-- Fetches Atom feeds and publishes to PubSub nodes

--

-- Depends: http://code.matthewwild.co.uk/lua-feeds

--

-- Config:

-- Component "pubsub.example.com" "pubsub"

-- modules_enabled = {

--   "pubsub_feed";

-- }

-- feeds = { -- node -> url

--   prosody_blog = "http://blog.prosody.im/feed/atom.xml";

-- }

-- feed_pull_interval = 20 -- minutes

--

-- Reference

-- http://pubsubhubbub.googlecode.com/svn/trunk/pubsubhubbub-core-0.3.html

local modules = hosts[module.host].modules;

if not modules.pubsub then

	--FIXME Should this throw an error() instead?

	module:log("warn", "Pubsub needs to be loaded on this host");

end

local t_insert = table.insert;

local add_task = require "util.timer".add_task;

local date, time = os.date, os.time;

local dt_parse, dt_datetime = require "util.datetime".parse, require "util.datetime".datetime;

local uuid = require "util.uuid".generate;

local hmac_sha1 = require "util.hmac".sha1;

local parse_feed = require "feeds".feed_from_string;

local st = require "util.stanza";

local http = require "net.http";

local httpserver = require "net.httpserver";

local formdecode = http.formdecode;

local formencode = http.formencode;

local urldecode  = http.urldecode;

local urlencode  = http.urlencode;

local config = module:get_option("feeds") or {

	planet_jabber = "http://planet.jabber.org/atom.xml";

	prosody_blog = "http://blog.prosody.im/feed/atom.xml";

};

local refresh_interval = module:get_option_number("feed_pull_interval", 15) * 60;

local use_pubsubhubub = module:get_option_boolean("use_pubsubhubub", true); -- HTTP by default or not?

local httphost = module:get_option_string("pubsubhubub_httphost", module.host); -- If module.host IN A doesn't point to this server, use this to override.

local feed_list = { }

for node, url in pairs(config) do

	feed_list[node] = { url = url; node = node; last_update = 0 };

end

-- TODO module:hook("config-reloaded", above loop);

-- Also, keeping it somewhere persistent in order to avoid duplicated publishes?

-- Thanks to Maranda for this

local port, base, ssl = 5280, "callback", false;

local ports = module:get_option("feeds_ports") or { port = port, base = base, ssl = ssl };

-- FIXME If ports isn't a table, this will cause an error

local _, first_port = next(ports); -- We base the callback URL on the first port config

if first_port then

	if type(first_port) == "number" then

		port = first_port;

	elseif type(first_port) == "table" then

		port, base, ssl =

			first_port.port or port,

			first_port.path or base,

			first_port.ssl or ssl;

	elseif type(first_port) == "string" then

		base = first_port;

	end

end

local response_codes = {

	["200"] = "OK";

	["202"] = "Accepted";

	["400"] = "Bad Request";

	["403"] = "Forbidden";

	["404"] = "Not Found";

	["501"] = "Not Implemented";

};

local function http_response(code, headers, body)

	return {

		status = (type(code) == "number" and code .. " " .. response_codes[tostring(code)]) or code;

		headers = headers or {};

		body = body or "<h1>" .. response_codes[tostring(code)] .. "</h1>\n";

	};

end

local actor = module.host.."/"..module.name;

function update_entry(item)

	local node = item.node;

	--module:log("debug", "parsing %d bytes of data in node %s", #item.data or 0, node)

	local feed = parse_feed(item.data);

	module:log("debug", "updating node %s", node);

	for _, entry in ipairs(feed) do

		entry.attr.xmlns = "http://www.w3.org/2005/Atom";

		local e_published = entry:get_child_text("published");

		e_published = e_published and dt_parse(e_published);

		local e_updated = entry:get_child_text("updated");

		e_updated = e_updated and dt_parse(e_updated);

		local timestamp = e_updated or e_published or nil;

		--module:log("debug", "timestamp is %s, item.last_update is %s", tostring(timestamp), tostring(item.last_update));

		if not timestamp or not item.last_update or timestamp > item.last_update then

			local id = entry:get_child_text("id");

			id = id or item.url.."#"..dt_datetime(timestamp); -- Missing id, so make one up

			local xitem = st.stanza("item", { id = id }):add_child(entry);

