returnToStart

os.loadAPI("inv")
os.loadAPI("t")

local COAL = "coal"
local CHAR = "char"

local STARTX =
local STARTY =
local STARTZ =

function round(exact)
    quantum = 1
    local quant,frac = math.modf(exact/quantum)
    return quantum * (quant + (frac > 0.5 and 1 or 0))
end

function refuelIfNeeded()
    local fuelLevel = turtle.getFuelLevel()
    if fuelLevel < 70 then
        print("Fuel level is " .. fuelLevel .. ", refueling...")
        if inv.selectItem(COAL) then
            turtle.refuel(1)
            print("Refueled! new level is " .. turtle.getFuelLevel())
            return true
        end
        printError("No fuel in inventory!")
    end
    return false
end

turtle.turnLeft()

local x,y,z = gps.locate(15)

x = round(x)
y = round(y)
z = round(z)

print(x,y,z)

t.fw()

local newX, newY, newZ = gps.locate(15)

t.back()

newX = round(newX)
newY = round(newY)
newZ = round(newZ)

if x > newX then
    turtle.turnLeft()
    turtle.turnLeft()
end

if z > newZ then
    turtle.turnRight()
elseif z < newZ then
    turtle.turnLeft()
end

local difx = math.abs(x - STARTX)
local dify = math.abs(y - STARTY)
local difz = math.abs(z - STARTZ)

print(difx,dify,difz)

if x > STARTX then
    turtle.turnLeft()
    turtle.turnLeft()
    t.fw(difx)
    turtle.turnLeft()
    turtle.turnLeft()
elseif x < STARTX then
    t.fw(difx)
end

if z > STARTZ then
    turtle.turnLeft()
    t.fw(difz)
    turtle.turnRight()
elseif z < STARTZ then
    turtle.turnRight()
    t.fw(difz)
    turtle.turnLeft()
end

turtle.turnLeft()