@exogee/kew

A typed task queue with a simple API.

• Create a Queue
• Attach a Platform for storage and data persistence.
• Register one or more Action\ s to perform various types of tasks.
• Actions are simple objects with lifecycle methods.
• Add Task\ s to the Queue.

Example

// index.ts
import { Queue, TaskStatus, Action } from "@exogee/kew";
import { Platform } from "@exogee/kew-react-native-async-storage";

interface ReverseMessageProps {
    value: string;
 }

@Metadata("ReverseMessage")
class ReverseMessage extends Action<ReverseMessageProps> {

    @Start()
    async start() {
        this.props.value = this.props.value.split("").reverse().join("");
    }
}

// Create a new queue
const queue = new Queue({
  platform: new Platform("my_application_queue"),
  actions: [ReverseMessage],
});

// Register an event listener
queue.on(
  (task) => task.status === TaskStatus.FINISHED,
  ({ props }) => {
    console.log("Task completed: ", props.value);
    queue.stop();
  }
);

// Add task to the queue and start
(async () => {
    await queue.add("ReverseMessage", { value: "!olleH" });
  await queue.start();
})();

See @exogee/kew-example for a more complex example

API

const queue = new Queue({ platform?, actions? });

Create a new queue with optional platform and Actions

async queue.run(actionKey, props)

Run the action actionKey with optional props and return the result immediately, without adding to the queue.

async queue.add(actionKey, props)

Add a new task of action type actionKey to the queue with optional props - returns a unique task ID.

async queue.start()

Start the queue.

queue.stop()

Stop the queue.

queue.pause()

Pause the queue

queue.unpause()

Unpause the queue

async queue.reducer(reducerKey, initialValue, filter)

Run the reducer named reducerKey over the queue. Optionally, an initialValue can be provided which will be the initial value of the accumulator. Optionally, a filter function can be provided which will only apply the reducer if the filter returns true for a task.

Returns a promise with the reduced data result.

queue.addActions(...actions[])

Register one or more actions if not registered in the constructor.

queue.on(filter, callback): TaskQueueEventSubscription

Subscribe to a task queue event. Returns a subscription object with a remove() method to unsubscribe.

queue.tasks()

Get a list of all tasks.

async queue.clear()

Remove all tasks from the queue

Platforms

Example Platform

const AsyncStoragePlatform: Platform = {
  storage: {
    // load is called when the queue data needs to be reloaded.
    async load() {
      return await AsyncStorage.getItem("TASK_QUEUE")
        .then((tasksJSON) => callback(JSON.parse(tasksJSON)))
        .catch(() => ({}));
    },

    // sync is called with the new queue data whenever the queue is updated.
    async sync(queue: QueueStorageData) {
      await AsyncStorage.setItem("TASK_QUEUE", JSON.stringify(queue));
    },
  },
};

export default AsyncStoragePlatform;