sethmc ndisk node

-- store_node.lua

local modem = peripheral.find("modem") or error("No modem found")
local drive = peripheral.find("drive") or error("No disk drive found")

-- ============================================
-- SECURITY SETUP
-- ============================================

local STORAGE_SECRET = nil

if not fs.exists(".ndisk_secret") then
    term.clear()
    term.setCursorPos(1, 1)
    print("NDISK NODE SETUP")
    print("================")
    print("No security secret found.")
    write("Enter shared secret for cluster: ")
    local secret = read("*")

    local f = fs.open(".ndisk_secret", "w")
    f.write(secret)
    f.close()
    print("\nSecret saved.")
    sleep(1)
end

local f = fs.open(".ndisk_secret", "r")
STORAGE_SECRET = f.readAll()
f.close()

-- ============================================
-- NODE LOGIC
-- ============================================

modem.open(5) -- Open channel 5 for NDisk communication

local function sendResponse(id, response)
    modem.transmit(5, 5, {id = id, response = response})
end

local function handleRequest(sender, message)
    -- AUTHENTICATION CHECK
    if message.secret ~= STORAGE_SECRET then
        -- Silent drop for security (prevent scanning)
        return
    end

    if message.type == "discovery" then
        modem.transmit(5, 5, {type = "discovery_response", id = os.getComputerID()})
    elseif message.targetNode == os.getComputerID() then
        -- PATH SANITIZATION (Defense in Depth)
        if message.path and (message.path:find("%.%.") or message.path:find(":")) then
             sendResponse(message.id, {success = false, error = "Invalid path security"})
             return
        end

        if message.action == "write" then
            if not drive.isDiskPresent() then
                sendResponse(message.id, {success = false, error = "No disk present"})
                return
            end
            local path = fs.combine(drive.getMountPath(), message.path .. "_chunk_" .. message.chunk)
            local file = fs.open(path, "w")
            file.write(message.content)
            file.close()
            sendResponse(message.id, {success = true})
        elseif message.action == "read" then
            if not drive.isDiskPresent() then
                sendResponse(message.id, {success = false, error = "No disk present"})
                return
            end
            local path = fs.combine(drive.getMountPath(), message.path .. "_chunk_" .. message.chunk)
            if fs.exists(path) then
                local file = fs.open(path, "r")
                local content = file.readAll()
                file.close()
                sendResponse(message.id, {success = true, content = content})
            else
                sendResponse(message.id, {success = false, error = "File not found"})
            end
        elseif message.action == "delete" then
            if not drive.isDiskPresent() then
                sendResponse(message.id, {success = false, error = "No disk present"})
                return
            end
            local path = fs.combine(drive.getMountPath(), message.path .. "_chunk_" .. message.chunk)
            if fs.exists(path) then
                fs.delete(path)
                sendResponse(message.id, {success = true})
            else
                sendResponse(message.id, {success = false, error = "File not found"})
            end
        elseif message.action == "getSpace" then
            if not drive.isDiskPresent() then
                sendResponse(message.id, {success = false, error = "No disk present"})
                return
            end
            local freeSpace = fs.getFreeSpace(drive.getMountPath())
            sendResponse(message.id, {success = true, space = freeSpace})
        elseif message.action == "listFiles" then
            -- List all files on the disk (for orphan detection)
            if not drive.isDiskPresent() then
                sendResponse(message.id, {success = false, error = "No disk present"})
                return
            end
            local files = fs.list(drive.getMountPath())
            sendResponse(message.id, {success = true, files = files})
        elseif message.action == "deleteItem" then
            -- Delete a specific file or directory by name (for orphan cleanup)
            if not drive.isDiskPresent() then
                sendResponse(message.id, {success = false, error = "No disk present"})
                return
            end
            local path = fs.combine(drive.getMountPath(), message.itemName)
            if fs.exists(path) then
                fs.delete(path)
                sendResponse(message.id, {success = true})
            else
                sendResponse(message.id, {success = false, error = "Item not found"})
            end
        end
    end
end

print("Storage node ready (SECURE). Waiting for requests...")
print("Node ID: " .. os.getComputerID())

while true do
    local event, side, channel, replyChannel, message, distance = os.pullEvent("modem_message")
    if channel == 5 then
        handleRequest(side, message)
    end
end