typedrequest/ts/typedrequest.classes.virtualstream.ts

import * as plugins from './plugins.js';
import type { TypedRouter } from './typedrequest.classes.typedrouter.js';

export interface ICommFunctions {
  sendMethod?: (
    sendPayload: plugins.typedRequestInterfaces.IStreamRequest
  ) => Promise<plugins.typedRequestInterfaces.IStreamRequest>;
  typedrouter?: TypedRouter;
}

/**
 * 1. A VirtualStream connects over the network
 * 2. It is always paired to one other VirtualStream
 *    on the other side with the same streamId.
 * 3. It has a Readable and Writable side.
 * 4. The Writable side is Readable on the other side and vice versa.
 */
export class VirtualStream<T = ArrayBufferLike> implements plugins.typedRequestInterfaces.IVirtualStream<T> {
  // STATIC
  public static encodePayloadForNetwork(
    objectPayload: any,
    commFunctions: ICommFunctions,
    originalPayload?: any,
    path = []
  ): any {
    if (plugins.smartbuffer.isBufferLike(objectPayload)) {
      return objectPayload;
    }
    if (objectPayload instanceof VirtualStream) {
      if (!objectPayload.side && commFunctions.sendMethod) {
        objectPayload.side = 'requesting';
        objectPayload.sendMethod = commFunctions.sendMethod;
      }
      if (!objectPayload.side && commFunctions.typedrouter) {
        objectPayload.side = 'responding';
        objectPayload.typedrouter = commFunctions.typedrouter;
        commFunctions.typedrouter.registeredVirtualStreams.add(objectPayload);
      }
      if (!originalPayload.response || path.includes('response')) {
        objectPayload.startKeepAliveLoop();
        return {
          _isVirtualStream: true,
          streamId: objectPayload.streamId,
        };
      } else {
        return {
          _OBMITTED_VIRTUAL_STREAM: true,
          reason: 'path is under .request: obmitted for deduplication reasons in response cycle.',
        };
      }
    } else if (Array.isArray(objectPayload)) {
      const returnArray = [];
      for (const item of objectPayload) {
        returnArray.push(
          VirtualStream.encodePayloadForNetwork(
            item,
            commFunctions,
            originalPayload || objectPayload,
            path
          )
        );
      }
      return returnArray;
    } else if (objectPayload !== null && typeof objectPayload === 'object') {
      return Object.keys(objectPayload).reduce((acc, key) => {
        path.push(key);
        acc[key] = VirtualStream.encodePayloadForNetwork(
          objectPayload[key],
          commFunctions,
          originalPayload || objectPayload,
          path
        );
        return acc;
      }, {});
    } else {
      return objectPayload;
    }
  }

  public static decodePayloadFromNetwork(objectPayload: any, commFunctions: ICommFunctions): any {
    if (plugins.smartbuffer.isBufferLike(objectPayload)) {
      return objectPayload;
    }
    if (objectPayload !== null && typeof objectPayload === 'object') {
      if (objectPayload._isVirtualStream) {
        const virtualStream = new VirtualStream();
        virtualStream.streamId = objectPayload.streamId;
        if (!virtualStream.side && commFunctions.sendMethod) {
          virtualStream.side = 'requesting';
          virtualStream.sendMethod = commFunctions.sendMethod;
        }
        if (!virtualStream.side && commFunctions.typedrouter) {
          virtualStream.side = 'responding';
          virtualStream.typedrouter = commFunctions.typedrouter;
          commFunctions.typedrouter.registeredVirtualStreams.add(virtualStream);
        }
        virtualStream.startKeepAliveLoop();
        return virtualStream;
      } else if (Array.isArray(objectPayload)) {
        const returnArray = [];
        for (const item of objectPayload) {
          returnArray.push(VirtualStream.decodePayloadFromNetwork(item, commFunctions));
        }
        return returnArray;
      } else {
        return Object.keys(objectPayload).reduce((acc, key) => {
          acc[key] = VirtualStream.decodePayloadFromNetwork(objectPayload[key], commFunctions);
          return acc;
        }, {});
      }
    } else {
      return objectPayload;
    }
  }

