import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.util.*;

public static String createSign(Map<String, String> params, String apiKey) throws Exception {
    List<String> keys = new ArrayList<>(params.keySet());
    Collections.sort(keys);
    StringBuilder sb = new StringBuilder();
    for (String k : keys) {
        String v = params.get(k);
        if (v == null || v.isEmpty()) continue;
        if ("pay_md5sign".equals(k) || "sign".equals(k)) continue;
        sb.append(k).append('=').append(v).append('&');
    }
    sb.append("key=").append(apiKey);
    MessageDigest md = MessageDigest.getInstance("MD5");
    byte[] dig = md.digest(sb.toString().getBytes(StandardCharsets.UTF_8));
    StringBuilder hex = new StringBuilder();
    for (byte b : dig) hex.append(String.format("%02X", b));
    return hex.toString();
}

// 使用 HttpURLConnection / OkHttp 等 POST application/x-www-form-urlencoded
Map<String, String> p = new LinkedHashMap<>();
p.put("pay_memberid", "10001");
p.put("pay_orderid", "ORD" + System.currentTimeMillis());
p.put("pay_applydate", "2024-08-01 12:00:00");
p.put("pay_bankcode", "902");
p.put("pay_notifyurl", "https://merchant.example/notify");
p.put("pay_callbackurl", "https://merchant.example/return");
p.put("pay_amount", "100.00");
p.put("pay_productname", "Demo");
p.put("pay_md5sign", createSign(p, apiKey));
// POST {gateway}/Pay_Index.html
// 代付：Payment_Dfpay_add.html（可加 bankCode）
// 查询：Pay_Trade_query.html / Payment_Dfpay_query.html
// 余额：Payment_Dfpay_balance.html

// Servlet/Controller 读取 form 参数 → createSign 验签 → 业务处理 → response.getWriter().print("ok");

import hashlib
import requests
from urllib.parse import urlencode

def create_sign(params: dict, api_key: str) -> str:
    items = []
    for k in sorted(params.keys()):
        if k in ('pay_md5sign', 'sign'):
            continue
        v = params[k]
        if v is None or v == '':
            continue
        items.append(f'{k}={v}')
    raw = '&'.join(items) + f'&key={api_key}'
    return hashlib.md5(raw.encode('utf-8')).hexdigest().upper()

gateway = 'https://your-gateway.example'
api_key = 'YOUR_API_KEY'
params = {
    'pay_memberid': '10001',
    'pay_orderid': 'ORD202408010001',
    'pay_applydate': '2024-08-01 12:00:00',
    'pay_bankcode': '902',
    'pay_notifyurl': 'https://merchant.example/notify',
    'pay_callbackurl': 'https://merchant.example/return',
    'pay_amount': '100.00',
    'pay_productname': 'Demo',
}
params['pay_md5sign'] = create_sign(params, api_key)
r = requests.post(gateway + '/Pay_Index.html', data=params, timeout=30)
print(r.text)

# 代付
df = {
    'mchid': '10001', 'out_trade_no': 'DF202408010001', 'money': '50.00',
    'bankname': 'BCA(Bank Central Asia)', 'bankCode': '014',
    'subbranch': '-', 'accountname': 'John Doe', 'cardnumber': '1234567890',
    'province': '-', 'city': '-', 'currency_type': 'IDR',
    'notifyUrl': 'https://merchant.example/df/notify',
}
df['pay_md5sign'] = create_sign(df, api_key)
requests.post(gateway + '/Payment_Dfpay_add.html', data=df, timeout=30)

# Flask 示例
@app.route('/notify', methods=['POST'])
def notify():
    data = request.form.to_dict()
    sign = data.get('pay_md5sign') or data.get('sign', '')
    if create_sign(data, api_key).upper() != sign.upper():
        return 'sign error', 400
    # TODO: 幂等更新订单
    return 'ok'

const crypto = require('crypto');
const axios = require('axios');
const qs = require('querystring');

function createSign(params, apiKey) {
  const keys = Object.keys(params).sort();
  let buf = '';
  for (const k of keys) {
    if (k === 'pay_md5sign' || k === 'sign') continue;
    const v = params[k];
    if (v === undefined || v === null || v === '') continue;
    buf += `${k}=${v}&`;
  }
  return crypto.createHash('md5').update(buf + 'key=' + apiKey, 'utf8').digest('hex').toUpperCase();
}

async function payOrder(gateway, apiKey, params) {
  params.pay_md5sign = createSign(params, apiKey);
  const { data } = await axios.post(gateway + '/Pay_Index.html', qs.stringify(params), {
    headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
    timeout: 30000,
  });
  return data;
}

