package com.guo.learningprogresstracker.service.impl;

import com.baomidou.mybatisplus.core.toolkit.Wrappers;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.google.protobuf.ServiceException;
import com.guo.learningprogresstracker.dto.StudySessionsDto;
import com.guo.learningprogresstracker.dto.response.StudySessionResponse;
import com.guo.learningprogresstracker.entity.StudyReportFragmentsEntity;
import com.guo.learningprogresstracker.entity.StudyReportsEntity;
import com.guo.learningprogresstracker.entity.StudySessionsEntity;
import com.guo.learningprogresstracker.entity.TaskEntity;
import com.guo.learningprogresstracker.enums.StudySessionStateEnum;
import com.guo.learningprogresstracker.exception.ErrorParameterException;
import com.guo.learningprogresstracker.exception.NotFindEntitiesException;
import com.guo.learningprogresstracker.mapStruct.StudySessionConvert;
import com.guo.learningprogresstracker.mapper.StudyReportFragmentsMapper;
import com.guo.learningprogresstracker.mapper.StudyReportsMapper;
import com.guo.learningprogresstracker.mapper.StudySessionsMapper;
import com.guo.learningprogresstracker.service.StudyExpectationsService;
import com.guo.learningprogresstracker.service.StudySessionsService;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.time.LocalDateTime;
import java.util.ArrayList;
import java.util.Optional;
import java.util.stream.Collectors;

/**
 * 针对表【study_sessions(记录每次学习会话的具体数据)】的数据库操作Service实现
 */
@Slf4j
@Service
@RequiredArgsConstructor
public class StudySessionsServiceImpl extends ServiceImpl<StudySessionsMapper, StudySessionsEntity>
        implements StudySessionsService {

    public static final int WORK_DURATION = 25;

    private final TasksServiceImpl tasksServiceImpl;
    private final StudyReportFragmentsServiceImpl studyReportFragmentsServiceImpl;
    private final StudyReportFragmentsMapper studyReportFragmentsMapper;
    private final StudyReportsMapper studyReportsMapper;
    private final AiServiceClient aiServiceClient;
    private final StudyExpectationsService studyExpectationsService;

    public StudySessionResponse startOrContinueStudySession(String taskNum) throws NotFindEntitiesException, ServiceException {
        TaskEntity taskEntity = tasksServiceImpl.getOneOpt(
                        Wrappers.lambdaQuery(TaskEntity.class).eq(TaskEntity::getTaskNum, taskNum))
                .orElseThrow(() -> new NotFindEntitiesException(String.format("[%s]不存在", taskNum)));

        StudySessionsEntity session = this.getOneOpt(Wrappers.<StudySessionsEntity>lambdaQuery()
                        .eq(StudySessionsEntity::getTaskNum, taskNum)
                        .ne(StudySessionsEntity::getSessionState, StudySessionStateEnum.ENDED.name()))
                .orElseGet(() -> {
                    // 如果没有则创建新会话
                    StudySessionsEntity newSession = StudySessionsEntity.initNewSession();
                    newSession.setTaskNum(taskNum);
                    newSession.setLastStartTime(LocalDateTime.now());
                    this.save(newSession);
                    return newSession;
                });

        session.calculatePointerPosition();

        if (session.isOverTime()) {
            session.pausedStudySession(session.getLastStartTime().plusMinutes(WORK_DURATION));
            this.updateById(session);
        }

        StudySessionResponse response = StudySessionConvert.MAPPER.toStudySessionResponse(session);
        response.setTaskName(taskEntity.getTaskName());
        response.setMaterialUrl(taskEntity.getMaterialUrl());
        response.setTaskId(taskEntity.getId());

        if (session.isOverTime()) {
            response.setSystemMessage("上段学习任务已经超时25分钟，将仅计算为25分钟的有效学习时间，请注意休息！");
        }

        return response;
    }


    @Override
    public void pauseStudySession(String sessionNum, LocalDateTime endTime) throws ErrorParameterException, ServiceException {
        StudySessionsEntity studySessionsEntity = this.getOneOpt(Wrappers.lambdaQuery(StudySessionsEntity.class)
                        .eq(StudySessionsEntity::getSessionNum, sessionNum))
                .orElseThrow(() -> new ErrorParameterException("会话[" + sessionNum + "]不存在"));
        if (StudySessionStateEnum.PAUSED.name().equals(studySessionsEntity.getSessionState())) {
            log.error("会话[" + studySessionsEntity.getSessionNum() + "]重复暂停");
            throw new ErrorParameterException("会话[" + sessionNum + "]已经暂停，请勿重复暂停！");
        }
        studySessionsEntity.calculatePointerPosition();
        studySessionsEntity.pausedStudySession(endTime);
        this.updateById(studySessionsEntity);
    }


