/**
 * @author Martin Karkowski
 * @email m.karkowski@zema.de
 * @create date 2022-01-03 19:31:44
 * @modify date 2022-01-03 19:31:44
 * @desc [description]
 */

import { ILogger } from "js-logger";
import { waitFor } from "../../helpers/async";
import { generateId } from "../../helpers/idMethods";
import { MapBasedMergeData } from "../../helpers/mergedData";
import { SPLITCHAR } from "../../helpers/objectMethods";
import { defineNopeLogger } from "../../logger/getLogger";
import { DEBUG } from "../../logger/index.browser";
import { NopeGenericWrapper } from "../../module/index";
import {
  IAvailableInstancesMsg,
  ICommunicationBridge,
  IDisposeInstanceMsg,
  IGenericNopeModule,
  IInstanceCreationMsg,
  IInstanceDescriptionMsg,
  IMapBasedMergeData,
  INopeConnectivityManager,
  INopeCore,
  INopeDispatcherOptions,
  INopeModule,
  INopeModuleDescription,
  INopeObservable,
  INopeRpcManager,
  INopeStatusInfo,
  TValidAsssignmentChecker,
  ValidSelectorFunction,
} from "../../types/nope";
import {
  INopeInstanceManager,
  TConstructorCallback,
  TGenerateWrapperCallback,
} from "../../types/nope/nopeInstanceManager.interface";
import { NopeConnectivityManager } from "../ConnectivityManager";
import { NopeRpcManager } from "../RpcManager/NopeRpcManager";

export class NopeInstanceManager implements INopeInstanceManager {
  protected _logger: ILogger;

  /**
   * The used Communication interface
   *
   */
  protected readonly _communicator: ICommunicationBridge;

  /**
   * Flag to indicate, that the system is ready.
   *
   * @author M.Karkowski
   * @type {INopeObservable<boolean>}
   * @memberof NopeInstanceManager
   */
  public readonly ready: INopeObservable<boolean>;

  /**
   * Element holding the Mapping of the Dispatcher and its instance
   * generators
   *
   * Key = Dispatcher-ID
   * Value = Available Generators
   *
   * @protected
   * @type {Map<
   *     string,
   *     IAvailableInstanceGeneratorsMsg
   *   >}
   * @memberof NopeInstanceManager
   */
  protected _mappingOfRemoteDispatchersAndGenerators: Map<string, string[]>;

  protected _internalWrapperGenerators: Map<
    string,
    TGenerateWrapperCallback<INopeModule>
  >;

  protected _registeredConstructors: Map<
    string,
    (...args: any[]) => Promise<IInstanceDescriptionMsg>
  >;

  protected _instances: Map<
    string,
    {
      instance: INopeModule;
      usedBy: Array<string>;
      manual?: boolean;
    }
  >;

  protected _internalInstances: Set<string>;

  protected _mappingOfRemoteDispatchersAndInstances: Map<
    string,
    IAvailableInstancesMsg
  >;
  protected _externalInstancesNames: Set<string>;
  protected _externalInstances: Map<string, INopeModuleDescription>;
  protected _initializingInstance: Map<string, string>;

  /**
   * Element showing the available services.
   * Its more or less a map, that maps the
   * services with their dispatchers.
   *
   * T = services name.
   * K = dispatcher - ids
   *
   * @author M.Karkowski
   * @type {IMapBasedMergeData<string>}
   * @memberof NopeInstanceManager
   */
  public readonly constructors: IMapBasedMergeData<string, string, string[]>;

  /**
   * Element showing the available instances.
   * Its more or less a map, that maps the
   * instances with their dispatchers.
   *
   * T = INopeModuleDescription.
   * K = dispatcher - ids
   *
   * @author M.Karkowski
   * @type {IMapBasedMergeData<
   *     string,
   *     string,
   *     IAvailableInstancesMsg
   *   >}
   * @memberof NopeInstanceManager
   */
  public readonly instances: IMapBasedMergeData<
    INopeModuleDescription,
    string,
    IAvailableInstancesMsg
  >;

