+import { EventEmitter } from 'node:events'
+import type {
+ ErrorHandler,
+ ExitHandler,
+ IWorker,
+ IWorkerNode,
+ MessageHandler,
+ OnlineHandler,
+ WorkerType
+} from './worker'
+import type {
+ WorkerChoiceStrategy,
+ WorkerChoiceStrategyOptions
+} from './selection-strategies/selection-strategies-types'
+
+/**
+ * Enumeration of pool types.
+ */
+export const PoolTypes = Object.freeze({
+ /**
+ * Fixed pool type.
+ */
+ fixed: 'fixed',
+ /**
+ * Dynamic pool type.
+ */
+ dynamic: 'dynamic'
+} as const)
+
+/**
+ * Pool type.
+ */
+export type PoolType = keyof typeof PoolTypes
+
+/**
+ * Pool events emitter.
+ */
+export class PoolEmitter extends EventEmitter {}
+
+/**
+ * Enumeration of pool events.
+ */
+export const PoolEvents = Object.freeze({
+ full: 'full',
+ ready: 'ready',
+ busy: 'busy',
+ error: 'error',
+ taskError: 'taskError'
+} as const)
+
+/**
+ * Pool event.
+ */
+export type PoolEvent = keyof typeof PoolEvents
+
+/**
+ * Pool information.
+ */
+export interface PoolInfo {
+ readonly version: string
+ readonly type: PoolType
+ readonly worker: WorkerType
+ readonly ready: boolean
+ readonly strategy: WorkerChoiceStrategy
+ readonly minSize: number
+ readonly maxSize: number
+ /** Pool utilization. */
+ readonly utilization?: number
+ /** Pool total worker nodes. */
+ readonly workerNodes: number
+ /** Pool idle worker nodes. */
+ readonly idleWorkerNodes: number
+ /** Pool busy worker nodes. */
+ readonly busyWorkerNodes: number
+ readonly executedTasks: number
+ readonly executingTasks: number
+ readonly queuedTasks: number
+ readonly maxQueuedTasks: number
+ readonly failedTasks: number
+ readonly runTime?: {
+ readonly minimum: number
+ readonly maximum: number
+ readonly average: number
+ readonly median?: number
+ }
+ readonly waitTime?: {
+ readonly minimum: number
+ readonly maximum: number
+ readonly average: number
+ readonly median?: number
+ }
+}
+
+/**
+ * Worker tasks queue options.
+ */
+export interface TasksQueueOptions {
+ /**
+ * Maximum number of tasks that can be executed concurrently on a worker.
+ *
+ * @defaultValue 1
+ */
+ readonly concurrency?: number
+}
+
+/**
+ * Options for a poolifier pool.
+ *
+ * @typeParam Worker - Type of worker.
+ */
+export interface PoolOptions<Worker extends IWorker> {
+ /**
+ * A function that will listen for message event on each worker.
+ */
+ messageHandler?: MessageHandler<Worker>
+ /**
+ * A function that will listen for error event on each worker.
+ */
+ errorHandler?: ErrorHandler<Worker>
+ /**
+ * A function that will listen for online event on each worker.
+ */
+ onlineHandler?: OnlineHandler<Worker>
+ /**
+ * A function that will listen for exit event on each worker.
+ */
+ exitHandler?: ExitHandler<Worker>
+ /**
+ * The worker choice strategy to use in this pool.
+ *
+ * @defaultValue WorkerChoiceStrategies.ROUND_ROBIN
+ */
+ workerChoiceStrategy?: WorkerChoiceStrategy
+ /**
+ * The worker choice strategy options.
+ */
+ workerChoiceStrategyOptions?: WorkerChoiceStrategyOptions
+ /**
+ * Restart worker on error.
+ */
+ restartWorkerOnError?: boolean
+ /**
+ * Pool events emission.
+ *
+ * @defaultValue true
+ */
+ enableEvents?: boolean
+ /**
+ * Pool worker tasks queue.
+ *
+ * @defaultValue false
+ */
+ enableTasksQueue?: boolean
+ /**
+ * Pool worker tasks queue options.
+ */
+ tasksQueueOptions?: TasksQueueOptions
+}
+
/**
* Contract definition for a poolifier pool.
*
- * @template Data Type of data sent to the worker.
- * @template Response Type of response of execution.
+ * @typeParam Worker - Type of worker which manages this pool.
+ * @typeParam Data - Type of data sent to the worker. This can only be structured-cloneable data.
+ * @typeParam Response - Type of execution response. This can only be structured-cloneable data.
*/
-export interface IPool<Data = unknown, Response = unknown> {
+export interface IPool<
+ Worker extends IWorker,
+ Data = unknown,
+ Response = unknown
+> {
+ /**
+ * Pool information.
+ */
+ readonly info: PoolInfo
/**
- * Perform the task specified in the constructor with the data parameter.
+ * Pool worker nodes.
+ */
+ readonly workerNodes: Array<IWorkerNode<Worker, Data>>
+ /**
+ * Emitter on which events can be listened to.
+ *
+ * Events that can currently be listened to:
+ *
+ * - `'full'`: Emitted when the pool is dynamic and the number of workers created has reached the maximum size expected.
+ * - `'ready'`: Emitted when the number of workers created in the pool has reached the minimum size expected and are ready.
+ * - `'busy'`: Emitted when the number of workers created in the pool has reached the maximum size expected and are executing at least one task.
+ * - `'error'`: Emitted when an uncaught error occurs.
+ * - `'taskError'`: Emitted when an error occurs while executing a task.
+ */
+ readonly emitter?: PoolEmitter
+ /**
+ * Executes the specified function in the worker constructor with the task data input parameter.
*
- * @param data The input for the specified task.
- * @returns Promise that will be resolved when the task is successfully completed.
+ * @param data - The task input data for the specified worker function. This can only be structured-cloneable data.
+ * @param name - The name of the worker function to execute. If not specified, the default worker function will be executed.
+ * @returns Promise that will be fulfilled when the task is completed.
*/
- execute(data: Data): Promise<Response>
+ readonly execute: (data?: Data, name?: string) => Promise<Response>
/**
- * Shut down every current worker in this pool.
+ * Terminates all workers in this pool.
+ */
+ readonly destroy: () => Promise<void>
+ /**
+ * Sets the worker choice strategy in this pool.
+ *
+ * @param workerChoiceStrategy - The worker choice strategy.
+ * @param workerChoiceStrategyOptions - The worker choice strategy options.
+ */
+ readonly setWorkerChoiceStrategy: (
+ workerChoiceStrategy: WorkerChoiceStrategy,
+ workerChoiceStrategyOptions?: WorkerChoiceStrategyOptions
+ ) => void
+ /**
+ * Sets the worker choice strategy options in this pool.
+ *
+ * @param workerChoiceStrategyOptions - The worker choice strategy options.
+ */
+ readonly setWorkerChoiceStrategyOptions: (
+ workerChoiceStrategyOptions: WorkerChoiceStrategyOptions
+ ) => void
+ /**
+ * Enables/disables the worker tasks queue in this pool.
+ *
+ * @param enable - Whether to enable or disable the worker tasks queue.
+ * @param tasksQueueOptions - The worker tasks queue options.
+ */
+ readonly enableTasksQueue: (
+ enable: boolean,
+ tasksQueueOptions?: TasksQueueOptions
+ ) => void
+ /**
+ * Sets the worker tasks queue options in this pool.
+ *
+ * @param tasksQueueOptions - The worker tasks queue options.
*/
- destroy(): Promise<void>
+ readonly setTasksQueueOptions: (tasksQueueOptions: TasksQueueOptions) => void
}