wip prototyping queue, tasks and timer

src/tasks/Queue.ts

@@ -0,0 +1,165 @@
+import type { DB, DBTransaction, LevelPath } from '@matrixai/db';
+import type { TaskIdString } from './types';
+import type { PolykeyWorkerManagerInterface } from '../workers/types';
+import type { PromiseDeconstructed } from '../types';
+import Logger from '@matrixai/logger';
+import {
+  CreateDestroyStartStop,
+  ready,
+} from '@matrixai/async-init/dist/CreateDestroyStartStop';
+import * as tasksUtils from './utils';
+import * as tasksErrors from './errors';
+
+interface Queue extends CreateDestroyStartStop {}
+@CreateDestroyStartStop(
+  new tasksErrors.ErrorQueueRunning(),
+  new tasksErrors.ErrorQueueDestroyed(),
+)
+class Queue {
+
+  public static async createQueue({
+    db,
+    logger = new Logger(this.name),
+    fresh = false,
+  }: {
+    db: DB;
+    logger?: Logger;
+    fresh?: boolean;
+  }) {
+    logger.info(`Creating ${this.name}`);
+    const queue = new this({ db, logger });
+    await queue.start({ fresh });
+    logger.info(`Created ${this.name}`);
+    return queue;
+  }
+
+  protected logger: Logger;
+  protected db: DB;
+  protected workerManager?: PolykeyWorkerManagerInterface;
+  protected queueDbPath: LevelPath = [this.constructor.name];
+
+  // when the queue to execute the tasks
+  // the task id is generated outside
+  // you don't get a task id here
+  // you just "push" tasks there to be executed
+  // this is the "shared" set of promises to be maintained
+  protected promises: Map<TaskIdString, PromiseDeconstructed<any>> = new Map();
+
+  // /**
+  //  * Listeners for task execution
+  //  * When a task is executed, these listeners are synchronously executed
+  //  * The listeners are intended for resolving or rejecting task promises
+  //  */
+  // protected listeners: Map<TaskIdString, Array<TaskListener>> = new Map();
+
+  public constructor({
+    db,
+    logger
+  }: {
+    db: DB;
+    logger: Logger
+  }) {
+    this.logger = logger;
+    this.db = db;
+  }
+
+  public setWorkerManager(workerManager: PolykeyWorkerManagerInterface) {
+    this.workerManager = workerManager;
+  }
+
+  public unsetWorkerManager() {
+    delete this.workerManager;
+  }
+
+  public async start({
+    fresh = false,
+  }: {
+    fresh?: boolean;
+  } = {}): Promise<void> {
+    this.logger.info(`Starting ${this.constructor.name}`);
+    if (fresh) {
+      await this.db.clear(this.queueDbPath);
+    }
+    this.logger.info(`Started ${this.constructor.name}`);
+  }
+
+  public async stop(): Promise<void> {
+    this.logger.info(`Stopping ${this.constructor.name}`);
+    this.logger.info(`Stopped ${this.constructor.name}`);
+  }
+
+  public async destroy() {
+    this.logger.info(`Destroying ${this.constructor.name}`);
+    await this.db.clear(this.queueDbPath);
+    this.logger.info(`Destroyed ${this.constructor.name}`);
+  }
+
+  // promises are "connected" to events
+
+  /**
+   * IF a handler does not exist
+   * if the task is executed
+   * then an exception is thrown
+   * if listener exists, the exception is passed into this listener function
+   * if it doesn't exist, then it's just a reference exception in general, this can be logged
+   * There's nothing else to do
+   */
+  @ready(new tasksErrors.ErrorSchedulerNotRunning())
+  protected registerListener(
+    taskId: TaskId,
+    taskListener: TaskListener
+  ): void {
+    const taskIdString = taskId.toString() as TaskIdString;
+    const taskListeners = this.listeners.get(taskIdString);
+    if (taskListeners != null) {
+      taskListeners.push(taskListener);
+    } else {
+      this.listeners.set(taskIdString, [taskListener]);
+    }
+  }
+
+  @ready(new tasksErrors.ErrorSchedulerNotRunning())
+  protected deregisterListener(
+    taskId: TaskId,
+    taskListener: TaskListener
+  ): void {
+    const taskIdString = taskId.toString() as TaskIdString;
+    const taskListeners = this.listeners.get(taskIdString);
+    if (taskListeners == null || taskListeners.length < 1) return;
+    const index = taskListeners.indexOf(taskListener);
+    if (index !== -1) {
+      taskListeners.splice(index, 1);
+    }
+  }
+
+}
+
+export default Queue;
+
+
+// epic queue
+// need to do a couple things:
+// 1. integrate fast-check
+// 2. integrate span checks
+// 3. might also consider span logs?
+// 4. open tracing observability
+// 5. structured logging
+// 6. async hooks to get traced promises to understand the situation
+// 7. do we also get fantasy land promises? and async cancellable stuff?
+// 8. task abstractions?
+// need to use the db for this
+// 9. priority structure
+// 10. timers
+// abort controller
+
+// kinetic data structure
+// the priority grows as a function of time
+// order by priority <- this thing has a static value
+// in a key value DB, you can maintain sorted index of values
+// IDs can be lexicographically sortable
+
+// this is a persistent queue
+// of tasks that should be EXECUTED right now
+// the scheduler is a persistent scheduler of scheduled tasks
+// tasks get pushed from the scheduler into the queue
+// the queue connects to the WorkerManager