+import type { ClusterSettings } from 'node:cluster'
+import type { EventEmitterAsyncResource } from 'node:events'
+import type { TransferListItem, WorkerOptions } from 'node:worker_threads'
+
+import type { TaskFunctionProperties } from '../utility-types.js'
+import type { TaskFunction } from '../worker/task-functions.js'
+import type {
+ WorkerChoiceStrategy,
+ WorkerChoiceStrategyOptions
+} from './selection-strategies/selection-strategies-types.js'
+import type {
+ ErrorHandler,
+ ExitHandler,
+ IWorker,
+ IWorkerNode,
+ MessageHandler,
+ OnlineHandler,
+ WorkerType
+} from './worker.js'
+
+/**
+ * Enumeration of pool types.
+ */
+export const PoolTypes: Readonly<{
+ fixed: 'fixed'
+ dynamic: 'dynamic'
+}> = Object.freeze({
+ /**
+ * Fixed pool type.
+ */
+ fixed: 'fixed',
+ /**
+ * Dynamic pool type.
+ */
+ dynamic: 'dynamic'
+} as const)
+
+/**
+ * Pool type.
+ */
+export type PoolType = keyof typeof PoolTypes
+
+/**
+ * Enumeration of pool events.
+ */
+export const PoolEvents: Readonly<{
+ ready: 'ready'
+ busy: 'busy'
+ full: 'full'
+ empty: 'empty'
+ destroy: 'destroy'
+ error: 'error'
+ taskError: 'taskError'
+ backPressure: 'backPressure'
+}> = Object.freeze({
+ ready: 'ready',
+ busy: 'busy',
+ full: 'full',
+ empty: 'empty',
+ destroy: 'destroy',
+ error: 'error',
+ taskError: 'taskError',
+ backPressure: 'backPressure'
+} 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 started: boolean
+ readonly ready: boolean
+ readonly defaultStrategy: WorkerChoiceStrategy
+ readonly strategyRetries: number
+ readonly minSize: number
+ readonly maxSize: number
+ /** Pool utilization. */
+ readonly utilization?: number
+ /** Pool total worker nodes. */
+ readonly workerNodes: number
+ /** Pool stealing worker nodes. */
+ readonly stealingWorkerNodes?: 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 backPressure?: boolean
+ readonly stolenTasks?: 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 node tasks queue options.
+ */
+export interface TasksQueueOptions {
+ /**
+ * Maximum tasks queue size per worker node flagging it as back pressured.
+ *
+ * @defaultValue (pool maximum size)^2
+ */
+ readonly size?: number
+ /**
+ * Maximum number of tasks that can be executed concurrently on a worker node.
+ *
+ * @defaultValue 1
+ */
+ readonly concurrency?: number
+ /**
+ * Whether to enable task stealing on idle.
+ *
+ * @defaultValue true
+ */
+ readonly taskStealing?: boolean
+ /**
+ * Whether to enable tasks stealing under back pressure.
+ *
+ * @defaultValue false
+ */
+ readonly tasksStealingOnBackPressure?: boolean
+ /**
+ * Queued tasks finished timeout in milliseconds at worker node termination.
+ *
+ * @defaultValue 2000
+ */
+ readonly tasksFinishedTimeout?: number
+}
+
+/**
+ * Options for a poolifier pool.
+ *
+ * @typeParam Worker - Type of worker.
+ */
+export interface PoolOptions<Worker extends IWorker> {
+ /**
+ * A function that will listen for online event on each worker.
+ *
+ * @defaultValue `() => {}`
+ */
+ onlineHandler?: OnlineHandler<Worker>
+ /**
+ * A function that will listen for message event on each worker.
+ *
+ * @defaultValue `() => {}`
+ */
+ messageHandler?: MessageHandler<Worker>
+ /**
+ * A function that will listen for error event on each worker.
+ *
+ * @defaultValue `() => {}`
+ */
+ errorHandler?: ErrorHandler<Worker>
+ /**
+ * A function that will listen for exit event on each worker.
+ *
+ * @defaultValue `() => {}`
+ */
+ exitHandler?: ExitHandler<Worker>
+ /**
+ * Whether to start the minimum number of workers at pool initialization.
+ *
+ * @defaultValue true
+ */
+ startWorkers?: boolean
+ /**
+ * The default 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 integrated with async resource emission.
+ *
+ * @defaultValue true
+ */
+ enableEvents?: boolean
+ /**
+ * Pool worker node tasks queue.
+ *
+ * @defaultValue false
+ */
+ enableTasksQueue?: boolean
+ /**
+ * Pool worker node tasks queue options.
+ */
+ tasksQueueOptions?: TasksQueueOptions
+ /**
+ * Worker options.
+ *
+ * @see https://nodejs.org/api/worker_threads.html#new-workerfilename-options
+ */
+ workerOptions?: WorkerOptions
+ /**
+ * Key/value pairs to add to worker process environment.
+ *
+ * @see https://nodejs.org/api/cluster.html#cluster_cluster_fork_env
+ */
+ env?: Record<string, unknown>
+ /**
+ * Cluster settings.
+ *
+ * @see https://nodejs.org/api/cluster.html#cluster_cluster_settings
+ */
+ settings?: ClusterSettings
+}