  // INSTANCE

  public side: 'requesting' | 'responding';
  public streamId: string = plugins.isounique.uni();

  // integration with typedrequest mechanics
  public sendMethod: ICommFunctions['sendMethod'];
  public typedrouter: TypedRouter;

  // wether to keep the stream alive
  private keepAlive = true;
  private lastKeepAliveEvent: number;

  // backpressured arrays
  private sendBackpressuredArray =
    new plugins.lik.BackpressuredArray<T>(
      16
    );
  private receiveBackpressuredArray =
    new plugins.lik.BackpressuredArray<T>(
      16
    );

  constructor() {}

  /**
   * takes care of sending 
   */
  private async workOnQueue() {
    if(this.side === 'requesting') {
      let thisSideIsBackpressured = !this.receiveBackpressuredArray.checkSpaceAvailable();
      let otherSideHasNext = false;
      let otherSideIsBackpressured = false;
      
      // helper functions
      const getFeedback = async () => {
        const streamTr = await this.sendMethod({
          method: '##VirtualStream##',
          request: {
            streamId: this.streamId,
            cycleId: plugins.isounique.uni(),
            cycle: 'request',
            mainPurpose: 'feedback',
            next: this.sendBackpressuredArray.data.length > 0,
            backpressure: this.receiveBackpressuredArray.checkSpaceAvailable(),
          },
          response: null,
        }).catch(() => {
          console.log('stream ended immaturely');
          this.keepAlive = false;
        });
        if (streamTr && streamTr.response) {
          otherSideIsBackpressured = streamTr.response.backpressure
          otherSideHasNext = streamTr.response.next;
        }
      }
      await getFeedback();

      // do work loop
      while (this.sendBackpressuredArray.data.length > 0 || otherSideHasNext) {
        let dataArg: typeof this.sendBackpressuredArray.data[0];
        if (this.sendBackpressuredArray.data.length > 0) {
          dataArg = this.sendBackpressuredArray.shift();
        }
        let streamTr: plugins.typedRequestInterfaces.IStreamRequest;
        streamTr = await this.sendMethod({
          method: '##VirtualStream##',
          request: {
            streamId: this.streamId,
            cycleId: plugins.isounique.uni(),
            cycle: 'request',
            mainPurpose: dataArg ? 'chunk' : 'read',
            backpressure: thisSideIsBackpressured,
            next: this.sendBackpressuredArray.data.length > 0,
            ...dataArg ? { chunkData: dataArg } : {},
          },
          response: null,
        }).catch(() => {
          console.log('stream ended immaturely');
          this.keepAlive = false;
          return null;
        });

        if (streamTr && streamTr.response && streamTr.response.chunkData) {
          this.receiveBackpressuredArray.push(streamTr.response.chunkData);
        }
        thisSideIsBackpressured = this.receiveBackpressuredArray.checkSpaceAvailable();

        // lets care about looping
        otherSideHasNext = streamTr && streamTr.response && streamTr.response.next;
      }

    }
  }

  /**
   * This method handles the stream only on the responding side
   * @param streamTrArg
   * @returns
   */
  public async handleStreamTr(streamTrArg: plugins.typedRequestInterfaces.IStreamRequest) {
    if (streamTrArg.request.keepAlive === true && this.keepAlive === true) {
      this.lastKeepAliveEvent = Date.now();
    } else if (streamTrArg.request.keepAlive === false) {
      this.keepAlive = false;
    }

    // keepAlive handling
    if (streamTrArg.request.mainPurpose === 'keepAlive') {
      // if the main purpose is keepAlive, we answer with a keepAlive
      streamTrArg.response = {
        streamId: this.streamId,
        cycleId: streamTrArg.request.cycleId,
        cycle: 'response',
        mainPurpose: 'keepAlive',
        keepAlive: this.keepAlive,
        next: this.sendBackpressuredArray.data.length > 0,
        backpressure: this.receiveBackpressuredArray.checkSpaceAvailable(),
      };
    }

