nope/lib/communication/bridge.ts

/**
 * @author Martin Karkowski
 * @email m.karkowski@zema.de
 * @create date 2020-11-06 08:52:36
 * @modify date 2021-03-24 07:58:29
 * @desc [description]
 */

import { EventEmitter } from "events";
import * as Logger from "js-logger";
import { ILogger } from "js-logger";
import { generateId } from "../helpers/idMethods";
import { copy } from "../helpers/objectMethods";
import { getNopeLogger } from "../logger/getLogger";
import { LoggerLevel } from "../logger/nopeLogger";
import { NopeObservable } from "../observables/nopeObservable";
import {
  ICommunicationBridge,
  ICommunicationInterface,
  ICommunicationMirror,
  IEmitter,
  ValidEventTypesOfMirror
} from "../types/nope/nopeCommunication.interface";
import { INopeObservable } from "../types/nope/nopeObservable.interface";

const EMITTING_METHODS: Array<keyof ICommunicationInterface> = [
  "emitAurevoir",
  "emitBonjour",
  "emitNewInstanceGeneratorsAvailable",
  "emitNewInstancesAvailable",
  "emitNewObersvablesAvailable",
  "emitNewServicesAvailable",
  "emitStatusUpdate",
  "emitTaskCancelation"
];

const EMITTING_SPECIFIC_METHODS: Array<keyof ICommunicationInterface> = [
  "emitEvent",
  "emitRpcRequest",
  "emitRpcResponse"
];

const ON_METHODS: Array<keyof ICommunicationInterface> = [
  "onAurevoir",
  "onBonjour",
  "onNewInstanceGeneratorsAvailable",
  "onNewInstancesAvailable",
  "onNewObservablesAvailable",
  "onNewServicesAvailable",
  "onStatusUpdate",
  "onTaskCancelation"
];

const ON_SPECIFIC_METHODS: Array<keyof ICommunicationInterface> = [
  "onEvent",
  "onRpcRequest",
  "onRpcResponse"
];

const UNSPECIFIC_TO_METHODS: {
  [index: string]: {
    emit: keyof ICommunicationInterface;
    subscribe: keyof ICommunicationInterface;
  };
} = {
  Aurevoir: {
    emit: "emitAurevoir",
    subscribe: "onAurevoir"
  },
  Bonjour: {
    emit: "emitBonjour",
    subscribe: "onBonjour"
  },
  NewInstancesAvailable: {
    emit: "emitNewInstancesAvailable",
    subscribe: "onNewInstancesAvailable"
  },
  NewInstanceGeneratorsAvailable: {
    emit: "emitNewInstanceGeneratorsAvailable",
    subscribe: "onNewInstanceGeneratorsAvailable"
  },
  NewObersvablesAvailable: {
    emit: "emitNewObersvablesAvailable",
    subscribe: "onNewObservablesAvailable"
  },
  NewServicesAvailable: {
    emit: "emitNewServicesAvailable",
    subscribe: "onNewServicesAvailable"
  },
  StatusUpdate: {
    emit: "emitStatusUpdate",
    subscribe: "onStatusUpdate"
  },
  TaskCancelation: {
    emit: "emitTaskCancelation",
    subscribe: "onTaskCancelation"
  }
};

const LAYER_METHOD_TO_EVENT: {
  [P in keyof ICommunicationInterface]: string;
} = {
  // Specific:
  onEvent: "event/",
  emitEvent: "event/",
  onRpcRequest: "",
  emitRpcRequest: "",
  onRpcResponse: "",
  emitRpcResponse: ""
};

for (const eventName in UNSPECIFIC_TO_METHODS) {
  const data = UNSPECIFIC_TO_METHODS[eventName];
  LAYER_METHOD_TO_EVENT[data.emit as any] = eventName;
  LAYER_METHOD_TO_EVENT[data.subscribe as any] = eventName;
}

// Define additionally a Mapping between the Events

const MIRROR_METHOD_TO_EVENT: {
  [P in keyof ICommunicationInterface]: ValidEventTypesOfMirror;
} = copy(LAYER_METHOD_TO_EVENT) as any;

MIRROR_METHOD_TO_EVENT.onEvent = "Event";
MIRROR_METHOD_TO_EVENT.emitEvent = "Event";
MIRROR_METHOD_TO_EVENT.onRpcRequest = "RpcRequest";
MIRROR_METHOD_TO_EVENT.emitRpcRequest = "RpcRequest";
MIRROR_METHOD_TO_EVENT.onRpcResponse = "RpcResponse";
MIRROR_METHOD_TO_EVENT.emitRpcResponse = "RpcResponse";

const MIRROR_EVENT_TO_EMIT: {
  [P in keyof ValidEventTypesOfMirror]: keyof ICommunicationInterface;
} = {} as any;

