feat(tracks): show summary sheet on track stop; 2-min minimum

TrackSummarySheet: bottom sheet showing distance (nm), duration,
max/avg speed, avg wind and waves (when available, waves in ft).
Only shown for tracks ≥ 2 minutes — shorter tracks are discarded silently.

MainViewModel: exposes trackSummary SharedFlow (replay=0) and trackStartMs.
MainActivity: observes flow, shows sheet after stopTrack completes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

4 files changed, 126 insertions, 6 deletions

diff --git a/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt b/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
index 022b748..d64ce8d 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
@@ -109,6 +109,13 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
                 fabRecordTrack.contentDescription = if (recording) "Stop Recording" else "Record Track"
             }
         }
+        lifecycleScope.launch {
+            viewModel.trackSummary.collect { summary ->
+                org.terst.nav.track.TrackSummarySheet
+                    .from(summary, viewModel.trackStartMs)
+                    .show(supportFragmentManager, "track_summary")
+            }
+        }
     }
 
     private fun setupBottomSheet() {
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/track/TrackRepository.kt b/android-app/app/src/main/kotlin/org/terst/nav/track/TrackRepository.kt
index ed32497..228a484 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/track/TrackRepository.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/track/TrackRepository.kt
@@ -12,7 +12,10 @@ class TrackRepository(context: Context) {
         private set
 
     private val activePoints = mutableListOf<TrackPoint>()
-    private var trackStartMs = 0L
+
+    /** Epoch-ms when the current (or last) track started. Exposed for the summary sheet title. */
+    var trackStartMs: Long = 0L
+        private set
 
     // Loaded lazily from Documents/Nav/ on first access
     private val _pastTracks = mutableListOf<List<TrackPoint>>()
@@ -26,18 +29,22 @@ class TrackRepository(context: Context) {
 
     /**
      * Stops the active track, computes a [TrackSummary], persists the track
-     * to shared storage, and returns the summary. Returns null if no points
-     * were recorded.
+     * to shared storage, and returns the summary. Returns null if the track
+     * was too short (< 2 minutes) or had no points.
      */
+
     suspend fun stopTrack(): TrackSummary? = withContext(Dispatchers.IO) {
         if (!isRecording) return@withContext null
         isRecording = false
         val points = activePoints.toList()
         activePoints.clear()
-        if (points.isEmpty()) return@withContext null
+        if (points.size < 2) return@withContext null
 
