feat: battery heater overlay on drive detail charts

app/src/main/java/com/matedroid/data/api/models/DriveModels.kt

@@ -128,14 +128,23 @@ data class DrivePosition(
     @Json(name = "power") val power: Int? = null,
     @Json(name = "battery_level") val batteryLevel: Int? = null,
     @Json(name = "elevation") val elevation: Int? = null,
-    @Json(name = "climate_info") val climateInfo: DriveClimateInfo? = null
+    @Json(name = "climate_info") val climateInfo: DriveClimateInfo? = null,
+    @Json(name = "battery_info") val batteryInfo: DriveBatteryInfo? = null
 ) {
     // Convenience accessors
     val insideTemp: Double? get() = climateInfo?.insideTemp
     val outsideTemp: Double? get() = climateInfo?.outsideTemp
     val isClimateOn: Boolean get() = climateInfo?.isClimateOn == true
+    val isBatteryHeaterOn: Boolean get() = batteryInfo?.batteryHeater == true
 }
 
+@JsonClass(generateAdapter = true)
+data class DriveBatteryInfo(
+    @Json(name = "battery_heater") val batteryHeater: Boolean? = null,
+    @Json(name = "battery_heater_on") val batteryHeaterOn: Boolean? = null,
+    @Json(name = "battery_heater_no_power") val batteryHeaterNoPower: Boolean? = null
+)
+
 @JsonClass(generateAdapter = true)
 data class DriveClimateInfo(
     @Json(name = "inside_temp") val insideTemp: Double? = null,

app/src/main/java/com/matedroid/ui/components/ChartDrawUtils.kt

@@ -11,6 +11,7 @@ import androidx.compose.ui.graphics.drawscope.Stroke
 import androidx.compose.ui.graphics.drawscope.clipRect
 import androidx.compose.ui.graphics.nativeCanvas
 import androidx.compose.ui.graphics.toArgb
+import androidx.compose.ui.geometry.Size
 import androidx.compose.ui.unit.dp
 import kotlin.math.abs
 import kotlin.math.sqrt
@@ -51,6 +52,17 @@ data class DualSelectedPoint(
     val position: Offset
 )
 
+/**
+ * Represents an annotation range to highlight on a chart.
+ * Fractions are normalized 0.0–1.0 across the X axis.
+ */
+data class AnnotationRange(
+    val startFraction: Float,
+    val endFraction: Float,
+    val color: Color,
+    val label: String? = null
+)
+
 // ── Data Preparation ────────────────────────────────────────────────────────
 
 fun prepareChartData(
@@ -244,6 +256,45 @@ private fun computeMonotoneTangents(xs: FloatArray, ys: FloatArray): FloatArray
 private val dashEffect = PathEffect.dashPathEffect(floatArrayOf(6f, 4f))
 private val crosshairDashEffect = PathEffect.dashPathEffect(floatArrayOf(8f, 6f))
 
+/**
+ * Draws Grafana-style annotation bands on the chart.
+ * Each range is rendered as a semi-transparent vertical band spanning the full chart height,
+ * with thin border lines at the start and end edges.
+ */
+fun DrawScope.drawAnnotationRanges(
+    ranges: List<AnnotationRange>,
+    width: Float,
+    chartHeight: Float
+) {
+    for (range in ranges) {
+        val startX = range.startFraction * width
+        val endX = range.endFraction * width
+        val bandWidth = (endX - startX).coerceAtLeast(1f)
+
+        // Semi-transparent fill band
+        drawRect(
+            color = range.color.copy(alpha = 0.12f),
+            topLeft = Offset(startX, 0f),
+            size = Size(bandWidth, chartHeight)
+        )
+
+        // Thin border lines at edges
+        val edgeColor = range.color.copy(alpha = 0.4f)
+        drawLine(
+            color = edgeColor,
+            start = Offset(startX, 0f),
+            end = Offset(startX, chartHeight),
+            strokeWidth = 1f
+        )
+        drawLine(
+            color = edgeColor,
+            start = Offset(endX, 0f),
+            end = Offset(endX, chartHeight),
+            strokeWidth = 1f
+        )
+    }
+}
+
 /**
  * Draws dashed grid lines at 25%, 50%, 75% positions (3 interior lines).
  */

app/src/main/java/com/matedroid/ui/components/FullscreenLineChart.kt

@@ -60,7 +60,8 @@ fun FullscreenLineChart(
     convertValue: (Float) -> Float = { it },
     externalSelectedFraction: Float? = null,
     onXSelected: ((Float?) -> Unit)? = null,
-    fractionToTimeLabel: ((Float) -> String)? = null
+    fractionToTimeLabel: ((Float) -> String)? = null,
+    annotationRanges: List<AnnotationRange> = emptyList()
 ) {
     if (data.size < 2) return
 