// Define all Events, that must be considered in a mirror.
Object.getOwnPropertyNames(MIRROR_METHOD_TO_EVENT).map((method) => {
  if (method.startsWith("emit")) {
    MIRROR_EVENT_TO_EMIT[
      MIRROR_METHOD_TO_EVENT[method]
    ] = method as keyof ICommunicationInterface;
  }
});

const OFF_METHODS: Array<keyof ICommunicationInterface> = [
  "offEvent",
  "offRpcRequest",
  "offRpcResponse"
];

//@ts-ignore Ignore the Interface. Its implemented manually
export class Bridge implements ICommunicationBridge {
  public connected: INopeObservable<boolean>;

  public considerConnection = true;
  public allowServiceRedundancy = false;
  public ownDispatcherId: string;
  public id: string;

  protected _logger: ILogger;
  protected _internalEmitter: EventEmitter;
  protected _layers: Map<
    string,
    {
      layer: ICommunicationInterface;
      considerConnection: boolean;
      forwardData: boolean;
    }
  >;

  protected _mirrors: Map<
    ICommunicationMirror,
    { considerConnection: boolean }
  >;

  protected _callbacks: Map<
    string, // Method
    Array<(...args) => any>
  >;

  protected _specificCallbacks: Array<{
    callback: (...args) => any;
    method: keyof ICommunicationInterface;
    event: string;
  }>;

  /**
   * Creates an instance of Bridge.
   * @param {*} [id=generateId()] The ID. (this can be adapted later and is only used to simplify debugging)
   * @param {string} [loggerName="bridge"] The Name of the Logger.
   * @param {LoggerLevel} [level="info"] The Level of the Logger.
   * @memberof Bridge
   */
  constructor(
    id = generateId(),
    loggerName = "bridge",
    level: LoggerLevel = "info"
  ) {
    this._internalEmitter = new EventEmitter();
    this._callbacks = new Map();
    this._specificCallbacks = [];
    this._layers = new Map();
    this._mirrors = new Map();
    this._logger = getNopeLogger(loggerName, level);
    this.id = id;

    const _this = this;

    // Now we use the loops to define the functions,
    // required by the interface.
    for (const method of ON_METHODS) {
      this[method] = async (cb) => {
        _this._on(method, cb);
      };
    }
    for (const method of ON_SPECIFIC_METHODS) {
      this[method] = async (event: string, cb) => {
        _this._onSpecific(method, event, cb);
      };
    }
    for (const method of OFF_METHODS) {
      this[method] = async (event: string, cb) => {
        _this._off(cb);
      };
    }
    for (const method of EMITTING_METHODS) {
      const eventName = LAYER_METHOD_TO_EVENT[method];
      this[method] = async (data) => {
        _this._emit(eventName, null, data);
      };
    }
    for (const method of EMITTING_SPECIFIC_METHODS) {
      this[method] = async (event: string, data) => {
        _this._emitSpecific(method, null, event, data);
      };
    }

    this.connected = new NopeObservable();
    this.connected.setContent(false);

    // Add a custom handler for the connect flag.
    // the Flag is defined as true, if every socket
    // is connected.
    this.connected.getter = () => {
      for (const data of _this._layers.values()) {
        if (data.considerConnection && !data.layer.connected.getContent()) {
          return false;
        }
      }
      for (const [mirror, { considerConnection }] of _this._mirrors.entries()) {
        if (considerConnection && !mirror.connected.getContent()) {
          return false;
        }
      }
      return true;
    };
  }

  /**
   * Helper Function, which will internally subscribe to the Events of the Layer.
   *
   * @protected
   * @param {ICommunicationInterface} layer The Layer to consinder, on this layer, we will subscribe to the events
   * @param {keyof ICommunicationInterface} method The method used for subscription
   * @param {string} event The name of the Event
   * @param {boolean} forwardData Flag, showing whether data will be forwarded or not.
   * @memberof BridgeV2
   */
  protected _subscribeToCallback(
    layer: ICommunicationInterface,
    method: keyof ICommunicationInterface,
    event: string,
    forwardData: boolean
  ): void {
    const _this = this;

    if (ON_SPECIFIC_METHODS.includes(method)) {
      layer[method as any](event, (data) => {
        // Define the Method to Forward data.
        _this._internalEmitter.emit(event, data);

