rss.lua
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rss.lua
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	--[[
	mattata v2.0 - RSS Plugin
	Subscribe groups to RSS/Atom feeds with automatic polling.
	Feeds are checked every 5 minutes via cron (staggered).
	All state stored in Redis — no database procedures needed.
	]]

	local plugin = {}
	plugin.name = 'rss'
	plugin.category = 'utility'
	plugin.description = 'Subscribe to RSS/Atom feeds in group chats'
	plugin.commands = { 'rss' }
	plugin.help = '/rss add <url> - Subscribe to a feed\n/rss remove <url> - Unsubscribe\n/rss list - List active subscriptions'
	plugin.group_only = true
	plugin.admin_only = true

	local http = require('src.core.http')
	local tools = require('telegram-bot-lua.tools')
	local logger = require('src.core.logger')

	local MAX_FEEDS_PER_CHAT = 5
	local POLL_INTERVAL = 300 -- 5 minutes between checks per feed
	local MAX_FEEDS_PER_TICK = 3 -- max feeds to check per cron tick
	local MAX_ITEMS = 5 -- only process latest 5 items per fetch
	local MAX_SEEN = 200 -- keep last N entry IDs in seen set

	local function url_hash(url)
	local h = 0
	for i = 1, #url do
	h = (h * 31 + url:byte(i)) % 2147483647
	end
	return tostring(h)
	end

	-- Parse RSS 2.0 items
	local function parse_rss(body)
	local items = {}
	for item in body:gmatch('<item>(.-)</item>') do
	local title = item:match('<title><!%[CDATA%[(.-)%]%]>') or item:match('<title>(.-)</title>') or 'Untitled'
	local link = item:match('<link>(.-)</link>') or ''
	local guid = item:match('<guid>(.-)</guid>') or link
	title = title:gsub('<[^>]+>', '')
	table.insert(items, { title = title, link = link, guid = guid })
	if #items >= MAX_ITEMS then break end
	end
	return items
	end

	-- Parse Atom entries
	local function parse_atom(body)
	local items = {}
	for entry in body:gmatch('<entry>(.-)</entry>') do
	local title = entry:match('<title>(.-)</title>') or 'Untitled'
	local link = entry:match('<link[^>]href="([^"])"') or entry:match('<link>(.-)</link>') or ''
	local id = entry:match('<id>(.-)</id>') or link
	title = title:gsub('<[^>]+>', '')
	table.insert(items, { title = title, link = link, guid = id })
	if #items >= MAX_ITEMS then break end
	end
	return items
	end

	local function parse_feed(body)
	if body:match('<feed') then
	return parse_atom(body)
	else
	return parse_rss(body)
	end
	end

	-- Extract feed title from XML
	local function extract_feed_title(body)
	-- Try channel/title for RSS
	local channel = body:match('<channel>(.-)<item')
	if channel then
	local title = channel:match('<title><!%[CDATA%[(.-)%]%]>') or channel:match('<title>(.-)</title>')
	if title then return title:gsub('<[^>]+>', '') end
	end
	-- Try feed/title for Atom
	local title = body:match('<feed[^>]*>.-<title>(.-)</title>')
	if title then return title:gsub('<[^>]+>', '') end
	return 'Untitled Feed'
	end

	local function handle_add(api, message, ctx)
	local url = message.args and message.args:match('^add%s+(.+)$')
	if not url then
	return api.send_message(message.chat.id, 'Usage: <code>/rss add https://example.com/feed.xml</code>', { parse_mode = 'html' })
	end

	url = url:match('^%s(.-)%s$') -- trim whitespace

	if not url:match('^https?://') then
	return api.send_message(message.chat.id, 'Invalid URL. Must start with http:// or https://')
	end

	-- Block internal/private IP ranges to prevent SSRF
	local host = url:match('^https?://([^/:]+)')
	if host then
	local h = host:lower()
	if h == 'localhost' or h:match('^127%.') or h:match('^10%.') or h:match('^192%.168%.')
	or h:match('^172%.1[6-9]%.') or h:match('^172%.2%d%.') or h:match('^172%.3[01]%.')
	or h:match('^0%.') or h:match('^%[') or h:match('^169%.254%.') then
	return api.send_message(message.chat.id, 'Invalid URL. Internal addresses are not allowed.')
	end
	end

	local feed_key = 'rss:feeds:' .. message.chat.id
	local count = ctx.redis.scard(feed_key)
	if tonumber(count) >= MAX_FEEDS_PER_CHAT then
	return api.send_message(
	message.chat.id,
	string.format('This chat already has %d subscriptions (max %d). Remove one first.', count, MAX_FEEDS_PER_CHAT)
	)
	end