  constructor(
    public options: INopeDispatcherOptions,
    protected _generateObservable: <T>() => INopeObservable<T>,
    protected _defaultSelector: ValidSelectorFunction,
    protected readonly _id: string = null,
    protected _statusManager: INopeConnectivityManager = null,
    protected _rpcManager: INopeRpcManager = null,
    protected _core: INopeCore = null
  ) {
    this._communicator = options.communicator;

    if (_id == null) {
      this._id = generateId();
    }

    if (_statusManager == null) {
      // Creating a new Status-Manager.
      this._statusManager = new NopeConnectivityManager(
        options,
        _generateObservable,
        this._id
      );
    }

    if (_rpcManager == null) {
      // Creating a new Status-Manager.
      this._rpcManager = new NopeRpcManager(
        options,
        _generateObservable,
        async () => "test",
        this._id
      );
    }

    this._logger = defineNopeLogger(options.logger, `core.instance-manager`);

    // Flag to show if the system is ready or not.
    this.ready = this._generateObservable();
    this.ready.setContent(false);

    // Define teh constructors
    const _this = this;
    this._mappingOfRemoteDispatchersAndGenerators = new Map();
    this.constructors = new MapBasedMergeData(
      this._mappingOfRemoteDispatchersAndGenerators
    );

    this._mappingOfRemoteDispatchersAndInstances = new Map();
    this.instances = new MapBasedMergeData(
      this._mappingOfRemoteDispatchersAndInstances
    );

    // We will subscribe to some generators.
    this._rpcManager.services.data.subscribe((_) => {
      // Clear the Mapping of the Generators
      _this._mappingOfRemoteDispatchersAndGenerators.clear();
      for (const [
        dispatcher,
        services,
      ] of _this._rpcManager.services.originalData.entries()) {
        // Filter the Generators based on the existing services
        const generators = services.services.filter((svc) =>
          svc.startsWith("nope.core.constructors.")
        );

        // If the Dispatcher has a generator we will add it.
        if (generators.length) {
          _this._mappingOfRemoteDispatchersAndGenerators.set(
            dispatcher,
            generators
          );
        }
      }

      // Update the Generators
      _this.constructors.update();
    });

    if (this._logger) {
      this._logger.info("core.instance-manager online");
    }

    this.reset();
    this._init().catch((error) => {
      if (_this._logger) {
        _this._logger.error("Failed to intialize the Dispatcher", error);
      }
    });
  }

  /**
   * Update the Available Instances
   *
   * @protected
   * @memberof NopeInstanceManager
   */
  protected _sendAvailableInstances(): void {
    const _this = this;
    // Update the Instances provided by this module.
    this._communicator.emit("InstancesChanged", {
      dispatcher: this._id,
      // We will send the descriptions.
      instances: Array.from(this._internalInstances).map((identifier) =>
        // Generate the Module Description for every identifier:
        _this._instances.get(identifier).instance.toDescription()
      ),
    });
  }

  /**
   * Internal Function, used to initialize the Dispatcher.
   * It subscribes to the "Messages" of the communicator.
   *
   * @protected
   * @memberof NopeInstanceManager
   */
  protected async _init(): Promise<void> {
    const _this = this;

    // Wait until the Element is connected.
    await this._communicator.connected.waitFor();
    await this._statusManager.ready.waitFor();
    await this._rpcManager.ready.waitFor();

    this.registerInternalWrapperGenerator(
      "*",
      async (dispather, description) => {
        const mod = new NopeGenericWrapper(
          dispather,
          _this._generateObservable
        );
        await mod.fromDescription(description, "overwrite");
        return mod;
      }
    );

    // We will use our status-manager to listen to changes.
    this._statusManager.dispatchers.onChange.subscribe((changes) => {
      if (changes.added.length) {
        // If there are dispatchers online,
        // We will emit our available services.
        _this._sendAvailableInstances();
      }
      if (changes.removed.length) {
        // Remove the dispatchers.
        changes.removed.map((item) => _this.removeDispatcher(item.id));
      }
    });

