-- Function to get user input safely
local function getNumber(prompt)
    print(prompt)
    local n = tonumber(read())
    while not n or n < 1 do
        print("Please enter a positive number.")
        n = tonumber(read())
    end
    return math.floor(n)
end

-- Prompt for dimensions and options
local length = getNumber("Enter length:")
local width = getNumber("Enter width:")
local height = getNumber("Enter height:")
print("Start at TOP or BOTTOM? (type 'top' or 'bottom')")
local startPos = read():lower()
while startPos ~= "top" and startPos ~= "bottom" do
    print("Please type 'top' or 'bottom'")
    startPos = read():lower()
end

-- Save orientation and position tracking
local pos = {x = 0, y = 0, z = 0}
local dir = 0 -- 0=+X, 1=+Z, 2=-X, 3=-Z

local function turnLeft()
    turtle.turnLeft()
    dir = (dir - 1) % 4
end

local function turnRight()
    turtle.turnRight()
    dir = (dir + 1) % 4
end

local function face(d)
    while dir ~= d do turnRight() end
end

-- Movement wrappers to track position
local function tryDig() while turtle.detect() do turtle.dig(); sleep(0.2) end end
local function tryDigDown() while turtle.detectDown() do turtle.digDown(); sleep(0.2) end end
local function tryDigUp() while turtle.detectUp() do turtle.digUp(); sleep(0.2) end end

local function forward()
    tryDig()
    while not turtle.forward() do sleep(0.2) end
    if dir == 0 then pos.x = pos.x + 1
    elseif dir == 1 then pos.z = pos.z + 1
    elseif dir == 2 then pos.x = pos.x - 1
    elseif dir == 3 then pos.z = pos.z - 1 end
end

local function up()
    tryDigUp()
    while not turtle.up() do sleep(0.2) end
    pos.y = pos.y + 1
end

local function down()
    tryDigDown()
    while not turtle.down() do sleep(0.2) end
    pos.y = pos.y - 1
end

local function back()
    while not turtle.back() do turtle.turnLeft(); turtle.turnLeft(); tryDig(); turtle.turnLeft(); turtle.turnLeft(); sleep(0.2) end
    if dir == 0 then pos.x = pos.x - 1
    elseif dir == 1 then pos.z = pos.z - 1
    elseif dir == 2 then pos.x = pos.x + 1
    elseif dir == 3 then pos.z = pos.z + 1 end
end

-- Estimate fuel usage
local volume = length * width * height
local estimatedFuel = volume * 3 + (length + width + height) * 2
if turtle.getFuelLevel() < estimatedFuel then
    print("Not enough fuel! Required: " .. estimatedFuel)
    return
end

-- Dig one horizontal layer
local function digLayer()
    for w = 1, width do
        for l = 1, length - 1 do forward() end
        if w < width then
            if w % 2 == 1 then
                turnRight(); forward(); turnRight()
            else
                turnLeft(); forward(); turnLeft()
            end
        end
    end
    -- Return to starting row
    if width % 2 == 1 then
        face(2) -- Turn around
        for i = 1, length - 1 do forward() end
        face(3) -- Back to default facing
    else
        face(3)
        for i = 1, width - 1 do forward() end
        face(0)
    end
end

-- Move to correct start level
if startPos == "top" then
    for i = 1, height - 1 do down() end
end

-- Main dig loop
for h = 1, height do
    digLayer()
    if h < height then
        if startPos == "bottom" then up() else down() end
    end
end

-- Return to Y level
if startPos == "bottom" then
    for i = 1, height - 1 do down() end
else
    for i = 1, height - 1 do up() end
end

-- Return to (0,0,0)
if pos.z > 0 then face(3) for i = 1, pos.z do forward() end
elseif pos.z < 0 then face(1) for i = 1, -pos.z do forward() end end

if pos.x > 0 then face(2) for i = 1, pos.x do forward() end
elseif pos.x < 0 then face(0) for i = 1, -pos.x do forward() end end

-- Return to original height
while pos.y > 0 do down() end
while pos.y < 0 do up() end

-- Face original direction
face(0)
print("Excavation complete. Returned to start.")