			-- TODO Put data from /feed into item/source

			module:log("debug", "publishing to %s, id %s", node, id);

			local ok, err = modules.pubsub.service:publish(node, actor, id, xitem);

			if not ok then

				if err == "item-not-found" then -- try again

					module:log("debug", "got item-not-found, creating %s and trying again", node);

					local ok, err = modules.pubsub.service:create(node, actor);

					if not ok then

						module:log("error", "could not create node %s: %s", node, err);

						return;

					end

					local ok, err = modules.pubsub.service:publish(node, actor, id, xitem);

					if not ok then

						module:log("error", "could not create or publish node %s: %s", node, err);

						return

					end

				else

					module:log("error", "publishing %s failed: %s", node, err);

				end

			end

		end

	end

	if use_pubsubhubub and not item.subscription then

		module:log("debug", "check if %s has a hub", item.node);

		local hub = feed.links and feed.links.hub;

		if hub then

			item.hub = hub;

			module:log("debug", "%s has a hub: %s", item.node, item.hub);

			subscribe(item);

		end

	end

end

function fetch(item, callback) -- HTTP Pull

	local headers = { };

	if item.data and item.last_update then

		headers["If-Modified-Since"] = date("!%a, %d %b %Y %H:%M:%S %Z", item.last_update);

		--COMPAT We could have saved 6 bytes here, but Microsoft apparently hates %T, so you got this gigantic comment instead.

	end

	http.request(item.url, { headers = headers }, function(data, code, req) 

		if code == 200 then

			item.data = data;

			if callback then callback(item) end

			item.last_update = time();

		end

		if code == 304 then

			item.last_update = time();

		end

	end);

end

function refresh_feeds()

	--module:log("debug", "Refreshing feeds");

	for node, item in pairs(feed_list) do

		--FIXME Don't fetch feeds which have a subscription

		-- Otoho, what if the subscription expires or breaks?

		if item.last_update + refresh_interval < time() then 

			module:log("debug", "checking %s", item.node);

			fetch(item, update_entry);

		end

	end

	return refresh_interval;

end

local function format_url(secure, host, port, path, node)

	return ("%s://%s:%d/%s?node=%s"):format(secure and "https" or "http", host, port, path, urlencode(node));

end	

function subscribe(feed)

	feed.token = uuid();

	feed.secret = uuid();

	local body = formencode{

		["hub.callback"] = format_url(ssl, httphost, port, base, feed.node);

		["hub.mode"] = "subscribe"; --TODO unsubscribe

		["hub.topic"] = feed.url;

		["hub.verify"] = "async";

		["hub.verify_token"] = feed.token;

		["hub.secret"] = feed.secret;

		--["hub.lease_seconds"] = "";

	};

	--module:log("debug", "subscription request, body: %s", body);

	--FIXME The subscription states and related stuff

	feed.subscription = "subscribe";

	http.request(feed.hub, { body = body }, function(data, code, req) 

		local code = tostring(code);

		module:log("debug", "subscription to %s submitted, staus %s", feed.node, code);

	end);

end

function handle_http_request(method, body, request)

	--module:log("debug", "%s request to %s%s with body %s", method, request.url.path, request.url.query and "?" .. request.url.query or "", #body > 0 and body or "empty");

	local query = request.url.query or {};

	if query and type(query) == "string" then

		query = formdecode(query);

		--module:log("debug", "GET data: %s", dump(query));

	end

	--module:log("debug", "Headers: %s", dump(request.headers));

	if method == "GET" then

		if query.node and feed_list[query.node] then

			local feed = feed_list[query.node];

			if query["hub.topic"] ~= feed.url then

				module:log("debug", "Invalid topic: %s", tostring(query["hub.topic"]))

				return http_response(404)

			end

			if query["hub.mode"] ~= feed.subscription then

				module:log("debug", "Invalid mode: %s", tostring(query["hub.mode"]))

				return http_response(400)

				-- Would this work for unsubscribe?

				-- Also, if feed.subscription is changed here,

				-- it would probably invalidate the subscription

				-- when/if the hub asks if it should be renewed

			end

			if query["hub.verify_token"] ~= feed.token then

				module:log("debug", "Invalid verify_token: %s", tostring(query["hub.verify_token"]))

				return http_response(403)

			end

			module:log("debug", "Confirming %s request to %s", feed.subscription, feed.url)

			return http_response(200, nil, query["hub.challenge"])

		end

		return http_response(400);

	elseif method == "POST" then

		if #body > 0 and feed_list[query.node] then

			module:log("debug", "got %d bytes PuSHed for %s", #body, query.node);

			local feed = feed_list[query.node];

			local signature = request.headers["x-hub-signature"];

			if feed.secret then

				local localsig = "sha1=" .. hmac_sha1(feed.secret, body, true);

				if localsig ~= signature then

					module:log("debug", "Invalid signature");

					return http_response(403);

				end

				module:log("debug", "Valid signature");

			end

			feed.data = body;

			update_entry(feed);

			feed.last_update = time();

			return http_response(202);

		end

		return http_response(400);

	end

	return http_response(501);

end

function init()

	module:log("debug", "initiating", module.name);

	if use_pubsubhubub then

		module:log("debug", "Starting http server on %s", format_url(ssl, httphost, port, base, "NODE"));

		httpserver.new_from_config( ports, handle_http_request, { base = "callback" } );

	end

	add_task(0, refresh_feeds);

end

if prosody.start_time then -- already started

	init();

else

	module:hook_global("server-started", init);

end