CC Item metadata

------------------------------------------------------------
-- Item Metadata Watcher
--
-- This program waits for a rednet message with protocol "items".
-- The message must contain a list of item IDs.
-- After receiving the list, the program enters an infinite loop.
--
-- In each iteration, it goes through each item, looks up its
-- display name (via getName) and stock status (via isInStock).
-- It caches that information in-memory. If the metadata for an
-- item has changed (or if this is the first time), it sends an
-- "itemMetadata" event back to the original sender with the updated
-- metadata.
------------------------------------------------------------

------------------------------------------------------------
--- Load the meUtils library for item lookups.
------------------------------------------------------------
local meUtils = require("lib/meUtils")

-- Open rednet on a modem (adjust side as necessary)
rednet.open("top")  -- Change "back" to the appropriate side if needed

-- Wait for a rednet message with protocol "items"
print("Waiting for 'items' event...")
local senderId, message, protocol = rednet.receive("items")
if type(message) ~= "table" then
  error("Expected a table of item IDs in the 'items' event")
end
local itemList = message  -- List of item IDs
local origin = senderId   -- Remember the sender for future replies
print("Received item list from computer:", origin)
-- Uncomment the following line for debugging:
-- print(textutils.serialize(itemList))

-- In-memory cache for item metadata.
-- cache[itemID] = { displayName = ..., inStock = ... }
local cache = {}

------------------------------------------------------------
-- Return whether the given item is in stock.
------------------------------------------------------------
local function isInStock(itemID)
  local count = meUtils.getItemCount(itemID)
  return count > 0
end

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--- Return the name of the given item.
------------------------------------------------------------
local function getItemName(itemID)
  return meUtils.getItemName(itemID)
end

-- Function to update an item's metadata.
local function updateItem(itemID)
  local name = getItemName(itemID)
  local inStock = isInStock(itemID)
  return { name = name, inStock = inStock }
end

-- Enter infinite loop; each iteration update each item's metadata.
while true do
  for i, itemID in ipairs(itemList) do
    local newMeta = updateItem(itemID)
    local oldMeta = cache[itemID]
    -- If this is the first time or if anything has changed:
    if not oldMeta or newMeta.displayName ~= oldMeta.displayName or newMeta.inStock ~= oldMeta.inStock then
      cache[itemID] = newMeta
      rednet.send(origin, { item = itemID, metadata = newMeta }, "itemMetadata")

      -- Only print if ID begins with "createcafe:" (for debugging)
      if string.find(itemID, "^createcafe:") then
        print("Sent metadata for item:", itemID)
        print("  Old metadata:", textutils.serialize(oldMeta))
        print("  New metadata:", textutils.serialize(newMeta))
      end
      --print("Updated metadata for item:", itemID)
    end
  end
  print("Waiting for next iteration...")
  sleep(1)  -- Adjust the interval as needed.
end