-- 2-Wide Vertical Shaft Digger (2 blocks wide, 1 block long)
-- Digs entire 2-wide shaft first, then places ladders on left side while returning
-- Slot 1: Ladders | Slot 2: Cobblestone (backing/lava protection)

function refuelIfNeeded(minFuel)
    if turtle.getFuelLevel() == "unlimited" then return true end
    while turtle.getFuelLevel() < minFuel do
        for i = 3, 16 do
            turtle.select(i)
            if turtle.refuel(1) then break end
        end
        if turtle.getFuelLevel() < minFuel then
            print("Add more fuel...")
            os.sleep(2)
        end
    end
end

function digShaft(depth)
    for i = 1, depth do
        -- Dig right column (main position)
        while turtle.detectDown() do turtle.digDown() sleep(0.1) end

        -- Move left and dig left column
        turtle.turnLeft()
        turtle.forward()
        while turtle.detectDown() do turtle.digDown() sleep(0.1) end

        -- Descend both columns
        turtle.down()  -- Left side
        turtle.back()
        turtle.turnRight()
        turtle.down()  -- Right side

        -- Check for lava and protect
        local success, data = turtle.inspectDown()
        if success and data.name == "minecraft:lava" then
            turtle.select(2)
            turtle.placeDown()
        end
    end
end

function placeLadders(depth)
    -- Position turtle on left side at bottom
    turtle.turnLeft()
    turtle.forward()

    for i = 1, depth do
        -- Ensure cobblestone backing exists
        if not turtle.inspect() then
            turtle.select(2)
            turtle.place()  -- Place backing
        end

        -- Place ladder from below
        turtle.select(1)
        turtle.placeDown()

        -- Ascend to next level
        while not turtle.up() do
            turtle.digUp()
            sleep(0.1)
        end
    end

    -- Return to right side and ascend to surface
    turtle.back()
    turtle.turnRight()
    for i = 1, depth do
        while not turtle.up() do
            turtle.digUp()
            sleep(0.1)
        end
    end
end

-- === MAIN PROGRAM ===
print("Enter shaft depth:")
local depth = tonumber(read())

if not depth or depth < 1 then
    print("Invalid depth")
    return
end

refuelIfNeeded(depth * 10 + 20)  -- Extra fuel buffer

print("Digging 2-wide shaft...")
digShaft(depth)

print("Placing ladders on left side...")
placeLadders(depth)

print("✅ 2-wide ladder shaft complete!")