// 代付 / 查询 / 余额：同样 createSign 后 POST
// Payment_Dfpay_add.html | Payment_Dfpay_query.html | Payment_Dfpay_balance.html

// Express
app.post('/notify', express.urlencoded({ extended: false }), (req, res) => {
  const data = req.body;
  const sign = data.pay_md5sign || data.sign || '';
  if (createSign(data, apiKey).toUpperCase() !== String(sign).toUpperCase()) {
    return res.status(400).send('sign error');
  }
  // TODO: 幂等更新
  res.send('ok');
});

package pay

import (
    "crypto/md5"
    "encoding/hex"
    "net/http"
    "net/url"
    "sort"
    "strings"
)

func CreateSign(params map[string]string, apiKey string) string {
    keys := make([]string, 0, len(params))
    for k := range params {
        keys = append(keys, k)
    }
    sort.Strings(keys)
    var b strings.Builder
    for _, k := range keys {
        if k == "pay_md5sign" || k == "sign" {
            continue
        }
        v := params[k]
        if v == "" {
            continue
        }
        b.WriteString(k)
        b.WriteByte('=')
        b.WriteString(v)
        b.WriteByte('&')
    }
    b.WriteString("key=")
    b.WriteString(apiKey)
    sum := md5.Sum([]byte(b.String()))
    return strings.ToUpper(hex.EncodeToString(sum[:]))
}

func PostForm(endpoint string, params map[string]string) (*http.Response, error) {
    form := url.Values{}
    for k, v := range params {
        form.Set(k, v)
    }
    return http.PostForm(endpoint, form)
}

params := map[string]string{
    "pay_memberid": "10001",
    "pay_orderid": "ORD202408010001",
    "pay_applydate": "2024-08-01 12:00:00",
    "pay_bankcode": "902",
    "pay_notifyurl": "https://merchant.example/notify",
    "pay_callbackurl": "https://merchant.example/return",
    "pay_amount": "100.00",
    "pay_productname": "Demo",
}
params["pay_md5sign"] = CreateSign(params, apiKey)
PostForm(gateway+"/Pay_Index.html", params)
// 代付带 bankCode: Payment_Dfpay_add.html

using System.Security.Cryptography;
using System.Text;

static string CreateSign(SortedDictionary<string, string> parameters, string apiKey)
{
    var sb = new StringBuilder();
    foreach (var kv in parameters)
    {
        if (kv.Key == "pay_md5sign" || kv.Key == "sign") continue;
        if (string.IsNullOrEmpty(kv.Value)) continue;
        sb.Append(kv.Key).Append('=').Append(kv.Value).Append('&');
    }
    sb.Append("key=").Append(apiKey);
    using var md5 = MD5.Create();
    var hash = md5.ComputeHash(Encoding.UTF8.GetBytes(sb.ToString()));
    var hex = new StringBuilder();
    foreach (var b in hash) hex.Append(b.ToString("X2"));
    return hex.ToString();
}

// HttpClient + FormUrlEncodedContent
var p = new SortedDictionary<string, string>
{
    ["pay_memberid"] = "10001",
    ["pay_orderid"] = "ORD202408010001",
    ["pay_applydate"] = "2024-08-01 12:00:00",
    ["pay_bankcode"] = "902",
    ["pay_notifyurl"] = "https://merchant.example/notify",
    ["pay_callbackurl"] = "https://merchant.example/return",
    ["pay_amount"] = "100.00",
    ["pay_productname"] = "Demo",
};
p["pay_md5sign"] = CreateSign(p, apiKey);
using var client = new HttpClient();
var content = new FormUrlEncodedContent(p);
var resp = await client.PostAsync(gateway + "/Pay_Index.html", content);
var body = await resp.Content.ReadAsStringAsync();
// 代付 / 查询 / 余额同理，注意 bankCode 有值时参与签名

// ASP.NET Core: 读取 form → CreateSign 验签 → 返回 Content("ok")