Add shared export infrastructure

LehrerApp.Desktop/ViewModels/Workload/WorkloadViewModels.cs

@@ -3,6 +3,7 @@ using CommunityToolkit.Mvvm.Input;
 using LehrerApp.Core.Interfaces;
 using LehrerApp.Core.Models;
 using LehrerApp.Core.Services;
+using LehrerApp.Desktop.Services;
 using System.Collections.ObjectModel;
 using System.Globalization;
 
@@ -519,6 +520,7 @@ public class TimeEntryListItem(TimeEntry model, string? taskTitle)
 public class CategoryTimeSummary(string category, int minutes, double barFraction)
 {
     public string Category { get; } = category;
+    public int Minutes { get; } = minutes;
     public string MinutesDisplay { get; } = $"{minutes} min";
     public double BarFraction { get; } = barFraction;
 }
@@ -619,6 +621,20 @@ public partial class WorkloadEvaluationViewModel : ObservableObject
     public ObservableCollection<GroupTimeSummary> GroupSummaries { get; } = [];
     public string TotalMinutesDisplay { get; private set; } = "0 min";
     public string RequiredVsActualDisplay { get; private set; } = "";
+    public string ExportSuggestedFileName
+    {
+        get
+        {
+            if (PeriodMode == SchoolYearMode)
+                return $"Arbeitszeitauswertung_Schuljahr_{SelectedYear}-{SelectedYear + 1}.csv";
+            var month = MonthOptions.IndexOf(SelectedMonth) + 1;
+            return $"Arbeitszeitauswertung_{SelectedYear}-{month:00}.csv";
+        }
+    }
+
+    private DateOnly _periodFrom;
+    private DateOnly _periodTo;
+    private int _totalMinutes;
 
     public WorkloadEvaluationViewModel(ITimeEntryRepository entries, IGroupRepository groups,
         WorkloadSettingsService workloadSettings, SchoolYearService schoolYear)
@@ -671,6 +687,8 @@ public partial class WorkloadEvaluationViewModel : ObservableObject
     private void Refresh()
     {
         var (from, to) = CurrentPeriod();
+        _periodFrom = from;
+        _periodTo = to;
         var periodEntries = _entries.GetByDateRange(from, to);
         var groupNames = _groups.GetAll(includeInactive: true).ToDictionary(g => g.Id, g => g.Name);
 
@@ -698,6 +716,7 @@ public partial class WorkloadEvaluationViewModel : ObservableObject
         }
 
         var totalMinutes = periodEntries.Sum(e => e.DurationMinutes);
+        _totalMinutes = totalMinutes;
         TotalMinutesDisplay = $"{totalMinutes} min ({(totalMinutes / 60.0).ToString("0.#", CultureInfo.InvariantCulture)} h)";
 
         // Pflichtstunden-Abgleich (6.3.2): auf die Anzahl Wochen im Zeitraum hochgerechnet.
@@ -721,12 +740,52 @@ public partial class WorkloadEvaluationViewModel : ObservableObject
 
         OnPropertyChanged(nameof(TotalMinutesDisplay));
         OnPropertyChanged(nameof(RequiredVsActualDisplay));
+        OnPropertyChanged(nameof(ExportSuggestedFileName));
+    }
+
+    public string ExportCsv()
+    {
+        var germanCulture = CultureInfo.GetCultureInfo("de-DE");
+        var csv = new CsvBuilder()
+            .AddRow("Arbeitszeitauswertung")
+            .AddRow("Zeitraum", _periodFrom.ToString("dd.MM.yyyy", germanCulture),
+                _periodTo.ToString("dd.MM.yyyy", germanCulture))
+            .AddRow("Gesamtzeit (Minuten)", _totalMinutes)
+            .AddRow("Gesamtzeit (Stunden)", (_totalMinutes / 60.0).ToString("0.##", germanCulture));
+
+        if (_workloadSettings.RequiredWeeklyHours > 0)
+        {
+            var weeks = (_periodTo.DayNumber - _periodFrom.DayNumber + 1) / 7.0;
+            var requiredHours = _workloadSettings.RequiredWeeklyHours * weeks;
+            var actualHours = _totalMinutes / 60.0;
+            csv.AddRow("Pflichtstunden pro Woche",
+                    _workloadSettings.RequiredWeeklyHours.ToString("0.##", germanCulture))
+                .AddRow("Sollzeit (Stunden)", requiredHours.ToString("0.##", germanCulture))
+                .AddRow("Abweichung (Stunden)", (actualHours - requiredHours).ToString("0.##", germanCulture));
+        }
+
+        csv.AddBlankRow()
+            .AddRow("Nach Kategorie")
+            .AddRow("Kategorie", "Minuten", "Stunden");
+        foreach (var summary in CategorySummaries)
+            csv.AddRow(summary.Category, summary.Minutes,
+                (summary.Minutes / 60.0).ToString("0.##", germanCulture));
+
+        csv.AddBlankRow()
+            .AddRow("Nach Gruppe")
+            .AddRow("Gruppe", "Minuten", "Stunden");
+        foreach (var summary in GroupSummaries)
+            csv.AddRow(summary.GroupName, summary.Minutes,
+                (summary.Minutes / 60.0).ToString("0.##", germanCulture));
+
+        return csv.ToString();
     }
 }
 
 public class GroupTimeSummary(string groupName, int minutes, double barFraction)
 {
     public string GroupName { get; } = groupName;
+    public int Minutes { get; } = minutes;
     public string MinutesDisplay { get; } = $"{minutes} min";
     public double BarFraction { get; } = barFraction;
 }