util/events.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
  10 local pairs = pairs;
  11 local t_insert = table.insert;
  12 local t_remove = table.remove;
  13 local t_sort = table.sort;
  14 local setmetatable = setmetatable;
  15 local next = next;
  16
  17 local _ENV = nil;
  18
  19 local function new()
  20         -- Map event name to ordered list of handlers (lazily built): handlers[event_name] = array_of_handler_functions
  21         local handlers = {};
  22         -- Array of wrapper functions that wrap all events (nil if empty)
  23         local global_wrappers;
  24         -- Per-event wrappers: wrappers[event_name] = wrapper_function
  25         local wrappers = {};
  26         -- Event map: event_map[handler_function] = priority_number
  27         local event_map = {};
  28         -- Called on-demand to build handlers entries
  29         local function _rebuild_index(handlers, event)
  30                 local _handlers = event_map[event];
  31                 if not _handlers or next(_handlers) == nil then return; end
  32                 local index = {};
  33                 for handler in pairs(_handlers) do
  34                         t_insert(index, handler);
  35                 end
  36                 t_sort(index, function(a, b) return _handlers[a] > _handlers[b]; end);
  37                 handlers[event] = index;
  38                 return index;
  39         end;
  40         setmetatable(handlers, { __index = _rebuild_index });
  41         local function add_handler(event, handler, priority)
  42                 local map = event_map[event];
  43                 if map then
  44                         map[handler] = priority or 0;
  45                 else
  46                         map = {[handler] = priority or 0};
  47                         event_map[event] = map;
  48                 end
  49                 handlers[event] = nil;
  50         end;
  51         local function remove_handler(event, handler)
  52                 local map = event_map[event];
  53                 if map then
  54                         map[handler] = nil;
  55                         handlers[event] = nil;
  56                         if next(map) == nil then
  57                                 event_map[event] = nil;
  58                         end
  59                 end
  60         end;
  61         local function get_handlers(event)
  62                 return handlers[event];
  63         end;
  64         local function add_handlers(handlers)
  65                 for event, handler in pairs(handlers) do
  66                         add_handler(event, handler);
  67                 end
  68         end;
  69         local function remove_handlers(handlers)
  70                 for event, handler in pairs(handlers) do
  71                         remove_handler(event, handler);
  72                 end
  73         end;
  74         local function _fire_event(event_name, event_data)
  75                 local h = handlers[event_name];
  76                 if h then
  77                         for i=1,#h do
  78                                 local ret = h[i](event_data);
  79                                 if ret ~= nil then return ret; end
  80                         end
  81                 end
  82         end;
  83         local function fire_event(event_name, event_data)
  84                 local w = wrappers[event_name] or global_wrappers;
  85                 if w then
  86                         local curr_wrapper = #w;
  87                         local function c(event_name, event_data)
  88                                 curr_wrapper = curr_wrapper - 1;
  89                                 if curr_wrapper == 0 then
  90                                         if global_wrappers == nil or w == global_wrappers then
  91                                                 return _fire_event(event_name, event_data);
  92                                         end
  93                                         w, curr_wrapper = global_wrappers, #global_wrappers;
  94                                         return w[curr_wrapper](c, event_name, event_data);
  95                                 else
  96                                         return w[curr_wrapper](c, event_name, event_data);
  97                                 end
  98                         end
  99                         return w[curr_wrapper](c, event_name, event_data);
 100                 end
 101                 return _fire_event(event_name, event_data);
 102         end
 103         local function add_wrapper(event_name, wrapper)
 104                 local w;
 105                 if event_name == false then
 106                         w = global_wrappers;
 107                         if not w then
 108                                 w = {};
 109                                 global_wrappers = w;
 110                         end
 111                 else
 112                         w = wrappers[event_name];
 113                         if not w then
 114                                 w = {};
 115                                 wrappers[event_name] = w;
 116                         end
 117                 end
 118                 w[#w+1] = wrapper;
 119         end
 120         local function remove_wrapper(event_name, wrapper)
 121                 local w;
 122                 if event_name == false then
 123                         w = global_wrappers;
 124                 else
 125                         w = wrappers[event_name];
 126                 end
 127                 if not w then return; end
 128                 for i = #w, 1 do
 129                         if w[i] == wrapper then
 130                                 t_remove(w, i);
 131                         end
 132                 end
 133                 if #w == 0 then
 134                         if event_name == false then
 135                                 global_wrappers = nil;
 136                         else
 137                                 wrappers[event_name] = nil;
 138                         end
 139                 end
 140         end
 141         return {
 142                 add_handler = add_handler;
 143                 remove_handler = remove_handler;
 144                 add_handlers = add_handlers;
 145                 remove_handlers = remove_handlers;
 146                 get_handlers = get_handlers;
 147                 wrappers = {
 148                         add_handler = add_wrapper;
 149                         remove_handler = remove_wrapper;
 150                 };
 151                 add_wrapper = add_wrapper;
 152                 remove_wrapper = remove_wrapper;
 153                 fire_event = fire_event;
 154                 _handlers = handlers;
 155                 _event_map = event_map;
 156         };
 157 end
 158
 159 return {
 160         new = new;
 161 };