feat(wind): Level 0 — single wind arrow at GPS position

- MapHandler.setupWindLayer: registers ic_wind_arrow bitmap, adds GeoJSON
  source + SymbolLayer with rotation/size driven by direction/speed_kt props
- MapHandler.updateWindLayer(arrow): pushes updated feature to the source
- MainActivity: calls setupWindLayer after style load; fires loadWeather once
  on first GPS fix (weatherLoaded flag); observes windArrow StateFlow to
  drive updateWindLayer

https://claude.ai/code/session_01HXPjBsogsJVRwCiekDGkJX

2 files changed, 55 insertions, 0 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 f9d4dbd..5950844 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
@@ -49,6 +49,7 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
     private var mapHandler: MapHandler? = null
     private var anchorWatchHandler: AnchorWatchHandler? = null
     private val loadedStyleFlow = MutableStateFlow<Style?>(null)
+    private var weatherLoaded = false
 
     private lateinit var bottomSheetBehavior: BottomSheetBehavior<View>
     private lateinit var fragmentContainer: FrameLayout
@@ -244,7 +245,9 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
                 loadedStyleFlow.value = style
                 val anchorBitmap = rasterizeDrawable(R.drawable.ic_anchor)
                 val arrowBitmap = rasterizeDrawable(R.drawable.ic_tidal_arrow)
+                val windArrowBitmap = rasterizeDrawable(R.drawable.ic_wind_arrow)
                 mapHandler?.setupLayers(style, anchorBitmap, arrowBitmap)
+                mapHandler?.setupWindLayer(style, windArrowBitmap)
             }
         }
     }
@@ -255,6 +258,15 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
                 mapHandler?.centerOnLocation(gpsData.latitude, gpsData.longitude)
                 val sogKnots = gpsData.speedOverGround * 1.94384
                 viewModel.addGpsPoint(gpsData.latitude, gpsData.longitude, sogKnots, gpsData.courseOverGround.toDouble())
+                if (!weatherLoaded) {
+                    weatherLoaded = true
+                    viewModel.loadWeather(gpsData.latitude, gpsData.longitude)
+                }
+            }
+        }
+        lifecycleScope.launch {
+            viewModel.windArrow.collect { arrow ->
+                if (arrow != null) mapHandler?.updateWindLayer(arrow)
             }
         }
         lifecycleScope.launch {
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/ui/MapHandler.kt b/android-app/app/src/main/kotlin/org/terst/nav/ui/MapHandler.kt
index cbc2e90..cdf0c25 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/ui/MapHandler.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/ui/MapHandler.kt
@@ -6,6 +6,7 @@ import org.maplibre.android.camera.CameraUpdateFactory
 import org.maplibre.android.geometry.LatLng
 import org.maplibre.android.maps.MapLibreMap
 import org.maplibre.android.maps.Style
+import org.maplibre.android.style.expressions.Expression
 import org.maplibre.android.style.layers.CircleLayer
 import org.maplibre.android.style.layers.LineLayer
 import org.maplibre.android.style.layers.PropertyFactory
@@ -21,6 +22,7 @@ import org.maplibre.geojson.Point
 import org.maplibre.geojson.Polygon
 import org.terst.nav.AnchorWatchState
 import org.terst.nav.TidalCurrentState
+import org.terst.nav.data.model.WindArrow
 import org.terst.nav.track.TrackPoint
 import kotlin.math.cos
 import kotlin.math.sin
@@ -43,10 +45,15 @@ class MapHandler(private val maplibreMap: MapLibreMap) {
     private val TRACK_SOURCE_ID = "track-source"
     private val TRACK_LAYER_ID = "track-line"
 
+    private val WIND_SOURCE_ID = "wind-source"
+    private val WIND_LAYER_ID = "wind-arrows"
+    private val WIND_ARROW_ICON_ID = "wind-arrow"
+
     private var anchorPointSource: GeoJsonSource? = null
     private var anchorCircleSource: GeoJsonSource? = null
     private var tidalCurrentSource: GeoJsonSource? = null
     private var trackSource: GeoJsonSource? = null
+    private var windSource: GeoJsonSource? = null
 
     /**
      * Initializes map layers for anchor watch and tidal currents.
@@ -135,6 +142,42 @@ class MapHandler(private val maplibreMap: MapLibreMap) {
     }
 
     /**
+     * Registers the wind-arrow bitmap in the style. Call once after style loads.
+     */
+    fun setupWindLayer(style: Style, arrowBitmap: Bitmap) {
+        style.addImage(WIND_ARROW_ICON_ID, arrowBitmap)
+        windSource = GeoJsonSource(WIND_SOURCE_ID)
+        style.addSource(windSource!!)
+        style.addLayer(SymbolLayer(WIND_LAYER_ID, WIND_SOURCE_ID).apply {
+            setProperties(
+                PropertyFactory.iconImage(WIND_ARROW_ICON_ID),
+                PropertyFactory.iconRotate(Expression.get("direction")),
+                PropertyFactory.iconRotationAlignment("map"),
+                PropertyFactory.iconAllowOverlap(true),
+                PropertyFactory.iconSize(
+                    Expression.interpolate(
+                        Expression.linear(),
+                        Expression.get("speed_kt"),
+                        Expression.stop(0, 0.6f),
+                        Expression.stop(30, 1.4f)
+                    )
+                )
+            )
+        })
+    }
+
+    /**
+     * Places or moves the single wind arrow at the GPS position.
+     */
+    fun updateWindLayer(arrow: WindArrow) {
+        val feature = Feature.fromGeometry(Point.fromLngLat(arrow.lon, arrow.lat)).apply {
+            addNumberProperty("direction", arrow.directionDeg)
+            addNumberProperty("speed_kt", arrow.speedKt)
+        }
+        windSource?.setGeoJson(FeatureCollection.fromFeature(feature))
+    }
+
+    /**
      * Updates the GPS track polyline on the map. Lazily initialises the layer on first call.
      */
     fun updateTrackLayer(style: Style, points: List<TrackPoint>) {