import * as crypto from 'crypto';
import { Injectable, UnauthorizedException } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { createRemoteJWKSet, jwtVerify } from 'jose';

@Injectable()
export class AppleAuthService {
  private readonly appleIssuer: string;
  private readonly appleBundleId: string;
  private readonly jwks: ReturnType<typeof createRemoteJWKSet>;

  constructor(private readonly configService: ConfigService) {
    this.appleIssuer = this.configService.get<string>(
      'apple.issuer',
      'https://appleid.apple.com',
    );
    this.appleBundleId = this.configService.get<string>('apple.bundleId', '');
    this.jwks = createRemoteJWKSet(
      new URL('https://appleid.apple.com/auth/keys'),
    );
  }

  async verifyIdentityToken(identityToken: string): Promise<{
    appleUserId: string;
    email?: string;
    emailVerified?: boolean;
  }> {
    if (!this.appleBundleId) {
      return this.verifyMock(identityToken);
    }
    return this.verifyReal(identityToken);
  }

  private verifyMock(identityToken: string): {
    appleUserId: string;
  } {
    if (!identityToken || identityToken.trim().length < 4) {
      throw new UnauthorizedException('identityToken 无效');
    }
    return {
      appleUserId: crypto
        .createHash('sha256')
        .update(`apple-mock:${identityToken}`)
        .digest('hex')
        .slice(0, 64),
    };
  }

  private async verifyReal(identityToken: string): Promise<{
    appleUserId: string;
    email?: string;
    emailVerified?: boolean;
  }> {
    try {
      const { payload } = await jwtVerify(identityToken, this.jwks, {
        issuer: this.appleIssuer,
        audience: this.appleBundleId,
      });

      return {
        appleUserId: payload.sub!,
        email:
          typeof payload.email === 'string' ? payload.email : undefined,
        emailVerified: payload.email_verified === true || payload.email_verified === 'true',
      };
    } catch (err: any) {
      const msg: string = err?.message ?? '';
      if (msg.includes('audience')) {
        throw new UnauthorizedException(
          `identityToken audience 不匹配，期望 ${this.appleBundleId}`,
        );
      }
      if (msg.includes('issuer')) {
        throw new UnauthorizedException('identityToken issuer 无效');
      }
      throw new UnauthorizedException('identityToken 验证失败');
    }
  }
}