package com.xuekairui.user.config;

import com.xuekairui.common.TraceIdGenerator;
import lombok.extern.slf4j.Slf4j;
import org.jetbrains.annotations.NotNull;
import org.slf4j.MDC;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.task.TaskDecorator;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;

import java.util.concurrent.Executor;
import java.util.concurrent.ThreadPoolExecutor;

/**
 * 异步任务与定时调度线程池配置
 */
@Configuration
@Slf4j
public class AsyncConfig {

    /**
     * 审计日志专用线程池
     * 核心线程数2，最大线程数5，队列容量100
     * 拒绝策略：CallerRunsPolicy（队列满时由调用线程执行，保证日志不丢失）
     */
    @Bean("auditLogExecutor")
    public Executor auditLogExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(2);
        executor.setMaxPoolSize(5);
        executor.setQueueCapacity(100);
        executor.setThreadNamePrefix("audit-log-");
        executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
        executor.initialize();
        return executor;
    }

    /**
     * 定时任务调度线程池
     *
     * <p>Spring 默认 @Scheduled 使用单线程（scheduling-1），所有定时任务串行执行，
     * 若某个任务阻塞会拖累其他任务。配置独立线程池后：
     * <ul>
     *   <li>各 @Scheduled 方法可并发执行，互不阻塞</li>
     *   <li>线程名前缀 scheduling- 便于日志排查</li>
     *   <li>核心线程数 2 覆盖当前 2 个定时任务，预留扩容空间</li>
     * </ul>
     *
     * <p>当前定时任务：
     * <ul>
     *   <li>PaymentOrderService.cleanupExpiredOrders() — 每分钟清理过期订单</li>
     *   <li>CrawlerQuotaGrantService.cleanupExpiredGrants() — 每小时清理过期配额</li>
     * </ul>
     */
    @Bean
    public ThreadPoolTaskScheduler taskScheduler() {
        ThreadPoolTaskScheduler scheduler = new ThreadPoolTaskScheduler();
        scheduler.setPoolSize(2);
        scheduler.setThreadNamePrefix("scheduling-");
        scheduler.setAwaitTerminationSeconds(60);
        scheduler.setWaitForTasksToCompleteOnShutdown(true);
        scheduler.setTaskDecorator(new MdcTraceIdTaskDecorator());
        scheduler.setErrorHandler(t ->
                log.error("定时任务执行异常", t));
        return scheduler;
    }

    /**
     * 定时任务 MDC 装饰器：为每个任务生成独立 traceId，便于无 HTTP 上下文时定位问题
     */
    public static class MdcTraceIdTaskDecorator implements TaskDecorator {

        private static final String TRACE_ID_KEY = "traceId";

        @NotNull
        @Override
        public Runnable decorate(@NotNull Runnable runnable) {
            return () -> {
                String traceId = generateTraceId();
                MDC.put(TRACE_ID_KEY, traceId);
                try {
                    runnable.run();
                } finally {
                    MDC.clear();
                }
            };
        }

        private String generateTraceId() {
            return TraceIdGenerator.generate();
        }
    }
}