/**
 * @author Martin Karkowski
 * @email m.karkowski@zema.de
 * @create date 2020-11-06 08:52:30
 * @modify date 2020-11-11 16:22:10
 * @desc [description]
 */

import * as amqp from 'amqplib';
import { getNopeLogger } from "../logger/getLogger";
import { IAvailableInstanceGeneratorsMsg, IAvailableServicesMsg, IAvailableTopicsMsg, ICommunicationInterface, IExternalEventMsg, IRequestTaskMsg, IResponseTaskMsg, ITaskCancelationMsg } from '../types/nope/nopeCommunication.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,
    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 {
    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;

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

            _this._socket.createChannel
        });

        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();

        let _sub: amqp.Replies.Consume = null;

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

            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 = {}) {
        // 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 = {}) {

        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 = {}) {
        // 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);
        }
    }

    close(){
        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 emitNewTopicsAvailable(topics: IAvailableTopicsMsg): Promise<void> {
        await this.emit('publish','newTopicsAvailable',topics);
    }
    async onNewTopicsAvailable(cb: (topics: IAvailableTopicsMsg) => 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) {
        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 onRpcResult(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) {
        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
    }

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

}