import * as plugins from '../plugins.js';
import type { TsView } from '../tsview.classes.tsview.js';
import type * as interfaces from './interfaces.streaming.js';
import type { IS3ChangeEvent } from '@push.rocks/smartbucket';

/**
 * Subscription entry tracking a client's subscription to a resource
 */
interface ISubscriptionEntry {
  connectionId: string;
  subscriptionId: string;
  createdAt: Date;
}

/**
 * MongoDB watcher entry
 */
interface IMongoWatcherEntry {
  watcher: plugins.mongodb.ChangeStream;
  subscriptions: Map<string, ISubscriptionEntry>; // connectionId -> subscription
}

/**
 * S3 watcher entry
 */
interface IS3WatcherEntry {
  watcher: plugins.smartbucket.BucketWatcher;
  subscriptions: Map<string, ISubscriptionEntry>; // connectionId -> subscription
}

/**
 * ChangeStreamManager manages real-time change streaming for both MongoDB and S3.
 *
 * Features:
 * - MongoDB Change Streams for real-time database updates
 * - S3 BucketWatcher for polling-based S3 change detection
 * - Subscription management per WebSocket client
 * - Activity stream with ring buffer for recent events
 * - Automatic cleanup on client disconnect
 */
export class ChangeStreamManager {
  private tsview: TsView;
  private typedSocket: plugins.typedserver.TypedServer['typedsocket'] | null = null;

  // MongoDB watchers: "db/collection" -> watcher entry
  private mongoWatchers: Map<string, IMongoWatcherEntry> = new Map();

  // S3 watchers: "bucket/prefix" -> watcher entry
  private s3Watchers: Map<string, IS3WatcherEntry> = new Map();

  // Activity subscribers: connectionId -> subscription entry
  private activitySubscribers: Map<string, ISubscriptionEntry> = new Map();

  // Activity ring buffer (max 1000 events)
  private activityBuffer: interfaces.IActivityEvent[] = [];
  private readonly ACTIVITY_BUFFER_SIZE = 1000;

  // Counter for generating unique subscription IDs
  private subscriptionCounter = 0;

  constructor(tsview: TsView) {
    this.tsview = tsview;
  }

  /**
   * Initialize the manager with a TypedSocket instance
   */
  public setTypedSocket(typedSocket: plugins.typedserver.TypedServer['typedsocket']): void {
    this.typedSocket = typedSocket;
  }

  /**
   * Generate a unique subscription ID
   */
  private generateSubscriptionId(): string {
    return `sub_${Date.now()}_${++this.subscriptionCounter}`;
  }

  /**
   * Get the MongoDB key for a database/collection pair
   */
  private getMongoKey(database: string, collection: string): string {
    return `${database}/${collection}`;
  }

  /**
   * Get the S3 key for a bucket/prefix pair
   */
  private getS3Key(bucket: string, prefix?: string): string {
    return prefix ? `${bucket}/${prefix}` : bucket;
  }

  // ===========================================
  // MongoDB Change Streams
  // ===========================================

  /**
   * Subscribe a client to MongoDB collection changes
   */
  public async subscribeToMongo(
    connectionId: string,
    database: string,
    collection: string
  ): Promise<{ success: boolean; subscriptionId: string }> {
    const key = this.getMongoKey(database, collection);

    let entry = this.mongoWatchers.get(key);

    // Create watcher if it doesn't exist
    if (!entry) {
      const watcher = await this.createMongoWatcher(database, collection);
      if (!watcher) {
        return { success: false, subscriptionId: '' };
      }

      entry = {
        watcher,
        subscriptions: new Map(),
      };
      this.mongoWatchers.set(key, entry);
    }

    // Add subscription
    const subscriptionId = this.generateSubscriptionId();
    entry.subscriptions.set(connectionId, {
      connectionId,
      subscriptionId,
      createdAt: new Date(),
    });

    console.log(`[ChangeStream] MongoDB subscription added: ${key} for connection ${connectionId}`);
    return { success: true, subscriptionId };
  }

  /**
   * Unsubscribe a client from MongoDB collection changes
   */
  public async unsubscribeFromMongo(
    connectionId: string,
    database: string,
    collection: string
  ): Promise<boolean> {
    const key = this.getMongoKey(database, collection);
    const entry = this.mongoWatchers.get(key);

    if (!entry) {
      return false;
    }

    entry.subscriptions.delete(connectionId);
    console.log(`[ChangeStream] MongoDB subscription removed: ${key} for connection ${connectionId}`);