    // Listen to newly created instances.
    await this._communicator.on("InstancesChanged", (message) => {
      // Store the instances:
      _this._mappingOfRemoteDispatchersAndInstances.set(
        message.dispatcher,
        message
      );
      // Update the Mapping:
      _this.instances.update();

      if (_this._logger?.enabledFor(DEBUG)) {
        // If there is a Logger:
        _this._logger.debug(
          'Remote Dispatcher "' +
            message.dispatcher +
            '" updated its available instances'
        );
      }
    });

    if (this._logger) {
      this._logger.info("core.instance-manager", this._id, "initialized");
    }

    this.ready.setContent(true);
  }

  /**
   * Helper to get the corresponding Service name
   * @param {string} name  name
   * @param {"constructor" | "dispose"} type The desired type of the requested service name
   * @returns {string} the name.
   */
  protected _getServiceName(name: string, type: "constructor" | "dispose") {
    switch (type) {
      case "constructor":
        return `nope${SPLITCHAR}core${SPLITCHAR}constructor.${name}`;
      case "dispose":
        return `nope${SPLITCHAR}core${SPLITCHAR}destructor.${name}`;
      default:
        throw Error("The given type is not correct.");
    }
  }

  /**
   * Function, that will extract the information of the instance and the
   * the providing dispatcher.
   *
   * @author M.Karkowski
   * @param {string} identifier The identifier of instance
   * @return {*}  {(INopeModuleDescription & { dispatcher: IDispatcherInfo })}
   * @memberof nopeDispatcher
   */
  protected _getInstanceInfo(identifier: string):
    | {
        description: INopeModuleDescription;
        dispatcher: INopeStatusInfo;
      }
    | undefined {
    // First check if the instance exists.
    if (!this.instanceExists(identifier, false)) {
      return undefined;
    }

    // Define the return type
    const ret: {
      description: INopeModuleDescription;
      dispatcher: INopeStatusInfo;
    } = {} as any;

    // First we check if we are taking care of an internal instance, if so
    // we will use this instance to enrich the description, otherwise, we
    // will look in the external instances.
    if (this._instances.has(identifier)) {
      ret.description = this._instances
        .get(identifier)
        .instance.toDescription();
    } else {
      // Now extract teh
      for (const {
        instances,
      } of this._mappingOfRemoteDispatchersAndInstances.values()) {
        for (const instance of instances) {
          if (instance.identifier == identifier) {
            ret.description = instance;
            break;
          }
        }
      }
    }
    // Additionally add some information about the used dispatcher.
    ret.dispatcher = this.getManagerOfInstance(identifier);

    return ret;
  }

  /**
   * Helper to remove a dispatcher.
   *
   * @author M.Karkowski
   * @param {string} dispatcher
   * @memberof NopeRpcIn
   */
  public removeDispatcher(dispatcher: string): void {
    // Delete the Generators of the Instances.
    this._mappingOfRemoteDispatchersAndInstances.delete(dispatcher);
    this.instances.update();

    // Now we need to delete every Instance of the dispatcher.
    // All open calls will be handeled by the RpcManager.

    // TODO:
    // this.cancelRunningTasksOfDispatcher(
    //   dispatcher,
    //   new Error(
    //     "Dispatcher has been removed! Tasks cannot be executed any more."
    //   )
    // );
  }

  // See interface description
  public async registerConstructor<I extends INopeModule>(
    identifier: string,
    cb: TConstructorCallback<I>
  ): Promise<void> {
    const _this = this;

    if (this._logger?.enabledFor(DEBUG)) {
      this._logger.debug(
        'Adding instance generator for "' +
          identifier +
          '" to external Generators. Other Elements can now create instances of this type.'
      );
    }

    const _cb = await this._rpcManager.registerService(
      async (data: IInstanceCreationMsg) => {
        // Check if an instance exists or not.
        // if not => create an instance an store it.
        if (!_this._instances.has(data.identifier)) {
          const hashable = [data.identifier, data.params, data.type];
          const hash = "hashedSettings";

          // It might happen, that an instance is requested multiple times.
          // therefore we have to make shure, we wont create them multiple times:
          // We will test it by using the "_internalInstances" set
          if (!_this._initializingInstance.has(data.identifier)) {
            // Mark the Instance as available.
            _this._initializingInstance.set(data.identifier, hash);

            // Create an Instance
            const _instance = await cb(_this._core, data.identifier);

            // Make shure the Data is expressed as Array.
            if (!Array.isArray(data.params)) {
              data.params = [data.params];
            }

            // Initialize the instance with the parameters.
            await _instance.init(...data.params);

