import { Injectable, NotFoundException, BadRequestException } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository, Like, Not, In, FindOptionsWhere } from 'typeorm';
import { Student } from '../entities/student.entity';
import { Class } from '../entities/class.entity';
import { ClassStudent } from '../entities/class-student.entity';
import { ClassTeacher } from '../entities/class-teacher.entity';
import { AttendanceRecord } from '../entities/attendance-record.entity';
import { Organization } from '../entities/organization.entity';
import { CreateStudentDto, UpdateStudentDto } from './dto/student.dto';

@Injectable()
export class StudentsService {
  constructor(
    @InjectRepository(Student) private repo: Repository<Student>,
    @InjectRepository(ClassStudent) private classStudentRepo: Repository<ClassStudent>,
    @InjectRepository(Class) private classRepo: Repository<Class>,
    @InjectRepository(AttendanceRecord) private attendanceRepo: Repository<AttendanceRecord>,
    @InjectRepository(ClassTeacher) private classTeacherRepo: Repository<ClassTeacher>,
    @InjectRepository(Organization) private organizationRepo: Repository<Organization>,
  ) {}

  async getAccessibleClassIds(userId: number, canManageAll = false): Promise<number[] | undefined> {
    if (canManageAll) return undefined;
    const assignments = await this.classTeacherRepo.find({ where: { userId } });
    return [...new Set(assignments.map((assignment) => assignment.classId))];
  }

  async findAll(
    query?: {
      name?: string;
      status?: string;
      includeArchived?: boolean;
      organizationId?: number | string;
    },
    accessibleClassIds?: number[],
  ) {
    const where: FindOptionsWhere<Student> = {};
    if (query?.name) where.name = Like(`%${query.name}%`);
    if (query?.organizationId) where.organizationId = Number(query.organizationId);
    if (query?.status) {
      where.status = query.status;
    } else if (!query?.includeArchived) {
      where.status = Not(In(['archived', 'staff']));
    }
    if (accessibleClassIds) {
      if (accessibleClassIds.length === 0) return [];
      const classStudents = await this.classStudentRepo.find({
        where: { classId: In(accessibleClassIds), status: 'active' },
      });
      const studentIds = [...new Set(classStudents.map((item) => item.studentId))];
      if (studentIds.length === 0) return [];
      where.id = In(studentIds);
    }
    return this.repo.find({ where, order: { createdAt: 'DESC' }, relations: ['organization'] });
  }

  async findOne(id: number) {
    const student = await this.repo.findOne({
      where: { id },
      relations: ['occupancies', 'occupancies.room'],
    });
    if (!student) throw new NotFoundException('学生不存在');
    return student;
  }

  async create(dto: CreateStudentDto) {
    await this.assertActiveOrganization(dto.organizationId);
    return this.repo.save(this.repo.create(dto));
  }

  async update(id: number, dto: UpdateStudentDto) {
    await this.findOne(id);
    if (dto.organizationId) await this.assertActiveOrganization(dto.organizationId);
    await this.repo.update(id, dto);
    return this.repo.findOne({ where: { id } });
  }

  async remove(id: number) {
    const student = await this.findOne(id);
    if (student.status === 'archived') {
      throw new BadRequestException('该学生已归档');
    }
    await this.repo.update(id, { status: 'archived' });
    return { message: '已归档（数据已保留，可随时恢复）' };
  }

  async batchRemove(ids: number[]) {
    if (!ids || ids.length === 0) throw new BadRequestException('请选择要归档的学生');
    const students = await this.repo.find({ where: { id: In(ids) } });
    const skipped: string[] = [];
    const targetIds: number[] = [];
    for (const s of students) {
      if (s.status === 'archived') skipped.push(s.name);
      else targetIds.push(s.id);
    }
    let affected = 0;
    if (targetIds.length > 0) {
      const result = await this.repo
        .createQueryBuilder()
        .update()
        .set({ status: 'archived' })
        .where('id IN (:...ids)', { ids: targetIds })
        .execute();
      affected = result.affected || 0;
    }
    const message =
      skipped.length > 0
        ? `成功归档 ${affected} 人；${skipped.length} 人已是归档状态被跳过（${skipped.slice(0, 5).join('、')}${skipped.length > 5 ? '…' : ''}）`
        : `已批量归档 ${affected} 人（数据已保留，可随时恢复）`;
    return { message, archived: affected, skipped: skipped.length };
  }

  async restore(id: number) {
    const student = await this.findOne(id);
    if (student.status !== 'archived') {
      throw new BadRequestException('该学生未被归档');
    }
    await this.repo.update(id, { status: 'active' });
    return { message: '已恢复' };
  }

