feat(prefs): app preferences over the kit's PrefStore

SettingsPrefs exposes the appearance slice; DataModule builds the DataStore on
the kit's @IoDispatcher. The store is created with a corruption handler that
replaces an unreadable file with empty preferences, so a truncated
clockula_prefs.preferences_pb cannot leave the app crashing on every launch
with no recovery short of clearing app data.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

app/src/test/java/de/jeanlucmakiola/clockula/data/di/DataModuleTest.kt

@@ -0,0 +1,53 @@
+package de.jeanlucmakiola.clockula.data.di
+
+import com.google.common.truth.Truth.assertThat
+import de.jeanlucmakiola.clockula.data.prefs.SettingsPrefs
+import de.jeanlucmakiola.floret.prefs.PrefStore
+import de.jeanlucmakiola.floret.prefs.ThemeMode
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.test.TestScope
+import kotlinx.coroutines.test.UnconfinedTestDispatcher
+import kotlinx.coroutines.test.runTest
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.io.TempDir
+import java.io.File
+import java.nio.file.Path
+
+/**
+ * The store as `DataModule` builds it. The preference file feeds the theme
+ * before the first frame, so an unreadable one must degrade to defaults rather
+ * than throw `CorruptionException` out of every launch.
+ */
+class DataModuleTest {
+
+    private fun TestScope.newStore(file: File) = createDataStore(
+        scope = CoroutineScope(UnconfinedTestDispatcher(testScheduler) + Job()),
+        produceFile = { file },
+    )
+
+    @Test
+    fun `a corrupted preference file reads back as the defaults`(@TempDir tempDir: Path) = runTest {
+        val file = tempDir.resolve("clockula_prefs.preferences_pb").toFile()
+        file.writeBytes(byteArrayOf(0x07, 0x2A, 0x13, 0x37, 0x00, 0x42))
+
+        val prefs = SettingsPrefs(PrefStore(newStore(file)))
+
+        assertThat(prefs.themeMode.first()).isEqualTo(ThemeMode.SYSTEM)
+        assertThat(prefs.dynamicColor.first()).isTrue()
+    }
+
+    @Test
+    fun `the store is writable again after replacing a corrupted file`(@TempDir tempDir: Path) = runTest {
+        val file = tempDir.resolve("clockula_prefs.preferences_pb").toFile()
+        file.writeBytes(byteArrayOf(0x07, 0x2A, 0x13, 0x37, 0x00, 0x42))
+        val prefs = SettingsPrefs(PrefStore(newStore(file)))
+
+        prefs.setThemeMode(ThemeMode.DARK)
+
+        assertThat(prefs.themeMode.first()).isEqualTo(ThemeMode.DARK)
+        // ...and the replacement is a real file, so the next launch reads it back.
+        assertThat(file.length()).isGreaterThan(0L)
+    }
+}

app/src/test/java/de/jeanlucmakiola/clockula/data/prefs/SettingsPrefsTest.kt

@@ -0,0 +1,108 @@
+package de.jeanlucmakiola.clockula.data.prefs
+
+import androidx.datastore.core.DataStore
+import androidx.datastore.preferences.core.PreferenceDataStoreFactory
+import androidx.datastore.preferences.core.Preferences
+import androidx.datastore.preferences.core.stringPreferencesKey
+import app.cash.turbine.test
+import com.google.common.truth.Truth.assertThat
+import de.jeanlucmakiola.floret.prefs.Appearance
+import de.jeanlucmakiola.floret.prefs.PrefStore
+import de.jeanlucmakiola.floret.prefs.ThemeMode
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.test.TestScope
+import kotlinx.coroutines.test.UnconfinedTestDispatcher
+import kotlinx.coroutines.test.runTest
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.io.TempDir
+import java.nio.file.Path
+
+/**
+ * Clockula's appearance preferences over a real DataStore, one temp file per
+ * test. These values feed the theme before the first frame, so a missing or
+ * corrupted one must resolve rather than throw.
+ */
+class SettingsPrefsTest {
+
+    private fun TestScope.newDataStore(tempDir: Path): DataStore<Preferences> =
+        PreferenceDataStoreFactory.create(
+            scope = CoroutineScope(UnconfinedTestDispatcher(testScheduler) + Job()),
+            produceFile = { tempDir.resolve("clockula_prefs_test.preferences_pb").toFile() },
+        )
+
+    @Test
+    fun `a fresh install follows the system theme with dynamic colour on`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(PrefStore(newDataStore(tempDir)))
+
+        val appearance = listOf(prefs.themeMode.first(), prefs.dynamicColor.first())
+
+        assertThat(appearance).containsExactly(ThemeMode.SYSTEM, true).inOrder()
+    }
+
+    @Test
+    fun `the theme mode round-trips`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(PrefStore(newDataStore(tempDir)))
+
+        prefs.setThemeMode(ThemeMode.DARK)
+
+        assertThat(prefs.themeMode.first()).isEqualTo(ThemeMode.DARK)
+    }
+
+    @Test
+    fun `the dynamic colour choice round-trips`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(PrefStore(newDataStore(tempDir)))
+
+        prefs.setDynamicColor(false)
+
+        assertThat(prefs.dynamicColor.first()).isFalse()
+    }
+
+    @Test
+    fun `appearance carries both stored choices`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(PrefStore(newDataStore(tempDir)))
+        prefs.setThemeMode(ThemeMode.DARK)
+        prefs.setDynamicColor(false)
+
+        val appearance = prefs.appearance.first()
+
+        assertThat(appearance).isEqualTo(Appearance(ThemeMode.DARK, dynamicColor = false))
+    }
+
+    @Test
+    fun `the theme mode is written under the family's key name`(@TempDir tempDir: Path) = runTest {
+        val dataStore = newDataStore(tempDir)
+        val prefs = SettingsPrefs(PrefStore(dataStore))
+
+        prefs.setThemeMode(ThemeMode.LIGHT)
+
+        assertThat(dataStore.data.first()[stringPreferencesKey("theme_mode")]).isEqualTo("LIGHT")
+    }
+
+    @Test
+    fun `a corrupted theme mode falls back to following the system`(@TempDir tempDir: Path) = runTest {
+        val dataStore = newDataStore(tempDir)
+        val prefs = SettingsPrefs(PrefStore(dataStore))
+
+        dataStore.updateData { stored ->
+            stored.toMutablePreferences().apply { this[stringPreferencesKey("theme_mode")] = "FUNDAY" }
+        }
+
+        assertThat(prefs.themeMode.first()).isEqualTo(ThemeMode.SYSTEM)
+    }
+
+    @Test
+    fun `the theme mode does not re-emit when an unrelated preference is written`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(PrefStore(newDataStore(tempDir)))
+
+        prefs.themeMode.test {
+            assertThat(awaitItem()).isEqualTo(ThemeMode.SYSTEM)
+
+            prefs.setDynamicColor(true)
+
+            expectNoEvents()
+            cancel()
+        }
+    }
+}