    // Close watcher if no more subscribers
    if (entry.subscriptions.size === 0) {
      await this.closeMongoWatcher(key);
    }

    return true;
  }

  /**
   * Create a MongoDB change stream for a collection
   */
  private async createMongoWatcher(
    database: string,
    collection: string
  ): Promise<plugins.mongodb.ChangeStream | null> {
    try {
      const db = await this.tsview.getMongoDb();
      if (!db) {
        console.error('[ChangeStream] MongoDB not configured');
        return null;
      }

      const client = (db as any).mongoDbClient;
      const mongoDb = client.db(database);
      const mongoCollection = mongoDb.collection(collection);

      // Create change stream
      const changeStream = mongoCollection.watch([], {
        fullDocument: 'updateLookup',
      });

      // Handle change events
      changeStream.on('change', (change: any) => {
        this.handleMongoChange(database, collection, change);
      });

      changeStream.on('error', (error: Error) => {
        console.error(`[ChangeStream] MongoDB error for ${database}/${collection}:`, error);
      });

      console.log(`[ChangeStream] MongoDB watcher created for ${database}/${collection}`);
      return changeStream;
    } catch (error) {
      console.error(`[ChangeStream] Failed to create MongoDB watcher for ${database}/${collection}:`, error);
      return null;
    }
  }

  /**
   * Handle a MongoDB change event
   */
  private handleMongoChange(database: string, collection: string, change: any): void {
    const key = this.getMongoKey(database, collection);
    const entry = this.mongoWatchers.get(key);

    if (!entry) return;

    // Convert MongoDB change event to our interface
    const event: interfaces.IMongoChangeEvent = {
      type: change.operationType as interfaces.IMongoChangeEvent['type'],
      database,
      collection,
      documentId: change.documentKey?._id?.toString(),
      document: change.fullDocument,
      updateDescription: change.updateDescription,
      timestamp: new Date().toISOString(),
    };

    // Add to activity buffer
    this.addToActivityBuffer('mongodb', event);

    // Push to all subscribed clients
    this.pushMongoChangeToClients(key, event);
  }

  /**
   * Push MongoDB change to subscribed clients
   */
  private async pushMongoChangeToClients(
    key: string,
    event: interfaces.IMongoChangeEvent
  ): Promise<void> {
    const entry = this.mongoWatchers.get(key);
    if (!entry || !this.typedSocket) return;

    for (const [connectionId, _sub] of entry.subscriptions) {
      try {
        // Find the connection and push the event
        const connection = await this.typedSocket.findTargetConnection(async (conn: any) => {
          return conn.alias === connectionId || conn.socketId === connectionId;
        });

        if (connection) {
          const request = this.typedSocket.createTypedRequest<interfaces.IReq_PushMongoChange>(
            'pushMongoChange',
            connection
          );
          await request.fire({ event });
        }
      } catch (error) {
        console.error(`[ChangeStream] Failed to push MongoDB change to ${connectionId}:`, error);
      }
    }
  }

  /**
   * Close a MongoDB change stream
   */
  private async closeMongoWatcher(key: string): Promise<void> {
    const entry = this.mongoWatchers.get(key);
    if (!entry) return;

    try {
      await entry.watcher.close();
      this.mongoWatchers.delete(key);
      console.log(`[ChangeStream] MongoDB watcher closed for ${key}`);
    } catch (error) {
      console.error(`[ChangeStream] Error closing MongoDB watcher for ${key}:`, error);
    }
  }

  // ===========================================
  // S3 Change Watching
  // ===========================================

  /**
   * Subscribe a client to S3 bucket/prefix changes
   */
  public async subscribeToS3(
    connectionId: string,
    bucket: string,
    prefix?: string
  ): Promise<{ success: boolean; subscriptionId: string }> {
    const key = this.getS3Key(bucket, prefix);

    let entry = this.s3Watchers.get(key);

    // Create watcher if it doesn't exist
    if (!entry) {
      const watcher = await this.createS3Watcher(bucket, prefix);
      if (!watcher) {
        return { success: false, subscriptionId: '' };
      }

      entry = {
        watcher,
        subscriptions: new Map(),
      };
      this.s3Watchers.set(key, entry);
    }

