/**
 * Fabric Gateway Node.js 后端
 * 将链码调用映射为 REST API
 */
import { Gateway, Wallets, Contract } from 'fabric-gateway';
import * as grpc from '@grpc/grpc-js';
import { readFileSync } from 'fs';

interface ConnectionProfile {
  url: string;
  tlsCACert: string;
  peerName: string;
}

class FabricClientService {
  private gateway: Gateway;
  private contract: Contract;
  
  async connect(profile: ConnectionProfile, userId: string, org: string) {
    // 加载 TLS 根证书
    const tlsRootCert = readFileSync(profile.tlsCACert);
    const client = new grpc.Channel(profile.url, grpc.credentials.createSsl(Buffer.from(tlsRootCert)));
    
    // 加载用户身份钱包
    const wallet = await Wallets.newFileSystemWallet('./wallet');
    const identity = await wallet.get(userId);
    if (!identity) throw new Error(`身份 ${userId} 不存在于钱包`);
    
    // 建立 Gateway 连接
    const gateway = new Gateway()// 内部使用 gRPC
    // 通过 gateway 获取网络与合约
    this.gateway = gateway;
    const network = gateway.getNetwork('mychannel');
    this.contract = network.getContract('assettransfer');
  }
  
  // === 只读查询：evaluate（单个 peer）
  async getAsset(id: string): Promise<Asset> {
    const result = await this.contract.evaluateTransaction('ReadAsset', id);
    return JSON.parse(Buffer.from(result).toString());
  }
  
  // === 写入交易：submit（完整背书→排序→提交）
  async createAsset(asset: Asset): Promise<string> {
    const result = await this.contract.submitTransaction(
      'CreateAsset',
      asset.id,
      asset.color,
      asset.owner,
      asset.size.toString(),
      asset.appraisedValue.toString(),
    );
    // 返回交易 ID
    return Buffer.from(result).toString();
  }
  
  // 转移（需要写交易）
  async transferAsset(id: string, newOwner: string): Promise<string> {
    return this.contract.submitTransaction('TransferAsset', id, newOwner)
      .then(r => Buffer.from(r).toString());
  }
  
  async disconnect() {
    this.gateway.close();
  }
}

// Express REST API 封装
import express from 'express';
const app = express();
const fabric = new FabricClientService();

app.get('/assets/:id', async (req, res) => {
  const asset = await fabric.getAsset(req.params.id);
  res.json(asset);
});

app.post('/assets', async (req, res) => {
  const txId = await fabric.createAsset(req.body);
  res.json({ transactionId: txId, status: 'submitted' });
});

app.put('/assets/:id/transfer', async (req, res) => {
  const txId = await fabric.transferAsset(req.params.id, req.body.newOwner);
  res.json({ transactionId: txId });
});

// 对比：公链中用户用 MetaMask 签名
// 联盟链中后端代签（因为是服务端服务）
// 后端持有用户注册的钱包密钥（或 HSM 托管）