Feat: UserRepository 내 캐싱 로직 및 Mutex를 이용한 Race Condition 방지 로직 구현

Author: wjdrjs00

data/src/main/java/com/threegap/bitnagil/data/user/repositoryImpl/UserRepositoryImpl.kt

@@ -1,14 +1,50 @@
 package com.threegap.bitnagil.data.user.repositoryImpl
 
-import com.threegap.bitnagil.data.user.datasource.UserDataSource
+import com.threegap.bitnagil.data.user.datasource.UserLocalDataSource
+import com.threegap.bitnagil.data.user.datasource.UserRemoteDataSource
 import com.threegap.bitnagil.data.user.model.response.toDomain
 import com.threegap.bitnagil.domain.user.model.UserProfile
 import com.threegap.bitnagil.domain.user.repository.UserRepository
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.emitAll
+import kotlinx.coroutines.flow.filterNotNull
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.sync.Mutex
+import kotlinx.coroutines.sync.withLock
 import javax.inject.Inject
+import javax.inject.Singleton
 
+@Singleton
 class UserRepositoryImpl @Inject constructor(
-    private val userDataSource: UserDataSource,
+    private val userLocalDataSource: UserLocalDataSource,
+    private val userRemoteDataSource: UserRemoteDataSource,
 ) : UserRepository {
-    override suspend fun fetchUserProfile(): Result<UserProfile> =
-        userDataSource.fetchUserProfile().map { it.toDomain() }
+    private val fetchMutex = Mutex()
+
+    override fun observeUserProfile(): Flow<Result<UserProfile>> = flow {
+        if (userLocalDataSource.userProfile.value == null) {
+            fetchMutex.withLock {
+                if (userLocalDataSource.userProfile.value == null) {
+                    userRemoteDataSource.fetchUserProfile()
+                        .onSuccess { response ->
+                            userLocalDataSource.saveUserProfile(response.toDomain())
+                        }
+                        .onFailure {
+                            emit(Result.failure(it))
+                        }
+                }
+            }
+        }
+
+        emitAll(
+            userLocalDataSource.userProfile
+                .filterNotNull()
+                .map { Result.success(it) },
+        )
+    }
+
+    override fun clearCache() {
+        userLocalDataSource.clearCache()
+    }
 }

domain/src/main/java/com/threegap/bitnagil/domain/user/repository/UserRepository.kt

@@ -1,7 +1,9 @@
 package com.threegap.bitnagil.domain.user.repository
 
 import com.threegap.bitnagil.domain.user.model.UserProfile
+import kotlinx.coroutines.flow.Flow
 
 interface UserRepository {
-    suspend fun fetchUserProfile(): Result<UserProfile>
+    fun observeUserProfile(): Flow<Result<UserProfile>>
+    fun clearCache()
 }