Add shared export infrastructure

2026-08-18 21:21:56 +02:00
parent 41bf2c0756
commit 26461bd2f2
13 changed files with 336 additions and 63 deletions
@@ -0,0 +1,45 @@
+using System.Text;
+
+namespace LehrerApp.Desktop.Services;
+
+/// <summary>
+/// Erzeugt semikolongetrennte CSV-Daten für die deutsche Excel-Umgebung und maskiert Felder
+/// nach RFC-4180-Regeln. Das Trennzeichen bleibt bewusst konfigurierbar für weitere Exportformate.
+/// </summary>
+public sealed class CsvBuilder(char separator = ';')
+{
+    private readonly StringBuilder _content = new();
+
+    public CsvBuilder AddRow(params object?[] values)
+    {
+        for (var index = 0; index < values.Length; index++)
+        {
+            if (index > 0) _content.Append(separator);
+            AppendEscaped(values[index]?.ToString() ?? "");
+        }
+        _content.AppendLine();
+        return this;
+    }
+
+    public CsvBuilder AddBlankRow()
+    {
+        _content.AppendLine();
+        return this;
+    }
+
+    public override string ToString() => _content.ToString();
+
+    private void AppendEscaped(string value)
+    {
+        if (!value.Contains(separator) && !value.Contains('"') &&
+            !value.Contains('\r') && !value.Contains('\n'))
+        {
+            _content.Append(value);
+            return;
+        }
+
+        _content.Append('"');
+        _content.Append(value.Replace("\"", "\"\"", StringComparison.Ordinal));
+        _content.Append('"');
+    }
+}
@@ -0,0 +1,75 @@
+using Avalonia.Platform.Storage;
+using System.Text;
+
+namespace LehrerApp.Desktop.Services;
+
+public sealed record ExportFormat(string Label, string Extension, string MimeType)
+{
+    public static ExportFormat Csv { get; } = new("CSV-Dateien", ".csv", "text/csv");
+    public static ExportFormat Json { get; } = new("JSON-Dateien", ".json", "application/json");
+}
+
+public sealed record ExportFile(
+    string DialogTitle,
+    string SuggestedFileName,
+    ExportFormat Format,
+    ReadOnlyMemory<byte> Content)
+{
+    public static ExportFile Csv(string dialogTitle, string suggestedFileName, string content) =>
+        FromText(dialogTitle, suggestedFileName, ExportFormat.Csv, content, includeUtf8Bom: true);
+
+    public static ExportFile Json(string dialogTitle, string suggestedFileName, string content) =>
+        FromText(dialogTitle, suggestedFileName, ExportFormat.Json, content);
+
+    private static ExportFile FromText(string dialogTitle, string suggestedFileName,
+        ExportFormat format, string content, bool includeUtf8Bom = false)
+    {
+        var encoding = new UTF8Encoding(encoderShouldEmitUTF8Identifier: includeUtf8Bom);
+        var preamble = encoding.GetPreamble();
+        var text = encoding.GetBytes(content);
+        var bytes = new byte[preamble.Length + text.Length];
+        preamble.CopyTo(bytes, 0);
+        text.CopyTo(bytes, preamble.Length);
+        return new ExportFile(dialogTitle,
+            EnsureExtension(SanitizeFileName(suggestedFileName), format.Extension), format, bytes);
+    }
+
+    private static string EnsureExtension(string fileName, string extension) =>
+        fileName.EndsWith(extension, StringComparison.OrdinalIgnoreCase) ? fileName : fileName + extension;
+
+    private static string SanitizeFileName(string fileName)
+    {
+        var invalidCharacters = Path.GetInvalidFileNameChars();
+        return string.Concat(fileName.Select(character =>
+            invalidCharacters.Contains(character) ? '_' : character));
+    }
+}
+
+/// <summary>Zentrale Dateiauswahl und Stream-Ausgabe für alle Exportformate.</summary>
+public sealed class ExportService
+{
+    public async Task<bool> SaveAsync(IStorageProvider storageProvider, ExportFile export)
+    {
+        var file = await storageProvider.SaveFilePickerAsync(new FilePickerSaveOptions
+        {
+            Title = export.DialogTitle,
+            SuggestedFileName = export.SuggestedFileName,
+            DefaultExtension = export.Format.Extension.TrimStart('.'),
+            FileTypeChoices =
+            [
+                new FilePickerFileType(export.Format.Label)
+                {
+                    Patterns = [$"*{export.Format.Extension}"],
+                    MimeTypes = [export.Format.MimeType],
+                },
+            ],
+        });
+
+        if (file is null) return false;
+
+        await using var stream = await file.OpenWriteAsync();
+        if (stream.CanSeek) stream.SetLength(0);
+        await stream.WriteAsync(export.Content);
+        return true;
+    }
+}