import java.security.MessageDigest;
import java.util.*;
import java.net.http.*;
import java.net.URI;

/**
 * 彩虹易支付 Java SDK 示例
 * 文档: https://xxkkfz.cn/apidoc.html
 */
public class EpaySubmit {
    
    public static String md5(String input) throws Exception {
        MessageDigest md = MessageDigest.getInstance("MD5");
        byte[] digest = md.digest(input.getBytes("UTF-8"));
        StringBuilder sb = new StringBuilder();
        for (byte b : digest) sb.append(String.format("%02x", b));
        return sb.toString();
    }
    
    public static String submit(Map<String, String> params, String key) throws Exception {
        // 排序并签名
        TreeMap<String, String> sorted = new TreeMap<>(params);
        StringBuilder sb = new StringBuilder();
        for (Map.Entry<String, String> e : sorted.entrySet()) {
            if (!e.getKey().equals("sign") && !e.getValue().isEmpty()) {
                sb.append(e.getKey()).append("=").append(e.getValue()).append("&");
            }
        }
        String signStr = sb.toString().replaceAll("&$", "");
        params.put("sign", md5(signStr + key));
        params.put("sign_type", "MD5");
        
        // 请求
        HttpClient client = HttpClient.newHttpClient();
        HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create("https://xxkkfz.cn/api/submit.php"))
            .header("Content-Type", "application/x-www-form-urlencoded")
            .POST(HttpRequest.BodyPublishers.ofString(buildForm(params)))
            .build();
        return client.send(request, HttpResponse.BodyHandlers.ofString()).body();
    }
    
    public static void main(String[] args) throws Exception {
        Map<String, String> p = new HashMap<>();
        p.put("pid", "1001");
        p.put("type", "alipay");
        p.put("out_trade_no", "ORDER" + System.currentTimeMillis());
        p.put("notify_url", "https://你的域名/notify");
        p.put("return_url", "https://你的域名/return");
        p.put("name", "测试商品");
        p.put("money", "0.01");
        System.out.println(submit(p, "你的商户密钥"));
    }
}