feat : 인증시 사용될 CustomOAuth2User를 생성하는 CustomOAuth2UserService 구현 (#112)

src/main/java/gdsc/binaryho/imhere/core/member/infrastructure/MemberRepository.java

@@ -8,4 +8,5 @@ public interface MemberRepository extends JpaRepository<Member, Long> {
 
     Optional<Member> findById(Long id);
     Optional<Member> findByUnivId(String univId);
+    Optional<Member> findByGitHubResource_Id(String gitHubId);
 }

src/main/java/gdsc/binaryho/imhere/security/oauth/CustomOAuth2UserService.java

@@ -0,0 +1,44 @@
+package gdsc.binaryho.imhere.security.oauth;
+
+import gdsc.binaryho.imhere.core.member.Member;
+import gdsc.binaryho.imhere.core.member.infrastructure.MemberRepository;
+import lombok.RequiredArgsConstructor;
+import org.springframework.security.oauth2.client.userinfo.DefaultOAuth2UserService;
+import org.springframework.security.oauth2.client.userinfo.OAuth2UserRequest;
+import org.springframework.security.oauth2.core.OAuth2AuthenticationException;
+import org.springframework.security.oauth2.core.user.OAuth2User;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+@Service
+@RequiredArgsConstructor
+public class CustomOAuth2UserService extends DefaultOAuth2UserService {
+
+    private final MemberRepository memberRepository;
+
+    @Override
+    @Transactional
+    public OAuth2User loadUser(OAuth2UserRequest userRequest) throws OAuth2AuthenticationException {
+        GitHubUser gitHubUser = new GitHubUser(super.loadUser(userRequest));
+
+        Member member = memberRepository.findByGitHubResource_Id(gitHubUser.getId())
+            .orElseGet(() -> {
+                Member guest = createGuestMember(gitHubUser);
+                return memberRepository.save(guest);
+            });
+
+        updateGitHubHandleIfChanged(member, gitHubUser.getHandle());
+        return new CustomOAuth2User(gitHubUser, member);
+    }
+
+    private static Member createGuestMember(GitHubUser gitHubUser) {
+        return Member.createGuestMember(
+            gitHubUser.getId(), gitHubUser.getHandle(), gitHubUser.getAvatarUrl());
+    }
+
+    private void updateGitHubHandleIfChanged(Member member, String gitHubHandle) {
+        if (!member.getGitHubResource().getHandle().equals(gitHubHandle)) {
+            member.updateGitHubHandle(gitHubHandle);
+        }
+    }
+}