/**
 * @author Martin Karkowski
 * @email m.karkowski@zema.de
 * @create date 2020-11-06 08:52:30
 * @modify date 2020-12-03 16:13:58
 * @desc [description]
 */

import * as amqp from "amqplib";
import { getNopeLogger } from "../logger/getLogger";
import { NopeObservable } from "../observables/nopeObservable";
import {
  IAvailableInstanceGeneratorsMsg,
  IAvailableInstancesMsg,
  IAvailableServicesMsg,
  IAvailableTopicsMsg,
  ICommunicationInterface,
  IExternalEventMsg,
  IRequestTaskMsg,
  IResponseTaskMsg,
  ITaskCancelationMsg
} from "../types/nope/nopeCommunication.interface";
import { INopeObservable } from "../types/nope/nopeObservable.interface";

export type QueuePublishOptions = {
  subscribeOptions?: amqp.Options.AssertQueue;
  consumeOptions?: amqp.Options.Consume;
  deleteOptions?: amqp.Options.DeleteQueue;
  prefetch?: number;
};

export type QueueSubscribeOptions = {
  subscribeOptions?: amqp.Options.AssertQueue;
  consumeOptions?: amqp.Options.Consume;
  deleteOptions?: amqp.Options.DeleteQueue;
  prefetch?: number;
};

export type SubscriptionOptions = {
  subscribeOptions?: amqp.Options.AssertExchange;
  exchangeType?: "direct" | "topic" | "fanout" | "headers";
  consumeOptions?: amqp.Options.Consume;
  deleteOptions?: amqp.Options.DeleteQueue;
  prefetch?: number;
};

interface IConnection {
  channel: amqp.Channel;
  connectionLost: () => void;
  delete: (
    event?: string,
    deleteOptions?: amqp.Options.DeleteQueue
  ) => Promise<void>;
  subscribe: (
    event?: string,
    consumeOptions?: amqp.Options.Consume,
    prefetch?: number
  ) => Promise<void>;
  unsubscribe: () => Promise<void>;
  isSubscribed(): boolean;
  send: (...arg) => boolean;
}

/**
 * A Communication Layer for the Dispatchers.
 * In this Layer AMQP (Rabbit-MQ) is used.
 * Functions are matched to Queues.
 *
 * @export
 * @class AmqpLayer
 * @implements {ICommunicationInterface}
 */
export class AmqpInterface {
  connected: INopeObservable<boolean>;

  async off(event: string, cb: (data: any, msg: amqp.Message) => void) {
    // Store the Function
    const _set = this._userDefinedCallbacks.get(event) || new Set();
    // Delete the callback.
    _set.delete(cb);
    // Based on the Numbers of Elements which are included in here
    // the Queue is subscribed.
    if (_set.size > 0) {
      this._userDefinedCallbacks.set(event, _set);
    } else {
      const _connection = this._connections.get(event);

      if (_connection?.unsubscribe) {
        const _this = this;
        await _connection.unsubscribe().catch((e) => {
          _this._logger.error("failed unsubscribing");
          _this._logger.error(e);
        });

        await _connection.delete().catch((e) => {
          _this._logger.error("failed deleting");
          _this._logger.error(e);
        });
      }
    }
  }

  protected _socket: amqp.Connection;

  protected _connections: Map<string, IConnection>;

  /**
   * Map holding a set of function for user defined events.
   *
   * @protected
   * @memberof AmqpInterface
   */
  protected _userDefinedCallbacks: Map<
    string,
    Set<(data: any, msg: amqp.Message) => void>
  >;

  constructor(public uri: string) {
    // Adapt the URI if required:
    this.uri = uri.startsWith("amqp://") ? uri : "amqp://" + uri;
    this.connected = new NopeObservable();
    this.connected.setContent(false);

    const _this = this;
    amqp.connect(this.uri).then((connection) => {
      _this._socket = connection;
      _this._logger.info("Connection established with " + _this.uri);

