startup.lua

local originX = -2511
local originY = 58
local originZ = 972

local x, y, z

function setCoordinates()
    repeat
        print("Locating (" .. textutils.formatTime(os.time(), false) .. ")")
        x, y, z = gps.locate(5)
    until not((not x) or (not y) or (not z))
end

function distanceToOrigin()
    return math.abs((originX - x) + (originY - y) + (originZ - z))
end

function forward()
    turtle.forward()
    setCoordinates()
end
function back()
    turtle.back()
    setCoordinates()
end
function up()
    turtle.up()
    setCoordinates()
end
function down()
    turtle.down()
    setCoordinates()
end

function completeRefuel()
    for slot = 1, 16 do
        turtle.select(slot)
        if turtle.refuel(0) then
            turtle.refuel()
        end
    end
end

function checkForOre(success, data)
    if success then
        if string.find(data.name, "ore") then
            return true
        end
    end
    return false
end

function mineOres()
    local success, data

    success, data = turtle.inspect()
    if checkForOre(success, data) then
        turtle.dig()
        forward()
        mineOres()
        back()
    end

    turtle.turnRight()
    success, data = turtle.inspect()
    if checkForOre(success, data) then
        turtle.dig()
        forward()
        mineOres()
        back()
    end

    turtle.turnRight()
    turtle.turnRight()
    success, data = turtle.inspect()
    if checkForOre(success, data) then
        turtle.dig()
        forward()
        mineOres()
        back()
    end

    turtle.turnRight()

    success, data = turtle.inspectUp()
    if checkForOre(success, data) then
        turtle.digUp()
        up()
        mineOres()
        down()
    end

    success, data = turtle.inspectDown()
    if checkForOre(success, data) then
        turtle.digDown()
        down()
        mineOres()
        up()
    end
end

function returnToOrigin()
    if y > originY then
        repeat
            turtle.digDown()
            down()
        until y == originY
    elseif y < originY then
        repeat
            turtle.digUp()
            up()
        until y  == originY
    end

    local oldDistanceToOrigin
    while x ~= originX and z~= originZ do
        print("A")
        oldDistanceToOrigin = distanceToOrigin()
        turtle.dig()
        forward()
        if distanceToOrigin() > oldDistanceToOrigin then
            turtle.turnRight()
            turtle.turnRight()
        end
        if x == originX or z == originZ then
            turtle.turnRight()
        end
    end

    for slot = 1, 16 do
        turtle.select(slot)
        if not turtle.refuel(0) then
            turtle.dropUp()
        end
    end
end

setCoordinates()

completeRefuel()
returnToOrigin()

while true do
    completeRefuel()
    if distanceToOrigin() >= turtle.getFuelLevel() then
        returnToOrigin()
    end

    mineOres()
    turtle.dig()
    turtle.digDown()
    forward()
end