            // A Function is registered, taking care of removing
            // an instances, if it isnt needed any more.
            _this._rpcManager.registerService(
              async (_data: IDisposeInstanceMsg) => {
                if (_this._instances.get(data.identifier)?.usedBy) {
                  // Get the Index of the dispatcher, which is using
                  // the element
                  const idx = _this._instances
                    .get(data.identifier)
                    .usedBy.indexOf(_data.dispatcherId);

                  if (idx > -1) {
                    _this._instances.get(data.identifier).usedBy.splice(idx, 1);
                  }

                  if (
                    _this._instances.get(data.identifier).usedBy.length == 0
                  ) {
                    // Unmark as internal instance
                    _this._internalInstances.delete(data.identifier);

                    // Remove the Instance.
                    await _instance.dispose();

                    // Delete the Entry.
                    _this._instances.delete(data.identifier);

                    // Remove the Function itself
                    _this._rpcManager.unregisterService(
                      _this._getServiceName(data.identifier, "dispose")
                    );
                  }
                }
              },
              {
                id: _this._getServiceName(data.identifier, "dispose"),
              }
            );

            // Store the Instance.
            _this._instances.set(data.identifier, {
              instance: _instance,
              usedBy: [data.dispatcherId],
            });

            _this._internalInstances.add(data.identifier);

            // Update the available instances:
            _this._sendAvailableInstances();

            // Make shure, we remove this instance.hash
            _this._initializingInstance.delete(data.identifier);
          } else if (_this._initializingInstance.get(data.identifier) != hash) {
            throw Error(
              "Providing different Parameters for the same Identifier"
            );
          } else {
            // Check if the Instance is ready.
            let firstHint = true;
            await waitFor(
              () => {
                if (firstHint) {
                  _this._logger.warn(
                    `Parallel request for the same Instance "${data.identifier}" => Waiting until the Instance has been initialized`
                  );
                  firstHint = false;
                }
                return _this._instances.has(data.identifier);
              },
              {
                testFirst: true,
                delay: 100,
              }
            );
          }
        } else {
          // If an Element exists => Add the Element.
          _this._instances.get(data.identifier).usedBy.push(data.dispatcherId);
        }

        // Define the Response.
        const response: IInstanceDescriptionMsg = {
          description: _this._instances
            .get(data.identifier)
            .instance.toDescription(),
          type: data.type,
        };

        // Send the Response
        return response;
      },
      {
        // We will add the Name to our service.
        id: this._getServiceName(identifier, "constructor"),
        // We dont want to add a prefix
        addNopeServiceIdPrefix: false,
      }
    );
    // Store the Generator.
    this._registeredConstructors.set(identifier, _cb);
  }

  // See interface description
  public async unregisterConstructor(identifier: string): Promise<void> {
    if (this._registeredConstructors.has(identifier)) {
      if (this._logger?.enabledFor(DEBUG)) {
        this._logger.debug(
          'Removing instance generator for "' +
            identifier +
            '" from external Generators. Other Elements cant create instances of this type anymore.'
        );
      }

      // We will just unregister the service from our
      // system. Therefore we just use the rpcManager
      await this._rpcManager.unregisterService(
        this._registeredConstructors.get(identifier)
      );
      this._registeredConstructors.delete(identifier);
    }
  }

  // See interface description
  public registerInternalWrapperGenerator<I extends INopeModule>(
    identifier: string,
    cb: TGenerateWrapperCallback<I>
  ): void {
    if (this._logger?.enabledFor(DEBUG)) {
      this._logger.debug(
        'Adding instance generator for "' +
          identifier +
          '" as internal Generator. This Generator wont be used externally.'
      );
    }
    this._internalWrapperGenerators.set(identifier, cb);
  }

  // See interface description
  public unregisterInternalWrapperGenerator(identifier: string): void {
    if (this._logger?.enabledFor(DEBUG)) {
      this._logger.debug(
        'Rmoving instance generator for "' +
          identifier +
          '" from internal Generator. The sytem cant create elements of this type any more.'
      );
    }
    this._internalWrapperGenerators.delete(identifier);
  }

  // See interface description
  public instanceExists(identifier: string, externalOnly = true): boolean {
    if (externalOnly) {
      return this._externalInstances.has(identifier);
    } else {
      this._externalInstances.has(identifier) ||
        this._instances.has(identifier);
    }
  }