  async batchImport(
    rows: {
      name: string;
      phone?: string;
      idNumber?: string;
      gender?: string;
      ethnicity?: string;
      emergencyContact?: string;
      emergencyPhone?: string;
      organization?: string;
      supervisor?: string;
      organizationId?: number;
    }[],
  ) {
    let imported = 0;
    let skipped = 0;
    for (const row of rows) {
      if (!row.name || !row.name.trim()) {
        skipped++;
        continue;
      }
      const exists = await this.repo.findOne({ where: { name: row.name.trim() } });
      if (exists) {
        skipped++;
        continue;
      }
      await this.repo.save(
        this.repo.create({
          name: row.name.trim(),
          phone: row.phone?.trim() || undefined,
          idNumber: row.idNumber?.trim() || undefined,
          gender: row.gender || undefined,
          ethnicity: row.ethnicity || undefined,
          emergencyContact: row.emergencyContact || undefined,
          emergencyPhone: row.emergencyPhone || undefined,
          supervisor: row.supervisor || undefined,
          organizationId: row.organizationId || (await this.getHostOrganizationId()),
        }),
      );
      imported++;
    }
    return {
      message: `成功导入 ${imported} 名学生，跳过 ${skipped} 条（重复或空行）`,
      imported,
      skipped,
    };
  }

  async matchImport(
    rows: {
      name: string;
      phone?: string;
      idNumber?: string;
      gender?: string;
      ethnicity?: string;
      emergencyContact?: string;
      emergencyPhone?: string;
      organization?: string;
      supervisor?: string;
      organizationId?: number;
    }[],
  ) {
    let matched = 0;
    let skipped = 0;
    for (const row of rows) {
      if (!row.name || !row.name.trim()) {
        skipped++;
        continue;
      }
      // Match by phone first, then idNumber
      let student = row.phone?.trim()
        ? await this.repo.findOne({ where: { phone: row.phone.trim() } })
        : null;
      if (!student && row.idNumber?.trim()) {
        student = await this.repo.findOne({ where: { idNumber: row.idNumber.trim() } });
      }
      if (!student) {
        skipped++;
        continue;
      }
      // Update matched student with non-empty imported fields
      const updates: Partial<
        Pick<
          Student,
          | 'name'
          | 'phone'
          | 'idNumber'
          | 'gender'
          | 'ethnicity'
          | 'emergencyContact'
          | 'emergencyPhone'
          | 'supervisor'
          | 'organizationId'
        >
      > = {};
      if (row.name?.trim()) updates.name = row.name.trim();
      if (row.phone?.trim()) updates.phone = row.phone.trim();
      if (row.idNumber?.trim()) updates.idNumber = row.idNumber.trim();
      if (row.gender) updates.gender = row.gender;
      if (row.ethnicity) updates.ethnicity = row.ethnicity;
      if (row.emergencyContact) updates.emergencyContact = row.emergencyContact;
      if (row.emergencyPhone) updates.emergencyPhone = row.emergencyPhone;
      if (row.supervisor) updates.supervisor = row.supervisor;
      if (row.organizationId) updates.organizationId = row.organizationId;
      await this.repo.update(student.id, updates as Partial<Student>);
      matched++;
    }
    return {
      message: `匹配更新 ${matched} 人，跳过 ${skipped} 条（无匹配）`,
      matched,
      skipped,
    };
  }

  private async assertActiveOrganization(id: number) {
    const organization = await this.organizationRepo.findOne({ where: { id, status: 'active' } });
    if (!organization) throw new BadRequestException('所属机构不存在或已归档');
  }

  private async getHostOrganizationId() {
    const organization = await this.organizationRepo.findOne({
      where: { isHost: true, status: 'active' },
    });
    if (!organization) throw new BadRequestException('尚未配置本机构');
    return organization.id;
  }

  async compareClasses(studentId: number) {
    const student = await this.repo.findOne({ where: { id: studentId } });
    if (!student) throw new NotFoundException('学生不存在');

    const enrollments = await this.classStudentRepo.find({
      where: { studentId },
      relations: ['class'],
    });

    if (enrollments.length === 0) {
      return { student, enrollments: [] };
    }

    const classIds = enrollments.map((e) => e.classId);
    const attendanceRecords = await this.attendanceRepo.find({
      where: { studentId, classId: In(classIds) },
    });

    const attendanceByClass = new Map<number, AttendanceRecord[]>();
    for (const r of attendanceRecords) {
      const list = attendanceByClass.get(r.classId) || [];
      list.push(r);
      attendanceByClass.set(r.classId, list);
    }

    const comparison = enrollments.map((e) => {
      const records = attendanceByClass.get(e.classId) || [];
      const total = records.length;
      const present = records.filter((r) => r.status === 'present' || r.status === '正常').length;
      const absent = records.filter((r) => r.status === 'absent' || r.status === '缺勤').length;
      const late = records.filter((r) => r.status === 'late' || r.status === '迟到').length;
      const leave = records.filter((r) => r.status === 'leave' || r.status === '请假').length;

      return {
        classId: e.classId,
        className: e.class?.name || '',
        classType: e.class?.classType || '',
        startDate: e.class?.startDate || '',
        endDate: e.class?.endDate || '',
        joinDate: e.joinDate,
        leaveDate: e.leaveDate,
        status: e.status,
        attendanceStats: {
          total,
          present,
          absent,
          late,
          leave,
          rate: total > 0 ? Math.round((present / total) * 100) : 0,
        },
      };
    });

    return { student, enrollments: comparison };
  }
}