Circular Excavate

args = {...}

radius = 15
height = 10

if tonumber(args[1]) ~= nil and tonumber(args[2]) ~= nil then
    radius = args[1]
    height = args[2]
end

xCoord = 0
zCoord = 0
yCoord = 0

xStartRing = 0
zStartRing = 0

orientation = 4
orientations = {"north", "east", "south", "west"}

zDiff = {-1, 0, 1, 0}
xDiff = {0, 1, 0, -1}


function left()
    orientation = orientation - 1
    orientation = (orientation - 1) % 4
    orientation = orientation + 1
    turtle.turnLeft()
end



function right()
    orientation = orientation - 1
    orientation = (orientation + 1) % 4
    orientation = orientation + 1

    turtle.turnRight()
end



function moveForward()
    xCoord = xCoord + xDiff[orientation]
    zCoord = zCoord + zDiff[orientation]

    moved = false
    while not(moved) do
        turtle.dig()
        SmartRefuel()
        moved = turtle.forward()
    end
end



function moveUp()
    yCoord = yCoord + 1

    turtle.digUp()

    moved = false
    while not(moved) do
        moved = turtle.up()
    end
end

function moveDown()

    yCoord = yCoord - 1
    turtle.digDown()

    moved = false

    while not(moved) do
        moved = turtle.down()
    end

end

function look(direction)
    while direction ~= orientations[orientation] do
        right()
    end
end


function round(n)
    decimal = n - math.floor(n)
    if decimal >= 0.5 then
        return math.ceil(n)
    else
        return math.floor(n)
    end
end

function withinRadius(x, z)
    return round( math.sqrt((x * x) + (z * z)) ) <= radius
end


function forwardWithinRadius()

    xNext = xCoord + xDiff[orientation]
    zNext = zCoord + zDiff[orientation]

    return withinRadius(xNext, zNext)
end

function gotoEdge()
    while forwardWithinRadius() do
        moveForward()
    end

    left()

    xStartRing = xCoord
    zStartRing = zCoord
end

function digRing()

    repeat

        while forwardWithinRadius() do
            moveForward()
        end
        while not(forwardWithinRadius()) do
            left()
        end
        moveForward()
        right()

    until xCoord == xStartRing and zCoord == zStartRing

    left()
    left()
    for i = 1,radius do
        moveForward()
    end
    left()
    left()
end

function digLayer()
    r = radius
    for i = 1,r do
        radius = i
        gotoEdge()
        digRing()
    end
end

function digCylinder()
    for i = 1,height do
        digLayer()
        moveDown()
    end
end

--[[ Calculate fuel:
Calculate how much fuel we have left and refuel if needed
returns true if we can get home on our current fuel level
returns false if we need to go back now
]]--
function SmartRefuel()
    -- refuel if we need to
    local cur_fuel = turtle.getFuelLevel() -- current fuel
    if cur_fuel == 0 then
        for i = 1,16,1 do
            if not (turtle.getItemCount(i) == nil) then
                if turtle.getItemDetail(i)["name"] == "minecraft:coal" then
                    turtle.select(i)
                    turtle.refuel()
                    turtle.select(1)
                    print("Refuelled.")
                    break
                end
            end
        end
    end
end

digCylinder()