import { twilioConfig } from '../config/twilio';

export interface TokenRequest {
  identity: string;
  roomName: string;
  apiKey?: string;
  apiSecret?: string;
}

export interface TokenResponse {
  token: string;
  identity: string;
  roomName: string;
}

// 模拟Token生成服务
// 在实际生产环境中，这应该是一个后端API服务
export class TokenService {
  // 生成访问令牌
  async generateAccessToken(request: TokenRequest): Promise<TokenResponse> {
    try {
      // 在实际应用中，这里应该调用后端API
      // 这里我们创建一个模拟的token
      const mockToken = this.generateMockToken(request.identity, request.roomName);
      
      return {
        token: mockToken,
        identity: request.identity,
        roomName: request.roomName,
      };
    } catch (error) {
      console.error('Error generating access token:', error);
      throw new Error('Failed to generate access token');
    }
  }

  // 生成模拟Token（仅用于开发测试）
  private generateMockToken(identity: string, roomName: string): string {
    // 这是一个简化的JWT模拟
    // 实际应用中应该使用Twilio SDK在后端生成真实的token
    const header = {
      typ: 'JWT',
      alg: 'HS256',
      cty: 'twilio-fpa;v=1'
    };

    const payload = {
      iss: twilioConfig.apiKey,
      sub: twilioConfig.accountSid,
      nbf: Math.floor(Date.now() / 1000),
      exp: Math.floor(Date.now() / 1000) + 3600, // 1小时有效期
      jti: `${twilioConfig.apiKey}-${Date.now()}`,
      grants: {
        identity: identity,
        video: {
          room: roomName
        }
      }
    };

    // 在实际应用中，这里应该用正确的签名算法
    const encodedHeader = btoa(JSON.stringify(header));
    const encodedPayload = btoa(JSON.stringify(payload));
    const signature = btoa(`${twilioConfig.apiSecret}-signature`);

    return `${encodedHeader}.${encodedPayload}.${signature}`;
  }

  // 验证Token（模拟）
  validateToken(token: string): boolean {
    try {
      const parts = token.split('.');
      if (parts.length !== 3) return false;

      const payload = JSON.parse(atob(parts[1]));
      const now = Math.floor(Date.now() / 1000);
      
      return payload.exp > now;
    } catch {
      return false;
    }
  }

  // 解析Token信息
  parseToken(token: string): { identity: string; roomName: string } | null {
    try {
      const parts = token.split('.');
      if (parts.length !== 3) return null;

      const payload = JSON.parse(atob(parts[1]));
      
      return {
        identity: payload.grants?.identity || '',
        roomName: payload.grants?.video?.room || '',
      };
    } catch {
      return null;
    }
  }
}

export const tokenService = new TokenService();

// Express.js API端点示例（如果需要真实的后端服务）
export const createTokenEndpoint = () => {
  return async (req: any, res: any) => {
    try {
      const { identity, roomName } = req.body;
      
      if (!identity || !roomName) {
        return res.status(400).json({ 
          error: 'Identity and roomName are required' 
        });
      }

      const tokenResponse = await tokenService.generateAccessToken({
        identity,
        roomName,
      });

      res.json(tokenResponse);
    } catch (error) {
      console.error('Token generation error:', error);
      res.status(500).json({ 
        error: 'Failed to generate token' 
      });
    }
  };
};