feat: 랜덤 유저 id 생성기 추가

Author: dongho108

backend/src/main/java/com/woowacourse/ternoko/auth/application/AuthService.java

@@ -22,7 +22,6 @@
 import java.io.IOException;
 import java.util.NoSuchElementException;
 import java.util.Optional;
-import java.util.concurrent.atomic.AtomicLong;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
@@ -44,8 +43,7 @@ public class AuthService {
     private final String clientId;
     private final String clientSecret;
 
-    private final static AtomicLong ATOMIC_COACH_ID = new AtomicLong(0L);
-    private final static AtomicLong ATOMIC_CREW_ID = new AtomicLong(0L);
+    private final RandomMemberIdGenerator memberIdGenerator = RandomMemberIdGenerator.of(111, 210, 11, 110);
 
     public AuthService(final MethodsClientImpl slackMethodClient,
                        final MemberRepository memberRepository,
@@ -64,15 +62,15 @@ public AuthService(final MethodsClientImpl slackMethodClient,
     }
 
     public LoginResponse loginCoach() {
-        long coachId = (ATOMIC_COACH_ID.getAndAdd(1)) % 100 + 11;
+        final Long coachId = memberIdGenerator.getRandomCoachId();
         final Member member = memberRepository.findById(coachId)
                 .orElseThrow(() -> new NoSuchElementException("로그인할 coachId가 존재하지 않습니다."));
 
         return LoginResponse.of(COACH, jwtProvider.createToken(member), true);
     }
 
     public LoginResponse loginCrew()  {
-        long crewId = (ATOMIC_CREW_ID.getAndAdd(1)) % 100 + 111;
+        final Long crewId = memberIdGenerator.getRandomCrewId();
         final Member member = memberRepository.findById(crewId)
                 .orElseThrow(() -> new NoSuchElementException("로그인할 crewId가 존재하지 않습니다."));
 

backend/src/main/java/com/woowacourse/ternoko/auth/application/RandomMemberIdGenerator.java

@@ -0,0 +1,71 @@
+package com.woowacourse.ternoko.auth.application;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Random;
+import org.jetbrains.annotations.NotNull;
+
+public class RandomMemberIdGenerator {
+
+    final static Random RANDOM = new Random(System.currentTimeMillis());
+
+    final long startCrewId;
+    final long endCrewId;
+    final long startCoachId;
+    final long endCoachId;
+    List<Long> crewIds;
+    List<Long> coachIds;
+
+    public RandomMemberIdGenerator(final long startCrewId, final long endCrewId, final long startCoachId,
+                                   final long endCoachId,
+                                   final List<Long> crewIds, final List<Long> coachIds) {
+        this.startCrewId = startCrewId;
+        this.endCrewId = endCrewId;
+        this.startCoachId = startCoachId;
+        this.endCoachId = endCoachId;
+        this.crewIds = crewIds;
+        this.coachIds = coachIds;
+    }
+
+    public static RandomMemberIdGenerator of(final long startCrewId,
+                                             final long endCrewId,
+                                             final long startCoachId,
+                                             final long endCoachId) {
+        final List<Long> crewIds = getIds(startCrewId, endCrewId);
+
+        final List<Long> coachIds = new ArrayList<>();
+        for (long i = startCoachId; i <= endCoachId; i++) {
+            coachIds.add(i);
+        }
+
+        return new RandomMemberIdGenerator(startCrewId, endCrewId, startCoachId, endCoachId, crewIds, coachIds);
+    }
+
+    @NotNull
+    private static List<Long> getIds(final long startId, final long endId) {
+        final List<Long> ids = Collections.synchronizedList(new ArrayList<>());
+        for (long i = startId; i <= endId; i++) {
+            ids.add(i);
+        }
+        return ids;
+    }
+
+    public Long getRandomCrewId() {
+        if (crewIds.size() == 0) {
+            crewIds = getIds(startCrewId, endCrewId);
+        }
+
+        final int randomIndex = RANDOM.nextInt(crewIds.size());
+        return crewIds.remove(randomIndex);
+    }
+
+    public Long getRandomCoachId() {
+        if (coachIds.size() == 0) {
+            coachIds = getIds(startCoachId, endCoachId);
+        }
+
+        final int randomIndex = RANDOM.nextInt(coachIds.size());
+        return coachIds.remove(randomIndex);
+    }
+}