package com.srsystem.service;

import com.srsystem.dto.TrainingSummary;
import com.srsystem.dto.UpdateProgressRequest;
import com.srsystem.entity.Employee;
import com.srsystem.entity.TrainingProgress;
import com.srsystem.entity.enums.TrainingStatus;
import com.srsystem.exception.BusinessException;
import com.srsystem.exception.ErrorCode;
import com.srsystem.repository.EmployeeRepository;
import com.srsystem.repository.TrainingProgressRepository;
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;

@Service
@RequiredArgsConstructor
@Transactional(readOnly = true)
public class TrainingService {

    private final TrainingProgressRepository trainingProgressRepository;
    private final EmployeeRepository employeeRepository;

    public List<TrainingProgress> getMyProgress(Long userId) {
        return trainingProgressRepository.findByUser_EmpId(userId);
    }

    @Transactional
    public TrainingProgress updateProgress(Long progressId, UpdateProgressRequest request) {
        TrainingProgress progress = trainingProgressRepository.findById(progressId)
                .orElseThrow(() -> new BusinessException(ErrorCode.REPORT_NOT_FOUND));

        if (request.progressRate() != null) {
            progress.setProgressRate(request.progressRate());
        }
        if (request.status() != null) {
            progress.setStatus(request.status());
        }

        if (progress.getProgressRate() == 100) {
            progress.setStatus(TrainingStatus.COMPLETED);
        }

        return trainingProgressRepository.save(progress);
    }

    public List<TrainingSummary> getSummary() {
        List<Employee> employees = employeeRepository.findAll();
        
        return employees.stream()
                .map(emp -> {
                    List<TrainingProgress> progresses = trainingProgressRepository.findByUser_EmpId(emp.getEmpId());
                    long totalCourses = progresses.size();
                    long completedCount = progresses.stream()
                            .filter(p -> p.getStatus() == TrainingStatus.COMPLETED)
                            .count();
                    double avgProgressRate = progresses.stream()
                            .mapToInt(TrainingProgress::getProgressRate)
                            .average()
                            .orElse(0.0);
                    
                    return new TrainingSummary(
                            emp.getEmpId(),
                            emp.getName(),
                            totalCourses,
                            completedCount,
                            avgProgressRate
                    );
                })
                .collect(Collectors.toList());
    }
}