-- Turtle Smart Fill with True Robust Layer Return and Chest Dump

local function askNumber(prompt)
    print(prompt)
    local val = tonumber(read())
    while not val do
        print("Please enter a valid number:")
        val = tonumber(read())
    end
    return math.floor(val)
end

local function askDirection()
    print("Build direction? Type 'up' for bottom-to-top or 'down' for top-to-bottom:")
    local dir = read()
    while dir ~= "up" and dir ~= "down" do
        print("Please type 'up' or 'down':")
        dir = read()
    end
    return dir
end

local moves = {}
local heading = 0 -- 0: forward, 1: right, 2: back, 3: left

local function forward()
    while not turtle.forward() do
        turtle.dig()
        sleep(0.2)
    end
    table.insert(moves, {action="fwd"})
end

local function moveUp()
    while not turtle.up() do
        turtle.digUp()
        sleep(0.2)
    end
end

local function moveDown()
    while not turtle.down() do
        turtle.digDown()
        sleep(0.2)
    end
end

local function turnRight()
    turtle.turnRight()
    heading = (heading + 1) % 4
    table.insert(moves, {action="tr"})
end

local function turnLeft()
    turtle.turnLeft()
    heading = (heading + 3) % 4
    table.insert(moves, {action="tl"})
end

local function turnRightRaw() turtle.turnRight(); heading = (heading + 1) % 4 end
local function turnLeftRaw() turtle.turnLeft(); heading = (heading + 3) % 4 end

local function refuelIfNeeded(needed)
    turtle.select(1)
    if turtle.getFuelLevel() == "unlimited" then return true end
    if turtle.getFuelLevel() < needed then
        print("Refueling from slot 1...")
        if not turtle.refuel(64) then
            print("⚠️ Could not refuel from slot 1.")
        else
            print("Fuel level: "..turtle.getFuelLevel())
        end
    end
    if turtle.getFuelLevel() < needed then
        print("❌ Not enough fuel. Need at least "..needed..".")
        return false
    end
    return true
end

local function dumpToChest()
    print("Dumping items to chest...")
    for i = 2, 16 do
        turtle.select(i)
        local item = turtle.getItemDetail()
        if item then
            if not (item.name == targetBlockName) then
                turtle.drop()
            end
        end
    end
end

local function isInventoryFull()
    for i = 3, 16 do
        if turtle.getItemCount(i) == 0 then return false end
    end
    return true
end

local function placeSlot2Block()
    turtle.digDown()
    if turtle.detectDown() then return true end
    for i = 2, 16 do
        turtle.select(i)
        local item = turtle.getItemDetail()
        if item and item.name == targetBlockName then
            return turtle.placeDown()
        end
    end
    print("⚠️ No matching block left to place.")
    return false
end

-- Ask user
local length = askNumber("Enter length:")
local width = askNumber("Enter width:")
local height = askNumber("Enter height:")
local direction = askDirection()

-- Fuel estimate/check
local estimatedMoves = length * width * height * 3 + (height - 1) * (length + width)
print("Estimated fuel needed: "..estimatedMoves)
if not refuelIfNeeded(estimatedMoves) then return end

-- Block type from slot 2
turtle.select(2)
local slot2Block = turtle.getItemDetail()
if not slot2Block then
    print("❌ No block found in slot 2. Please load desired block.")
    return
end
targetBlockName = slot2Block.name
print("📦 Using only block type: "..targetBlockName)
turtle.select(2)

print("Place a chest in front of turtle's starting position for dumps.")

-- Move forward to first block (starting reference)
forward()

-- True robust: return to origin of the layer and clear moves
local function returnToOrigin()
    -- Face forward
    while heading ~= 0 do
        turnRightRaw()
    end
    -- Undo all moves in reverse order
    for i = #moves, 1, -1 do
        local move = moves[i]
        if move.action == "fwd" then
            turtle.back()
        elseif move.action == "up" then
            turtle.down()
        elseif move.action == "down" then
            turtle.up()
        elseif move.action == "tr" then
            turtle.turnLeft()
            heading = (heading + 3) % 4
        elseif move.action == "tl" then
            turtle.turnRight()
            heading = (heading + 1) % 4
        end
    end
    moves = {}
end

-- Build one layer, robust return at end
local function buildLayer()
    for w = 1, width do
        for l = 1, length do
            turtle.dig()
            if not placeSlot2Block() then return false end
            if isInventoryFull() then
                print("Inventory full! Returning to dump in chest.")
                return "dump"
            end
            if l < length then forward() end
        end
        if w < width then
            if w % 2 == 1 then
                turnRight()
                forward()
                turnRight()
            else
                turnLeft()
                forward()
                turnLeft()
            end
        end
    end
    -- Always return to start of layer (lower/upper left corner, facing original)
    returnToOrigin()
    return true
end

-- Main build logic, moving up/down *after* return, clearing moves each time
local function build()
    if direction == "up" then
        for h = 1, height do
            print("Building layer "..h.." / "..height)
            local layerResult = buildLayer()
            if layerResult == "dump" then
                dumpToChest()
                print("Please clear inventory and re-run script to finish the area!")
                return
            elseif not layerResult then return end
            if h < height then
                moveUp()
                moves = {} -- CLEAR move log at start of new layer
            end
        end
    else
        for i = 1, height - 1 do moveUp() end
        for h = height, 1, -1 do
            print("Building layer "..h.." / "..height)
            local layerResult = buildLayer()
            if layerResult == "dump" then
                dumpToChest()
                print("Please clear inventory and re-run script to finish the area!")
                return
            elseif not layerResult then return end
            if h > 1 then
                moveDown()
                moves = {} -- CLEAR move log at start of new layer
            end
        end
    end
    dumpToChest()
    -- At very end, turtle is back at original start, facing forward.
end

build()
print("✅ Build complete! Returned to starting point and dumped inventory.")