// MemberRepository
import com.devkobe.hello_spring.domain.Member;
import java.util.List;
import java.util.Optional;


public interface MemberRepository {
	Member save(Member member);
	Optional<Member> findById(Long id);
	Optional<Member> findByName(String name);
	List<Member> findAll();
}

// MemoryMemberRepository
import com.devkobe.hello_spring.domain.Member;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import org.springframework.stereotype.Repository;

@Repository
public class MemoryMemberRepository implements MemberRepository {

	private static Map<Long, Member> store = new HashMap<>();
	private static long sequence = 0L;

	@Override
	public Member save(Member member) {
		member.setId(++sequence);
		store.put(member.getId(), member);
		return member;
	}

	@Override
	public Optional<Member> findById(Long id) {
		return Optional.ofNullable(store.get(id));
	}

	@Override
	public Optional<Member> findByName(String name) {
		return store.values().stream()
				.filter(member -> member.getName().equals(name))
				.findAny();
	}

	@Override
	public List<Member> findAll() {
		return new ArrayList<>(store.values());
	}

	public void clearStore() {
		store.clear();
	}
}

// MemberService
import com.devkobe.hello_spring.domain.Member;
import com.devkobe.hello_spring.repository.MemberRepository;
import com.devkobe.hello_spring.repository.MemoryMemberRepository;
import java.util.List;
import java.util.Optional;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class MemberService {
	private final MemberRepository memberRepository;

	@Autowired
	public MemberService(MemberRepository memberRepository) {
		this.memberRepository = memberRepository;
	}

	/*
	 * 회원 가입
	 */
	public Long join(Member member) {

		validateDuplicateMember(member); // 중복 회원 검증
		memberRepository.save(member);
		return member.getId();
	}

	private void validateDuplicateMember(Member member) {
		memberRepository.findByName(member.getName())
				.ifPresent(m -> {
					throw new IllegalStateException("이미 존재하는 회원입니다.");
				});
	}

	/*
	 * 전체 회원 조회
	 */
	public List<Member> findMembers() {
		return memberRepository.findAll();
	}

	public Optional<Member> findOne(Long memberId) {
		return memberRepository.findById(memberId);
	}
}