	-- Check if already subscribed
	local is_member = ctx.redis.sismember(feed_key, url)
	if tonumber(is_member) == 1 then
	return api.send_message(message.chat.id, 'This chat is already subscribed to that feed.')
	end

	-- Fetch and validate the feed
	local body, code = http.get(url)
	if not body or code ~= 200 then
	return api.send_message(
	message.chat.id,
	string.format('Failed to fetch feed (HTTP %s). Check the URL and try again.', tostring(code))
	)
	end

	local items = parse_feed(body)
	if #items == 0 then
	return api.send_message(message.chat.id, 'No feed items found at that URL. Make sure it is a valid RSS or Atom feed.')
	end

	local feed_title = extract_feed_title(body)
	local hash = url_hash(url)

	-- Store subscription
	ctx.redis.sadd(feed_key, url)
	ctx.redis.sadd('rss:subs:' .. hash, tostring(message.chat.id))
	ctx.redis.sadd('rss:active_feeds', hash)

	-- Store metadata
	local meta_key = 'rss:meta:' .. hash
	ctx.redis.hset(meta_key, 'title', feed_title)
	ctx.redis.hset(meta_key, 'url', url)
	ctx.redis.hset(meta_key, 'last_checked', tostring(os.time()))

	-- Mark all current entries as seen so we don't flood on first add
	local seen_key = 'rss:seen:' .. hash
	for _, item in ipairs(items) do
	if item.guid and item.guid ~= '' then
	ctx.redis.sadd(seen_key, item.guid)
	end
	end

	return api.send_message(
	message.chat.id,
	string.format('Subscribed to <b>%s</b>.', tools.escape_html(feed_title)),
	{ parse_mode = 'html' }
	)
	end

	local function handle_remove(api, message, ctx)
	local url = message.args and message.args:match('^remove%s+(.+)$')
	if not url then
	return api.send_message(message.chat.id, 'Usage: <code>/rss remove https://example.com/feed.xml</code>', { parse_mode = 'html' })
	end

	url = url:match('^%s(.-)%s$') -- trim whitespace

	local feed_key = 'rss:feeds:' .. message.chat.id
	local removed = ctx.redis.srem(feed_key, url)
	if tonumber(removed) == 0 then
	return api.send_message(message.chat.id, 'This chat is not subscribed to that feed.')
	end

	local hash = url_hash(url)
	ctx.redis.srem('rss:subs:' .. hash, tostring(message.chat.id))

	-- If no more subscribers, clean up
	local remaining = ctx.redis.scard('rss:subs:' .. hash)
	if tonumber(remaining) == 0 then
	ctx.redis.del('rss:meta:' .. hash)
	ctx.redis.del('rss:seen:' .. hash)
	ctx.redis.srem('rss:active_feeds', hash)
	end

	return api.send_message(message.chat.id, 'Unsubscribed from feed.')
	end

	local function handle_list(api, message, ctx)
	local feed_key = 'rss:feeds:' .. message.chat.id
	local urls = ctx.redis.smembers(feed_key)

	if not urls or #urls == 0 then
	return api.send_message(message.chat.id, 'No active feed subscriptions for this chat.')
	end

	local lines = { '<b>RSS Subscriptions</b>' }
	for i, feed_url in ipairs(urls) do
	local hash = url_hash(feed_url)
	local title = ctx.redis.hget('rss:meta:' .. hash, 'title') or 'Unknown'
	table.insert(lines, string.format('%d. <b>%s</b>\n <code>%s</code>', i, tools.escape_html(title), tools.escape_html(feed_url)))
	end

	return api.send_message(message.chat.id, table.concat(lines, '\n'), { parse_mode = 'html', link_preview_options = { is_disabled = true } })
	end

	function plugin.on_message(api, message, ctx)
	if not message.args or message.args == '' then
	return api.send_message(
	message.chat.id,
	'<b>RSS Feed Subscriptions</b>\n\n'
	.. '<code>/rss add <url></code> - Subscribe to a feed\n'
	.. '<code>/rss remove <url></code> - Unsubscribe\n'
	.. '<code>/rss list</code> - List active subscriptions\n\n'
	.. string.format('Max %d feeds per chat. Feeds are checked every %d minutes.', MAX_FEEDS_PER_CHAT, POLL_INTERVAL / 60),
	{ parse_mode = 'html' }
	)
	end

