Turtle GPS goto 1

dirString = { north=0, east=1, south=2, west=3}
-- South= +z, East= +x

fuelSlot = 16
x=0
y=0
z=0
f=-1

local function saveAll()
    save = fs.open(".persistLoc","w")
    save.write(textutils.serialize({x,y,z,f,fuelSlot}))
    save.close()
end

local function loadAll()
    if fs.exists(".persistLoc") then
       load = fs.open(".persistLoc","r")
       x,y,z,f,fuelSlot = unpack(textutils.unserialize(load.readAll()))
       load.close()
    end
end

function findFuel()
    for i=1,16 do
        if i ~= fuelSlot then
            turtle.select(i)
            if turtle.refuel(0) then
                return i
            end
        end
    end
end

function checkFuel()
    if turtle.getFuelLevel() <= math.abs(2 * (100 - y)) then
        turtle.select(fuelSlot)
        if turtle.getItemCount(fuelSlot) == 0 or turtle.refuel(0) == false then
            newFuel = findFuel()
            if newFuel then
                turtle.select(newFuel)
            else
                return false
            end
        end
        turtle.refuel(1)
        return true
    end
end

function setFuelSlot(slot)
    if slot >= 1 and slot <= 16 then
        fuelSlot = slot
    else
        error("Invalid slot designation: " .. slot, 2)
    end
end

function updateLoc(backward)
    backward = backward or false
    if backward then
        factor = -1
    else
        factor = 1
    end

    if f==0 then
        z=z-factor
    elseif f==1 then
        x=x+factor
    elseif f==2 then
        z=z+factor
    elseif f==3 then
        x=x-factor
    else
        error("What direction again?")
    end
    saveAll()
end

function initFacing()
    fd(1)
    fx,fy,fz = gps.locate(3)
    if fx ~= nil then
        if x ~= fx then
            if fx > x then
                f = 1
            else
                f = 3
            end
        elseif z ~= fz then
            if fz > z then
                f = 2
            else
                f = 0
            end
        end
    end
    bk(1)
end

function initLoc()
    rednet.open("right")
    ix,iy,iz = gps.locate(3)
    if ix ~= nil then
        x,y,z = ix,iy,iz
    else
        print("t: Failed to get coordinates from GPS.")
    end
    if f == -1 then
        initFacing()
    end
    saveAll()
    rednet.close("right")
end

function getLoc()
    return x,y,z
end

function getX()
    return x
end

function getY()
    return y
end

function getZ()
    return z
end

function rt(ct)
    ct = ct or 1
    for i=1,ct do
        turtle.turnRight()
        f = (f+1)%4
        saveAll()
    end
    return true
end

function lt(ct)
    ct = ct or 1
    for i=1,ct do
        turtle.turnLeft()
        f = (f+3)%4
        saveAll()
    end
    return true
end

function up(ct,force)
    ct = ct or 1
    force = force or false
    local wait = 0
    for i=1,ct do
        checkFuel()
        while not turtle.up() do
            if wait == 5 then
                return i - 1
            end
            if force then
                turtle.digUp()
                turtle.attackUp()
                sleep(0.5)
                turtle.attackUp()
            end
            wait = wait + 1
            sleep(3)
        end
        y = y + 1
        saveAll()
    end
    return ct
end

function dn(ct,force)
    ct = ct or 1
    force = force or false
    local wait = 0
    for i=1,ct do
        checkFuel()
        while not turtle.down() do
            if wait == 5 then
                return i - 1
            end
            if force then
                turtle.digDown()
                turtle.attackDown()
                sleep(0.5)
                turtle.attackDown()
            end
            wait = wait + 1
            sleep(3)
        end
        y = y - 1
        saveAll()
    end
    return ct
end

function fd(ct,force)
    ct = ct or 1
    force = force or false
    local wait = 0
    for i=1,ct do
        checkFuel()
        while not turtle.forward() do
            if wait == 5 then
                return i - 1
            end
            if force then
                turtle.dig()
                turtle.attack()
                sleep(0.5)
                turtle.attack()
            end
            wait = wait + 1
            sleep(3)
        end
        updateLoc()
    end
    return ct
end

function bk(ct,force)
    ct = ct or 1
    force = force or false
    local wait = 0
    for i=1,ct do
        checkFuel()
        while not turtle.back() do
            if wait == 5 then
                return i - 1
            end
            if force then
                rt(2)
                turtle.dig()
                turtle.attack()
                sleep(0.5)
                turtle.attack()
                rt(2)
            end
            wait = wait + 1
            sleep(3)
        end
        updateLoc(true)
    end
    return ct
end

function face(d)
    if type(d) == "string" then
        dirs = {north=0, east=1, south=2, west=3}
        d = dirs[d]
    elseif type(d) == "number" then
        if d < 0 or d > 4 then
            error("Directional number out of range (0-3).",2)
        end
    end
    if d == nil then error("No direction specified.",2) end
-- F 0=North, 1=East, 2=South, 3=West
-- South= +z, East= +x
    local dir = -1
    if dirString[d] ~= nil then
        dir = dirString[d]
    else
        dir = d
    end

    if dir == 0 and f == 3 then
        rt()
    elseif dir == 3 and f == 0 then
        lt()
    elseif dir > f then
        rt(dir - f)
    elseif dir < f then
        lt(f - dir)
    end
end

function gotoX(toX,force)
    if toX == nil then error("No coordinate specified.",2) end
    force = force or false
    if x < toX then
        face("east")
    elseif x > toX then
        face("west")
    end

    while x ~= toX do
        fd(1,force)
    end
end

function gotoY(toY,force)
    if toY == nil then error("No coordinate specified.",2) end
    force = force or false
    if y < toY then
        move = up
        dig = turtle.digUp
    elseif y > toY then
        move = dn
        dig = turtle.digDown
    end

    while y ~= toY do
        move(1,force)
    end
end

function gotoZ(toZ,force)
    if toZ == nil then error("No coordinate specified.",2) end
    force = force or false
    if z < toZ then
        face("south")
    elseif z > toZ then
        face("north")
    end

    while z ~= toZ do
        fd(1,force)
    end
end

function goto(toX, toY, toZ)
    toX = toX or x
    toY = toY or y
    toZ = toZ or z

    gotoX(toX)
    gotoZ(toZ)
    gotoY(toY)
end

loadAll()
initLoc()
print("Loaded t API. ID:" .. os.getComputerID())