Move weather fetching and SVG generation to native Kotlin

CLAUDE.md

@@ -46,11 +46,9 @@ lib/
 ├── models/
 │   └── weather_data.dart    # WeatherData, HourlyData classes
 ├── services/
-│   ├── weather_service.dart      # Open-Meteo API client
 │   ├── location_service.dart     # Geolocator wrapper with fallback
 │   ├── widget_service.dart       # home_widget integration
-│   ├── background_service.dart   # home_widget callbacks for background updates
-│   └── svg_chart_generator.dart  # Pure Dart SVG generation
+│   └── native_svg_service.dart   # Method channel to native (weather fetch, SVG gen, cache)
 ├── theme/
 │   └── app_theme.dart       # MeteogramColors, WeatherGradients
 ├── widgets/
@@ -61,11 +59,14 @@ lib/
 android/app/src/main/
 ├── kotlin/.../
 │   ├── MainActivity.kt
-│   ├── MeteogramApplication.kt       # Registers event receivers
+│   ├── MeteogramApplication.kt       # Registers event receivers, theme observer
 │   ├── MeteogramWidgetProvider.kt    # Extends HomeWidgetProvider
 │   ├── WidgetEventReceiver.kt        # Handles system broadcasts
 │   ├── WidgetUtils.kt                # Widget helper functions
-│   ├── WeatherUpdateWorker.kt        # WorkManager periodic refresh
+│   ├── WeatherUpdateWorker.kt        # WorkManager periodic refresh (~30 min)
+│   ├── WeatherFetcher.kt             # Native HTTP client for Open-Meteo API
+│   ├── WeatherDataParser.kt          # Parse cached weather JSON
+│   ├── SvgChartGenerator.kt          # Native SVG generation (single source)
 │   ├── MaterialYouColorExtractor.kt  # Native Material You color extraction
 │   ├── SvgChartPlatformView.kt       # Native SVG rendering for in-app
 │   └── SvgChartViewFactory.kt        # PlatformView factory
@@ -119,15 +120,14 @@ Android widgets use RemoteViews which only support:
 **NOT supported:** View, Space, custom views, most Material widgets
 
 ### Data Flow
-1. `home_screen.dart` loads weather → generates SVG via `SvgChartGenerator`
-2. In-app: SVG rendered via `NativeSvgChartView` (Android PlatformView)
-3. Widget: SVG saved to file, `HomeWidget.updateWidget()` triggers native update
-4. `MeteogramWidgetProvider.kt` reads SVG file, renders via AndroidSVG → ImageView
+1. **In-app**: `home_screen.dart` gets location → calls `NativeSvgService.fetchWeather()` → Kotlin fetches from Open-Meteo → caches to SharedPreferences → Dart reads cache → Kotlin generates SVG → rendered via `NativeSvgChartView`
+2. **Widget**: Native code reads cached weather from SharedPreferences → `SvgChartGenerator.kt` generates SVG → AndroidSVG renders to bitmap → ImageView
 
-### Background Refresh
+### Background Refresh (fully native)
 - **WorkManager periodic**: `WeatherUpdateWorker.kt` runs ~30 min (battery-efficient, OS batches work)
-- **Event-driven**: `WidgetEventReceiver.kt` handles unlock, network, locale changes
-- **home_widget callbacks**: `background_service.dart` handles `weatherUpdate` and `chartReRender` URIs
+- **Weather fetching**: `WeatherFetcher.kt` calls Open-Meteo API directly (no Dart involved)
+- **Event-driven**: `WidgetEventReceiver.kt` handles unlock, network, locale/timezone changes
+- **Material You**: `ContentObserver` + `MaterialYouColorWorker.kt` detect theme changes
 
 ## Build Commands
 
@@ -153,10 +153,10 @@ Do not commit code with analyzer warnings or test failures.
 ## Common Tasks
 
 ### Modify chart appearance
-Edit `lib/services/svg_chart_generator.dart`:
-- `_writeTemperatureLine()` - line style, gradient fill
-- `_writePrecipitationBars()` - bar colors, width
-- `_writeSunshineBars()` - daylight intensity display
+Edit `android/.../SvgChartGenerator.kt`:
+- `writeTemperatureLine()` - line style, gradient fill
+- `writePrecipitationBars()` - bar colors, width
+- `writeSunshineBars()` - daylight intensity display
 - `SvgChartColors` - color definitions for light/dark themes
 
