util/filters.lua

   1 -- Prosody IM
   2 -- Copyright (C) 2008-2010 Matthew Wild
   3 -- Copyright (C) 2008-2010 Waqas Hussain
   4 --
   5 -- This project is MIT/X11 licensed. Please see the
   6 -- COPYING file in the source package for more information.
   7 --
   8
   9 local t_insert, t_remove = table.insert, table.remove;
  10
  11 local _ENV = nil;
  12
  13 local new_filter_hooks = {};
  14
  15 local function initialize(session)
  16         if not session.filters then
  17                 local filters = {};
  18                 session.filters = filters;
  19
  20                 function session.filter(type, data)
  21                         local filter_list = filters[type];
  22                         if filter_list then
  23                                 for i = 1, #filter_list do
  24                                         data = filter_list[i](data, session);
  25                                         if data == nil then break; end
  26                                 end
  27                         end
  28                         return data;
  29                 end
  30         end
  31
  32         for i=1,#new_filter_hooks do
  33                 new_filter_hooks[i](session);
  34         end
  35
  36         return session.filter;
  37 end
  38
  39 local function add_filter(session, type, callback, priority)
  40         if not session.filters then
  41                 initialize(session);
  42         end
  43
  44         local filter_list = session.filters[type];
  45         if not filter_list then
  46                 filter_list = {};
  47                 session.filters[type] = filter_list;
  48         elseif filter_list[callback] then
  49                 return; -- Filter already added
  50         end
  51
  52         priority = priority or 0;
  53
  54         local i = 0;
  55         repeat
  56                 i = i + 1;
  57         until not filter_list[i] or filter_list[filter_list[i]] < priority;
  58
  59         t_insert(filter_list, i, callback);
  60         filter_list[callback] = priority;
  61 end
  62
  63 local function remove_filter(session, type, callback)
  64         if not session.filters then return; end
  65         local filter_list = session.filters[type];
  66         if filter_list and filter_list[callback] then
  67                 for i=1, #filter_list do
  68                         if filter_list[i] == callback then
  69                                 t_remove(filter_list, i);
  70                                 filter_list[callback] = nil;
  71                                 return true;
  72                         end
  73                 end
  74         end
  75 end
  76
  77 local function add_filter_hook(callback)
  78         t_insert(new_filter_hooks, callback);
  79 end
  80
  81 local function remove_filter_hook(callback)
  82         for i=1,#new_filter_hooks do
  83                 if new_filter_hooks[i] == callback then
  84                         t_remove(new_filter_hooks, i);
  85                 end
  86         end
  87 end
  88
  89 return {
  90         initialize = initialize;
  91         add_filter = add_filter;
  92         remove_filter = remove_filter;
  93         add_filter_hook = add_filter_hook;
  94         remove_filter_hook = remove_filter_hook;
  95 };