-- Prompt for depth
print("Enter staircase depth (number of steps):")
local depth = tonumber(read())

if not depth or depth <= 0 then
    print("Invalid depth.")
    return
end

local stepsTaken = 0

-- === Utility Functions ===
local function tryDig() while turtle.detect() do turtle.dig() sleep(0.1) end end
local function tryDigDown() while turtle.detectDown() do turtle.digDown() sleep(0.1) end end
local function tryDigUp() while turtle.detectUp() do turtle.digUp() sleep(0.1) end end

local function tryForward()
    tryDig()
    while not turtle.forward() do
        tryDig()
        sleep(0.1)
    end
end

local function tryDown()
    tryDigDown()
    while not turtle.down() do
        tryDigDown()
        sleep(0.1)
    end
end

local function tryUp()
    tryDigUp()
    while not turtle.up() do
        tryDigUp()
        sleep(0.1)
    end
end

local function tryBack()
    if not turtle.back() then
        turtle.turnLeft()
        turtle.turnLeft()
        tryDig()
        turtle.turnLeft()
        turtle.turnLeft()
        turtle.back()
    end
end

-- === Fuel Estimation ===
local function ensureFuel(needed)
    if turtle.getFuelLevel() < needed then
        print("Attempting refuel...")
        for i = 1, 16 do
            turtle.select(i)
            if turtle.refuel(0) then turtle.refuel() end
        end
        turtle.select(1)
    end
    if turtle.getFuelLevel() < needed then
        print("❌ Not enough fuel. Aborting.")
        return false
    end
    return true
end

-- === Dig 2-Wide Step ===
local function dig2WideStep()
    -- Dig center forward, up, down
    tryDig()
    tryDigUp()
    tryDigDown()

    -- Dig right side
    turtle.turnRight()
    tryDig()
    tryDigUp()
    tryDigDown()
    turtle.turnLeft()

    -- Dig left retaining wall if necessary
    turtle.turnLeft()
    if turtle.detect() then turtle.dig() end
    turtle.turnRight()

    -- Dig right retaining wall if necessary
    turtle.turnRight()
    if turtle.detect() then turtle.dig() end
    turtle.turnLeft()
end

-- === Step Forward and Down ===
local function stepForwardDown()
    tryForward()
    tryDown()
    stepsTaken = stepsTaken + 1
end

-- === MAIN EXECUTION ===

local estimatedFuel = depth * 8 + 10
print("Estimated fuel needed: " .. estimatedFuel)
print("Current fuel: " .. turtle.getFuelLevel())

if not ensureFuel(estimatedFuel) then return end

-- Dig staircase
for i = 1, depth do
    dig2WideStep()
    stepForwardDown()
end

print("✅ Staircase complete. Returning to start...")

-- Return to starting position
for i = 1, stepsTaken do
    tryUp()
    tryBack()
end

-- Face original direction
turtle.turnLeft()
turtle.turnLeft()

print("✅ Returned to start.")