 ### Modify widget layout
@@ -180,14 +180,16 @@ adb logcat | grep -i "Error inflating"
 
 | File | Purpose |
 |------|---------|
-| `lib/services/svg_chart_generator.dart` | Pure Dart SVG generation (core chart) |
-| `lib/widgets/native_svg_chart_view.dart` | In-app SVG display via PlatformView |
-| `lib/services/background_service.dart` | home_widget callbacks for background updates |
-| `lib/theme/app_theme.dart` | All colors and gradients |
-| `android/.../MeteogramWidgetProvider.kt` | Native widget code |
-| `android/.../WeatherUpdateWorker.kt` | WorkManager periodic refresh |
+| `android/.../SvgChartGenerator.kt` | Native SVG generation (single source of truth) |
+| `android/.../WeatherFetcher.kt` | Native HTTP client for background weather fetching |
+| `android/.../WeatherDataParser.kt` | Parse cached weather JSON from SharedPreferences |
+| `android/.../MeteogramWidgetProvider.kt` | Widget update handling |
+| `android/.../WeatherUpdateWorker.kt` | WorkManager periodic refresh (~30 min) |
 | `android/.../MaterialYouColorExtractor.kt` | Native Material You color extraction |
-| `android/.../WidgetEventReceiver.kt` | System event handler |
+| `android/.../WidgetEventReceiver.kt` | System event handler (unlock, network, etc.) |
+| `lib/services/native_svg_service.dart` | Method channel to native (weather, SVG, cache) |
+| `lib/services/location_service.dart` | GPS/manual location with city search |
+| `lib/theme/app_theme.dart` | All colors and gradients |
 
 ## Gotchas
 

android/app/src/main/kotlin/org/bortnik/meteogram/MainActivity.kt

@@ -2,15 +2,20 @@ package org.bortnik.meteogram
 
 import android.graphics.Bitmap
 import android.graphics.Canvas
+import android.os.Build
+import android.text.format.DateFormat
+import android.util.Log
 import com.caverock.androidsvg.SVG
 import io.flutter.embedding.android.FlutterActivity
 import io.flutter.embedding.engine.FlutterEngine
 import io.flutter.plugin.common.MethodChannel
 import java.io.ByteArrayInputStream
 import java.io.ByteArrayOutputStream
+import java.util.Locale
 
 class MainActivity : FlutterActivity() {
     private val CHANNEL = "org.bortnik.meteogram/svg"
+    private val TAG = "MainActivity"
 
     override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
         // Extract Material You colors BEFORE Flutter engine starts
@@ -27,6 +32,29 @@ class MainActivity : FlutterActivity() {
 
         MethodChannel(flutterEngine.dartExecutor.binaryMessenger, CHANNEL).setMethodCallHandler { call, result ->
             when (call.method) {
+                "generateSvg" -> {
+                    val width = call.argument<Int>("width") ?: 0
+                    val height = call.argument<Int>("height") ?: 0
+                    val isLight = call.argument<Boolean>("isLight") ?: true
+                    val usesFahrenheit = call.argument<Boolean>("usesFahrenheit") ?: false
+
+                    if (width <= 0 || height <= 0) {
+                        result.error("INVALID_ARGS", "Invalid dimensions: ${width}x${height}", null)
+                        return@setMethodCallHandler
+                    }
+
+                    try {
+                        val svgString = generateSvgFromCache(width, height, isLight, usesFahrenheit)
+                        if (svgString != null) {
+                            result.success(svgString)
+                        } else {
+                            result.error("NO_DATA", "No weather data available", null)
+                        }
+                    } catch (e: Exception) {
+                        Log.e(TAG, "Error generating SVG", e)
+                        result.error("GENERATE_ERROR", e.message, null)
+                    }
+                }
                 "renderSvg" -> {
                     val svgString = call.argument<String>("svg")
                     val width = call.argument<Int>("width") ?: 0
@@ -44,11 +72,103 @@ class MainActivity : FlutterActivity() {
                         result.error("RENDER_ERROR", e.message, null)
                     }
                 }
+                "fetchWeather" -> {
+                    val latitude = call.argument<Double>("latitude")
+                    val longitude = call.argument<Double>("longitude")
+
+                    if (latitude == null || longitude == null) {
+                        result.error("INVALID_ARGS", "Missing latitude or longitude", null)
+                        return@setMethodCallHandler
+                    }
+
+                    // Run on background thread
+                    Thread {
+                        try {
+                            val success = WeatherFetcher.fetchWeatherSync(this, latitude, longitude)
+                            runOnUiThread {
+                                if (success) {
+                                    result.success(true)
+                                } else {
+                                    result.error("FETCH_FAILED", "Failed to fetch weather data", null)
+                                }
+                            }
+                        } catch (e: Exception) {
+                            Log.e(TAG, "Error fetching weather", e)
+                            runOnUiThread {
+                                result.error("FETCH_ERROR", e.message, null)
+                            }
+                        }
+                    }.start()
+                }
                 else -> result.notImplemented()
             }
         }
     }
 
