-- Turtle Dig Down Script with Full Perimeter Safety and Return Logic
-- Digs down while maintaining blocks in all 4 horizontal directions
-- Removes any liquids encountered below
-- Returns to original position when finished
-- Uses any available blocks for placement

local tArgs = {...}
local depth = tonumber(tArgs[1])
local shouldReturn = tArgs[2] == "return" or tArgs[2] == "true"

if not depth or depth < 1 then
    print("Usage: digdown <depth> [return]")
    print("Example: digdown 20")
    print("Example with return: digdown 20 return")
    return
end

-- Track movements for return trip
local movements = {}
local currentY = 0

-- Function to check if block is liquid
local function isLiquid(block)
    return block and (block.name:find("water") or block.name:find("lava"))
end

-- Function to find any placeable block in inventory
local function findPlaceableBlock()
    for slot = 1, 16 do
        turtle.select(slot)
        if turtle.getItemCount(slot) > 0 then
            return true
        end
    end
    return false
end

-- Function to ensure all 4 directions have blocks
local function ensurePerimeter()
    -- Check and place blocks in all 4 directions
    for i = 1, 4 do
        local success, data = turtle.inspect()
        if not success or isLiquid(data) then
            -- Try to place any available block
            if findPlaceableBlock() then
                if not turtle.place() then
                    print("Warning: Failed to place block in slot "..turtle.getSelectedSlot())
                end
            else
                print("Error: No placeable blocks in inventory!")
                return false
            end
        end
        turtle.turnRight() -- Rotate to next direction
    end
    return true
end

-- Function to safely dig down and maintain perimeter
local function safeDigDown()
    -- First ensure perimeter is solid
    if not ensurePerimeter() then
        return false
    end

    -- Check block below
    local success, data = turtle.inspectDown()
    if success then
        if isLiquid(data) then
            -- Handle liquid below with any available block
            if findPlaceableBlock() then
                if not turtle.placeDown() then
                    print("Warning: Failed to place block below")
                end
            else
                print("Error: No blocks to place below!")
                return false
            end
        end
        turtle.digDown()
    end

    -- Move down and record movement
    if turtle.down() then
        currentY = currentY - 1
        table.insert(movements, "down")
        -- Ensure new level has perimeter
        return ensurePerimeter()
    end
    return false
end

-- Function to return to surface
local function returnToSurface()
    print("Returning to surface...")

    -- Reverse movement log
    for i = #movements, 1, -1 do
        local move = movements[i]
        if move == "down" then
            while not turtle.up() do
                turtle.digUp()
                sleep(0.5)
            end
            currentY = currentY + 1
        end
    end

    print("Returned to surface successfully! Current Y: "..currentY)
end

-- Check initial fuel requirements
local requiredFuel = depth * 3 -- Extra for return trip and perimeter building
if turtle.getFuelLevel() < requiredFuel then
    print("Need at least "..requiredFuel.." fuel units")
    print("Current fuel: "..turtle.getFuelLevel())
    return
end

-- Check for any blocks at all
local hasBlocks = false
for i = 1, 16 do
    if turtle.getItemCount(i) > 0 then
        hasBlocks = true
        break
    end
end

if not hasBlocks then
    print("Warning: No blocks in inventory for perimeter building!")
    print("Recommend bringing at least "..depth.." blocks")
end

-- Main digging loop
print("Starting descent to depth "..depth.."...")
for i = 1, depth do
    if not safeDigDown() then
        print("Stopped at level "..i.." due to error")
        if shouldReturn then returnToSurface() end
        return
    end

    print("Level "..i.." - Fuel: "..turtle.getFuelLevel())

    -- Periodic status report
    if i % 5 == 0 then
        local remaining = depth - i
        if turtle.getFuelLevel() < remaining * 3 then
            print("Warning: Low fuel! "..turtle.getFuelLevel().." left, needs ~"..remaining*3)
        end
    end
end

print("Successfully reached depth "..depth.." with full perimeter safety!")

-- Return to surface if requested
if shouldReturn then
    returnToSurface()
end