node-state-machine/src/model/Transition.js

State machine for NodeJS.

// @flow

/**
 *  Class representing a transition that has a certain trigger (function) and a
 *  destination node (string). It also has a list of middlewares which can be
 *  executed when the transition is executed.
 *  @author Jensen Bernard
 */
class Transition {

  _checker: (v: string) => boolean;
  _destination: string;
  _middlewares: Array<(v: string) => void>;

  /**
   *  Creates a new instance of a transition with the given checker/trigger,
   *  destination node and list of middlewares.
   *  @param  checker {string} The trigger of the transition.
   *  @param  destination {string} The destination of the transition.
   *  @param  middlewares {array} The middlewares executed.
   */
  constructor(checker: (v: string) => boolean,
              destination: string,
              middlewares: Array<(v: string) => void> = []) {
    this._checker = checker;
    this._destination = destination;
    this._middlewares = [];
    for(var middleware of middlewares)
      this._middlewares.push(middleware);
  }

  /**
   *  Checks whether or not the transition has middleswares. Returns true if
   *  and only if this._middlewares.length > 0.
   *  @return {boolean} Whether or not the transition has middlewares.
   */
  hasMiddlewares(): boolean { return this._middlewares.length > 0; }

  /**
   *  Returns the list of middlewares of the current transition. This list will
   *  be the same one that is passed as an argument in the constructor.
   *  @return {array} List of middlewares.
   */
  middlewares(): Array<(v: string) => void> { return this._middlewares; }

  /**
   *  Checks whether or not the current transition fires based on the checker/
   *  trigger that is provided when this transition was created.
   *  @return {boolean} Whether or not this transition should fire.
   */
  fires(v: string): boolean { return this._checker(v); }

  /**
   *  Returns the destination of the current transition. This is the one that
   *  is provided as an argument when this transition is created.
   *  @return {string} The destination state of this transition.
   */
  destination(): string { return this._destination; }

  /**
   *  Returns a string representation of this transition.
   *  @return {string} A string representation of this transition.
   */
  toString(): string {
    return `(f() > ${this._destination} (${this._middlewares.length}M))`;
  }

}

module.exports.Transition = Transition;