+import EventEmitterAsyncResource from 'node:events'
+import type {
+ ErrorHandler,
+ ExitHandler,
+ IWorker,
+ MessageHandler,
+ OnlineHandler,
+ WorkerNode
+} 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
+
+/**
+ * Enumeration of worker types.
+ */
+export const WorkerTypes = Object.freeze({
+ cluster: 'cluster',
+ thread: 'thread'
+} as const)
+
+/**
+ * Worker type.
+ */
+export type WorkerType = keyof typeof WorkerTypes
+
+/**
+ * Pool events emitter.
+ */
+export class PoolEmitter extends EventEmitterAsyncResource {}
+
+/**
+ * Enumeration of pool events.
+ */
+export const PoolEvents = Object.freeze({
+ full: 'full',
+ busy: 'busy',
+ error: 'error',
+ taskError: 'taskError'
+} as const)
+
+/**
+ * Pool event.
+ */
+export type PoolEvent = keyof typeof PoolEvents
+
+/**
+ * Pool information.
+ */
+export interface PoolInfo {
+ type: PoolType
+ worker: WorkerType
+ minSize: number
+ maxSize: number
+ workerNodes: number
+ idleWorkerNodes: number
+ busyWorkerNodes: number
+ executedTasks: number
+ executingTasks: number
+ queuedTasks: number
+ maxQueuedTasks: number
+ failedTasks: number
+}
+
+/**
+ * Worker tasks queue options.
+ */
+export interface TasksQueueOptions {
+ /**
+ * Maximum number of tasks that can be executed concurrently on a worker.
+ *
+ * @defaultValue 1
+ */
+ 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 serializable data.
+ * @typeParam Response - Type of execution response. This can only be serializable 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<WorkerNode<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 full.
+ * - `'busy'`: Emitted when the pool is busy.
+ * - `'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 task input data for the specified worker function. This can only be serializable 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, name?: string) => Promise<Response>
+ /**
+ * Terminate every current worker in this pool.
+ */
+ destroy: () => Promise<void>
+ /**
+ * Sets the worker choice strategy in this pool.
+ *
+ * @param workerChoiceStrategy - The worker choice strategy.
+ * @param workerChoiceStrategyOptions - The worker choice strategy options.
+ */
+ setWorkerChoiceStrategy: (
+ workerChoiceStrategy: WorkerChoiceStrategy,
+ workerChoiceStrategyOptions?: WorkerChoiceStrategyOptions
+ ) => void
+ /**
+ * Sets the worker choice strategy options in this pool.
*
- * @param data The input for the specified task.
- * @returns Promise that will be resolved when the task is successfully completed.
+ * @param workerChoiceStrategyOptions - The worker choice strategy options.
*/
- execute(data: Data): Promise<Response>
+ setWorkerChoiceStrategyOptions: (
+ workerChoiceStrategyOptions: WorkerChoiceStrategyOptions
+ ) => void
/**
- * Shut down every current worker in this pool.
+ * 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.
+ */
+ 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>
+ setTasksQueueOptions: (tasksQueueOptions: TasksQueueOptions) => void
}