feat: density-based activity classifier and data import/export

app/build.gradle.kts

@@ -52,7 +52,12 @@ android {
     }
 
     buildTypes {
+        debug {
+            // applicationIdSuffix = ".dev"  // Temporarily disabled for one-time migration
+            resValue("string", "app_name", "Podometer-dev")
+        }
         release {
+            resValue("string", "app_name", "Podometer")
             isMinifyEnabled = true
             isShrinkResources = true
             signingConfig = if (System.getenv("RELEASE_KEYSTORE_PATH") != null) {

app/src/main/java/com/podometer/MainActivity.kt

@@ -146,6 +146,7 @@ class MainActivity : ComponentActivity() {
                             onSetAutoStartEnabled = viewModel::setAutoStartEnabled,
                             onSetNotificationStyle = viewModel::setNotificationStyle,
                             onExportData = viewModel::exportData,
+                            onImportData = viewModel::importData,
                             onResetExportState = viewModel::resetExportState,
                             onNavigateToDonate = {
                                 navController.navigate(Screen.Donate.route)

app/src/main/java/com/podometer/data/db/ActivityTransitionDao.kt

@@ -27,6 +27,10 @@ interface ActivityTransitionDao {
     @Insert
     suspend fun insertTransition(transition: ActivityTransition)
 
+    /** Inserts multiple [ActivityTransition] rows. */
+    @Insert
+    suspend fun insertAllTransitions(transitions: List<ActivityTransition>)
+
     /** Updates an existing [ActivityTransition] row (matched by primary key). */
     @Update
     suspend fun updateTransition(transition: ActivityTransition)

app/src/main/java/com/podometer/data/db/CyclingSessionDao.kt

@@ -30,6 +30,10 @@ interface CyclingSessionDao {
     @Insert
     suspend fun insertSession(session: CyclingSession): Long
 
+    /** Inserts multiple [CyclingSession] rows. */
+    @Insert
+    suspend fun insertAllSessions(sessions: List<CyclingSession>)
+
     /** Updates an existing [CyclingSession] row (matched by primary key). */
     @Update
     suspend fun updateSession(session: CyclingSession)

app/src/main/java/com/podometer/data/db/PodometerDatabase.kt

@@ -14,6 +14,8 @@ import androidx.sqlite.db.SupportSQLiteDatabase
  *       daily summaries, and cycling sessions.
  *   2 — Added sensor_windows table for raw classifier window storage
  *       (7-day retention, ~6 MB).
+ *   3 — Consolidate 5-second sensor windows into 30-second windows.
+ *       Keeps the window with the highest magnitudeVariance per 30 s slot.
  */
 @Database(
     entities = [
@@ -23,7 +25,7 @@ import androidx.sqlite.db.SupportSQLiteDatabase
         CyclingSession::class,
         SensorWindow::class,
     ],
-    version = 2,
+    version = 3,
     exportSchema = false,
 )
 abstract class PodometerDatabase : RoomDatabase() {
@@ -55,5 +57,32 @@ abstract class PodometerDatabase : RoomDatabase() {
                 )
             }
         }
+
+        /**
+         * Migration from version 2 to 3: consolidate 5-second sensor windows
+         * into 30-second windows.
+         *
+         * For each 30-second time slot (timestamp / 30000), keeps only the
+         * window with the highest magnitudeVariance. This preserves the
+         * cycling signal (which depends on variance) while reducing storage
+         * by ~6x. The stepFrequencyHz already encodes a 30-second sliding
+         * window, so no information is lost from the step frequency perspective.
+         */
+        val MIGRATION_2_3 = object : Migration(2, 3) {
+            override fun migrate(db: SupportSQLiteDatabase) {
+                db.execSQL(
+                    """
+                    DELETE FROM sensor_windows WHERE id NOT IN (
+                        SELECT id FROM (
+                            SELECT id, ROW_NUMBER() OVER (
+                                PARTITION BY timestamp / 30000
+                                ORDER BY magnitudeVariance DESC
+                            ) AS rn FROM sensor_windows
+                        ) WHERE rn = 1
+                    )
+                    """.trimIndent(),
+                )
+            }
+        }
     }
 }

app/src/main/java/com/podometer/data/db/SensorWindowDao.kt

@@ -28,6 +28,13 @@ interface SensorWindowDao {
     @Query("SELECT * FROM sensor_windows WHERE timestamp BETWEEN :startMs AND :endMs ORDER BY timestamp")
     fun getWindowsBetween(startMs: Long, endMs: Long): Flow<List<SensorWindow>>
 
