package cn.teammodel.utils;

import cn.teammodel.common.CommonConstant;
import cn.teammodel.config.exception.ServiceException;
import cn.teammodel.model.entity.school.School;
import org.apache.commons.lang3.tuple.Pair;

import java.time.LocalDate;
import java.util.Comparator;
import java.util.List;

/**
 * 学校中年级,学年,日期相关的工具类
 * @author winter
 * @create 2023-11-28 10:15
 */
public class SchoolDateUtil {

    /**
    * 通过当前时间与学校的学期安排获取当前的学年
     * 学校学期:
     * <pre>
     * "semesters": [
     *         {
     *           "name": "下学期",
     *           "start": 0,
     *           "month": 3,
     *           "day": 1,
     *           "id": "2"
     *         },
     *         {
     *           "name": "上学期",
     *           "start": 1,
     *           "month": 9,
     *           "day": 1,
     *           "id": "1"
     *         }
     *         <pre/>
     * <p>
     *     示例: 传参 2023.11.28 返回 2023学年上学期
     *     注意: 处理跨年问题 -> 2024.1.1, 应该也是 2023学年上学期,同时你需要注意,semesters 可能不止两个学期
     * </p>
    */
    public static Pair<String, LocalDate> getSemesterByNow(List<School.Semester> semesters, LocalDate date) {
        if (semesters == null || semesters.isEmpty() || date == null) {
            throw new ServiceException("semesters and date must not be null or empty.");
        }

        // 将 semester 根据大小排序
        semesters.sort(Comparator.comparing(s -> LocalDate.of(date.getYear(), s.getMonth(), s.getDay())));

        // i = 0 的日期是开学最早, i = size - 1 是开学最晚
        int size = semesters.size();
        // 拿到最晚开学的日期,将年份 - 1后,与头节点组成可跨年区间
        School.Semester lastSemester = semesters.get(size - 1);
        LocalDate lastSemesterStart = LocalDate.of(date.getYear() - 1, lastSemester.getMonth(), lastSemester.getDay());
        String lastSemesterId = lastSemester.getId();
        for (School.Semester semester : semesters) {
            // 特判头尾的提起,分别将学期区间提前和延后一年(不用延后),例如 2023.3.1 与 2023.9.1 我们分别向添加一个节点,划分其为 3 个区间:
            // 2022.9.1 - 2023.3.1, 2023.3.1 - 2023.9.1, 2023.9.1 - 2024.3.1
            LocalDate curSemesterStart = LocalDate.of(date.getYear(), semester.getMonth(), semester.getDay());
            if (date.isEqual(lastSemesterStart) || date.isAfter(lastSemesterStart) && date.isBefore(curSemesterStart)) {
                return Pair.of(lastSemesterId, lastSemesterStart);
            }
            lastSemesterStart = curSemesterStart;
            lastSemesterId = semester.getId();
        }

        // 剩下的时间段, 学年应该就是最后一个学年
        return Pair.of(lastSemester.getId(), LocalDate.of(date.getYear(), lastSemester.getMonth(), lastSemester.getDay()));
    }

    /**
    * 返回 ID -> 学年(组合 id: 学年-semesterId -> 2023-{semesterId})
    */
    public static String generateAcademicId(List<School.Semester> semesters, LocalDate date) {
        Pair<String, LocalDate> pair = getSemesterByNow(semesters, date);
        String semesterId = pair.getLeft();
        LocalDate academicYear = pair.getRight();
        return academicYear.getYear() + CommonConstant.DASH + semesterId;
    }


}