@@ -81,6 +82,7 @@ fun FullscreenLineChart(
             externalSelectedFraction = externalSelectedFraction,
             onXSelected = onXSelected,
             fractionToTimeLabel = fractionToTimeLabel,
+            annotationRanges = annotationRanges,
             modifier = Modifier.fillMaxWidth()
         )
 
@@ -119,6 +121,7 @@ fun FullscreenLineChart(
             fixedMinMax = fixedMinMax,
             timeLabels = timeLabels,
             convertValue = convertValue,
+            annotationRanges = annotationRanges,
             activity = activity,
             onDismiss = { isFullscreen = false }
         )
@@ -134,6 +137,7 @@ private fun FullscreenChartOverlay(
     fixedMinMax: Pair<Float, Float>?,
     timeLabels: List<String>,
     convertValue: (Float) -> Float,
+    annotationRanges: List<AnnotationRange>,
     activity: Activity?,
     onDismiss: () -> Unit
 ) {
@@ -219,6 +223,7 @@ private fun FullscreenChartOverlay(
                 fixedMinMax = fixedMinMax,
                 timeLabels = timeLabels,
                 convertValue = convertValue,
+                annotationRanges = annotationRanges,
                 chartHeight = availableChartHeight,
                 modifier = Modifier
                     .fillMaxWidth()

app/src/main/java/com/matedroid/ui/components/OptimizedLineChart.kt

@@ -63,7 +63,8 @@ fun OptimizedLineChart(
     chartHeight: Dp = 120.dp,
     externalSelectedFraction: Float? = null,
     onXSelected: ((Float?) -> Unit)? = null,
-    fractionToTimeLabel: ((Float) -> String)? = null
+    fractionToTimeLabel: ((Float) -> String)? = null,
+    annotationRanges: List<AnnotationRange> = emptyList()
 ) {
     if (data.size < 2) return
 
@@ -181,6 +182,11 @@ fun OptimizedLineChart(
             // Dashed grid lines (3 interior lines)
             drawGridLines(gridColor, width, chartHeightPx)
 
+            // Annotation ranges (Grafana-style bands behind the data)
+            if (annotationRanges.isNotEmpty()) {
+                drawAnnotationRanges(annotationRanges, width, chartHeightPx)
+            }
+
             // Zero line if needed (for power chart with negative values)
             if (showZeroLine && chartData.minValue < 0 && chartData.maxValue > 0) {
                 drawZeroLine(surfaceColor, chartData.minValue, chartData.range, width, chartHeightPx)

app/src/main/java/com/matedroid/ui/screens/drives/DriveDetailScreen.kt

@@ -77,6 +77,7 @@ import com.matedroid.data.api.models.DrivePosition
 import com.matedroid.data.api.models.Units
 import com.matedroid.data.repository.WeatherPoint
 import com.matedroid.domain.model.UnitFormatter
+import com.matedroid.ui.components.AnnotationRange
 import com.matedroid.ui.components.FullscreenLineChart
 import com.matedroid.ui.theme.CarColorPalettes
 import org.osmdroid.config.Configuration
@@ -287,6 +288,11 @@ private fun DriveDetailContent(
                     } ?: ""
                 }
 
+                // Compute battery heater annotation ranges
+                val heaterAnnotations = remember(positions) {
+                    computeBatteryHeaterRanges(positions)
+                }
+
                 SpeedChartCard(
                     positions = detail.positions,
                     units = units,
@@ -300,14 +306,16 @@ private fun DriveDetailContent(
                     timeLabels = timeLabels,
                     externalSelectedFraction = sharedXFraction,
                     onXSelected = { sharedXFraction = it },
-                    fractionToTimeLabel = fractionToTimeLabel
+                    fractionToTimeLabel = fractionToTimeLabel,
+                    annotationRanges = heaterAnnotations
                 )
                 BatteryChartCard(
                     positions = detail.positions,
                     timeLabels = timeLabels,
                     externalSelectedFraction = sharedXFraction,
                     onXSelected = { sharedXFraction = it },
-                    fractionToTimeLabel = fractionToTimeLabel
+                    fractionToTimeLabel = fractionToTimeLabel,
+                    annotationRanges = heaterAnnotations
                 )
                 if (detail.positions.any { it.elevation != null && it.elevation != 0 }) {
                     ElevationChartCard(
@@ -699,7 +707,8 @@ private fun PowerChartCard(
     timeLabels: List<String>,
     externalSelectedFraction: Float? = null,
     onXSelected: ((Float?) -> Unit)? = null,
-    fractionToTimeLabel: ((Float) -> String)? = null
+    fractionToTimeLabel: ((Float) -> String)? = null,
+    annotationRanges: List<AnnotationRange> = emptyList()
 ) {
     val powers = positions.mapNotNull { it.power?.toFloat() }
     if (powers.size < 2) return
@@ -714,7 +723,8 @@ private fun PowerChartCard(
         timeLabels = timeLabels,
         externalSelectedFraction = externalSelectedFraction,
         onXSelected = onXSelected,
-        fractionToTimeLabel = fractionToTimeLabel
+        fractionToTimeLabel = fractionToTimeLabel,
+        annotationRanges = annotationRanges
     )
 }
 
