package com.xtrh.discovery.util;

import com.xtrh.common.config.Settings;

import java.net.InetSocketAddress;
import java.net.InetAddress;
import java.net.Inet4Address;
import java.net.NetworkInterface;
import java.net.Socket;
import java.net.URI;
import java.util.Collections;

/**
 * 选择节点对外登记的地址，不把本机回环地址默认当成跨电脑播放地址。
 * 多网卡时根据到已认证总控的实际网络路由选择本机地址，而非主机名的首个解析结果。
 */
public final class NodeAddress {
    private NodeAddress() {}

    public static String host(Settings settings, String coordinator) throws Exception {
        if (!settings.advertisedHost.isBlank()) {
            // 特殊网络或播放域名由部署配置覆盖，最终注册仍执行服务根地址校验。
            return settings.advertisedHost;
        }

        // 主执行端通过本机入口领取任务，对外登记地址必须另外选择，供其他电脑播放。
        if (settings.role.equals("coordinator")) return localHost(settings);
        URI uri = URI.create(coordinator);
        try (Socket route = new Socket()) {
            // 连接只用于查询操作系统选出的本机接口，关闭后不会持续占用控制连接。
            // HTTPS 未显式写端口时按 443 查询路由，HTTP 按 80。
            route.connect(new InetSocketAddress(
                uri.getHost(),
                uri.getPort() > 0 ? uri.getPort() : (uri.getScheme().equals("https") ? 443 : 80)),
                1000);
            InetAddress local = route.getLocalAddress();
            // 同电脑的独立子节点可能连接 localhost，同样不能把回环默认发布给远端观看者。
            return local.isLoopbackAddress() ? localHost(settings) : local.getHostAddress();
        }
    }

    /** 自注册只访问本实例已绑定的控制入口，网络发送仍走正常签名认证。 */
    public static String controlUrl(Settings settings) {
        if (!settings.httpReady()) throw new IllegalStateException("Waiting for local HTTP server");
        String host = wildcard(settings.bindHost) ? "127.0.0.1" : settings.bindHost;
        return httpUrl(host, settings.port);
    }

    // 发布实际 HTTP 端口；主节点的控制和媒体入口共用同一端口，不增开第二个执行进程。
    public static String url(Settings settings, String coordinator) throws Exception {
        return httpUrl(host(settings, coordinator), settings.port);
    }

    /** 对外地址优先尊重显式绑定与发现网卡，多网卡部署仍可用 advertised-host 指定。 */
    private static String localHost(Settings settings) throws Exception {
        if (!wildcard(settings.bindHost)) return settings.bindHost;
        if (!settings.discoveryAddress.isBlank()) {
            InetAddress configured = InetAddress.getByName(settings.discoveryAddress);
            if (!configured.isLoopbackAddress() && !configured.isAnyLocalAddress()) return configured.getHostAddress();
        }
        // 只考虑启用的真实 IPv4 网卡，避免默认发布回环、链路本地或虚拟接口的地址。
        var interfaces = Collections.list(NetworkInterface.getNetworkInterfaces());
        InetAddress preferred = null;
        try { preferred = InetAddress.getLocalHost(); } catch (Exception ignored) { }
        String first = null;
        for (NetworkInterface card : interfaces) {
            if (!card.isUp() || card.isLoopback() || card.isVirtual()) continue;
            for (InetAddress address : Collections.list(card.getInetAddresses())) {
                if (!(address instanceof Inet4Address) || address.isLoopbackAddress() || address.isLinkLocalAddress()) continue;
                if (address.equals(preferred)) return address.getHostAddress();
                if (first == null) first = address.getHostAddress();
            }
        }
        // 无局域网网卡的纯本机环境仍可运行；跨电脑使用须发布观看端可访问的地址。
        return first == null ? "127.0.0.1" : first;
    }

    private static boolean wildcard(String host) {
        return host.isBlank() || host.equals("0.0.0.0") || host.equals("::") || host.equals("[::]");
    }

    // IPv6 字面量需要方括号，确保绑定特定网卡时仍生成合法 URL。
    private static String httpUrl(String host, int port) {
        String authority = host.contains(":") && !host.startsWith("[") ? "[" + host + "]" : host;
        return "http://" + authority + ":" + port;
    }
}