+    /**
+     * Generate SVG string from cached weather data.
+     */
+    private fun generateSvgFromCache(
+        width: Int,
+        height: Int,
+        isLight: Boolean,
+        usesFahrenheit: Boolean
+    ): String? {
+        val weatherData = WeatherDataParser.parseFromPrefs(this)
+        if (weatherData == null) {
+            Log.d(TAG, "No cached weather data for SVG generation")
+            return null
+        }
+
+        val displayData = weatherData.getDisplayRange()
+        val nowIndex = weatherData.getNowIndex()
+
+        // Get colors with Material You support
+        val colors = getChartColors(isLight)
+
+        val generator = SvgChartGenerator()
+        return generator.generate(
+            data = displayData,
+            nowIndex = nowIndex,
+            latitude = weatherData.latitude,
+            longitude = weatherData.longitude,
+            colors = colors,
+            width = width.toDouble(),
+            height = height.toDouble(),
+            locale = Locale.getDefault(),
+            usesFahrenheit = usesFahrenheit,
+            use24HourFormat = DateFormat.is24HourFormat(this)
+        )
+    }
+
+    /**
+     * Get chart colors with Material You support.
+     */
+    private fun getChartColors(isLight: Boolean): SvgChartColors {
+        val baseColors = if (isLight) SvgChartColors.light else SvgChartColors.dark
+
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.S) {
+            return baseColors
+        }
+
+        val prefs = getSharedPreferences(WidgetUtils.PREFS_NAME, MODE_PRIVATE)
+
+        val tempColorKey = if (isLight) "material_you_light_on_primary_container" else "material_you_dark_primary"
+        val timeColorKey = if (isLight) "material_you_light_tertiary" else "material_you_dark_tertiary"
+
+        val tempColor = prefs.getInt(tempColorKey, 0)
+        val timeColor = prefs.getInt(timeColorKey, 0)
+
+        if (tempColor == 0 || timeColor == 0) {
+            return baseColors
+        }
+
+        return baseColors.withDynamicColors(
+            temperatureLine = SvgColor.fromArgb(tempColor),
+            timeLabel = SvgColor.fromArgb(timeColor)
+        )
+    }
+
     private fun renderSvgToPng(svgString: String, width: Int, height: Int): ByteArray {
         val svg = SVG.getFromInputStream(ByteArrayInputStream(svgString.toByteArray()))
         svg.documentWidth = width.toFloat()

android/app/src/main/kotlin/org/bortnik/meteogram/MaterialYouColorWorker.kt

@@ -75,8 +75,8 @@ class MaterialYouColorWorker(
         try {
             // Check if colors actually changed
             if (MaterialYouColorExtractor.updateColorsIfChanged(applicationContext)) {
-                Log.d(TAG, "Material You colors changed - triggering re-render for all widgets")
-                WidgetUtils.rerenderAllWidgets(applicationContext)
+                Log.d(TAG, "Material You colors changed - triggering native re-render for all widgets")
+                WidgetUtils.rerenderAllWidgetsNative(applicationContext)
             } else {
                 Log.d(TAG, "Colors unchanged or already up to date")
             }

android/app/src/main/kotlin/org/bortnik/meteogram/MeteogramApplication.kt

@@ -47,8 +47,8 @@ class MeteogramApplication : Application() {
                 override fun onChange(selfChange: Boolean) {
                     Log.d(TAG, "Theme customization changed (ContentObserver)")
                     if (MaterialYouColorExtractor.updateColorsIfChanged(applicationContext)) {
-                        Log.d(TAG, "Material You colors changed - triggering re-render for all widgets")
-                        WidgetUtils.rerenderAllWidgets(applicationContext)
+                        Log.d(TAG, "Material You colors changed - triggering native re-render for all widgets")
+                        WidgetUtils.rerenderAllWidgetsNative(applicationContext)
                     }
                 }
             }