import { Injectable, Logger, UnauthorizedException } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import { ApiKey } from '../database/entities/api-key.entity';
import * as crypto from 'crypto';

@Injectable()
export class ApiKeysService {
  private readonly logger = new Logger(ApiKeysService.name);

  constructor(
    @InjectRepository(ApiKey)
    private readonly apiKeyRepo: Repository<ApiKey>,
  ) {}

  async createApiKey(
    name: string,
    expiresDays?: number,
  ): Promise<{ plainKey: string; entity: ApiKey }> {
    const prefix = 'pm_';
    const randomPart = crypto.randomBytes(24).toString('hex'); // 48 chars hex
    const plainKey = `${prefix}${randomPart}`;

    const keyHash = this.hashKey(plainKey);

    const apiKey = this.apiKeyRepo.create({
      name,
      keyPrefix: prefix,
      keyHash,
      expiresAt: expiresDays
        ? new Date(Date.now() + expiresDays * 24 * 60 * 60 * 1000)
        : null,
    });

    const savedKey = await this.apiKeyRepo.save(apiKey);

    return {
      plainKey,
      entity: savedKey,
    };
  }

  async validateKey(plainKey: string): Promise<ApiKey> {
    const keyHash = this.hashKey(plainKey);

    const apiKey = await this.apiKeyRepo.findOne({
      where: { keyHash },
    });

    if (!apiKey) {
      throw new UnauthorizedException('Invalid API Key');
    }

    if (apiKey.expiresAt && apiKey.expiresAt < new Date()) {
      throw new UnauthorizedException('API Key has expired');
    }

    // Update last used timestamp (async, don't wait for it to return response faster)
    apiKey.lastUsedAt = new Date();
    this.apiKeyRepo
      .save(apiKey)
      .catch((err) =>
        this.logger.error('Fehler beim Aktualisieren von lastUsedAt', err),
      );

    return apiKey;
  }

  async listKeys(): Promise<ApiKey[]> {
    return this.apiKeyRepo.find({
      order: { createdAt: 'DESC' },
    });
  }

  async deleteKey(id: string): Promise<void> {
    await this.apiKeyRepo.delete(id);
  }

  private hashKey(key: string): string {
    return crypto.createHash('sha256').update(key).digest('hex');
  }
}