Test shaders

druid/event_queue.lua

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+local event = require("event.event")
+
+---@class event.queue
+local M = {}
+
+local event_handlers = {}
+local pending_callbacks = {}
+
+
+---Request to handle a specified event and processes the queue of callbacks associated with it.
+---If event has already been triggered, the callback will be executed immediately.
+---If event not triggered yet, callback will be executed when event will be triggered.
+---It triggered only once and then removed from the queue.
+---@param event_name string The name of the event to trigger.
+---@param callback fun() The callback function to execute upon triggering.
+---@param ... any Additional arguments for the callback.
+function M.request(event_name, callback, ...)
+	pending_callbacks[event_name] = pending_callbacks[event_name] or {}
+	table.insert(pending_callbacks[event_name], { event.create(callback), ... })
+
+	M.process_pending_callbacks(event_name)
+end
+
+
+---Subscribes to a specified event and executes a callback when the event is triggered.
+-- If the event has already been triggered, the callback will be executed immediately.
+---@param event_name string The name of the event to subscribe to.
+---@param callback fun() The function to call when the event is triggered.
+function M.subscribe(event_name, callback)
+	event_handlers[event_name] = event_handlers[event_name] or event.create()
+
+	if event_handlers[event_name] then
+		event_handlers[event_name]:subscribe(callback)
+	end
+
+	M.process_pending_callbacks(event_name)
+end
+
+
+---Unsubscribes a callback function from a specified event.
+---@param event_name string The name of the event to unsubscribe from.
+---@param callback fun() The function to remove from the event's subscription list.
+function M.unsubscribe(event_name, callback)
+	if event_handlers[event_name] then
+		event_handlers[event_name]:unsubscribe(callback)
+	end
+end
+
+
+---Processes the queue for a given event name, executing callbacks and handling results.
+---Processed callbacks are removed from the queue.
+---@param event_name string The name of the event for which to process the queue.
+function M.process_pending_callbacks(event_name)
+	local callbacks_to_process = pending_callbacks[event_name]
+	local event_handler = event_handlers[event_name]
+
+	if not callbacks_to_process or not event_handler then
+		return
+	end
+
+	-- Loop through the queue in reverse to prevent index errors during removal
+	for i = #callbacks_to_process, 1, -1 do
+		local callback_entry = callbacks_to_process[i]
+		-- Better to figure out how to make it without 2 unpacks, but ok for all our cases now
+		local args = { unpack(callback_entry, 2) }
+
+		-- Safely call the event handler and handle errors
+		local success, result = pcall(event_handler.trigger, event_handler, unpack(args))
+
+		if success and result then
+			local callback_function = callback_entry[1]
+			pcall(callback_function, result) -- Safely invoke the callback, catching any errors
+			table.remove(callbacks_to_process, i) -- Remove the processed callback from the queue
+		end
+	end
+
+	-- Clean up if the callback queue is empty
+	if #callbacks_to_process == 0 then
+		pending_callbacks[event_name] = nil
+	end
+end
+
+
+return M