package com.imutil.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.imutil.entity.DistQueue;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Update;

import java.time.OffsetDateTime;
import java.util.List;

/**
 * 分发队列 Mapper
 * <p>
 * 提供 FOR UPDATE SKIP LOCKED 抢占消费的 SQL。
 *
 * @author imutil
 */
public interface DistQueueMapper extends BaseMapper<DistQueue> {

    /**
     * 抢占式拉取待分发记录：SELECT ... FOR UPDATE SKIP LOCKED
     *
     * @param limit     每轮条数
     * @param lockedBy  抢占者标识
     * @param lockTime  锁定时间
     * @return 抢占到的记录
     */
    @org.apache.ibatis.annotations.Select(
            "SELECT id, msg_key, tenant_id, conv_id, target_url, payload, status, retry_count " +
                    "FROM dist_queue " +
                    "WHERE status = 0 AND next_retry_at <= #{now} " +
                    "ORDER BY next_retry_at, id " +
                    "LIMIT #{limit} " +
                    "FOR UPDATE SKIP LOCKED")
    List<DistQueue> fetchPending(@Param("now") OffsetDateTime now,
                                 @Param("limit") int limit);

    /**
     * 标记抢占：将 pending 置为 processing
     */
    @Update("UPDATE dist_queue SET status = 1, locked_by = #{lockedBy}, locked_at = #{lockTime}, " +
            "updated_at = #{lockTime} " +
            "WHERE id = #{id} AND status = 0")
    int lock(@Param("id") Long id,
             @Param("lockedBy") String lockedBy,
             @Param("lockTime") OffsetDateTime lockTime);

    /**
     * 标记分发成功
     */
    @Update("UPDATE dist_queue SET status = 2, updated_at = #{now} WHERE id = #{id} AND status = 1")
    int markDone(@Param("id") Long id, @Param("now") OffsetDateTime now);

    /**
     * 标记失败并安排重试（指数退避）
     */
    @Update("UPDATE dist_queue SET status = CASE WHEN retry_count + 1 >= #{maxRetry} THEN 3 ELSE 0 END, " +
            "retry_count = retry_count + 1, next_retry_at = #{nextRetryAt}, updated_at = #{now} " +
            "WHERE id = #{id} AND status = 1")
    int markRetry(@Param("id") Long id,
                  @Param("maxRetry") int maxRetry,
                  @Param("nextRetryAt") OffsetDateTime nextRetryAt,
                  @Param("now") OffsetDateTime now);

    /**
     * 巡检：重置超时未回执的 processing 回到 pending（工作线程宕机恢复）
     */
    @Update("UPDATE dist_queue SET status = 0, locked_by = NULL, locked_at = NULL, updated_at = #{now} " +
            "WHERE status = 1 AND locked_at < #{threshold}")
    int recoverStuck(@Param("threshold") OffsetDateTime threshold, @Param("now") OffsetDateTime now);

    /**
     * 死信重发：将 status=3(dead) 的记录重置为 pending（retry_count 归零），供工作线程重新消费
     *
     * @return 影响行数（0 表示该记录非死信或已处理）
     */
    @Update("UPDATE dist_queue SET status = 0, retry_count = 0, next_retry_at = now(), " +
            "locked_by = NULL, locked_at = NULL, updated_at = now() " +
            "WHERE id = #{id} AND status = 3")
    int redeliverDead(@Param("id") Long id);
}