        // Now we are able to iterate over the Methods and forward the content
        // but only if the Layer forwards the content
        if (forwardData) {
          _this._emitSpecific(method, layer, event, data);
        }
      }).catch((error) => {
        _this._logger.error("failed subscribing", method);
        _this._logger.error(error);
      });
    } else {
      // Subscribe to the Event.
      layer[method as any]((data) => {
        // Define the Method to Forward data.
        _this._internalEmitter.emit(LAYER_METHOD_TO_EVENT[method], data);

        // Now we are able to iterate over the Methods and forward the content
        // but only if the Layer forwards the content
        if (forwardData) {
          _this._emit(method, layer, data);
        }
      }).catch((error) => {
        _this._logger.error("failed subscribing", method);
        _this._logger.error(error);
      });
    }
  }

  protected _on(method: keyof ICommunicationInterface, cb): void {
    // Determine the Corresponding Event, that should be used
    // to subescribe to.
    const event = LAYER_METHOD_TO_EVENT[method];

    // Subscribe on the Event
    this._internalEmitter.setMaxListeners(
      this._internalEmitter.getMaxListeners() + 1
    );

    if (this._logger.enabledFor(Logger.DEBUG) && event !== "StatusUpdate") {
      this._logger.debug("subscribe to", event);

      // If logging is enable, we subscribe to that.
      const _this = this;
      this._internalEmitter.on(event, (data) => {
        _this._logger.debug("received", event, data);
      });
    }
    this._internalEmitter.on(event, cb);

    // Store the Unspecific callbacks
    if (!this._callbacks.has(method)) {
      this._callbacks.set(method, [cb]);
    } else {
      this._callbacks.get(method).push(cb);
    }

    // Iterate over the Layers and on the connected Layers,
    // subscribe the methods.
    for (const data of this._layers.values()) {
      if (data.layer.connected.getContent()) {
        this._subscribeToCallback(data.layer, method, event, data.forwardData);
      }
    }
  }

  protected _onSpecific(
    method: keyof ICommunicationInterface,
    event: string,
    callback
  ): void {
    // Determine the event that we are using internally.
    // It is a mix between the method alias channel and
    // the event.
    const eventToUse = LAYER_METHOD_TO_EVENT[method] + event;

    // Subscribe on the Event
    this._internalEmitter.setMaxListeners(
      this._internalEmitter.getMaxListeners() + 1
    );

    if (this._logger.enabledFor(Logger.DEBUG) && event !== "StatusUpdate") {
      this._logger.debug("subscribe ", method, "specifically on", eventToUse);

      const _this = this;
      this._internalEmitter.on(eventToUse, (data) => {
        _this._logger.debug("received", event, data);
      });
    }
    this._internalEmitter.on(eventToUse, callback);

    // Add the callbacks.
    this._specificCallbacks.push({
      callback,
      method,
      event
    });

    // Iterate over the Layers and on the connected Layers,
    // subscribe the methods.
    for (const data of this._layers.values()) {
      if (data.layer.connected.getContent()) {
        this._subscribeToCallback(data.layer, method, event, data.forwardData);
      }
    }
  }

  protected _off(cb): void {
    // Determine the event that we are using internally.
    // It is a mix between the method alias channel and
    // the event.

    for (let i = 0; i < this._specificCallbacks.length; i++) {
      if (this._specificCallbacks[i].callback == cb) {
        this._specificCallbacks.splice(i, 1);
        break;
      }
    }

    // Theoretically we must remove the subscriptions.
    // But we wont do this, because if the connection has
    // been lost, or the Layer has been removed, the stored
    // callbacks wont be called any more.
  }

  protected _emit(
    eventName: string,
    toExclude: ICommunicationInterface | ICommunicationMirror = null,
    dataToSend: any
  ): void {
    if (this._logger.enabledFor(Logger.WARN) && eventName !== "StatusUpdate") {
      this._logger.debug("emitting", eventName, dataToSend);
    }
    // Emit the Event on the internal Layer.
    this._internalEmitter.emit(eventName, dataToSend);

    const _this = this;
    const _method = UNSPECIFIC_TO_METHODS[eventName].emit;

    // Iterate over the Layers.
    for (const data of this._layers.values()) {
      // If the Layer has been conneced
      if (data.layer !== toExclude && data.layer.connected.getContent()) {
        // Only Publish the Data, on which we are forwarding
        data.layer[_method as any](dataToSend).catch((error) => {
          _this._logger.error("failed executing", _method);
          _this._logger.error(error);
        });
      }
    }

    for (const mirror of this._mirrors.keys()) {
      if (mirror != toExclude && mirror.connected.getContent()) {
        mirror.emit(eventName, dataToSend);
      }
    }
  }

  protected _emitSpecific(
    method: keyof ICommunicationInterface,
    toExclude: ICommunicationInterface | ICommunicationMirror = null,
    event: string,
    dataToSend: any
  ): void {
    if (this._logger.enabledFor(Logger.DEBUG) && event !== "StatusUpdate") {
      this._logger.debug(
        "emitting",
        LAYER_METHOD_TO_EVENT[method] + event,
        dataToSend
      );
    }