    // feedback handling
    if (streamTrArg.request.mainPurpose === 'feedback') {
      streamTrArg.response = {
        streamId: this.streamId,
        cycleId: streamTrArg.request.cycleId,
        cycle: 'response',
        mainPurpose: 'feedback',
        next: this.sendBackpressuredArray.data.length > 0,
        backpressure: this.receiveBackpressuredArray.checkSpaceAvailable(),
      };
    }

    // chunk handling
    if (streamTrArg.request.mainPurpose === 'chunk') {
      this.receiveBackpressuredArray.push(streamTrArg.request.chunkData);
      if (this.sendBackpressuredArray.data.length > 0 && streamTrArg.response.backpressure === false) {
        const dataArg = this.sendBackpressuredArray.shift();
        streamTrArg.response = {
          streamId: this.streamId,
          cycleId: streamTrArg.request.cycleId,
          cycle: 'response',
          mainPurpose: 'chunk',
          next: this.sendBackpressuredArray.data.length > 1,
          backpressure: this.receiveBackpressuredArray.checkSpaceAvailable(),
          chunkData: this.sendBackpressuredArray.shift(),
        };
      } else {
        streamTrArg.response = {
          streamId: this.streamId,
          cycleId: streamTrArg.request.cycleId,
          cycle: 'response',
          mainPurpose: 'feedback',
          next: this.sendBackpressuredArray.data.length > 0,
        };
      }
      streamTrArg.request = null;
    }

    return streamTrArg;
  }

  // lifecycle methods
  /**
   * closes the virtual stream
   */
  public async cleanup() {
    if (this.typedrouter) {
      this.typedrouter.registeredVirtualStreams.remove(this);
    }
  }

  /**
   * a keepAlive loop that works across technologies
   */
  private async startKeepAliveLoop() {
    // initially wait for a second
    await plugins.smartdelay.delayFor(0);
    let counter = 0;
    keepAliveLoop: while (this.keepAlive) {
      const triggerResult = await this.triggerKeepAlive();
      await plugins.smartdelay.delayFor(1000);
    }
    await plugins.smartdelay.delayFor(1000);
    await this.cleanup();
    console.log(`cleaned up for stream ${this.streamId}`);
  }

  private async triggerKeepAlive() {
    if (this.side === 'requesting') {
      console.log(`keepalive sent.`);
      const streamTr = await this.sendMethod({
        method: '##VirtualStream##',
        request: {
          streamId: this.streamId,
          cycleId: plugins.isounique.uni(),
          cycle: 'request',
          mainPurpose: 'keepAlive',
          keepAlive: true,
        },
        response: null,
      }).catch(() => {
        this.keepAlive = false;
      });

      // lets handle keepAlive
      if (streamTr && streamTr.response && streamTr.response.keepAlive === false) {
        this.keepAlive = false;
      } else {
        this.lastKeepAliveEvent = Date.now();
      }
      if (streamTr && streamTr.response && streamTr.response.next) {
        this.workOnQueue();
      }
    }
    if (Date.now() - this.lastKeepAliveEvent > 10000) {
      console.log(`closing stream for ${this.streamId}`);
      this.keepAlive = false;
    }
  }
  
  // Data sending and receiving
  public async sendData(dataArg: T): Promise<void> {
    this.sendBackpressuredArray.push(dataArg);
    this.workOnQueue();
    await this.sendBackpressuredArray.waitForSpace();
  }

  public async fetchData(): Promise<T> {
    if (this.receiveBackpressuredArray.hasSpace) {
      // do something maybe?
    }
    await this.receiveBackpressuredArray.waitForItems();
    const dataPackage = this.receiveBackpressuredArray.shift();
    return dataPackage;
  }

  /**
   * reads from a Readable and sends it to the other side
   * @param readableStreamArg
   */
  public async readFromWebstream(readableStreamArg: ReadableStream<T>) {
    const reader = readableStreamArg.getReader();
    let streamIsDone = false;
    while(!streamIsDone) {
      const { value, done } = await reader.read();
      if(value) {
        await this.sendData(value);
      }
      streamIsDone = done;
    }
  }

  public async writeToWebstream(writableStreamArg: WritableStream<T>) {
    const writer = writableStreamArg.getWriter();
    while(this.keepAlive) {
      await writer.write(await this.fetchData());
    }
  }
}