package com.example.classroomattendance.service;

import com.example.classroomattendance.model.Student;
import com.example.classroomattendance.repository.StudentRepository;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.io.IOException;
import java.io.InputStream;
import java.util.*;

@Service
public class AttendanceService {
    @Autowired
    private StudentRepository studentRepository;

    public List<Student> getAllStudents() {
        return studentRepository.findAll();
    }

    public void addPoints(Long studentId, double points) {
        Optional<Student> student = studentRepository.findById(studentId);
        student.ifPresent(s -> {
            s.setPoints(s.getPoints() + points);
            studentRepository.save(s);
        });
    }

    public Student pickRandomStudent() {
        List<Student> students = getAllStudents();
        Collections.shuffle(students, new Random(System.nanoTime()));
        return students.get(0);
    }

    public void loadStudentsFromExcel(InputStream inputStream) throws IOException {
        List<Student> students = new ArrayList<>();
        try (Workbook workbook = new XSSFWorkbook(inputStream)) {
            Sheet sheet = workbook.getSheetAt(0);
            for (Row row : sheet) {
                if (row.getRowNum() == 0) {
                    continue;
                }
                String name = row.getCell(0).getStringCellValue();
                String studentId = row.getCell(1).getStringCellValue();
                double points = row.getCell(2).getNumericCellValue();
                students.add(new Student(name, studentId, points));
            }
        }
        studentRepository.saveAll(students);
    }
}