import { Injectable, CanActivate, ExecutionContext } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { Request, Response } from 'express';
import { rateLimit } from 'express-rate-limit';

@Injectable()
export class IpRateLimiterGuard implements CanActivate {
  private readonly limiter: ReturnType<typeof rateLimit>;

  constructor(private readonly configService: ConfigService) {
    const isProduction = this.configService.get('NODE_ENV') === 'production';
    this.limiter = rateLimit({
      windowMs: 15 * 60 * 1000, // 15 minutes
      max: isProduction ? 50 : 100, // Stricter in production
      standardHeaders: false,
      legacyHeaders: false,
      skip: () =>
        !isProduction &&
        this.configService.get('DISABLE_RATE_LIMIT') === 'true', // Skip in dev if needed
      keyGenerator: (req) => {
        // Use IP or user ID if available
        return isProduction ? req.ip : ''; // Less strict in development
      },
      handler: (req, res) => {
        res.status(429).json({
          statusCode: 429,
          message: isProduction
            ? 'Too many requests'
            : 'Dev Mode: Rate limit warning (not enforced)',
        });
      },
    });
  }

  async canActivate(context: ExecutionContext): Promise<boolean> {
    const httpContext = context.switchToHttp();
    const req = httpContext.getRequest<Request>();
    const res = httpContext.getResponse<Response>();
    return new Promise((resolve) => {
      this.limiter(req, res, (err?: unknown) => {
        if (err) {
          return resolve(false);
        }
        resolve(true);
      });
    });
  }
}