// ===========================================
// 多班级版班级管理系统 - Go 后端
//
// 开发者: Canglan
// 联系方式: admin@sea-studio.top
// 版权归属: Sea Network Technology Studio
// 许可证: Apache License 2.0
//
// 版权所有 © Sea Network Technology Studio
// ===========================================

package repository

import (
	"time"

	"gorm.io/gorm"

	"hz-gitea.sea-studio.top/canglan/SharedClassManager/internal/model"
)

// AttendanceRepo 考勤数据访问层
type AttendanceRepo struct {
	db *gorm.DB
}

// NewAttendanceRepo 创建考勤 Repository
func NewAttendanceRepo(db *gorm.DB) *AttendanceRepo {
	return &AttendanceRepo{db: db}
}

// GetStudentRecords 获取学生考勤记录
func (r *AttendanceRepo) GetStudentRecords(studentID int, month string) ([]model.AttendanceRecord, error) {
	var records []model.AttendanceRecord
	query := r.db.Where("student_id = ?", studentID)

	if month != "" {
		query = query.Where("DATE_FORMAT(date, '%Y-%m') = ?", month)
	}

	if err := query.Order("date DESC").Find(&records).Error; err != nil {
		return nil, err
	}
	return records, nil
}

// GetClassRecords 获取班级考勤记录（支持多种过滤条件）
func (r *AttendanceRepo) GetClassRecords(classID int, date string, studentID int, slot string) ([]model.AttendanceRecord, error) {
	var records []model.AttendanceRecord
	query := r.db.Table("attendance_records ar").
		Select("ar.*, s.name as student_name, s.student_no").
		Joins("JOIN students s ON ar.student_id = s.student_id").
		Where("1 = 1")

	if classID > 0 {
		query = query.Where("s.class_id = ?", classID)
	}
	if date != "" {
		query = query.Where("ar.date = ?", date)
	}
	if studentID > 0 {
		query = query.Where("ar.student_id = ?", studentID)
	}
	if slot != "" {
		query = query.Where("ar.slot = ?", slot)
	}

	if err := query.Order("ar.date DESC, s.student_no").Find(&records).Error; err != nil {
		return nil, err
	}
	return records, nil
}

// CreateRecordResult 创建或更新考勤记录的结果
type CreateRecordResult struct {
	AttendanceID      int
	IsUpdate          bool
	OldDeductionApplied int8
	OldDeductionRecordID *int64
}

// CreateRecord 创建或更新考勤记录（存在则更新），使用事务+行锁防止并发竞态
func (r *AttendanceRepo) CreateRecord(record *model.AttendanceRecord) (*CreateRecordResult, error) {
	var result CreateRecordResult
	err := r.db.Transaction(func(tx *gorm.DB) error {
		// 使用 SELECT ... FOR UPDATE 锁定记录，防止并发请求同时判定为"不存在"
		var existing model.AttendanceRecord
		findErr := tx.Set("gorm:query_option", "FOR UPDATE").
			Where("student_id = ? AND date = ? AND slot = ?",
				record.StudentID, record.Date, record.Slot).
			First(&existing).Error

		if findErr == nil {
			// 更新已有记录
			if updateErr := tx.Model(&existing).Updates(map[string]interface{}{
				"status":      record.Status,
				"reason":      record.Reason,
				"recorder_id": record.RecorderID,
			}).Error; updateErr != nil {
				return updateErr
			}
			result = CreateRecordResult{
				AttendanceID:         existing.AttendanceID,
				IsUpdate:             true,
				OldDeductionApplied:  existing.DeductionApplied,
				OldDeductionRecordID: existing.DeductionRecordID,
			}
			return nil
		}

		if findErr != gorm.ErrRecordNotFound {
			return findErr
		}

		// 插入新记录
		if createErr := tx.Create(record).Error; createErr != nil {
			return createErr
		}
		result = CreateRecordResult{
			AttendanceID: record.AttendanceID,
			IsUpdate:     false,
		}
		return nil
	})
	if err != nil {
		return nil, err
	}
	return &result, nil
}

// GetAttendanceStatsBySemester 批量查询学期内所有学生的考勤统计
func (r *AttendanceRepo) GetAttendanceStatsBySemester(semesterID int, startDate, endDate string) ([]struct {
	StudentID int
	Status    string
	Count     int64
}, error) {
	var stats []struct {
		StudentID int
		Status    string
		Count     int64
	}
	err := r.db.Model(&model.AttendanceRecord{}).
		Select("student_id, status, COUNT(*) as count").
		Where("semester_id = ? OR (semester_id IS NULL AND `date` BETWEEN ? AND ?)", semesterID, startDate, endDate).
		Group("student_id, status").
		Find(&stats).Error
	if err != nil {
		return nil, err
	}
	return stats, nil
}

// GetAttendanceStatsByDateRange 通过日期范围查询学生考勤统计
func (r *AttendanceRepo) GetAttendanceStatsByDateRange(startDate, endDate time.Time, classID int) ([]struct {
	StudentID int
	Status    string
	Count     int64
}, error) {
	var stats []struct {
		StudentID int
		Status    string
		Count     int64
	}
	query := r.db.Model(&model.AttendanceRecord{}).
		Select("student_id, status, COUNT(*) as count").
		Where("date BETWEEN ? AND ?", startDate, endDate)

	if classID > 0 {
		query = query.Where("student_id IN (SELECT student_id FROM students WHERE class_id = ?)", classID)
	}

	err := query.Group("student_id, status").Find(&stats).Error
	if err != nil {
		return nil, err
	}
	return stats, nil
}

// AssociateSemester 将考勤记录关联到学期
func (r *AttendanceRepo) AssociateSemester(attendanceID int, semesterID int) error {
	return r.db.Model(&model.AttendanceRecord{}).
		Where("attendance_id = ? AND semester_id IS NULL", attendanceID).
		Update("semester_id", semesterID).Error
}