ComputerCraft Mining Program 2

local a = 0
local b = 0
local fuelNeed
local inventory_full
local item

local function Inventory()
    inventory_full = turtle.getItemCount(16)
    if inventory_full > 0
    then
        turtle.digDown()
        turtle.select(1)
        turtle.placeDown()
        for i = 1,16
        do
            turtle.select(i)
            if turtle.getItemCount() > 0
            then
                if turtle.getFuelLevel() < 1000
                then
                    fuelNeed = true
                else
                    fuelNeed = false
                end
                item = turtle.getItemDetail()
                if item.name == "minecraft:coal" and fuelNeed == true
                then
                    print("This is coal")
                    turtle.refuel(64)
                end
            end
            turtle.dropDown()
        end
        turtle.select(1)
        turtle.digDown()
    end
end

local function GravelCheck()
    blockCheck, blockData = turtle.inspect()
    while blockData.name == "minecraft:gravel"
    do
        blockCheck, blockData = turtle.inspect()
        turtle.dig()
        sleep(1)
    end
end

while true do

    b = b + 1
    if b == 2
    then
        b = 0
        a = a + 1
    end

    for a = 1,a,1
    do
        turtle.dig()
        GravelCheck()
        turtle.forward()
        turtle.digDown()
        turtle.digUp()
        Inventory()
    end

    turtle.turnRight()
end