sphinxql/src/Queue.ts

SphinxQL query builder for Node.JS. Supports Sphinx search(2.x and 3.x) and Manticore search

import * as yallist from 'yallist';
import BaseStatement from './Statements/BaseStatement';
import ClientInterface from './ClientInterface';

/**
 * Simple queue using doubly linked lists using yallist package.
 * It has the minimal methods to make this work.
 * 
 * As Manticore Search and Sphinx documentation said there is only
 * support for the following statements used in a batch:
 * - SELECT
 * - SHOW WARNINGS
 * - SHOW STATUS
 * - SHOW META
 * 
 * For more information, read the Manticore documentation regarded this topic
 * https://docs.manticoresearch.com/latest/html/sphinxql_reference/multi-statement_queries.html
 */
export default class Queue {
  protected list = yallist.create([]);
  
  constructor(protected connection: ClientInterface) {}

  /**
   *Adds to the queue an statement.
   *
   * @param {BaseStatement} statement
   * @memberof Queue
   */
  public push(statement: BaseStatement): Queue {
    this.list.push(statement);

    return this;
  }

  /**
   * Removes the statement in the head of the queue.
   *
   * @returns {BaseStatement}
   * @memberof Queue
   */
  public shift(): BaseStatement {
    return this.list.shift();
  }

  /**
   * Returns the number of queries in the queue.
   *
   * @returns {number}
   * @memberof Queue
   */
  public size(): number {
    return this.list.length;
  }

  /**
   * Checks if the queue is empty.
   *
   * @returns {boolean}
   * @memberof Queue
   */
  public empty(): boolean {
    return this.size() === 0;
  }

  /**
   * Joins the queries in the queue using a semicolon (;).
   * Using semicolon allows to separate queries.
   *
   * @returns {string}
   * @memberof Queue
   */
  public joinQueries(): string {
    const sqlStrings: string[] = this.list.toArray().map((query: BaseStatement) => query.generate());
    
    return sqlStrings.join(';');
  }

  /**
   * Processes the queue and returns a promise with the result sets.
   * In case of the queue is empty it throws a Error instance with a message
   * that describes perfectly the error.
   *
   * @returns {Promise<any>}
   * @memberof Queue
   */
  public process(): Promise<any> {
    if (!this.list.length) {
      return Promise.reject(new Error('Empty list can not be joined'));
    }
    const sql: string = this.joinQueries();
    
    return this.connection.query(sql);
  }
}