import { AppError } from '../common/errors/app-error';
import { Injectable } from '@nestjs/common';
import { DatabaseService } from '../database/database.service';
import { hashToken } from './tokens';

@Injectable()
export class RateLimitService {
  constructor(private readonly db: DatabaseService) {}
  async consume(key: string, limit: number, seconds: number): Promise<void> {
    const digest = hashToken(key);
    const [row] = await this.db.$queryRaw<
      Array<{ hits: number; expiresAt: Date }>
    >`
      INSERT INTO rate_limits (key, hits, expires_at)
      VALUES (${digest}, 1, NOW() + ${seconds} * INTERVAL '1 second')
      ON CONFLICT (key) DO UPDATE SET
        hits = CASE WHEN rate_limits.expires_at <= NOW() THEN 1 ELSE rate_limits.hits + 1 END,
        expires_at = CASE WHEN rate_limits.expires_at <= NOW()
          THEN NOW() + ${seconds} * INTERVAL '1 second' ELSE rate_limits.expires_at END
      RETURNING hits, expires_at AS "expiresAt"
    `;
    if (row.hits > limit)
      throw new AppError(
        'RATE_LIMITED',
        key.split(':')[0],
        undefined,
        Math.max(1, Math.ceil((row.expiresAt.getTime() - Date.now()) / 1000)),
      );
  }
}