package com.zsjz.gateway.registry;

import com.zsjz.gateway.config.GatewayProperties;
import jakarta.annotation.PostConstruct;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.cloud.gateway.event.RefreshRoutesEvent;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

import java.util.List;
import java.util.Optional;

/**
 * 服务/节点配置的内存快照（事实来源是 PostgreSQL，Redis 与内存都只是缓存/快照）。
 *
 * <ul>
 *   <li>启动时：gateway_service 为空则用 YAML 播种，然后加载快照；</li>
 *   <li>运行中：本实例管理接口写库后立即 {@link #reload()}；其他实例每 10 秒对账一次，
 *       快照变化时发布 {@link RefreshRoutesEvent} 刷新路由缓存。</li>
 * </ul>
 */
@Slf4j
@Component
@RequiredArgsConstructor
public class GatewayRegistry {

    private final GatewayConfigRepository repository;
    private final GatewayProperties properties;
    private final ApplicationEventPublisher eventPublisher;

    private volatile List<ServiceInfo> services = List.of();

    /**
     * 首次加载（@PostConstruct 阶段）不能发布 RefreshRoutesEvent：启动期事件监听会
     * 拉起路由基础设施（CachingRouteLocator -> 路由定义仓库 -> 本类），形成循环依赖。
     * 初始路由定义由 CachingRouteLocator 自己创建时拉取，不需要事件；后续变更才需要。
     */
    private volatile boolean initialized = false;

    @PostConstruct
    void init() {
        seedFromYamlIfNeeded();
        reload();
    }

    /** 首次启动播种：表为空时把 gateway.services 写入数据库；之后 YAML 不再覆盖 */
    void seedFromYamlIfNeeded() {
        if (repository.countServices() > 0) {
            return;
        }
        List<GatewayProperties.ServiceDef> defs = properties.getServices();
        if (defs == null || defs.isEmpty()) {
            log.warn("gateway_service 表为空且 gateway.services 未配置，网关没有任何可转发服务");
            return;
        }
        for (GatewayProperties.ServiceDef def : defs) {
            GatewayConfigRepository.validateServiceId(def.getId());
            GatewayConfigRepository.validatePathPrefix(def.getPathPrefix());
            repository.seedService(def.getId(), def.getName(), def.getPathPrefix(),
                    def.getLoginPath(), def.getHealthPath(), def.getDefaultNodeId());
            if (def.getNodes() != null) {
                for (GatewayProperties.NodeDef node : def.getNodes()) {
                    GatewayConfigRepository.validateNodeId(node.getId());
                    GatewayConfigRepository.validateBaseUrl(node.getBaseUrl());
                    repository.seedNode(node.getId(), def.getId(), node.getName(), node.getBaseUrl());
                }
            }
        }
        log.info("已按 YAML 播种 {} 个网关服务", defs.size());
    }

    /**
     * 从数据库重载快照；有变化时发布路由刷新事件。
     *
     * @return true 表示快照发生了变化
     */
    public synchronized boolean reload() {
        List<ServiceInfo> fresh = repository.loadAll();
        boolean changed = !fresh.equals(services);
        if (changed) {
            services = fresh;
            if (initialized) {
                eventPublisher.publishEvent(new RefreshRoutesEvent(this));
            }
            log.info("网关配置已重载：{} 个服务 {}", fresh.size(),
                    fresh.stream().map(ServiceInfo::id).toList());
        }
        initialized = true;
        return changed;
    }

    /** 其他网关实例写库后的对账（多实例共享 PG，写侧只刷新自己，读侧靠这里收敛） */
    @Scheduled(fixedDelayString = "${gateway.registry-poll-interval:10s}")
    void pollForChanges() {
        try {
            reload();
        } catch (Exception ex) {
            log.warn("网关配置对账失败，下一轮重试：{}", ex.toString());
        }
    }

    public List<ServiceInfo> getServices() {
        return services;
    }

    public Optional<ServiceInfo> getService(String serviceId) {
        return services.stream().filter(s -> s.id().equals(serviceId)).findFirst();
    }

    /** 按路径前缀找服务（快照已按前缀长度降序，第一个命中的即最长前缀） */
    public Optional<ServiceInfo> findServiceByPath(String rawPath) {
        return services.stream().filter(s -> s.matchesPath(rawPath)).findFirst();
    }
}