      _this.connected.setContent(true);
    });

    this._connections = new Map();
    this._userDefinedCallbacks = new Map();
  }

  protected async _createConnection(
    event: string,
    options: QueuePublishOptions = {}
  ) {
    if (this._connections.has(event)) {
      return {
        connection: this._connections.get(event),
        created: false
      };
    }

    const _this = this;
    const _channel = await this._socket.createChannel();
    const connectionLost = () => {
      _this.connected.setContent(false);
    };
    _channel.on("close", connectionLost);

    let _sub: amqp.Replies.Consume = null;

    // Define a Connection Object.
    const _connection: IConnection = {
      channel: _channel,
      connectionLost,

      send(data) {
        return _channel.sendToQueue(event, Buffer.from(JSON.stringify(data)), {
          contentEncoding: "application/json"
        });
      },

      isSubscribed() {
        return _sub !== null;
      },

      async subscribe(_event: string = event, _opts = options.consumeOptions) {
        if (_sub === null) {
          _sub = await _channel.consume(
            _event,
            (msg) => {
              // Transform the Data:
              const data = JSON.parse(msg.content.toString("utf-8"));
              for (const _func of _this._userDefinedCallbacks.get(event) ||
                []) {
                _func(data, msg);
              }
            },
            options.consumeOptions
          );
        }
      },

      async unsubscribe() {
        if (_sub !== null) {
          // Delte the Subscription
          await _channel.cancel(_sub.consumerTag);
          _sub = null;
        }
      },

      async delete(_event: string = event, _opts = options.deleteOptions) {
        try {
          await _channel.deleteQueue(_event, _opts);
        } catch (e) {}
      }
    };

    this._connections.set(event, _connection);

    return {
      connection: _connection,
      created: true
    };
  }

  public async createQueue(
    event: string,
    options: QueuePublishOptions = {}
  ): Promise<IConnection> {
    // Get the Connection
    const _res = await this._createConnection(event, options);

    if (_res.created) {
      // Extract the Connection
      const _connection: IConnection = _res.connection;
      // Create a Queue
      const _queue = await _connection.channel.assertQueue(
        event,
        options.subscribeOptions
      );

      // Enable Prefetch
      if (options.prefetch > 0) {
        await _connection.channel.prefetch(options.prefetch);
      } else if (typeof options.prefetch === "undefined") {
        await _connection.channel.prefetch(1);
      }
    }

    return _res.connection;
  }

  /**
   * Function to create an Subscription in the RabbitMQ-Broker
   *
   * @param {string} event
   * @param {SubscriptionOptions} [options={}]
   * @memberof AmqpInterface
   */
  public async createSubscription(
    event: string,
    options: SubscriptionOptions = {}
  ): Promise<IConnection> {
    options.consumeOptions = Object.assign(
      {
        noAck: false
      },
      options.consumeOptions || {}
    );

    // Get the Connection
    const _res = await this._createConnection(event, options);

    if (_res.created) {
      // Extract the Connection
      const _connection: IConnection = _res.connection;

      // Create a Queue
      // It will contain the subscribed Messages.
      const _queue = await _connection.channel.assertQueue("", {
        exclusive: true
      });

      // Create an Exchange.
      const _exchange = await _connection.channel.assertExchange(
        "event",
        options.exchangeType || "topic",
        options.subscribeOptions
      );

      // Bind the Queue to the Exchange.
      _connection.channel.bindQueue(_queue.queue, _exchange.exchange, event);

      // Enable Prefetch
      if (options.prefetch > 0) {
        await _connection.channel.prefetch(options.prefetch);
      }

      // Update the Send Message.
      _connection.send = (data) => {
        return _connection.channel.publish(
          "event",
          event,
          Buffer.from(JSON.stringify(data)),
          {
            contentEncoding: "application/json"
          }
        );
      };

      // Store a reference to the original Method
      const _delete = _connection.delete;

