import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpServer;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.InetSocketAddress;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.MessageDigest;
import java.time.Instant;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Locale;
import java.util.Set;
import java.util.UUID;
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

/** ABCPAY Java 8 示例：发送六类请求，也可接收两类回调。 */
public class AbcpayExample {
    private static final Set<String> PATHS = new HashSet<>(Arrays.asList(
            "/abcpay/collection/create", "/abcpay/payout/create",
            "/abcpay/wallet/balance", "/abcpay/upi/query",
            "/abcpay/utr/query", "/abcpay/order/query"));

    private static String required(String name) {
        String value = System.getenv(name);
        if (value == null || value.isEmpty()) throw new IllegalArgumentException("请设置环境变量 " + name);
        return value;
    }

    private static byte[] readAll(InputStream input) throws Exception {
        ByteArrayOutputStream output = new ByteArrayOutputStream();
        byte[] buffer = new byte[4096];
        int count;
        while ((count = input.read(buffer)) != -1) output.write(buffer, 0, count);
        return output.toByteArray();
    }

    private static String hex(byte[] bytes) {
        char[] alphabet = "0123456789abcdef".toCharArray();
        char[] result = new char[bytes.length * 2];
        for (int i = 0; i < bytes.length; i++) {
            result[i * 2] = alphabet[(bytes[i] >>> 4) & 15];
            result[i * 2 + 1] = alphabet[bytes[i] & 15];
        }
        return new String(result);
    }

    private static String sign(String key, String method, String path,
                               String timestamp, String nonce, byte[] body) throws Exception {
        String digest = hex(MessageDigest.getInstance("SHA-256").digest(body));
        String source = "ABCPAY-OPEN-1\n" + method.toUpperCase(Locale.ROOT) + "\n"
                + path + "\n" + timestamp + "\n" + nonce + "\n" + digest;
        Mac mac = Mac.getInstance("HmacSHA256");
        mac.init(new SecretKeySpec(key.getBytes(StandardCharsets.UTF_8), "HmacSHA256"));
        return hex(mac.doFinal(source.getBytes(StandardCharsets.UTF_8)));
    }

    private static void send(String[] args) throws Exception {
        String path = args.length == 0 ? "/abcpay/wallet/balance" : args[0];
        if (!PATHS.contains(path)) throw new IllegalArgumentException("接口路径不在示例范围内");
        byte[] body = args.length < 2 ? "{}".getBytes(StandardCharsets.UTF_8)
                : Files.readAllBytes(Paths.get(args[1]));
        String base = System.getenv("ABCPAY_BASE_URL");
        if (base == null || base.isEmpty()) base = "https://abc.yamipay.cc";
        String timestamp = Long.toString(Instant.now().getEpochSecond());
        String nonce = UUID.randomUUID().toString().replace("-", "");
        URL url = new URL(base.replaceAll("/+$", "") + path);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("POST");
        connection.setConnectTimeout(10000);
        connection.setReadTimeout(20000);
        connection.setDoOutput(true);
        connection.setRequestProperty("Content-Type", "application/json; charset=UTF-8");
        connection.setRequestProperty("Abcpay-Merchant", required("ABCPAY_MERCHANT"));
        connection.setRequestProperty("Abcpay-Timestamp", timestamp);
        connection.setRequestProperty("Abcpay-Nonce", nonce);
        connection.setRequestProperty("Abcpay-Signature",
                sign(required("ABCPAY_API_KEY"), "POST", path, timestamp, nonce, body));
        try (OutputStream output = connection.getOutputStream()) {
            output.write(body);
        }
        int status = connection.getResponseCode();
        InputStream response = status < 400 ? connection.getInputStream() : connection.getErrorStream();
        byte[] responseBody = response == null ? new byte[0] : readAll(response);
        if (response != null) response.close();
        System.out.println("HTTP " + status);
        System.out.println(new String(responseBody, StandardCharsets.UTF_8));
        connection.disconnect();
    }

    private static void reply(HttpExchange exchange, int status, String text) throws Exception {
        byte[] body = text.getBytes(StandardCharsets.UTF_8);
        exchange.getResponseHeaders().set("Content-Type", "text/plain; charset=UTF-8");
        exchange.sendResponseHeaders(status, body.length);
        try (OutputStream output = exchange.getResponseBody()) {
            output.write(body);
        }
    }

    private static void callback(HttpExchange exchange) {
        try {
            String path = exchange.getRequestURI().getRawPath();
            if (!"POST".equals(exchange.getRequestMethod()) ||
                    !("/notify/collection".equals(path) || "/notify/payout".equals(path))) {
                reply(exchange, 405, "请求方式或路径不正确");
                return;
            }
            byte[] body = readAll(exchange.getRequestBody());
            String merchant = exchange.getRequestHeaders().getFirst("Abcpay-Merchant");
            String timestamp = exchange.getRequestHeaders().getFirst("Abcpay-Timestamp");
            String nonce = exchange.getRequestHeaders().getFirst("Abcpay-Nonce");
            String signature = exchange.getRequestHeaders().getFirst("Abcpay-Signature");
            if (!required("ABCPAY_MERCHANT").equals(merchant) || timestamp == null ||
                    !timestamp.matches("[0-9]{1,15}") ||
                    Math.abs(Instant.now().getEpochSecond() - Long.parseLong(timestamp)) > 300 ||
                    nonce == null || !nonce.matches("[A-Za-z0-9_-]{16,64}") ||
                    signature == null || !signature.matches("(?i)[0-9a-f]{64}")) {
                reply(exchange, 401, "回调鉴权失败");
                return;
            }
            String expected = sign(required("ABCPAY_API_KEY"), "POST", path, timestamp, nonce, body);
            if (!MessageDigest.isEqual(expected.getBytes(StandardCharsets.US_ASCII),
                    signature.toLowerCase(Locale.ROOT).getBytes(StandardCharsets.US_ASCII))) {
                reply(exchange, 401, "回调签名错误");
                return;
            }
            // 演示接收：正式业务应先持久化 noticeId 并完成幂等处理，再返回 ACK。
            System.out.println(new String(body, StandardCharsets.UTF_8));
            reply(exchange, 200, "ACK");
        } catch (Exception error) {
            try { reply(exchange, 500, "回调处理失败"); } catch (Exception ignored) { }
        }
    }

    private static void serve() throws Exception {
        int port = Integer.parseInt(System.getenv().getOrDefault("ABCPAY_CALLBACK_PORT", "8080"));
        HttpServer server = HttpServer.create(new InetSocketAddress(port), 0);
        server.createContext("/notify/collection", AbcpayExample::callback);
        server.createContext("/notify/payout", AbcpayExample::callback);
        server.start();
        System.out.println("回调监听端口：" + port);
    }

    public static void main(String[] args) throws Exception {
        if (args.length > 0 && "serve".equals(args[0])) serve();
        else send(args);
    }
}