dynamoose/lib/Plugin.js

Dynamoose is a modeling tool for Amazon's DynamoDB (inspired by Mongoose)

const debug = require('debug')('dynamoose:plugin');
const Listener = require('./Listener');

function Plugin(model, func, options, registerPlugin) {
  this.name = '';
  this.description = '';
  this.listeners = [];
  this._model = model;
  this.registerPlugin = registerPlugin;

  func({
    setName: (name) => {
      this.name = name;
      debug(`Set plugin name to ${name}`);
    },
    setDescription: (description) => {
      this.description = description;
      debug(`Set description to ${description}`);
    },

    // Ability for plugin to add listeners on certain events emmited from Dynamoose
    on: (type, stage, func) => {
      // If type is not passed in then set func to type, and stage to null, and type to null, this will make type an optional catch all parameter
      if (typeof type === 'function') {
        func = type;
        type = null;
        stage = null;
      }
      // If stage is not passed in then set func to stage, and stage to null, this will make stage an optional parameter
      else if (typeof stage === 'function') {
        func = stage;
        stage = null;
      }

      if (type === '*') {
        type = null;
      }
      if (stage === '*') {
        stage = null;
      }

      this.listeners.push(new Listener(type, stage, func, this));
    }
  }, options);
  this.emit('plugin', 'init');
}

Plugin.prototype.emit = async function (type, stage, obj) {
  debug('Received emit');
  debug(`Type: ${type}`);
  debug(`Stage: ${stage}`);
  debug('Filtering listeners that match type and stage');
  const listenersToRun = this.listeners.filter((listener) => {
    // filter listeners where type is the same and stage is null or the same
    return ((!listener.type || listener.type === type) && (!listener.stage || listener.stage === stage));
  });

  // If obj is undefined set to empty object
  if (!obj) {
    obj = {};
  }
  // If obj.actions is undefined set to empty object
  if (!obj.actions) {
    obj.actions = {};
  }

  // Map actions.registerPlugin to Model.plugin function
  obj.actions.registerPlugin = this.registerPlugin;

  // Adding Model specific things to object
  obj.model = this._model;
  obj.modelName = this._model.$__.name;
  obj.plugins = this._model.$__.plugins;

  obj.plugin = this;
  for (let i = 0; i < listenersToRun.length; i++) {
    const listener = listenersToRun[i];
    const result = await listener.emit(type, stage, obj);
    if (result && (result.resolve || result.reject)) {
      return result;
    }
  }
};

module.exports = Plugin;