OpenIsle/backend/src/main/java/com/openisle/service/GoogleAuthService.java

package com.openisle.service;

import com.google.api.client.googleapis.auth.oauth2.GoogleIdToken;
import com.google.api.client.googleapis.auth.oauth2.GoogleIdTokenVerifier;
import com.google.api.client.http.javanet.NetHttpTransport;
import com.google.api.client.json.jackson2.JacksonFactory;
import com.openisle.model.Role;
import com.openisle.model.User;
import com.openisle.repository.UserRepository;
import lombok.RequiredArgsConstructor;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;
import com.openisle.service.AvatarGenerator;

import java.util.Collections;
import java.util.Optional;

@Service
@RequiredArgsConstructor
public class GoogleAuthService {

    private final UserRepository userRepository;
    private final AvatarGenerator avatarGenerator;

    @Value("${google.client-id:}")
    private String clientId;

    public Optional<User> authenticate(String idTokenString, com.openisle.model.RegisterMode mode) {
        GoogleIdTokenVerifier verifier = new GoogleIdTokenVerifier.Builder(new NetHttpTransport(), new JacksonFactory())
                .setAudience(Collections.singletonList(clientId))
                .build();
        try {
            GoogleIdToken idToken = verifier.verify(idTokenString);
            if (idToken == null) {
                return Optional.empty();
            }
            GoogleIdToken.Payload payload = idToken.getPayload();
            String email = payload.getEmail();
            String name = (String) payload.get("name");
            String picture = (String) payload.get("picture");
            return Optional.of(processUser(email, name, picture, mode));
        } catch (Exception e) {
            return Optional.empty();
        }
    }

    private User processUser(String email, String name, String avatar, com.openisle.model.RegisterMode mode) {
        Optional<User> existing = userRepository.findByEmail(email);
        if (existing.isPresent()) {
            User user = existing.get();
            if (!user.isVerified()) {
                user.setVerified(true);
                user.setVerificationCode(null);
                userRepository.save(user);
            }

            return user;
        }
        User user = new User();
        String baseUsername = email.split("@")[0];
        String username = baseUsername;
        int suffix = 1;
        while (userRepository.findByUsername(username).isPresent()) {
            username = baseUsername + suffix++;
        }
        user.setUsername(username);
        user.setEmail(email);
        user.setPassword("");
        user.setRole(Role.USER);
        user.setVerified(true);
        user.setApproved(mode == com.openisle.model.RegisterMode.DIRECT);
        if (avatar != null) {
            user.setAvatar(avatar);
        } else {
            user.setAvatar(avatarGenerator.generate(username));
        }
        return userRepository.save(user);
    }
}