	local subcommand = message.args:match('^(%S+)')
	if not subcommand then
	return api.send_message(message.chat.id, 'Unknown subcommand. Use /rss for help.')
	end

	subcommand = subcommand:lower()

	if subcommand == 'add' then
	return handle_add(api, message, ctx)
	elseif subcommand == 'remove' or subcommand == 'del' or subcommand == 'delete' then
	return handle_remove(api, message, ctx)
	elseif subcommand == 'list' then
	return handle_list(api, message, ctx)
	else
	return api.send_message(message.chat.id, 'Unknown subcommand. Use /rss for help.')
	end
	end

	function plugin.cron(api, ctx)
	-- Get all active feed hashes
	local active_feeds = ctx.redis.smembers('rss:active_feeds')
	if not active_feeds or #active_feeds == 0 then
	return
	end

	-- Find feeds due for checking (not checked in last POLL_INTERVAL seconds)
	local now = os.time()
	local due = {}
	for _, hash in ipairs(active_feeds) do
	local last_checked = ctx.redis.hget('rss:meta:' .. hash, 'last_checked')
	last_checked = tonumber(last_checked) or 0
	if now - last_checked >= POLL_INTERVAL then
	table.insert(due, hash)
	end
	if #due >= MAX_FEEDS_PER_TICK then break end
	end

	for _, hash in ipairs(due) do
	local feed_url = ctx.redis.hget('rss:meta:' .. hash, 'url')
	if not feed_url then
	-- Orphaned metadata, remove from active set
	ctx.redis.srem('rss:active_feeds', hash)
	else
	-- Update last_checked immediately to avoid double-polling
	ctx.redis.hset('rss:meta:' .. hash, 'last_checked', tostring(now))

	local ok, err = pcall(function()
	local body, code = http.get(feed_url)
	if not body or code ~= 200 then
	logger.warn('RSS: failed to fetch %s (HTTP %s)', feed_url, tostring(code))
	return
	end

	local items = parse_feed(body)
	if #items == 0 then return end

	local feed_title = ctx.redis.hget('rss:meta:' .. hash, 'title') or extract_feed_title(body)
	local seen_key = 'rss:seen:' .. hash

	-- Check items in reverse order so oldest new items are posted first
	local new_items = {}
	for _, item in ipairs(items) do
	if item.guid and item.guid ~= '' then
	local already_seen = ctx.redis.sismember(seen_key, item.guid)
	if tonumber(already_seen) == 0 then
	table.insert(new_items, item)
	end
	end
	end

	if #new_items == 0 then return end

	-- Mark new items as seen
	for _, item in ipairs(new_items) do
	ctx.redis.sadd(seen_key, item.guid)
	end

	-- Get all subscriber chats
	local subscribers = ctx.redis.smembers('rss:subs:' .. hash)
	if not subscribers or #subscribers == 0 then return end

	-- Send new items to all subscribers (oldest first)
	for i = #new_items, 1, -1 do
	local item = new_items[i]
	local text
	if item.link and item.link ~= '' then
	text = string.format(
	'<b>%s</b>\n<a href="%s">%s</a>',
	tools.escape_html(feed_title),
	tools.escape_html(item.link),
	tools.escape_html(item.title)
	)
	else
	text = string.format(
	'<b>%s</b>\n%s',
	tools.escape_html(feed_title),
	tools.escape_html(item.title)
	)
	end

	for _, chat_id in ipairs(subscribers) do
	local send_ok, send_err = pcall(
	api.send_message, chat_id, text,
	{ parse_mode = 'html', link_preview_options = { is_disabled = true } }
	)
	if not send_ok then
	logger.warn('RSS: failed to send to chat %s: %s', tostring(chat_id), tostring(send_err))
	end
	end
	end

	-- Trim seen set if it grows too large by using a TTL
	-- This avoids the data loss issue of rebuilding from current items only
	local seen_count = ctx.redis.scard(seen_key)
	if tonumber(seen_count) > MAX_SEEN * 2 then
	-- Set a 7-day TTL on the seen set to let it naturally expire
	-- rather than deleting entries that might cause re-posts
	ctx.redis.expire(seen_key, 604800)
	end
	end)

	if not ok then
	logger.error('RSS: error processing feed %s: %s', feed_url, tostring(err))
	end
	end
	end
	end

	return plugin

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