import type { EventHandler, EventSubscription, EventBusMessage } from './types';

/**
 * Simple in-memory event bus for testing
 */
export class SimpleEventBus {
  private subscriptions = new Map<string, Set<{ id: string; handler: EventHandler }>>();
  private subscriptionById = new Map<string, { id: string; channel: string; handler: EventHandler }>();
  private nextId = 1;

  subscribe(channel: string, handler: EventHandler): EventSubscription {
    const id = `sub-${this.nextId++}`;
    const subscription = { id, handler };

    if (!this.subscriptions.has(channel)) {
      this.subscriptions.set(channel, new Set());
    }
    this.subscriptions.get(channel)!.add(subscription);
    this.subscriptionById.set(id, { id, channel, handler });

    return { channel, handler };
  }

  unsubscribe(idOrSubscription: string | EventSubscription): boolean {
    if (typeof idOrSubscription === 'string') {
      const subscription = this.subscriptionById.get(idOrSubscription);
      if (!subscription) {
        return false;
      }
      
      const channelSubs = this.subscriptions.get(subscription.channel);
      if (channelSubs) {
        channelSubs.forEach(sub => {
          if (sub.id === idOrSubscription) {
            channelSubs.delete(sub);
          }
        });
        if (channelSubs.size === 0) {
          this.subscriptions.delete(subscription.channel);
        }
      }
      
      this.subscriptionById.delete(idOrSubscription);
      return true;
    } else {
      // Unsubscribe by matching handler and channel
      const channelSubs = this.subscriptions.get(idOrSubscription.channel);
      if (channelSubs) {
        let removed = false;
        channelSubs.forEach(sub => {
          if (sub.handler === idOrSubscription.handler) {
            channelSubs.delete(sub);
            this.subscriptionById.delete(sub.id);
            removed = true;
          }
        });
        if (channelSubs.size === 0) {
          this.subscriptions.delete(idOrSubscription.channel);
        }
        return removed;
      }
      return false;
    }
  }

  async publish(event: string, data: any): Promise<void> {
    const message: EventBusMessage = {
      id: `msg-${this.nextId++}`,
      type: event,
      source: 'simple-event-bus',
      timestamp: Date.now(),
      data,
    };

    const handlers: EventHandler[] = [];

    // Direct matches
    const directSubs = this.subscriptions.get(event);
    if (directSubs) {
      handlers.push(...Array.from(directSubs).map(s => s.handler));
    }

    // Pattern matches
    for (const [pattern, subs] of this.subscriptions) {
      if (pattern.includes('*') && this.matchPattern(pattern, event)) {
        handlers.push(...Array.from(subs).map(s => s.handler));
      }
    }

    // Execute all handlers
    await Promise.all(
      handlers.map(handler =>
        Promise.resolve(handler(message)).catch(err => {
          // Silently catch errors
        })
      )
    );
  }

  publishSync(event: string, data: any): void {
    const message: EventBusMessage = {
      id: `msg-${this.nextId++}`,
      type: event,
      source: 'simple-event-bus',
      timestamp: Date.now(),
      data,
    };

    const handlers: EventHandler[] = [];

    // Direct matches
    const directSubs = this.subscriptions.get(event);
    if (directSubs) {
      handlers.push(...Array.from(directSubs).map(s => s.handler));
    }

    // Pattern matches
    for (const [pattern, subs] of this.subscriptions) {
      if (pattern.includes('*') && this.matchPattern(pattern, event)) {
        handlers.push(...Array.from(subs).map(s => s.handler));
      }
    }

    // Execute all handlers synchronously
    handlers.forEach(handler => {
      try {
        handler(message);
      } catch {
        // Silently catch errors
      }
    });
  }

  once(event: string, handler: EventHandler): EventSubscription {
    let subId: string;
    const wrappedHandler: EventHandler = async (message) => {
      await handler(message);
      this.unsubscribe(subId);
    };

    const subscription = this.subscribe(event, wrappedHandler);
    // Find the subscription ID
    this.subscriptionById.forEach((value, key) => {
      if (value.handler === wrappedHandler) {
        subId = key;
      }
    });
    
    return subscription;
  }

  off(event: string, handler?: EventHandler): void {
    if (!handler) {
      // Remove all handlers for this event
      const subs = this.subscriptions.get(event);
      if (subs) {
        for (const sub of subs) {
          this.subscriptionById.delete(sub.id);
        }
        this.subscriptions.delete(event);
      }
    } else {
      // Remove specific handler
      const subs = this.subscriptions.get(event);
      if (subs) {
        const toRemove: string[] = [];
        subs.forEach(sub => {
          if (sub.handler === handler) {
            toRemove.push(sub.id);
          }
        });
        toRemove.forEach(id => {
          subs.forEach(sub => {
            if (sub.id === id) {
              subs.delete(sub);
            }
          });
          this.subscriptionById.delete(id);
        });
        if (subs.size === 0) {
          this.subscriptions.delete(event);
        }
      }
    }
  }

  hasSubscribers(event: string): boolean {
    return this.subscriptions.has(event) && this.subscriptions.get(event)!.size > 0;
  }

  clear(): void {
    this.subscriptions.clear();
    this.subscriptionById.clear();
  }

  private matchPattern(pattern: string, event: string): boolean {
    // Simple pattern matching: user.* matches user.created, user.updated, etc.
    const regex = new RegExp('^' + pattern.replace(/\*/g, '.*') + '$');
    return regex.test(event);
  }
}