    // Add subscription
    const subscriptionId = this.generateSubscriptionId();
    entry.subscriptions.set(connectionId, {
      connectionId,
      subscriptionId,
      createdAt: new Date(),
    });

    console.log(`[ChangeStream] S3 subscription added: ${key} for connection ${connectionId}`);
    return { success: true, subscriptionId };
  }

  /**
   * Unsubscribe a client from S3 bucket/prefix changes
   */
  public async unsubscribeFromS3(
    connectionId: string,
    bucket: string,
    prefix?: string
  ): Promise<boolean> {
    const key = this.getS3Key(bucket, prefix);
    const entry = this.s3Watchers.get(key);

    if (!entry) {
      return false;
    }

    entry.subscriptions.delete(connectionId);
    console.log(`[ChangeStream] S3 subscription removed: ${key} for connection ${connectionId}`);

    // Close watcher if no more subscribers
    if (entry.subscriptions.size === 0) {
      await this.closeS3Watcher(key);
    }

    return true;
  }

  /**
   * Create an S3 bucket watcher
   */
  private async createS3Watcher(
    bucket: string,
    prefix?: string
  ): Promise<plugins.smartbucket.BucketWatcher | null> {
    try {
      const smartbucket = await this.tsview.getSmartBucket();
      if (!smartbucket) {
        console.error('[ChangeStream] S3 not configured');
        return null;
      }

      const bucketInstance = await smartbucket.getBucketByName(bucket);

      // Create watcher using smartbucket's BucketWatcher
      const watcher = bucketInstance.createWatcher({
        prefix: prefix || '',
        pollIntervalMs: 5000,
        bufferTimeMs: 500,
      });

      // Subscribe to change events
      watcher.changeSubject.subscribe((eventOrEvents: IS3ChangeEvent | IS3ChangeEvent[]) => {
        const events = Array.isArray(eventOrEvents) ? eventOrEvents : [eventOrEvents];
        for (const event of events) {
          this.handleS3Change(bucket, prefix, event);
        }
      });

      // Start the watcher
      await watcher.start();
      await watcher.readyDeferred.promise;

      console.log(`[ChangeStream] S3 watcher created for ${bucket}${prefix ? '/' + prefix : ''}`);
      return watcher;
    } catch (error) {
      console.error(`[ChangeStream] Failed to create S3 watcher for ${bucket}:`, error);
      return null;
    }
  }

  /**
   * Handle an S3 change event
   */
  private handleS3Change(bucket: string, prefix: string | undefined, event: IS3ChangeEvent): void {
    const key = this.getS3Key(bucket, prefix);
    const entry = this.s3Watchers.get(key);

    if (!entry) return;

    // Add to activity buffer
    this.addToActivityBuffer('s3', event);

    // Push to all subscribed clients
    this.pushS3ChangeToClients(key, event);
  }

  /**
   * Push S3 change to subscribed clients
   */
  private async pushS3ChangeToClients(
    key: string,
    event: IS3ChangeEvent
  ): Promise<void> {
    const entry = this.s3Watchers.get(key);
    if (!entry || !this.typedSocket) return;

    for (const [connectionId, _sub] of entry.subscriptions) {
      try {
        const connection = await this.typedSocket.findTargetConnection(async (conn: any) => {
          return conn.alias === connectionId || conn.socketId === connectionId;
        });

        if (connection) {
          const request = this.typedSocket.createTypedRequest<interfaces.IReq_PushS3Change>(
            'pushS3Change',
            connection
          );
          await request.fire({ event });
        }
      } catch (error) {
        console.error(`[ChangeStream] Failed to push S3 change to ${connectionId}:`, error);
      }
    }
  }

  /**
   * Close an S3 bucket watcher
   */
  private async closeS3Watcher(key: string): Promise<void> {
    const entry = this.s3Watchers.get(key);
    if (!entry) return;

    try {
      await entry.watcher.stop();
      this.s3Watchers.delete(key);
      console.log(`[ChangeStream] S3 watcher closed for ${key}`);
    } catch (error) {
      console.error(`[ChangeStream] Error closing S3 watcher for ${key}:`, error);
    }
  }

  // ===========================================
  // Activity Stream
  // ===========================================