    @Override
    @Transactional
    public String endedStudySession(String sessionNum, String content) throws ErrorParameterException {
        StudySessionsEntity studySessionsEntity = this.getOneOpt(Wrappers.lambdaQuery(StudySessionsEntity.class)
                        .eq(StudySessionsEntity::getSessionNum, sessionNum))
                .orElseThrow(() -> new ErrorParameterException("会话[" + sessionNum + "]不存在"));
        boolean wasOngoing = StudySessionStateEnum.ONGOING.name().equals(studySessionsEntity.getSessionState());
        studySessionsEntity.endedStudySession();
        this.updateById(studySessionsEntity);
        StudyReportsEntity studyReportsEntity = new StudyReportsEntity();
        studyReportsEntity.setSessionNum(sessionNum);
        studyReportsEntity.setContent(content);
        studyReportsMapper.insert(studyReportsEntity);
        if (wasOngoing && studySessionsEntity.getEffectiveTime() == 0) {
            return "本次有效学习时间不足10分钟，不计入总学习时间";
        }
        return null;
    }

    @Override
    public StudySessionResponse getNotEndedStudySessionByTaskNum(String taskNum) throws ErrorParameterException {
        TaskEntity task = tasksServiceImpl.getOneOpt(Wrappers.lambdaQuery(TaskEntity.class)
                        .eq(TaskEntity::getTaskNum, taskNum))
                .orElseThrow(() -> new ErrorParameterException("任务[" + taskNum + "]不存在"));
        StudySessionsDto dto = Optional.ofNullable(studyReportsMapper.getNotEndedStudySessionDtoByTaskNum(taskNum))
                .orElseThrow(() -> new ErrorParameterException("任务[" + taskNum + "]不存在进行中或暂停中的会话"));
        return StudySessionConvert.MAPPER.toStudySessionResponse(dto);
    }

    @Override
    public ArrayList<String> getAllFragments(String sessionNum) throws ErrorParameterException {
        if (this.exists(Wrappers.lambdaQuery(StudySessionsEntity.class)
                .eq(StudySessionsEntity::getSessionNum, sessionNum))) {
            return studyReportFragmentsMapper.selectList(Wrappers.lambdaQuery(StudyReportFragmentsEntity.class)
                            .eq(StudyReportFragmentsEntity::getSessionNum, sessionNum))
                    .stream().map(StudyReportFragmentsEntity::getContent).collect(Collectors.toCollection(ArrayList::new));
        } else {
            throw new ErrorParameterException("会话[" + sessionNum + "]不存在");
        }
    }

    @Override
    @Transactional
    public void continueStudySession(String sessionNum) throws ErrorParameterException, ServiceException {
        StudySessionsEntity studySessionsEntity = this.getOneOpt(Wrappers.lambdaQuery(StudySessionsEntity.class)
                        .eq(StudySessionsEntity::getSessionNum, sessionNum))
                .orElseThrow(() -> new ErrorParameterException("会话[" + sessionNum + "]不存在"));
        if (StudySessionStateEnum.ONGOING.name().equals(studySessionsEntity.getSessionState())) {
            log.error("会话[" + studySessionsEntity.getSessionNum() + "]重复开始");
            throw new ErrorParameterException("会话[" + sessionNum + "]已经开始，请勿重复开始！");
        } else if (StudySessionStateEnum.ENDED.name().equals(studySessionsEntity.getSessionState())) {
            log.error("会话[" + studySessionsEntity.getSessionNum() + "]处于结束状态，不可开始该会话！");
            throw new ErrorParameterException("会话[" + sessionNum + "]处于结束状态，不可开始该会话！");
        }
        studySessionsEntity.continueStudySession();
        this.updateById(studySessionsEntity);
    }

    /**
     * 通过 sessionNum 获取学习会话
     */
    public StudySessionResponse getStudySessionBySessionNum(String sessionNum) throws ErrorParameterException {
        StudySessionsEntity session = this.getOneOpt(Wrappers.lambdaQuery(StudySessionsEntity.class)
                        .eq(StudySessionsEntity::getSessionNum, sessionNum))
                .orElseThrow(() -> new ErrorParameterException("会话[" + sessionNum + "]不存在"));
        return StudySessionConvert.MAPPER.toStudySessionResponse(session);
    }

