Added: util/events.lua: An event handling library

1 files changed, 96 insertions, 0 deletions

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;