  /**
   * Subscribe a client to the activity stream
   */
  public async subscribeToActivity(connectionId: string): Promise<{ success: boolean; subscriptionId: string }> {
    const subscriptionId = this.generateSubscriptionId();

    this.activitySubscribers.set(connectionId, {
      connectionId,
      subscriptionId,
      createdAt: new Date(),
    });

    console.log(`[ChangeStream] Activity subscription added for connection ${connectionId}`);
    return { success: true, subscriptionId };
  }

  /**
   * Unsubscribe a client from the activity stream
   */
  public async unsubscribeFromActivity(connectionId: string): Promise<boolean> {
    const result = this.activitySubscribers.delete(connectionId);
    if (result) {
      console.log(`[ChangeStream] Activity subscription removed for connection ${connectionId}`);
    }
    return result;
  }

  /**
   * Get recent activity events
   */
  public getRecentActivity(limit: number = 100): interfaces.IActivityEvent[] {
    const count = Math.min(limit, this.activityBuffer.length);
    return this.activityBuffer.slice(-count);
  }

  /**
   * Add an event to the activity buffer
   */
  private addToActivityBuffer(
    source: 'mongodb' | 's3',
    event: interfaces.IMongoChangeEvent | IS3ChangeEvent
  ): void {
    const activityEvent: interfaces.IActivityEvent = {
      id: `evt_${Date.now()}_${Math.random().toString(36).substr(2, 9)}`,
      source,
      event,
      timestamp: new Date().toISOString(),
    };

    this.activityBuffer.push(activityEvent);

    // Trim buffer if it exceeds max size
    if (this.activityBuffer.length > this.ACTIVITY_BUFFER_SIZE) {
      this.activityBuffer = this.activityBuffer.slice(-this.ACTIVITY_BUFFER_SIZE);
    }

    // Push to activity subscribers
    this.pushActivityToClients(activityEvent);
  }

  /**
   * Push activity event to subscribed clients
   */
  private async pushActivityToClients(event: interfaces.IActivityEvent): Promise<void> {
    if (!this.typedSocket || this.activitySubscribers.size === 0) return;

    for (const [connectionId, _sub] of this.activitySubscribers) {
      try {
        const connection = await this.typedSocket.findTargetConnection(async (conn: any) => {
          return conn.alias === connectionId || conn.socketId === connectionId;
        });

        if (connection) {
          const request = this.typedSocket.createTypedRequest<interfaces.IReq_PushActivityEvent>(
            'pushActivityEvent',
            connection
          );
          await request.fire({ event });
        }
      } catch (error) {
        console.error(`[ChangeStream] Failed to push activity to ${connectionId}:`, error);
      }
    }
  }

  // ===========================================
  // Connection Management
  // ===========================================

  /**
   * Handle client disconnect - clean up all subscriptions
   */
  public async handleDisconnect(connectionId: string): Promise<void> {
    console.log(`[ChangeStream] Cleaning up subscriptions for disconnected connection ${connectionId}`);

    // Clean up MongoDB subscriptions
    for (const [key, entry] of this.mongoWatchers) {
      if (entry.subscriptions.has(connectionId)) {
        entry.subscriptions.delete(connectionId);
        if (entry.subscriptions.size === 0) {
          await this.closeMongoWatcher(key);
        }
      }
    }

    // Clean up S3 subscriptions
    for (const [key, entry] of this.s3Watchers) {
      if (entry.subscriptions.has(connectionId)) {
        entry.subscriptions.delete(connectionId);
        if (entry.subscriptions.size === 0) {
          await this.closeS3Watcher(key);
        }
      }
    }

    // Clean up activity subscription
    this.activitySubscribers.delete(connectionId);
  }

  /**
   * Stop all watchers and clean up
   */
  public async stop(): Promise<void> {
    console.log('[ChangeStream] Stopping all watchers...');

    // Close all MongoDB watchers
    for (const key of this.mongoWatchers.keys()) {
      await this.closeMongoWatcher(key);
    }

    // Close all S3 watchers
    for (const key of this.s3Watchers.keys()) {
      await this.closeS3Watcher(key);
    }

    // Clear activity buffer and subscribers
    this.activityBuffer = [];
    this.activitySubscribers.clear();

    console.log('[ChangeStream] All watchers stopped');
  }
}