From 1192c1a1f5e66efdba705424cd54dbebc4203ae3 Mon Sep 17 00:00:00 2001
From: Waqas Hussain <waqas20@gmail.com>
Date: Mon, 30 Mar 2009 03:58:59 +0500
Subject: Added: util/events.lua: An event handling library

---
 util/events.lua | 96 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 util/events.lua

diff --git a/util/events.lua b/util/events.lua
new file mode 100644
index 00000000..b1f3811c
--- /dev/null
+++ b/util/events.lua
@@ -0,0 +1,96 @@
+
+local ipairs = ipairs;
+local pairs = pairs;
+local t_insert = table.insert;
+local select = select;
+
+module "events"
+
+function new()
+	local dispatchers = {};
+	local handlers = {};
+	local event_map = {};
+	local function _rebuild_index() -- TODO optimize index rebuilding
+		for event, _handlers in pairs(event_map) do
+			local index = handlers[event];
+			if index then
+				for i=#index,1,-1 do index[i] = nil; end
+			else index = {}; handlers[event] = index; end
+			for handler in pairs(_handlers) do
+				t_insert(index, handler);
+			end
+		end
+	end;
+	local function add_handler(event, handler)
+		local map = event_map[event];
+		if map then
+			map[handler] = true;
+		else
+			map = {[handler] = true};
+			event_map[event] = map;
+		end
+		_rebuild_index();
+	end;
+	local function remove_handler(event, handler)
+		local map = event_map[event];
+		if map then
+			map[handler] = nil;
+			_rebuild_index();
+		end
+	end;
+	local function add_plugin(plugin)
+		for event, handler in pairs(plugin) do
+			add_handler(event, handler);
+		end
+	end;
+	local function remove_plugin(plugin)
+		for event, handler in pairs(plugin) do
+			remove_handler(event, handler);
+		end
+	end;
+	local function _create_dispatcher(event) -- FIXME duplicate code in fire_event
+		local h = handlers[event];
+		if not h then h = {}; handlers[event] = h; end
+		local dispatcher = function(data)
+			for _, handler in ipairs(h) do
+				handler(data);
+			end
+		end;
+		dispatchers[event] = dispatcher;
+		return dispatcher;
+	end;
+	local function get_dispatcher(event)
+		return dispatchers[event] or _create_dispatcher(event);
+	end;
+	local function fire_event(event, data) -- FIXME duplicates dispatcher code
+		local h = handlers[event];
+		if h then
+			for _, handler in ipairs(h) do
+				handler(data);
+			end
+		end
+	end;
+	local function get_named_arg_dispatcher(event, ...)
+		local dispatcher = get_dispatcher(event);
+		local keys = {...};
+		local data = {};
+		return function(...)
+			for i, key in ipairs(keys) do data[key] = select(i, ...); end
+			dispatcher(data);
+		end;
+	end;
+	return {
+		add_handler = add_handler;
+		remove_handler = remove_handler;
+		add_plugin = add_plugin;
+		remove_plugin = remove_plugin;
+		get_dispatcher = get_dispatcher;
+		fire_event = fire_event;
+		get_named_arg_dispatcher = get_named_arg_dispatcher;
+		_dispatchers = dispatchers;
+		_handlers = handlers;
+		_event_map = event_map;
+	};
+end
+
+return _M;
-- 
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