    /**
     * 生成学习报告草稿：优先调用 lpt-ai 聚合残片，服务不可用时降级为按序拼接。
     * 草稿仅作为编辑起点返回，不落库——最终报告由用户确认后经 endedStudySession 保存。
     */
    public String generateReportDraft(String sessionNum) throws ErrorParameterException {
        StudySessionsEntity session = this.getOneOpt(Wrappers.lambdaQuery(StudySessionsEntity.class)
                        .eq(StudySessionsEntity::getSessionNum, sessionNum))
                .orElseThrow(() -> new ErrorParameterException("会话[" + sessionNum + "]不存在"));

        ArrayList<String> fragments = getAllFragments(sessionNum);
        if (fragments.isEmpty()) {
            return "";
        }

        String taskName = tasksServiceImpl.getOneOpt(
                        Wrappers.lambdaQuery(TaskEntity.class).eq(TaskEntity::getTaskNum, session.getTaskNum()))
                .map(TaskEntity::getTaskName)
                .orElse("学习任务");
        String expectation = Optional.ofNullable(studyExpectationsService.getBySessionNum(sessionNum))
                .map(e -> e.getDescription())
                .orElse(null);

        return aiServiceClient.aggregateReport(taskName, fragments, expectation)
                .orElseGet(() -> String.join("\n", fragments));
    }

    // ============ 分页查询任务的历史残片/报告 ============

    @Override
    public Page<StudyReportFragmentsEntity> getTaskFragments(String taskNum, int page, int size, String keyword) {
        Page<StudyReportFragmentsEntity> pg = new Page<>(page, size);
        var wrapper = Wrappers.lambdaQuery(StudyReportFragmentsEntity.class)
                .apply("session_num in (select session_num from study_sessions where task_num = {0})", taskNum)
                .orderByDesc(StudyReportFragmentsEntity::getCreatedTime);
        if (keyword != null && !keyword.isBlank()) {
            wrapper.like(StudyReportFragmentsEntity::getContent, keyword);
        }
        return studyReportFragmentsMapper.selectPage(pg, wrapper);
    }

    @Override
    public Page<StudyReportsEntity> getTaskReports(String taskNum, int page, int size, String keyword) {
        Page<StudyReportsEntity> pg = new Page<>(page, size);
        var wrapper = Wrappers.lambdaQuery(StudyReportsEntity.class)
                .apply("session_num in (select session_num from study_sessions where task_num = {0})", taskNum)
                .orderByDesc(StudyReportsEntity::getCreatedTime);
        if (keyword != null && !keyword.isBlank()) {
            wrapper.like(StudyReportsEntity::getContent, keyword);
        }
        Page<StudyReportsEntity> result = studyReportsMapper.selectPage(pg, wrapper);
        // 填充每个报告对应会话的预期目标
        for (StudyReportsEntity report : result.getRecords()) {
            if (report.getSessionNum() != null) {
                Optional.ofNullable(studyExpectationsService.getBySessionNum(report.getSessionNum()))
                        .ifPresent(e -> report.setSessionExpectation(e.getDescription()));
            }
        }
        return result;
    }

    // ============ 活跃会话查询 ============

    /**
     * 查询当前用户是否有活跃会话（ONGOING 或 PAUSED）。
     *
     * @param excludeTaskNum 可选，排除指定任务（同一任务继续学习时不会视为冲突）
     * @return 活跃会话响应；无活跃会话时返回 null
     */
    @Override
    public StudySessionResponse getActiveSession(String excludeTaskNum) {
        var wrapper = Wrappers.lambdaQuery(StudySessionsEntity.class)
                .in(StudySessionsEntity::getSessionState,
                        StudySessionStateEnum.ONGOING.name(),
                        StudySessionStateEnum.PAUSED.name())
                .orderByDesc(StudySessionsEntity::getCreatedTime)
                .last("LIMIT 1");

        StudySessionsEntity session = this.getOne(wrapper);
        if (session == null) return null;

        // 如果活跃会话属于被排除的任务，视为无冲突
        if (excludeTaskNum != null && excludeTaskNum.equals(session.getTaskNum())) {
            return null;
        }

        String taskName = tasksServiceImpl.getOneOpt(
                        Wrappers.lambdaQuery(TaskEntity.class).eq(TaskEntity::getTaskNum, session.getTaskNum()))
                .map(TaskEntity::getTaskName)
                .orElse(null);

        StudySessionResponse response = StudySessionConvert.MAPPER.toStudySessionResponse(session);
        response.setTaskName(taskName);
        return response;
    }

}