    // Emit the Event on the internal Layer.
    this._internalEmitter.emit(
      LAYER_METHOD_TO_EVENT[method] + event,
      dataToSend
    );

    const _this = this;

    // Iterate over the Layers.
    for (const data of this._layers.values()) {
      // If the Layer has been conneced
      if (data.layer !== toExclude && data.layer.connected.getContent()) {
        data.layer[method as any](event, dataToSend).catch((error) => {
          _this._logger.error("failed executing", method);
          _this._logger.error(error);
        });
      }
    }

    for (const mirror of this._mirrors.keys()) {
      if (mirror != toExclude && mirror.connected.getContent()) {
        mirror.emit(MIRROR_METHOD_TO_EVENT[method], {
          name: event,
          data: dataToSend
        });
      }
    }
  }

  public async addLayer(
    layer: ICommunicationInterface,
    forwardData = false,
    considerConnection = false
  ): Promise<void> {
    if (!this._layers.has(layer.id)) {
      // Store the Layers:
      this._layers.set(layer.id, {
        layer,
        considerConnection,
        forwardData
      });

      // Forward the Events of the Layer
      // being connected to our aggregated
      // state
      const _this = this;
      layer.connected.subscribe(() => {
        _this.connected.forcePublish();
      });

      // Wait until the Layer is connected.
      await layer.connected.waitFor((value) => value);

      // Register all know unspecific methods
      for (const [method, cbs] of this._callbacks.entries()) {
        for (const callback of cbs) {
          layer[method as any](callback);
        }
      }

      // Register all know specific methods
      for (const { method, event, callback } of this._specificCallbacks) {
        layer[method as any](event, callback);
      }
    }
  }

  public async removeLayer(layer: ICommunicationInterface): Promise<void> {
    if (this._layers.has(layer.id)) {
      this._layers.delete(layer.id);
    }
  }

  /**
   * Adds a Mirror to the System.
   *
   * @param {IEmitter} mirror the Mirror to use.
   * @return {*}  {Promise<void>}
   * @memberof Bridge
   */
  public addMirror(
    mirror: ICommunicationMirror,
    considerConnection = true
  ): void {
    if (!this._mirrors.has(mirror)) {
      // Add the Mirror
      this._mirrors.set(mirror, {
        considerConnection
      });

      const _this = this;

      // Subscribe for the Connected Flag.
      if (considerConnection) {
        // We just forward the Signal
        mirror.connected.subscribe(() => _this.connected.forcePublish());
      }

      // Now we wait until the connection has been established first time,
      // then, we will add our subscriptions.
      mirror.connected
        .waitFor((value) => value)
        .then(() => {
          for (const eventName of ValidEventTypesOfMirror) {
            if (UNSPECIFIC_TO_METHODS[eventName]) {
              mirror.on(eventName as ValidEventTypesOfMirror, (data) => {
                // Unless it is a Status-Update, we will log it.
                if (
                  _this._logger.enabledFor(Logger.DEBUG) &&
                  eventName !== "StatusUpdate"
                ) {
                  _this._logger.debug(
                    "received data from mirror on",
                    eventName,
                    ". Forwarding event to",
                    UNSPECIFIC_TO_METHODS[eventName].emit
                  );
                }
                // Now Forward the Data.
                _this._emit(eventName, mirror, data);
              });
            } else {
              mirror.on(eventName as ValidEventTypesOfMirror, (data) => {
                // If logging is enabled => Forward this information
                if (
                  _this._logger.enabledFor(Logger.DEBUG) &&
                  eventName !== "StatusUpdate"
                ) {
                  _this._logger.debug(
                    "received data from mirror on",
                    eventName,
                    data.name
                  );
                }

                // Now emit the data on the channel
                _this._emitSpecific(
                  MIRROR_EVENT_TO_EMIT[eventName],
                  mirror,
                  data.name,
                  data.data
                );
              });
            }
          }
        });
    }
  }

  /**
   * Removes a Mirror, from the system.
   *
   * @param {ICommunicationMirror} mirror
   * @return {*}  {boolean}
   * @memberof Bridge
   */
  public removeMirror(mirror: ICommunicationMirror): boolean {
    return this._mirrors.delete(mirror);
  }
}