Refactor WeatherHome to process data outside build method

.jules/bolt.md

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+## 2024-05-22 - [Refactoring Data Processing out of Build]
+**Learning:** In Flutter, complex data processing (parsing Dates, loops) inside `build` or `FutureBuilder.builder` runs on every rebuild, which can be frequent. Moving this logic to a separate processing step that returns a dedicated data object significantly reduces CPU usage during UI updates.
+**Action:** Always process API data into a display-ready View Model before passing it to the Widget tree, especially when using Futures.

lib/models/weather_display_data.dart

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+import 'dart:convert';
+
+class WeatherDisplayData {
+  final Map<String, dynamic> raw;
+
+  // Hourly Data (Filtered)
+  final List<dynamic> hourlyTime;
+  final List<dynamic> hourlyTemps;
+  final List<dynamic> hourlyWeatherCodes;
+  final List<dynamic> hourlyPrecpProb;
+  final List<dynamic> hourlyDewPoint;
+  final List<dynamic> hourlyVisibility;
+  final List<dynamic> hourlyUvIndex;
+
+  // Daily Data
+  final List<dynamic> dailyDates;
+  final List<dynamic> dailyTempsMin;
+  final List<dynamic> dailyTempsMax;
+  final List<dynamic> dailyPrecProb;
+  final List<dynamic> dailyPrecipSum;
+  final List<dynamic> dailyDaylightDuration;
+  final List<dynamic> dailyWeatherCodes;
+  final List<dynamic> sunriseTimes;
+  final List<dynamic> sunsetTimes;
+
+  // Processed Data
+  final Map<String, (DateTime, DateTime)> daylightMap;
+  final bool shouldShowRainBlock;
+  final int? rainStart;
+  final int? bestStart;
+  final int? bestEnd;
+  final List<String> timeNext12h;
+  final List<double> precpNext12h;
+  final List<int> precipProbNext12h;
+
+  WeatherDisplayData({
+    required this.raw,
+    required this.hourlyTime,
+    required this.hourlyTemps,
+    required this.hourlyWeatherCodes,
+    required this.hourlyPrecpProb,
+    required this.hourlyDewPoint,
+    required this.hourlyVisibility,
+    required this.hourlyUvIndex,
+    required this.dailyDates,
+    required this.dailyTempsMin,
+    required this.dailyTempsMax,
+    required this.dailyPrecProb,
+    required this.dailyPrecipSum,
+    required this.dailyDaylightDuration,
+    required this.dailyWeatherCodes,
+    required this.sunriseTimes,
+    required this.sunsetTimes,
+    required this.daylightMap,
+    required this.shouldShowRainBlock,
+    this.rainStart,
+    this.bestStart,
+    this.bestEnd,
+    required this.timeNext12h,
+    required this.precpNext12h,
+    required this.precipProbNext12h,
+  });
+}
+
+WeatherDisplayData processWeatherData(Map<String, dynamic> raw) {
+  final weatherData = raw['data'] ?? raw;
+
+  final hourly = weatherData['hourly'] ?? {};
+  final daily = weatherData['daily'] ?? {};
+
+  final List<dynamic> hourlyTimeNoFilter = hourly['time'] ?? [];
+  final List<dynamic> hourlyTempsNoFilter = hourly['temperature_2m'] ?? [];
+  final List<dynamic> hourlyWeatherCodesNoFilter = hourly['weather_code'] ?? [];
+  final List<dynamic> hourlyPrecpProbNoFilter = hourly['precipitation_probability'] ?? [];
+  final List<dynamic> hourlyDewPointNoFilter = hourly['dew_point_2m'] ?? [];
+  final List<dynamic> hourlyVisibilityNoFilter = hourly['visibility'] ?? [];
+  final List<dynamic> hourlyUvIndexNoFilter = hourly['uv_index'] ?? [];
+
+  // Filter hourly data
+  final now = DateTime.now();
+  final todayMidnight = DateTime(now.year, now.month, now.day);
+
+  final filteredIndices = <int>[];
+  for (int i = 0; i < hourlyTimeNoFilter.length; i++) {
+    final time = DateTime.parse(hourlyTimeNoFilter[i]);
+    if (time.isAfter(todayMidnight) || time.isAtSameMomentAs(todayMidnight)) {
+      filteredIndices.add(i);
+    }
+  }
+
+  final hourlyTime = filteredIndices.map((i) => hourlyTimeNoFilter[i]).toList();
+  final hourlyTemps = filteredIndices.map((i) => hourlyTempsNoFilter[i]).toList();
+  final hourlyWeatherCodes = filteredIndices.map((i) => hourlyWeatherCodesNoFilter[i]).toList();
+  final hourlyPrecpProb = filteredIndices.map((i) => hourlyPrecpProbNoFilter[i]).toList();
+
+  // Safe mapping for optional fields
+  final hourlyDewPoint = filteredIndices.map((i) => i < hourlyDewPointNoFilter.length ? hourlyDewPointNoFilter[i] : null).toList();
+  final hourlyVisibility = filteredIndices.map((i) => i < hourlyVisibilityNoFilter.length ? hourlyVisibilityNoFilter[i] : null).toList();
