Event.lua

local Event = {}
Event.__index = Event

function Event.new()
	return setmetatable({
		_listeners = {},
		_threads = {},

		-- TODO: Remove when Roblox fixes coroutine.yield in pcall
		_compatibilityEvent = Instance.new("BindableEvent")
	}, Event)
end

function Event:Fire(...)
	self._currentArgs = { ... }
	self._compatibilityEvent:Fire()
	self._currentArgs = nil

	for _, handler in pairs(self._listeners) do
		handler(...)
	end

	for _, thread in pairs(self._threads) do
		coroutine.resume(thread, ...)
	end
	
	self._threads = {}
end

function Event:Connect(handler)
	table.insert(self._listeners, handler)

	return {
		Connected = true,
		Disconnect = function(connection)
			if connection.Connected then
				connection.Connected = false
	
				for index, listener in pairs(self._listeners) do
					if listener == handler then
						return table.remove(self._listeners, index)
					end
				end
			end
		end
	}
end

function Event:Wait()
	table.insert(self._threads, coroutine.running())
	return coroutine.yield()
end

function Event:WaitCompatibility()
	self._compatibilityEvent.Event:Wait()
	return unpack(self._currentArgs)
end

return Event