         val summary = summarise(points)
-        _pastTracks.add(0, points)  // prepend so most recent is first
+        // Discard tracks shorter than 2 minutes — likely accidental taps
+        if (summary.durationMs < 2 * 60_000L) return@withContext null
+
+        _pastTracks.add(0, points)
         storage.saveTrack(points, trackStartMs)
         summary
     }
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/track/TrackSummarySheet.kt b/android-app/app/src/main/kotlin/org/terst/nav/track/TrackSummarySheet.kt
new file mode 100644
index 0000000..8d9d7c7
--- /dev/null
+++ b/android-app/app/src/main/kotlin/org/terst/nav/track/TrackSummarySheet.kt
@@ -0,0 +1,95 @@
+package org.terst.nav.track
+
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.LinearLayout
+import android.widget.TextView
+import com.google.android.material.bottomsheet.BottomSheetDialogFragment
+import org.terst.nav.R
+import java.time.Instant
+import java.time.ZoneId
+import java.time.format.DateTimeFormatter
+import java.util.Locale
+
+class TrackSummarySheet : BottomSheetDialogFragment() {
+
+    companion object {
+        private const val ARG_DISTANCE  = "distance_nm"
+        private const val ARG_DURATION  = "duration_ms"
+        private const val ARG_MAX_SOG   = "max_sog"
+        private const val ARG_AVG_SOG   = "avg_sog"
+        private const val ARG_AVG_WIND  = "avg_wind"   // -1 if absent
+        private const val ARG_AVG_WAVE  = "avg_wave_m" // -1 if absent
+        private const val ARG_START_MS  = "start_ms"
+
+        fun from(summary: TrackSummary, startMs: Long) = TrackSummarySheet().apply {
+            arguments = Bundle().apply {
+                putDouble(ARG_DISTANCE, summary.distanceNm)
+                putLong(ARG_DURATION,   summary.durationMs)
+                putDouble(ARG_MAX_SOG,  summary.maxSogKt)
+                putDouble(ARG_AVG_SOG,  summary.avgSogKt)
+                putDouble(ARG_AVG_WIND, summary.avgWindKt ?: -1.0)
+                putDouble(ARG_AVG_WAVE, summary.avgWaveHeightM ?: -1.0)
+                putLong(ARG_START_MS,   startMs)
+            }
+        }
+    }
+
+    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View =
+        inflater.inflate(R.layout.layout_track_summary_sheet, container, false)
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        val args = requireArguments()
+        val distanceNm = args.getDouble(ARG_DISTANCE)
+        val durationMs = args.getLong(ARG_DURATION)
+        val maxSog     = args.getDouble(ARG_MAX_SOG)
+        val avgSog     = args.getDouble(ARG_AVG_SOG)
+        val avgWind    = args.getDouble(ARG_AVG_WIND).takeIf { it >= 0 }
+        val avgWaveM   = args.getDouble(ARG_AVG_WAVE).takeIf { it >= 0 }
+        val startMs    = args.getLong(ARG_START_MS)
+
+        val titleFmt = DateTimeFormatter.ofPattern("dd MMM HH:mm", Locale.getDefault())
+            .withZone(ZoneId.systemDefault())
+        view.findViewById<TextView>(R.id.summary_title).text =
+            "Track · ${titleFmt.format(Instant.ofEpochMilli(startMs))}"
+
+        view.findViewById<TextView>(R.id.summary_distance).text =
+            "%.1f".format(Locale.getDefault(), distanceNm)
+
+        view.findViewById<TextView>(R.id.summary_duration).text = formatDuration(durationMs)
+
+        view.findViewById<TextView>(R.id.summary_max_sog).text =
+            "%.1f".format(Locale.getDefault(), maxSog)
+
+        view.findViewById<TextView>(R.id.summary_avg_sog).text =
+            "%.1f".format(Locale.getDefault(), avgSog)
+
+        val conditionsRow = view.findViewById<LinearLayout>(R.id.summary_conditions_row)
+        val windCell      = view.findViewById<LinearLayout>(R.id.summary_wind_cell)
+        val waveCell      = view.findViewById<LinearLayout>(R.id.summary_wave_cell)
+
+        if (avgWind != null) {
+            windCell.visibility = View.VISIBLE
+            view.findViewById<TextView>(R.id.summary_avg_wind).text =
+                "%.0f".format(Locale.getDefault(), avgWind)
+        }
+        if (avgWaveM != null) {
+            waveCell.visibility = View.VISIBLE
+            val waveFt = avgWaveM * 3.28084
+            view.findViewById<TextView>(R.id.summary_avg_wave).text =
+                "%.1f".format(Locale.getDefault(), waveFt)
+        }
+        if (avgWind != null || avgWaveM != null) {
+            conditionsRow.visibility = View.VISIBLE
+        }
+    }
+
+    private fun formatDuration(ms: Long): String {
+        val totalMinutes = ms / 60_000
+        val hours   = totalMinutes / 60
+        val minutes = totalMinutes % 60
+        return if (hours > 0) "${hours}h ${minutes}m" else "${minutes}m"
+    }
+}
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/ui/MainViewModel.kt b/android-app/app/src/main/kotlin/org/terst/nav/ui/MainViewModel.kt
index c1707ab..5797138 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/ui/MainViewModel.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/ui/MainViewModel.kt
@@ -15,10 +15,14 @@ import org.terst.nav.data.repository.WeatherRepository
 import com.squareup.moshi.Moshi
 import com.squareup.moshi.kotlin.reflect.KotlinJsonAdapterFactory
 import kotlinx.coroutines.async
+import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.SharedFlow
 import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asSharedFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.launch
+import org.terst.nav.track.TrackSummary
 import retrofit2.Retrofit
 import retrofit2.converter.moshi.MoshiConverterFactory
 
@@ -60,18 +64,25 @@ class MainViewModel(
     private val _pastTracks = MutableStateFlow<List<List<TrackPoint>>>(emptyList())
     val pastTracks: StateFlow<List<List<TrackPoint>>> = _pastTracks.asStateFlow()
 
+    private val _trackSummary = MutableSharedFlow<TrackSummary>(replay = 0)
+    val trackSummary: SharedFlow<TrackSummary> = _trackSummary.asSharedFlow()
+
     fun startTrack() {
         trackRepository.startTrack()
         _trackPoints.value = emptyList()
         _isRecording.value = true
     }
 
+    /** Epoch-ms when the current track started — for the summary sheet title. */
+    val trackStartMs: Long get() = trackRepository.trackStartMs
+
     fun stopTrack() {
         viewModelScope.launch {
-            trackRepository.stopTrack()
+            val summary = trackRepository.stopTrack()
             _pastTracks.value = trackRepository.getPastTracks()
             _trackPoints.value = emptyList()
             _isRecording.value = false
+            summary?.let { _trackSummary.emit(it) }
         }
     }