feat: Add atomicity and new getters to SafeBox

safebox/src/androidTest/java/com/harrytmthy/safebox/SafeBoxTest.kt

@@ -20,15 +20,19 @@ import android.content.Context
 import android.content.SharedPreferences
 import androidx.test.core.app.ApplicationProvider
 import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.harrytmthy.safebox.SafeBox.Companion.DEFAULT_KEY_ALIAS
 import com.harrytmthy.safebox.state.SafeBoxStateListener
 import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.launch
 import kotlinx.coroutines.test.UnconfinedTestDispatcher
 import kotlinx.coroutines.test.runTest
 import kotlinx.coroutines.withTimeout
 import org.junit.After
 import org.junit.runner.RunWith
+import java.io.File
+import java.util.concurrent.atomic.AtomicReference
 import kotlin.test.Test
 import kotlin.test.assertContentEquals
 import kotlin.test.assertEquals
@@ -48,9 +52,45 @@ class SafeBoxTest {
 
     @After
     fun tearDown() {
-        safeBox.edit()
-            .clear()
-            .commit()
+        SafeBox.getOrNull(fileName)
+            ?.edit()
+            ?.clear()
+            ?.commit()
+
+        File(context.noBackupFilesDir, "$fileName.bin").delete()
+        File(context.noBackupFilesDir, "$DEFAULT_KEY_ALIAS.bin").delete()
+    }
+
+    @Test
+    fun create_then_get_shouldReturnSameInstance() {
+        safeBox = createSafeBox()
+
+        val instance = SafeBox.get(fileName)
+
+        assertTrue(safeBox === instance)
+    }
+
+    @Test
+    fun create_withConcurrentCalls_shouldReturnSameInstance() = runTest {
+        val createdInstance = AtomicReference<SafeBox>()
+        repeat(10) {
+            launch(Dispatchers.IO) {
+                val newInstance = createSafeBox()
+                val previousInstance = createdInstance.getAndSet(newInstance) ?: return@launch
+                assertTrue(newInstance === previousInstance)
+            }
+        }
+    }
+
+    @Test
+    fun create_withDifferentFileName_shouldReturnDifferentInstances() {
+        safeBox = createSafeBox()
+
+        val anotherSafeBox = createSafeBox(fileName = "test_safebox.bin")
+
+        assertTrue(safeBox !== anotherSafeBox)
+        assertTrue(safeBox === createSafeBox())
+        File(context.noBackupFilesDir, "test_safebox.bin").delete()
     }
 
     @Test
@@ -187,6 +227,7 @@ class SafeBoxTest {
     }
 
     private fun createSafeBox(
+        fileName: String = this.fileName,
         ioDispatcher: CoroutineDispatcher = UnconfinedTestDispatcher(),
         stateListener: SafeBoxStateListener? = null,
     ): SafeBox =

safebox/src/main/java/com/harrytmthy/safebox/SafeBox.kt

@@ -418,23 +418,29 @@ public class SafeBox private constructor(
                 stateListener?.let(safeBox.stateManager::setStateListener)
                 return safeBox
             }
-            val aesGcmCipherProvider = AesGcmCipherProvider.create(
-                alias = valueKeyStoreAlias,
-                aad = additionalAuthenticatedData,
-            )
-            val keyProvider = SecureRandomKeyProvider.create(
-                context = context,
-                fileName = keyAlias,
-                keySize = ChaCha20CipherProvider.KEY_SIZE,
-                algorithm = ChaCha20CipherProvider.ALGORITHM,
-                cipherProvider = aesGcmCipherProvider,
-            )
-            val keyCipherProvider = ChaCha20CipherProvider(keyProvider, deterministic = true)
-            val valueCipherProvider = ChaCha20CipherProvider(keyProvider, deterministic = false)
-            val stateManager = SafeBoxStateManager(fileName, stateListener, ioDispatcher)
-            val blobStore = SafeBoxBlobStore.create(context, fileName)
-            return SafeBox(blobStore, keyCipherProvider, valueCipherProvider, stateManager)
-                .also { instances[fileName] = it }
+            return synchronized(instances) {
+                instances[fileName]?.let { safeBox ->
+                    stateListener?.let(safeBox.stateManager::setStateListener)
+                    return safeBox
+                }
+                val aesGcmCipherProvider = AesGcmCipherProvider.create(
+                    alias = valueKeyStoreAlias,
+                    aad = additionalAuthenticatedData,
+                )
+                val keyProvider = SecureRandomKeyProvider.create(
+                    context = context,
+                    fileName = keyAlias,
+                    keySize = ChaCha20CipherProvider.KEY_SIZE,
+                    algorithm = ChaCha20CipherProvider.ALGORITHM,
+                    cipherProvider = aesGcmCipherProvider,
+                )
+                val keyCipherProvider = ChaCha20CipherProvider(keyProvider, deterministic = true)
+                val valueCipherProvider = ChaCha20CipherProvider(keyProvider, deterministic = false)
+                val stateManager = SafeBoxStateManager(fileName, stateListener, ioDispatcher)
+                val blobStore = SafeBoxBlobStore.create(context, fileName)
+                SafeBox(blobStore, keyCipherProvider, valueCipherProvider, stateManager)
+                    .also { instances[fileName] = it }
+            }
         }
 
         /**
@@ -472,10 +478,34 @@ public class SafeBox private constructor(
                 stateListener?.let(safeBox.stateManager::setStateListener)
                 return safeBox
             }
-            val stateManager = SafeBoxStateManager(fileName, stateListener, ioDispatcher)
-            val blobStore = SafeBoxBlobStore.create(context, fileName)
-            return SafeBox(blobStore, keyCipherProvider, valueCipherProvider, stateManager)
-                .also { instances[fileName] = it }
+            return synchronized(instances) {
+                instances[fileName]?.let { safeBox ->
+                    stateListener?.let(safeBox.stateManager::setStateListener)
+                    return safeBox
+                }
+                val stateManager = SafeBoxStateManager(fileName, stateListener, ioDispatcher)
+                val blobStore = SafeBoxBlobStore.create(context, fileName)
+                SafeBox(blobStore, keyCipherProvider, valueCipherProvider, stateManager)
+                    .also { instances[fileName] = it }
+            }
         }
+
+        /**
+         * Returns the previously created instance for [fileName].
+         *
+         * @return The existing [SafeBox] instance.
+         * @throws IllegalStateException if [create] has not been called for this file.
+         */
+        @JvmStatic
+        public fun get(fileName: String): SafeBox =
+            instances[fileName] ?: error("SafeBox '$fileName' is not initialized.")
+
+        /**
+         * Returns the previously created instance for [fileName], or null if not initialized.
+         *
+         * @return The existing [SafeBox] instance, or null.
+         */
+        @JvmStatic
+        public fun getOrNull(fileName: String): SafeBox? = instances[fileName]
     }
 }