Throttle Guard

import { Injectable, ExecutionContext } from "@nestjs/common";
import {
  ThrottlerGuard,
  ThrottlerException,
  ThrottlerModuleOptions,
} from "@nestjs/throttler";
import { Reflector } from "@nestjs/core";

// Custom metadata keys for per-route limits
export const THROTTLE_LIMIT_KEY = "throttle_limit";
export const THROTTLE_TTL_KEY = "throttle_ttl";
export const SKIP_THROTTLE_KEY = "skip_throttle";

@Injectable()
export class CustomThrottlerGuard extends ThrottlerGuard {
  constructor(
    options: ThrottlerModuleOptions,
    storageService: any,
    reflector: Reflector
  ) {
    super(options, storageService, reflector);
  }

  // Skip throttling for certain routes
  protected async shouldSkip(context: ExecutionContext): Promise<boolean> {
    const skipThrottle = this.reflector.getAllAndOverride<boolean>(
      SKIP_THROTTLE_KEY,
      [context.getHandler(), context.getClass()]
    );
    return skipThrottle ?? false;
  }

  // Custom error message
  protected throwThrottlingException(context: ExecutionContext): void {
    const request = context.switchToHttp().getRequest();
    throw new ThrottlerException(
      `Too many requests. Please try again later. (IP: ${this.getTracker(request)})`
    );
  }

  // Use IP address as tracker
  protected getTracker(request: Record<string, any>): string {
    return (
      request.headers["x-forwarded-for"]?.split(",")[0] ||
      request.ip ||
      request.connection?.remoteAddress ||
      "unknown"
    );
  }
}

// Decorator helpers for per-route rate limiting
import { SetMetadata } from "@nestjs/common";

/**
 * Set custom throttle limit for a route.
 * 
 * Usage:
 * @Throttle(5, 60) // 5 requests per 60 seconds
 * @Post("login")
 * login() {}
 */
export const Throttle = (limit: number, ttl: number) =>
  SetMetadata("throttler", { limit, ttl });

/**
 * Skip throttling for a route.
 * 
 * Usage:
 * @SkipThrottle()
 * @Get("health")
 * health() {}
 */
export const SkipThrottle = () => SetMetadata(SKIP_THROTTLE_KEY, true);

// Module configuration example:
/*
import { Module } from "@nestjs/common";
import { ThrottlerModule } from "@nestjs/throttler";
import { APP_GUARD } from "@nestjs/core";
import { CustomThrottlerGuard } from "./guards/throttle.guard";

@Module({
  imports: [
    ThrottlerModule.forRoot([{
      ttl: 60000, // 1 minute
      limit: 100, // 100 requests
    }]),
  ],
  providers: [
    {
      provide: APP_GUARD,
      useClass: CustomThrottlerGuard,
    },
  ],
})
export class AppModule {}
*/