      // Delte additionally the exchange and dynamic queue
      _connection.delete = async () => {
        // Delte the Queue
        await _delete(_queue.queue);
        // Delte the Exchange.
        await _connection.channel.deleteExchange(_exchange.exchange);
      };

      const _subscribe = _connection.subscribe;
      _connection.subscribe = async () => {
        await _subscribe(_queue.queue);
      };
    }

    return _res.connection;
  }

  protected _logger = getNopeLogger("AMQP-Interface", "info");

  async on(
    mode: "queue" | "subscribe",
    event: string,
    cb: (data: any, msg: amqp.Message) => void,
    options: QueuePublishOptions | SubscriptionOptions = {}
  ): Promise<void> {
    // Store the Function
    const _set = this._userDefinedCallbacks.get(event) || new Set();
    // Add the callback.
    _set.add(cb);

    // Store the Set.
    this._userDefinedCallbacks.set(event, _set);

    // Based on the Numbers of Elements which are included in here
    // the Queue is subscribed.
    if (_set.size === 1) {
      let _connection: IConnection;
      switch (mode) {
        case "queue":
          _connection = await this.createQueue(
            event,
            options as QueueSubscribeOptions
          );
          await _connection.subscribe();
          break;
        case "subscribe":
          _connection = await this.createSubscription(
            event,
            options as SubscriptionOptions
          );
          await _connection.subscribe();
          break;
      }
    }
  }

  public async emit(
    mode: "queue" | "publish",
    event: string,
    data: any,
    options: QueuePublishOptions | SubscriptionOptions = {}
  ): Promise<void> {
    const _connection: IConnection = this._connections.get(event);
    if (_connection) {
      _connection.send(data);
    } else {
      // No Queue or Subscription is available =>
      // Create the corresponding queue / subscription
      switch (mode) {
        case "queue":
          await this.createQueue(event, options as QueueSubscribeOptions);
          break;
        case "publish":
          await this.createSubscription(event, options as SubscriptionOptions);
          break;
      }

      // Recall the Method.
      await this.emit(mode, event, data, options);
    }
  }

  public close(): void {
    this._socket.close();
  }
}

/**
 * A Communication Layer for the Dispatchers.
 * In this Layer AMQP (Rabbit-MQ) is used.
 * Functions are matched to Queues.
 *
 * @export
 * @class AmqpLayer
 * @implements {ICommunicationInterface}
 */
export class AmqpLayer
  extends AmqpInterface
  implements ICommunicationInterface {
  async onAurevoir(cb: (dispatcher: string) => void): Promise<void> {
    await this.on("subscribe", "aurevoir", cb);
  }

  async emitAurevoir(dispatcher: string): Promise<void> {
    await this.emit("publish", "aurevoir", dispatcher);
  }

  async onTaskCancelation(
    cb: (msg: ITaskCancelationMsg) => void
  ): Promise<void> {
    await this.on("subscribe", "taskCancelation", cb);
  }

  async emitTaskCancelation(msg: ITaskCancelationMsg): Promise<void> {
    await this.emit("publish", "taskCancelation", msg);
  }

  async emitNewObersvablesAvailable(
    topics: IAvailableTopicsMsg
  ): Promise<void> {
    await this.emit("publish", "newTopicsAvailable", topics);
  }
  async onNewObservablesAvailable(
    cb: (topics: IAvailableTopicsMsg) => void
  ): Promise<void> {
    await this.on("subscribe", "newTopicsAvailable", cb);
  }
  async onEvent(
    event: string,
    cb: (data: IExternalEventMsg) => void
  ): Promise<void> {
    await this.on("subscribe", "event." + event, cb);
  }
  async offEvent(
    event: string,
    cb: (data: IExternalEventMsg) => void
  ): Promise<void> {
    await this.off("event." + event, cb);
  }
  async emitEvent(event: string, data: IExternalEventMsg): Promise<void> {
    await this.emit("publish", "event." + event, data);
  }
  async emitNewInstanceGeneratorsAvailable(
    generators: IAvailableInstanceGeneratorsMsg
  ): Promise<void> {
    await this.emit("publish", "newInstanceGeneratorsAvailable", generators);
  }
  async onNewInstanceGeneratorsAvailable(
    cb: (generators: IAvailableInstanceGeneratorsMsg) => void
  ): Promise<void> {
    await this.on("subscribe", "newInstanceGeneratorsAvailable", cb);
  }
  async onBonjour(cb: (dispatcher: string) => void): Promise<void> {
    await this.on("subscribe", "bonjour", cb);
  }
  async emitBonjour(dispatcher: string): Promise<void> {
    await this.emit("publish", "bonjour", dispatcher);
  }

