package com.gcsc.guide.service;

import com.gcsc.guide.dto.StatsResponse;
import com.gcsc.guide.dto.UserResponse;
import com.gcsc.guide.entity.Role;
import com.gcsc.guide.entity.User;
import com.gcsc.guide.entity.UserStatus;
import com.gcsc.guide.exception.BusinessException;
import com.gcsc.guide.exception.ResourceNotFoundException;
import com.gcsc.guide.repository.LoginHistoryRepository;
import com.gcsc.guide.repository.RoleRepository;
import com.gcsc.guide.repository.UserRepository;
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.time.LocalDate;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

@Service
@RequiredArgsConstructor
public class UserService {

    private final UserRepository userRepository;
    private final RoleRepository roleRepository;
    private final LoginHistoryRepository loginHistoryRepository;

    @Transactional(readOnly = true)
    public List<UserResponse> getUsers(String status) {
        List<User> users;
        if (status != null && !status.isBlank()) {
            UserStatus userStatus = UserStatus.valueOf(status.toUpperCase());
            users = userRepository.findByStatus(userStatus);
        } else {
            users = userRepository.findAll();
        }
        return users.stream().map(UserResponse::from).toList();
    }

    @Transactional
    public UserResponse approveUser(Long userId) {
        User user = findUserById(userId);
        if (user.getStatus() != UserStatus.PENDING) {
            throw new BusinessException("PENDING 상태의 사용자만 승인할 수 있습니다 (현재: " + user.getStatus() + ")");
        }
        user.activate();
        return UserResponse.from(userRepository.save(user));
    }

    @Transactional
    public UserResponse rejectUser(Long userId) {
        User user = findUserById(userId);
        if (user.getStatus() != UserStatus.PENDING) {
            throw new BusinessException("PENDING 상태의 사용자만 거절할 수 있습니다 (현재: " + user.getStatus() + ")");
        }
        user.reject();
        return UserResponse.from(userRepository.save(user));
    }

    @Transactional
    public UserResponse disableUser(Long userId) {
        User user = findUserById(userId);
        if (user.getStatus() != UserStatus.ACTIVE) {
            throw new BusinessException("ACTIVE 상태의 사용자만 비활성화할 수 있습니다 (현재: " + user.getStatus() + ")");
        }
        user.disable();
        return UserResponse.from(userRepository.save(user));
    }

    @Transactional
    public UserResponse updateUserRoles(Long userId, List<Long> roleIds) {
        User user = findUserById(userId);
        Set<Role> roles = new HashSet<>(roleRepository.findAllById(roleIds));
        if (roles.size() != roleIds.size()) {
            throw new BusinessException("일부 롤을 찾을 수 없습니다");
        }
        user.updateRoles(roles);
        userRepository.save(user);

        return UserResponse.from(userRepository.findByIdWithRoles(userId).orElseThrow());
    }

    @Transactional
    public UserResponse grantAdmin(Long userId) {
        User user = findUserById(userId);
        user.grantAdmin();
        return UserResponse.from(userRepository.save(user));
    }

    @Transactional
    public UserResponse revokeAdmin(Long userId) {
        User user = findUserById(userId);
        user.revokeAdmin();
        return UserResponse.from(userRepository.save(user));
    }

    @Transactional(readOnly = true)
    public StatsResponse getStats() {
        long totalUsers = userRepository.count();
        long activeUsers = userRepository.countByStatus(UserStatus.ACTIVE);
        long pendingUsers = userRepository.countByStatus(UserStatus.PENDING);
        long rejectedUsers = userRepository.countByStatus(UserStatus.REJECTED);
        long disabledUsers = userRepository.countByStatus(UserStatus.DISABLED);
        long todayLogins = loginHistoryRepository.countByLoginAtAfter(
            LocalDate.now().atStartOfDay());
        long totalRoles = roleRepository.count();

        return new StatsResponse(
            totalUsers, activeUsers, pendingUsers,
            rejectedUsers, disabledUsers, todayLogins, totalRoles
        );
    }

    private User findUserById(Long userId) {
        return userRepository.findById(userId)
            .orElseThrow(() -> new ResourceNotFoundException("사용자", userId));
    }
}