  // See interface description
  public getManagerOfInstance(identifier: string): INopeStatusInfo | undefined {
    // Check if the instance exists in general
    if (!this.instanceExists(identifier, false)) {
      return undefined;
    }

    // First we will check if the instance is available internally.
    if (this._internalInstances.has(identifier)) {
      return this._statusManager.info;
    }

    // If that isnt the case, we will check all dispatchers and search the instance.
    for (const [
      dispatcher,
      { instances },
    ] of this._mappingOfRemoteDispatchersAndInstances.entries()) {
      for (const instance of instances) {
        if (instance.identifier == identifier) {
          return this._statusManager.getStatus(dispatcher);
        }
      }
    }

    return undefined;
  }

  // See interface description
  public getInstanceDescription(
    instanceIdentifier: string
  ): false | INopeModuleDescription {
    if (this._instances.has(instanceIdentifier)) {
      return this._instances.get(instanceIdentifier).instance.toDescription();
    }
    return false;
  }

  // See interface description
  public constructorExists(typeIdentifier: string): boolean {
    return this.constructors.data.getContent().includes(typeIdentifier);
  }

  // See interface description
  public async createInstance<I extends INopeModule = IGenericNopeModule>(
    description: Partial<IInstanceCreationMsg>,
    options: {
      selector?: ValidSelectorFunction;
      assignmentValid?: TValidAsssignmentChecker;
    } = {}
  ): Promise<I> {
    // Define the Default Description
    // which will lead to an error.
    const _defDescription: IInstanceCreationMsg = {
      dispatcherId: this._id,
      identifier: "error",
      params: [],
      type: "unkown",
    };

    // Assign the provided Description
    const _description = Object.assign(_defDescription, description, {
      dispatcherId: this._id,
    }) as IInstanceCreationMsg;

    // Check if the description is complete
    if (
      _defDescription.type === "unkown" ||
      _description.identifier === "error"
    ) {
      throw Error(
        'Please Provide at least a "type" and "identifier" in the paremeters'
      );
    }

    if (this._logger?.enabledFor(DEBUG)) {
      this._logger.debug(
        'Requesting an Instance of type: "' +
          _defDescription.type +
          '" with the identifier: "' +
          _defDescription.identifier +
          '"'
      );
    }

    try {
      let _type = _description.type;

      if (!this._internalWrapperGenerators.has(_type)) {
        // No default type is present for a remote
        // => assing the default type which is "*""
        _type = "*";
      }

      if (!this.constructorExists(_description.type)) {
        throw Error(
          'Generator "' + _description.type + '" isnt present in the network!'
        );
      }

      if (this._internalWrapperGenerators.has(_type)) {
        if (this._logger?.enabledFor(DEBUG)) {
          this._logger.debug(
            'No instance with the identifiert: "' +
              _defDescription.identifier +
              '" found, but an internal generator is available. Using the internal one for creating the instance and requesting the "real" instance externally'
          );
        }

        // Now test if there is allready an instance with this name and type.
        // If so, we check if we have the correct type etc. Additionally we
        // try to extract its dispatcher-id and will use that as selector
        // to allow the function be called.
        const _instanceDetails = this._getInstanceInfo(_description.identifier);
        if (
          _instanceDetails !== undefined &&
          _instanceDetails?.description.type !== _description.type
        ) {
          throw Error(
            "There exists an Instance named: '" +
              _description.identifier +
              "' but it uses a different type. Requested type: '" +
              _description.type +
              "', given type: '" +
              _instanceDetails?.description.type +
              "'"
          );
        }

        const usedDispatcher = _instanceDetails?.dispatcher.id;

        if (usedDispatcher && options.assignmentValid) {
          // If we have an dispatcher, which was been used to create the instance,
          // we have to check, the selected Dispatcher Matches our criteria.
          if (
            !(await options.assignmentValid(
              _instanceDetails.description,
              _instanceDetails.dispatcher
            ))
          ) {
            throw Error("Assignment is invalid.");
          }
        }

        const definedInstance =
          await this._rpcManager.performCall<IInstanceDescriptionMsg>(
            // Extract our Service Name:
            this._getServiceName(_description.type, "constructor"),
            // We will use our Description as Parameter.
            [_description],
            // Additionally we share the options:
            options
          );

        if (this._logger?.enabledFor(DEBUG)) {
          this._logger.debug(
            `Received a description for the instance "${definedInstance.description.identifier}"`
          );
        }