  subscriptionMode?: "individual" | "generic" = "individual";
  resultSharing?: "individual" | "generic" = "individual";

  protected _tasks = new Map<string, () => void>();

  async emitRpcRequest(name: string, request: IRequestTaskMsg): Promise<void> {
    await this.emit("queue", name, request, this.generateQueueOptions(name));
  }

  async emitRpcResult(name: string, result: IResponseTaskMsg): Promise<void> {
    // Ackknowlegde, that the Task was sucessfull
    if (this._tasks.has(result.taskId)) {
      // Send the Acknoledgement
      this._tasks.get(result.taskId)();
      this._tasks.delete(result.taskId);
    }
    await this.emit("publish", name, result);
  }

  async onRpcResponse(
    name: string,
    cb: (result: IResponseTaskMsg) => void
  ): Promise<void> {
    await this.on("subscribe", name, cb);
  }

  async offRpcResponse(
    name: string,
    cb: (result: IResponseTaskMsg) => void
  ): Promise<void> {
    await this.off(name, cb);
  }

  async onRpcRequest(
    name: string,
    cb: (req: IRequestTaskMsg) => void
  ): Promise<void> {
    const _this = this;
    await this.on(
      "queue",
      name,
      (req: IRequestTaskMsg, msg) => {
        _this._logger.debug("Getting new Request " + req.taskId);

        // Define a callback for finished Tasks.
        _this._tasks.set(req.taskId, () => {
          // Select the corresponding channel
          const _channel = _this._connections.get(name).channel;
          // Test if the Channel exists
          if (_channel) {
            _this._logger.debug(
              "Sending Acknowledgement of Request " + req.taskId
            );
            // Ackknowlegde the Message.
            _channel.ack(msg);
          }
        });

        // Perform the Original Callback.
        cb(req);
      },
      this.generateQueueOptions(name)
    );
  }

  async offRpcRequest(
    name: string,
    cb: (data: IRequestTaskMsg) => void
  ): Promise<void> {
    await this.off(name, cb);
  }

  async emitNewServicesAvailable(
    services: IAvailableServicesMsg
  ): Promise<void> {
    await this.emit("publish", "newServicesAvailable", services);
  }

  async onNewServicesAvailable(
    cb: (services: IAvailableServicesMsg) => void
  ): Promise<void> {
    await this.on("subscribe", "newServicesAvailable", cb);
  }

  protected _logger = getNopeLogger("AMQP-Event-Layer", "info");

  public generateQueueOptions: (name: string) => QueuePublishOptions = (
    name
  ) => {
    return {
      consumeOptions: {
        noAck: false
      },
      subscribeOptions: {
        durable: false
      }
    } as QueuePublishOptions;
  };

  async onNewInstancesAvailable(
    cb: (instances: IAvailableInstancesMsg) => void
  ): Promise<void> {
    await this.on("subscribe", "newInstancesAvailable", cb);
  }

  async emitNewInstancesAvailable(
    instances: IAvailableInstancesMsg
  ): Promise<void> {
    await this.emit("publish", "newInstancesAvailable", instances);
  }

  public generateSubscriptionOptions: (name: string) => SubscriptionOptions = (
    name
  ) => {
    return {};
  };
}