fix: Fixes overlapping power axis titles if max value is close to las…

…t horizontal line.

This partially reverts commit f1fc08b.

app/lib/ui/analytics/charts/analytics_day_chart.dart

@@ -4,6 +4,7 @@ import 'package:emma/application/analytics/power_data_point_dto.dart';
 import 'package:emma/ui/analytics/analytics_view_model.dart';
 import 'package:emma/ui/analytics/charts/analytics_chart_color_scheme.dart';
 import 'package:emma/ui/analytics/charts/analytics_chart_colors.dart';
+import 'package:emma/ui/analytics/charts/nice_scale.dart';
 import 'package:fl_chart/fl_chart.dart';
 import 'package:flutter/material.dart';
 import 'package:intl/intl.dart';
@@ -44,7 +45,7 @@ class AnalyticsDayChart extends StatelessWidget {
 
   LineChartData mainData(
       TextTheme textTheme, AnalyticsChartColorScheme colorScheme) {
-    final maxPower = [
+    final maxValue = [
       if (viewModel.chartControl.showHome.value) ...viewModel.day.value.home,
       if (viewModel.chartControl.showProduction.value)
         ...viewModel.day.value.production,
@@ -54,12 +55,21 @@ class AnalyticsDayChart extends StatelessWidget {
         ...viewModel.day.value.gridFeedIn,
     ].map((x) => x.power).fold(100.0, math.max);
 
+    final niceScale = NiceScale.calculate(
+      maxTicks: 10,
+      min: 0,
+      max: maxValue,
+    );
+
     const timeAxisInterval = 120.0;
     return LineChartData(
-      maxY: maxPower,
+      minY: niceScale.min,
+      maxY: niceScale.max,
       gridData: FlGridData(
         show: true,
         drawVerticalLine: false,
+        horizontalInterval: niceScale.tickInterval,
+        verticalInterval: timeAxisInterval,
         getDrawingHorizontalLine: (value) {
           return FlLine(
             color: colorScheme.mainGridLine,
@@ -87,6 +97,7 @@ class AnalyticsDayChart extends StatelessWidget {
         leftTitles: AxisTitles(
           sideTitles: SideTitles(
             showTitles: true,
+            interval: niceScale.tickInterval,
             getTitlesWidget: (value, meta) =>
                 _buildPowerAxisTitleWidget(textTheme, value, meta),
             reservedSize: 48,

app/lib/ui/analytics/charts/nice_scale.dart

@@ -0,0 +1,70 @@
+import 'dart:math' as math;
+
+// https://stackoverflow.com/a/16363437
+class NiceScale {
+  NiceScale._(
+      {required this.min, required this.max, required this.tickInterval});
+
+  final double min;
+  final double max;
+  final double tickInterval;
+
+  factory NiceScale.calculate({
+    required int maxTicks,
+    required double min,
+    required double max,
+  }) {
+    final range = _niceNum(max - min, _NiceNumMethod.ceil);
+    final tickInterval = _niceNum(range / (maxTicks - 1), _NiceNumMethod.round);
+    final niceMin = (min / tickInterval).floor() * tickInterval;
+    final niceMax = (max / tickInterval).ceil() * tickInterval;
+
+    return NiceScale._(
+      min: niceMin,
+      max: niceMax,
+      tickInterval: tickInterval,
+    );
+  }
+
+  static double _niceNum(double range, _NiceNumMethod method) {
+    final exponent = _log10(range).floor();
+    final fraction = range / math.pow(10, exponent);
+
+    late final double niceFraction;
+    switch (method) {
+      case _NiceNumMethod.round:
+        switch (fraction) {
+          case < 1.5:
+            niceFraction = 1;
+          case < 3:
+            niceFraction = 2;
+          case < 7:
+            niceFraction = 5;
+          default:
+            niceFraction = 10;
+        }
+        break;
+      case _NiceNumMethod.ceil:
+        switch (fraction) {
+          case <= 1:
+            niceFraction = 1;
+          case <= 2:
+            niceFraction = 2;
+          case <= 5:
+            niceFraction = 5;
+          default:
+            niceFraction = 10;
+        }
+        break;
+    }
+
+    return niceFraction * math.pow(10, exponent);
+  }
+
+  static double _log10(double x) => math.log(x) / math.ln10;
+}
+
+enum _NiceNumMethod {
+  round,
+  ceil,
+}