cksource/mgit2

/**
 * @license Copyright (c) 2003-2024, CKSource Holding sp. z o.o. All rights reserved.
 * For licensing, see LICENSE.md.
 */

'use strict';

const childProcess = require( 'child_process' );
const genericPool = require( 'generic-pool' );

/**
 * @param {String} childPath Path to module that will be forked.
 * @returns {Object} response
 * @returns {Boolean} response.isDone
 * @returns {Function} response.enqueue
 * @returns {Promise} response.killAll
 */
module.exports = function createForkPool( childPath ) {
    const forkPoolFactory = {
        create() {
            return new Promise( resolve => {
                resolve( childProcess.fork( childPath ) );
            } );
        },

        destroy( child ) {
            child.kill();
        }
    };

    const pool = genericPool.createPool( forkPoolFactory, {
        max: 4,
        min: 2
    } );

    return {
        get isDone() {
            return !pool.pending && !pool.borrowed;
        },

        enqueue( data ) {
            return new Promise( ( resolve, reject ) => {
                pool.acquire()
                    .then( child => {
                        child.once( 'message', returnedData => {
                            pool.release( child );

                            resolve( returnedData );
                        } );

                        child.send( data );
                    } )
                    .catch( reject );
            } );
        },

        killAll() {
            return pool.drain()
                .then( () => {
                    pool.clear();
                } );
        }
    };
};