Quarry

function cPrint(str)
    term.clear()
    term.setCursorPos(1,1)
    print(str)
end

cPrint('starting up quarry!')
os.sleep(1)
cPrint('')

os.loadAPI('nav.lua')
nav.calibrate()

function goBack(functionCalled)
    initx, inity, initz, initDir = nav.pos.x, nav.pos.y, nav.pos.z, nav.pos.dir
    if nav.pos.z ~= 0 then
        nav.up(math.abs(nav.pos.z))
    end
    nav.goDir(2)
    if nav.pos.y ~= 0 then
        nav.forward(math.abs(nav.pos.y))
    end
    if nav.pos.x ~= 0 then
        if nav.pos.x < 0 then
            nav.goDir(1)
            nav.forward(math.abs(nav.pos.x))
        else
            nav.goDir(3)
            nav.forward(math.abs(nav.pos.x)
        end
    end
    functionCalled()
    nav.turnRight(2)
    nav.forward(inity)
    if initx/math.abs(initx) = -1 do
        nav.turnLeft(1)
    elseif initx/math.abs(initx) = 1 do
        nav.turnRight(1)
    end
    if initx ~= 0 then
        nav.forward(math.abs(initx))
    end
    nav.down(initz)
    nav.goDir(initDir)
end

function refuel()
    if turtle.getFuelLevel() < 2*(math.abs(nav.pos.z) + math.abs(nav.pos.y) + math.abs(math.pos.x) + 10) then
        if not turtle.refuel() then
            goBack(grabFuel)
        end
    end
end

function checkInv()
    if turtle.getItemCount(16) ~= 0 then
        goBack(dropOff)
    end
end

function grabFuel()
    turtle.suckUp(64)
end

function dropOff()
    for i=2, 16 do
        turtle.select(i)
        turtle.drop(64)
    end
    turtle.select(1)
end

function forward(x)
    for i = 1, x do
        nav.forward(1)
        refuel()
        checkInv()
    end
end