        // Create the Wrapper for our instance.
        const wrapper = (await this._internalWrapperGenerators.get(_type)(
          this._core,
          definedInstance.description
        )) as I;

        if (this._logger?.enabledFor(DEBUG)) {
          this._logger.debug(
            `Created a Wrapper for the instance "${definedInstance.description.identifier}"`
          );
        }

        // Store the Instances.
        this._instances.set(_description.identifier, {
          instance: wrapper,
          usedBy: [_description.dispatcherId],
        });

        return wrapper;
      }

      throw Error("No internal generator Available!");
    } catch (e) {
      if (this._logger) {
        this._logger.error(
          "During creating an Instance, the following error Occurd"
        );
        this._logger.error(e);
      }
      throw e;
    }
  }

  // See interface description
  public async registerInstance<I extends INopeModule>(
    instance: I
  ): Promise<I> {
    // Store the Instances.
    this._instances.set(instance.identifier, {
      instance,
      usedBy: [],
      manual: true,
    });

    return instance;
  }

  // See interface description
  public async deleteInstance<I extends INopeModule>(
    instance: I | string,
    preventSendingUpdate = false
  ): Promise<boolean> {
    // Block to find the instance.
    // Based on the property (string or instance)
    // the corresponding instance object has to be select.
    let _instance: { instance: INopeModule; usedBy: Array<string> };
    if (typeof instance === "string") {
      _instance = this._instances.get(instance);
    } else {
      for (const data of this._instances.values()) {
        if (instance == data.instance) {
          _instance = data;
          break;
        }
      }
    }

    // if the instance has been found => delete the instance.
    if (_instance) {
      _instance.usedBy.pop();

      if (_instance.usedBy.length === 0) {
        const params: IDisposeInstanceMsg = {
          dispatcherId: this._id,
          identifier: _instance.instance.identifier,
        };

        // Call the corresponding Dispose Function for the "real" instance
        // All other elements are just accessors.
        await this._rpcManager.performCall(
          "instance_dispose_" + _instance.instance.identifier,
          [params]
        );

        // Delete the Identifier
        this._instances.delete(_instance.instance.identifier);

        // Check if an update should be emitted or not.
        if (!preventSendingUpdate) {
          // Update the Instances provided by this module.
          this._sendAvailableInstances();
        }

        // Dispose the Handler;
        await _instance.instance.dispose();
      }

      return true;
    }
    return false;
  }

  // See interface description
  public async getInstancesOfType<I extends INopeModule>(type: string) {
    const indentifier = this.instances.data
      .getContent()
      .filter((item) => item.type == type)
      .map((item) => item.identifier);

    const promises: Promise<I>[] = [];

    for (const identifier of indentifier) {
      promises.push(
        this.createInstance({
          identifier,
          type,
          params: [],
        })
      );
    }

    // Wait to generate all Instances.
    const result = await Promise.all(promises);

    return result;
  }

  // See interface description
  public reset(): void {
    this._mappingOfRemoteDispatchersAndGenerators = new Map();
    this._mappingOfRemoteDispatchersAndInstances = new Map();

    this._internalWrapperGenerators = new Map();
    this._registeredConstructors = new Map();

    // If Instances Exists => Delete them.
    if (this._instances) {
      const _this = this;

      // Dispose all Instances.
      for (const [name, instance] of this._instances.entries()) {
        // Remove the Instance.
        this.deleteInstance(name, true).catch((e) => {
          if (_this._logger) {
            _this._logger.error('Failed Removing Instance "' + name + '"');
            _this._logger.error(e);
          }
        });
      }
    }
    this._instances = new Map();
    this._externalInstances = new Map();
    this._internalInstances = new Set();
    this._initializingInstance = new Map();
    this._externalInstancesNames = new Set();

    if (this._communicator.connected.getContent()) {
      // Update the Instances
      this._sendAvailableInstances();
    }
  }

  // See interface description
  public async dispose() {
    this.instances.dispose();
  }
}