local slotCount = 16
local width = 10
local length = 10
local height = 3

local trash = {
    "minecraft:cobblestone", "minecraft:dirt", "minecraft:andesite",
    "minecraft:diorite", "minecraft:clay", "minecraft:sand",
    "minecraft:sandstone", "minecraft:limestone"
}

function purgeTrash()
    for slot = 1, slotCount, 1 do
        local item = turtle.getItemDetail(slot)

        if (item ~= nil) then
            for key, value in pairs(trash) do
                if (value == item.name) then end
            end
        end

    end
end

function forEach(table, func)
    for k, v in pairs(table) do func(v) end
    return true
end

function checkFuel()
  print('Checkng fuel...')
    if (turtle.getFuelLevel() < 20000) then
      print('fuel level sub-optimal')
        for slot = 1, slotCount, 1 do
            local item = turtle.getItemDetail(slot)
            if (item ~= nil) then
                if (item.name == "minecraft:coal") then
                    print('Attemping to refuel...')

                    turtle.select(slot)

                    local result = turtle.refuel()

                    print('Turtle refueled...')

                    return true
                end
            end
        end
        print('Did not find coal in inventory.. powering down D:')
        return false
    end
end

function main()
    for level = 1, height, 1 do
        for row = 1, width, 1 do
            for col = 1, length, 1 do checkFuel() end
            purgeTrash()
        end
    end
end

main()