+    /**
+     * Returns all sensor windows ordered by timestamp ascending.
+     * One-shot suspend query intended for data export — not a [Flow].
+     */
+    @Query("SELECT * FROM sensor_windows ORDER BY timestamp ASC")
+    suspend fun getAllWindows(): List<SensorWindow>
+
     /**
      * Deletes all sensor windows older than [cutoffMs].
      *

app/src/main/java/com/podometer/data/db/StepDao.kt

@@ -137,6 +137,14 @@ interface StepDao {
     """)
     suspend fun addCyclingMinutes(date: String, minutes: Int)
 
+    /** Inserts multiple [DailySummary] rows, replacing on conflict. */
+    @Insert(onConflict = OnConflictStrategy.REPLACE)
+    suspend fun insertAllDailySummaries(summaries: List<DailySummary>)
+
+    /** Inserts multiple [HourlyStepAggregate] rows, replacing on conflict. */
+    @Insert(onConflict = OnConflictStrategy.REPLACE)
+    suspend fun insertAllHourlyAggregates(aggregates: List<HourlyStepAggregate>)
+
     /**
      * Returns all [DailySummary] rows ordered by date ascending.
      * One-shot suspend query intended for data export — not a [Flow].

app/src/main/java/com/podometer/data/export/ExportModels.kt

@@ -21,6 +21,8 @@ data class ExportData(
     val activityTransitions: List<ExportActivityTransition>,
     /** All cycling sessions, ordered by start time ascending. */
     val cyclingSessions: List<ExportCyclingSession>,
+    /** All raw sensor classifier windows, ordered by timestamp ascending. */
+    val sensorWindows: List<ExportSensorWindow> = emptyList(),
 )
 
 /**
@@ -104,3 +106,20 @@ data class ExportCyclingSession(
     /** True when the user manually created or overrode this session. */
     val isManualOverride: Boolean,
 )
+
+/**
+ * Export model mirroring the Room [com.podometer.data.db.SensorWindow] entity.
+ */
+@Serializable
+data class ExportSensorWindow(
+    /** Database row ID. */
+    val id: Long,
+    /** Epoch-millisecond timestamp for the start of this window. */
+    val timestamp: Long,
+    /** Accelerometer magnitude variance (m/s²)² for this window. */
+    val magnitudeVariance: Double,
+    /** Step cadence in Hz. */
+    val stepFrequencyHz: Double,
+    /** Number of steps detected during this window. */
+    val stepCount: Int,
+)

app/src/main/java/com/podometer/data/sensor/AccelerometerSampleBuffer.kt

@@ -43,7 +43,7 @@ data class WindowFeatures(
  *   so contention overhead is negligible.
  *
  * @param capacity Maximum number of samples to retain. Default: [DEFAULT_CAPACITY]
- *   (75 slots = 15 seconds at ~5 Hz SENSOR_DELAY_NORMAL rate).
+ *   (150 slots = 30 seconds at ~5 Hz SENSOR_DELAY_NORMAL rate).
  */
 class AccelerometerSampleBuffer(val capacity: Int = DEFAULT_CAPACITY) {
 
@@ -184,10 +184,10 @@ class AccelerometerSampleBuffer(val capacity: Int = DEFAULT_CAPACITY) {
         /**
          * Default circular buffer capacity.
          *
-         * 75 slots covers 15 seconds at SENSOR_DELAY_NORMAL (~5 Hz delivery rate).
-         * This is sufficient for activity-classification sliding windows.
+         * 150 slots covers 30 seconds at SENSOR_DELAY_NORMAL (~5 Hz delivery rate),
+         * aligned with the 30-second classifier evaluation interval.
          */
-        const val DEFAULT_CAPACITY = 75
+        const val DEFAULT_CAPACITY = 150
 
         /**
          * Minimum number of samples required before [computeWindowFeatures] will