@@ -724,7 +734,8 @@ private fun BatteryChartCard(
     timeLabels: List<String>,
     externalSelectedFraction: Float? = null,
     onXSelected: ((Float?) -> Unit)? = null,
-    fractionToTimeLabel: ((Float) -> String)? = null
+    fractionToTimeLabel: ((Float) -> String)? = null,
+    annotationRanges: List<AnnotationRange> = emptyList()
 ) {
     val batteryLevels = positions.mapNotNull { it.batteryLevel?.toFloat() }
     if (batteryLevels.size < 2) return
@@ -739,7 +750,8 @@ private fun BatteryChartCard(
         timeLabels = timeLabels,
         externalSelectedFraction = externalSelectedFraction,
         onXSelected = onXSelected,
-        fractionToTimeLabel = fractionToTimeLabel
+        fractionToTimeLabel = fractionToTimeLabel,
+        annotationRanges = annotationRanges
     )
 }
 
@@ -782,7 +794,8 @@ private fun ChartCard(
     convertValue: (Float) -> Float = { it },
     externalSelectedFraction: Float? = null,
     onXSelected: ((Float?) -> Unit)? = null,
-    fractionToTimeLabel: ((Float) -> String)? = null
+    fractionToTimeLabel: ((Float) -> String)? = null,
+    annotationRanges: List<AnnotationRange> = emptyList()
 ) {
     Card(
         modifier = Modifier.fillMaxWidth(),
@@ -822,6 +835,7 @@ private fun ChartCard(
                 externalSelectedFraction = externalSelectedFraction,
                 onXSelected = onXSelected,
                 fractionToTimeLabel = fractionToTimeLabel,
+                annotationRanges = annotationRanges,
                 modifier = Modifier.fillMaxWidth()
             )
         }
@@ -882,3 +896,60 @@ private fun formatDuration(minutes: Int): String {
     val mins = minutes % 60
     return "%d:%02d".format(hours, mins)
 }
+
+/**
+ * Computes annotation ranges for periods where the battery heater was active.
+ *
+ * The battery_heater field tends to flap (single-point true surrounded by false/null gaps
+ * of ~30-60 positions) because the heater cycles on/off rapidly. To produce clean Grafana-style
+ * bands, nearby true-runs separated by gaps smaller than [mergeGap] positions are merged
+ * into a single continuous range.
+ *
+ * Returns fractional ranges (0.0–1.0) suitable for chart annotation overlays.
+ */
+private fun computeBatteryHeaterRanges(
+    positions: List<DrivePosition>,
+    mergeGap: Int = 80
+): List<AnnotationRange> {
+    if (positions.size < 2) return emptyList()
+
+    // Collect indices where heater is on
+    val heaterIndices = positions.indices.filter { positions[it].isBatteryHeaterOn }
+    if (heaterIndices.isEmpty()) return emptyList()
+
+    val heaterColor = Color(0xFFFF9800) // Material Orange
+    val lastIndex = positions.lastIndex.toFloat()
+
+    // Merge nearby indices into contiguous ranges
+    val ranges = mutableListOf<AnnotationRange>()
+    var rangeStart = heaterIndices[0]
+    var rangeEnd = heaterIndices[0]
+
+    for (i in 1 until heaterIndices.size) {
+        if (heaterIndices[i] - rangeEnd <= mergeGap) {
+            // Close enough — extend current range
+            rangeEnd = heaterIndices[i]
+        } else {
+            // Gap too large — emit current range and start a new one
+            ranges.add(
+                AnnotationRange(
+                    startFraction = rangeStart / lastIndex,
+                    endFraction = rangeEnd / lastIndex,
+                    color = heaterColor
+                )
+            )
+            rangeStart = heaterIndices[i]
+            rangeEnd = heaterIndices[i]
+        }
+    }
+    // Emit last range
+    ranges.add(
+        AnnotationRange(
+            startFraction = rangeStart / lastIndex,
+            endFraction = rangeEnd / lastIndex,
+            color = heaterColor
+        )
+    )
+
+    return ranges
+}