local array = require "util.array";

local id = require "util.id";

local it = require "util.iterators";

local set = require "util.set";

local st = require "util.stanza";

module:depends("pubsub_subscription");

local function new_rtbl_subscription(rtbl_service_jid, rtbl_node, handlers)

	local items = {};

	local function notify(event_type, hash)

		local handler = handlers[event_type];

		if not handler then return; end

		handler(hash);

	end

	module:add_item("pubsub-subscription", {

		service = rtbl_service_jid;

		node = rtbl_node;

		-- Callbacks:

		on_subscribed = function()

			module:log("info", "RTBL active: %s:%s", rtbl_service_jid, rtbl_node);

		end;

		on_error = function(err)

			module:log(

				"error",

				"Failed to subscribe to RTBL: %s:%s %s::%s:  %s",

				rtbl_service_jid,

				rtbl_node,

				err.type,

				err.condition,

				err.text

			);

		end;

		on_item = function(event)

			local hash = event.item.attr.id;

			if not hash then return; end

			module:log("debug", "Received new hash from %s:%s: %s", rtbl_service_jid, rtbl_node, hash);

			items[hash] = true;

			notify("added", hash);

		end;

		on_retract = function (event)

			local hash = event.item.attr.id;

			if not hash then return; end

			module:log("debug", "Retracted hash from %s:%s: %s", rtbl_service_jid, rtbl_node, hash);

			items[hash] = nil;

			notify("removed", hash);

		end;

		purge = function()

			module:log("debug", "Purge all hashes from %s:%s", rtbl_service_jid, rtbl_node);

			for hash in pairs(items) do

				items[hash] = nil;

				notify("removed", hash);

			end

		end;

	});

	local request_id = "rtbl-request-"..id.short();

	local function request_list()

		local items_request = st.iq({ to = rtbl_service_jid, from = module.host, type = "get", id = request_id })

			:tag("pubsub", { xmlns = "http://jabber.org/protocol/pubsub" })

				:tag("items", { node = rtbl_node }):up()

			:up();

		module:send(items_request);

	end

	local function update_list(event)

		local from_jid = event.stanza.attr.from;

		if from_jid ~= rtbl_service_jid then

			module:log("debug", "Ignoring RTBL response from unknown sender: %s", from_jid);

			return;

		end

		local items_el = event.stanza:find("{http://jabber.org/protocol/pubsub}pubsub/items");

		if not items_el then

			module:log("warn", "Invalid items response from RTBL service %s:%s", rtbl_service_jid, rtbl_node);

			return;

		end

		local old_entries = set.new(array.collect(it.keys(items)));

		local n_added, n_removed, n_total = 0, 0, 0;

		for item in items_el:childtags("item") do

			local hash = item.attr.id;

			if hash then

				n_total = n_total + 1;

				if not old_entries:contains(hash) then

					-- New entry

					n_added = n_added + 1;

					items[hash] = true;

					notify("added", hash);

				else

					-- Entry already existed

					old_entries:remove(hash);

				end

			end

		end

		-- Remove old entries that weren't in the received list

		for hash in old_entries do

			n_removed = n_removed + 1;

			items[hash] = nil;

			notify("removed", hash);

		end

		module:log("info", "%d RTBL entries received from %s:%s (%d added, %d removed)", n_total, from_jid, rtbl_node, n_added, n_removed);

		return true;

	end

	module:hook("iq-result/host/"..request_id, update_list);

	module:add_timer(0, request_list);

end

return {

	new_rtbl_subscription = new_rtbl_subscription;

}