-- Constants
local MAX_FUEL = 60000

local function cleanNonBuckets()
    for slot = 1, 16 do
        turtle.select(slot)
        local item = turtle.getItemDetail()
        if item and item.name ~= "minecraft:lava_bucket" and item.name ~= "minecraft:bucket" then
            print("Dropping non-bucket item: " .. item.name)
            turtle.drop()
        end
    end
end

local function refuelFromLavaBuckets()
    local gained = 0
    for slot = 1, 16 do
        if turtle.getFuelLevel() >= MAX_FUEL then break end
        turtle.select(slot)
        local item = turtle.getItemDetail()
        if item and item.name == "minecraft:lava_bucket" then
            local before = turtle.getFuelLevel()
            if turtle.refuel() then
                local after = turtle.getFuelLevel()
                gained = gained + (after - before)
                print("Slot " .. slot .. ": +" .. (after - before) .. " fuel (Total: " .. after .. ")")
            end
        end
    end
    return gained
end

local function returnEmptyBuckets()
    -- Stack all empty buckets into slot 16
    for slot = 1, 15 do
        turtle.select(slot)
        local item = turtle.getItemDetail()
        if item and item.name == "minecraft:bucket" then
            turtle.transferTo(16)
		turtle.suck()
        end
    end

    -- Drop stacked empty buckets
    turtle.select(16)
    local toDrop = turtle.getItemCount(16)
    if toDrop > 0 then
        print("Trying to return " .. toDrop .. " empty bucket(s)...")
        while not turtle.drop() do
            print("❌ Basin full or blocked. Retrying in 5 seconds...")
            sleep(5)
        end
        print("✅ Dropped " .. toDrop .. " empty bucket(s).")
    end
end


-- Main loop
print("Beginning continuous refuel from basin...")
while turtle.getFuelLevel() < MAX_FUEL do
    local currentFuel = turtle.getFuelLevel()

    -- Delay before checking basin again
    print("Waiting 30 seconds for lava supply...")
    sleep(30)

    -- Step 1: Suck lava & buckets from front
    local sucked = turtle.suck()
    if not sucked then
        print("No items pulled. Waiting...")
        sleep(2)
    end

    -- Step 2: Clean inventory
    cleanNonBuckets()

    -- Step 3: Refuel
    local added = refuelFromLavaBuckets()

    -- Step 4: Return empty buckets
    returnEmptyBuckets()

    if added == 0 and not sucked then
        print("No fuel gained and nothing to pull. Sleeping longer...")
        sleep(5)
    end

    print("Current fuel: " .. turtle.getFuelLevel() .. " / " .. MAX_FUEL)
end

turtle.select(1)
print("✅ Turtle fully refueled to " .. MAX_FUEL .. ". Done.")