-- Prosody IM

-- Copyright (C) 2008-2010 Matthew Wild

-- Copyright (C) 2008-2010 Waqas Hussain

--

-- This project is MIT/X11 licensed. Please see the

-- COPYING file in the source package for more information.

--

local t_insert, t_remove = table.insert, table.remove;

local _ENV = nil;

local new_filter_hooks = {};

local function initialize(session)

	if not session.filters then

		local filters = {};

		session.filters = filters;

		function session.filter(type, data)

			local filter_list = filters[type];

			if filter_list then

				for i = 1, #filter_list do

					data = filter_list[i](data, session);

					if data == nil then break; end

				end

			end

			return data;

		end

	end

	for i=1,#new_filter_hooks do

		new_filter_hooks[i](session);

	end

	return session.filter;

end

local function add_filter(session, type, callback, priority)

	if not session.filters then

		initialize(session);

	end

	local filter_list = session.filters[type];

	if not filter_list then

		filter_list = {};

		session.filters[type] = filter_list;

	elseif filter_list[callback] then

		return; -- Filter already added

	end

	priority = priority or 0;

	local i = 0;

	repeat

		i = i + 1;

	until not filter_list[i] or filter_list[filter_list[i]] < priority;

	t_insert(filter_list, i, callback);

	filter_list[callback] = priority;

end

local function remove_filter(session, type, callback)

	if not session.filters then return; end

	local filter_list = session.filters[type];

	if filter_list and filter_list[callback] then

		for i=1, #filter_list do

			if filter_list[i] == callback then

				t_remove(filter_list, i);

				filter_list[callback] = nil;

				return true;

			end

		end

	end

end

local function add_filter_hook(callback)

	t_insert(new_filter_hooks, callback);

end

local function remove_filter_hook(callback)

	for i=1,#new_filter_hooks do

		if new_filter_hooks[i] == callback then

			t_remove(new_filter_hooks, i);

		end

	end

end

return {

	initialize = initialize;

	add_filter = add_filter;

	remove_filter = remove_filter;

	add_filter_hook = add_filter_hook;

	remove_filter_hook = remove_filter_hook;

};