+  final hourlyUvIndex = filteredIndices.map((i) => i < hourlyUvIndexNoFilter.length ? hourlyUvIndexNoFilter[i] : null).toList();
+
+  // Daily Data
+  final List<dynamic> dailyDates = daily['time'] ?? [];
+  final List<dynamic> sunriseTimes = daily['sunrise'] ?? [];
+  final List<dynamic> sunsetTimes = daily['sunset'] ?? [];
+  final List<dynamic> dailyTempsMin = daily['temperature_2m_min'] ?? [];
+  final List<dynamic> dailyTempsMax = daily['temperature_2m_max'] ?? [];
+  final List<dynamic> dailyPrecProb = daily['precipitation_probability_max'] ?? [];
+  final List<dynamic> dailyPrecipSum = daily['precipitation_sum'] ?? [];
+  final List<dynamic> dailyDaylightDuration = daily['daylight_duration'] ?? [];
+  final List<dynamic> dailyWeatherCodes = daily['weather_code'] ?? [];
+
+  // Daylight Map
+  final Map<String, (DateTime, DateTime)> daylightMap = {};
+  if (dailyDates.isNotEmpty && sunriseTimes.isNotEmpty && sunsetTimes.isNotEmpty) {
+      for (int i = 0; i < dailyDates.length; i++) {
+        if (i < sunriseTimes.length && i < sunsetTimes.length) {
+            daylightMap[dailyDates[i]] = (
+                DateTime.parse(sunriseTimes[i]),
+                DateTime.parse(sunsetTimes[i])
+            );
+        }
+      }
+  }
+
+  // Rain Logic
+  const double rainThreshold = 0.5;
+  const int probThreshold = 40;
+
+  int offsetSeconds = 0;
+  if (weatherData['utc_offset_seconds'] != null) {
+      offsetSeconds = int.parse(weatherData['utc_offset_seconds'].toString());
+  }
+
+  DateTime utcNow = DateTime.now().toUtc();
+  DateTime nowPrecip = utcNow.add(Duration(seconds: offsetSeconds));
+  nowPrecip = DateTime(
+    nowPrecip.year,
+    nowPrecip.month,
+    nowPrecip.day,
+    nowPrecip.hour,
+    nowPrecip.minute,
+    nowPrecip.second,
+    nowPrecip.millisecond,
+    nowPrecip.microsecond,
+  );
+
+  final List<String> allTimeStrings = (hourly['time'] as List?)?.cast<String>() ?? [];
+  final List<double> allPrecip = (hourly['precipitation'] as List?)
+          ?.map((e) => (e as num?)?.toDouble() ?? 0.0)
+          .toList() ??
+      [];
+  final List<int> allPrecipProb = (hourly['precipitation_probability'] as List?)
+          ?.map((e) => (e as num?)?.toInt() ?? 0)
+          .toList() ??
+      [];
+
+  final List<String> timeNext12h = [];
+  final List<double> precpNext12h = [];
+  final List<int> precipProbNext12h = [];
+
+  for (int i = 0; i < allTimeStrings.length; i++) {
+    if (i >= allPrecip.length || i >= allPrecipProb.length) break;
+
+    final time = DateTime.parse(allTimeStrings[i]);
+    if (time.isAfter(nowPrecip) &&
+        time.isBefore(nowPrecip.add(Duration(hours: 12)))) {
+      timeNext12h.add(allTimeStrings[i]);
+      precpNext12h.add(allPrecip[i]);
+      precipProbNext12h.add(allPrecipProb[i]);
+    }
+  }
+
+  int? rainStart;
+  int longestRainLength = 0;
+  int? bestStart;
+  int? bestEnd;
+
+  for (int i = 0; i < precpNext12h.length; i++) {
+    if (precpNext12h[i] >= rainThreshold &&
+        precipProbNext12h[i] >= probThreshold) {
+      rainStart ??= i;
+    } else {
+      if (rainStart != null) {
+        final length = i - rainStart;
+        if (length >= 2 && length > longestRainLength) {
+          longestRainLength = length;
+          bestStart = rainStart;
+          bestEnd = i - 1;
+        }
+        rainStart = null;
+      }
+    }
+  }
+
+  if (rainStart != null) {
+    final length = precpNext12h.length - rainStart;
+    if (length >= 2 && length > longestRainLength) {
+      bestStart = rainStart;
+      bestEnd = precpNext12h.length - 1;
+    }
+  }
+
+  final bool shouldShowRainBlock = bestStart != null && bestEnd != null;
+
+  return WeatherDisplayData(
+    raw: raw,
+    hourlyTime: hourlyTime,
+    hourlyTemps: hourlyTemps,
+    hourlyWeatherCodes: hourlyWeatherCodes,
+    hourlyPrecpProb: hourlyPrecpProb,
+    hourlyDewPoint: hourlyDewPoint,
+    hourlyVisibility: hourlyVisibility,
+    hourlyUvIndex: hourlyUvIndex,
+    dailyDates: dailyDates,
+    dailyTempsMin: dailyTempsMin,
+    dailyTempsMax: dailyTempsMax,
+    dailyPrecProb: dailyPrecProb,
+    dailyPrecipSum: dailyPrecipSum,
+    dailyDaylightDuration: dailyDaylightDuration,
+    dailyWeatherCodes: dailyWeatherCodes,
+    sunriseTimes: sunriseTimes,
+    sunsetTimes: sunsetTimes,
+    daylightMap: daylightMap,
+    shouldShowRainBlock: shouldShowRainBlock,
+    rainStart: rainStart,
+    bestStart: bestStart,
+    bestEnd: bestEnd,
+    timeNext12h: timeNext12h,
+    precpNext12h: precpNext12h,
+    precipProbNext12h: precipProbNext12h,
+  );
+}