Add persistent account provider history to app preferences

libraries/preferences/impl/src/main/kotlin/io/element/android/libraries/preferences/impl/store/DefaultAppPreferencesStore.kt

@@ -8,6 +8,7 @@
 
 package io.element.android.libraries.preferences.impl.store
 
+import androidx.datastore.preferences.core.Preferences
 import androidx.datastore.preferences.core.booleanPreferencesKey
 import androidx.datastore.preferences.core.edit
 import androidx.datastore.preferences.core.intPreferencesKey
@@ -36,6 +37,7 @@ private val timelineMediaPreviewValueKey = stringPreferencesKey("timelineMediaPr
 private val liveLocationMinimumDistanceUpdateKey = intPreferencesKey("liveLocationMinimumDistanceUpdate")
 private val logLevelKey = stringPreferencesKey("logLevel")
 private val traceLogPacksKey = stringPreferencesKey("traceLogPacks")
+private val homeserverHistoryKey = stringPreferencesKey("homeserverHistory")
 private val messageSoundUriKey = stringPreferencesKey("notificationMessageSoundUri")
 private val messageSoundChannelVersionKey = intPreferencesKey("notificationMessageSoundChannelVersion")
 private val messageSoundDisplayNameKey = stringPreferencesKey("notificationMessageSoundDisplayName")
@@ -43,6 +45,10 @@ private val callRingtoneUriKey = stringPreferencesKey("notificationCallRingtoneU
 private val callRingtoneChannelVersionKey = intPreferencesKey("notificationCallRingtoneChannelVersion")
 private val callRingtoneDisplayNameKey = stringPreferencesKey("notificationCallRingtoneDisplayName")
 
+// URLs never contain a newline, so it is a safe delimiter to persist an ordered list in a single String.
+private const val HOMESERVER_HISTORY_DELIMITER = "\n"
+private const val MAX_HOMESERVER_HISTORY_SIZE = 10
+
 @ContributesBinding(AppScope::class)
 class DefaultAppPreferencesStore(
     private val buildMeta: BuildMeta,
@@ -168,6 +174,20 @@ class DefaultAppPreferencesStore(
         }
     }
 
+    override fun getHomeserverHistoryFlow(): Flow<List<String>> {
+        return store.data.map { prefs -> prefs.readHomeserverHistory() }
+    }
+
+    override suspend fun addHomeserverToHistory(url: String) {
+        val normalized = url.trim().lowercase()
+        if (normalized.isEmpty()) return
+        store.edit { prefs ->
+            val updated = (listOf(normalized) + prefs.readHomeserverHistory().filter { it != normalized })
+                .take(MAX_HOMESERVER_HISTORY_SIZE)
+            prefs[homeserverHistoryKey] = updated.joinToString(HOMESERVER_HISTORY_DELIMITER)
+        }
+    }
+
     override fun getMessageSoundFlow(): Flow<NotificationSound> {
         return store.data.map { prefs -> NotificationSound.fromStored(prefs[messageSoundUriKey]) }
     }
@@ -242,6 +262,13 @@ class DefaultAppPreferencesStore(
     }
 }
 
+private fun Preferences.readHomeserverHistory(): List<String> {
+    return this[homeserverHistoryKey]
+        ?.split(HOMESERVER_HISTORY_DELIMITER)
+        ?.filter { it.isNotEmpty() }
+        ?: emptyList()
+}
+
 private fun BuildMeta.defaultLogLevel(): LogLevel {
     return when (buildType) {
         BuildType.DEBUG -> LogLevel.TRACE

libraries/preferences/impl/src/test/kotlin/io/element/android/libraries/preferences/impl/store/DefaultAppPreferencesStoreTest.kt

@@ -54,4 +54,74 @@ class DefaultAppPreferencesStoreTest {
 
         assertThat(store.getLiveLocationMinimumDistanceInMetersUpdateFlow().first()).isEqualTo(25)
     }
+
+    @Test
+    fun `homeserver history is empty by default`() = runTest {
+        val store = createStore()
+        assertThat(store.getHomeserverHistoryFlow().first()).isEmpty()
+    }
+
+    @Test
+    fun `adding homeservers keeps the most recent first`() = runTest {
+        val store = createStore()
+
+        store.addHomeserverToHistory("https://matrix.org")
+        store.addHomeserverToHistory("https://example.com")
+
+        assertThat(store.getHomeserverHistoryFlow().first())
+            .containsExactly("https://example.com", "https://matrix.org")
+            .inOrder()
+    }
+
+    @Test
+    fun `adding an existing homeserver moves it to the front without duplicating`() = runTest {
+        val store = createStore()
+
+        store.addHomeserverToHistory("https://matrix.org")
+        store.addHomeserverToHistory("https://example.com")
+        store.addHomeserverToHistory("https://matrix.org")
+
+        assertThat(store.getHomeserverHistoryFlow().first())
+            .containsExactly("https://matrix.org", "https://example.com")
+            .inOrder()
+    }
+
+    @Test
+    fun `homeservers are normalised and deduplicated case-insensitively`() = runTest {
+        val store = createStore()
+
+        store.addHomeserverToHistory("  HTTPS://Matrix.ORG  ")
+        store.addHomeserverToHistory("https://matrix.org")
+
+        assertThat(store.getHomeserverHistoryFlow().first())
+            .containsExactly("https://matrix.org")
+    }
+
+    @Test
+    fun `blank homeservers are ignored`() = runTest {
+        val store = createStore()
+
+        store.addHomeserverToHistory("   ")
+
+        assertThat(store.getHomeserverHistoryFlow().first()).isEmpty()
+    }
+
+    @Test
+    fun `homeserver history is capped to the most recent entries`() = runTest {
+        val store = createStore()
+
+        repeat(15) { index ->
+            store.addHomeserverToHistory("https://server$index.org")
+        }
+
+        val history = store.getHomeserverHistoryFlow().first()
+        assertThat(history).hasSize(10)
+        assertThat(history.first()).isEqualTo("https://server14.org")
+        assertThat(history.last()).isEqualTo("https://server5.org")
+    }
+
+    private fun createStore() = DefaultAppPreferencesStore(
+        buildMeta = buildMeta,
+        preferenceDataStoreFactory = FakePreferenceDataStoreFactory(),
+    )
 }