)
end

function refuel(amount)
    fuel = turtle.getFuelLevel()
    total = fuel + amount
    for i=1, 16 do
        turtle.select(i)
        turtle.refuel(1)
        fuelVal = turtle.getFuelLevel() - fuel
        if (fuelVal > 0) then
            turtle.refuel(math.min(64,math.ceil(math.min(fuelLim, (amount - fuelVal)) / fuelVal)))
            fuel = turtle.getFuelLevel()
            amount = total - fuel
            if (amount <= 0) then
                return true
            end
        end
    end
    return false
end

function dig(toward, spaces)
    spaces = spaces or 1
    align(toward)

    for i=1, spaces do
        while not (turtle.forward()) do
            turtle.dig()
            turtle.attack()
        end

        if (dir == 0) then
            x = x + 1
        elseif (dir == 1) then
            z = z + 1
        elseif (dir == 2) then
            x = x - 1
        elseif (dir == 3) then
            z = z - 1
        end
    end
end

function digTo(newX, newY, newZ)
    xDist = newX - x
    yDist = newY - y
    zDist = newZ - z

    if (xDist > 0) then
        align(0)
    elseif (xDist < 0) then
        align(2)
    end
    dig(dir, math.abs(xDist))

    if (zDist > 0) then
        align(1)
    elseif (zDist < 0 ) then
        align(3)
    end
    dig(dir, math.abs(zDist))

    for i=1, math.abs(yDist) do
        if (yDist > 0) then
            while not (turtle.up()) do
                turtle.digUp()
                turtle.attackUp()
            end
            y = y + 1
        elseif (yDist < 0) then
            while not (turtle.down()) do
                turtle.digDown()
                turtle.attackDown()
            end
            y = y - 1
        end
    end
    return true
end

function digSquare(corner, width, length)
    --[[ corner values, width is always x, length is always z
        3----0
        |    |
        2----1
    ]]--


    if (corner == 0 or corner == 1) then
        align(3)
    elseif (corner == 2 or corner == 3) then
        align(1)
    else
        return 0
    end

    for i=1, length do
        if (i ~= 1) then
            if (i % 2 == corner % 2) then
                align(dir - 1)
                dig(dir)
                align(dir - 1)
            else
                align(dir + 1)
                dig(dir)
                align(dir + 1)
            end
        end
        dig(dir, width - 1)
    end
end

function digCube(corner, width, length, depth)
    for i=1, depth do
        digSquare(corner, width, length)
        digTo(x, y-1, z)
        align(0)
        if (length % 2 == 1) then
            corner = (corner + 2) % 4
        else
            corner = (corner + 1) - 2 * (corner % 2)
        end
    end
end