refactor(erd): export flows move out of ErdView into ErdExporter

lib/features/erd/erd_exporter.dart

@@ -0,0 +1,220 @@
+import 'dart:async';
+import 'dart:convert';
+import 'dart:typed_data';
+import 'dart:ui' as ui;
+
+import 'package:flutter/material.dart' as material;
+import 'package:flutter/rendering.dart';
+import 'package:flutter/services.dart' show Clipboard, ClipboardData;
+import 'package:querya_desktop/core/erd/erd_layout.dart';
+import 'package:querya_desktop/core/erd/erd_model.dart';
+import 'package:querya_desktop/core/erd/erd_router.dart';
+import 'package:querya_desktop/core/erd/erd_saved_layout.dart';
+import 'package:querya_desktop/core/export/image_pdf.dart';
+import 'package:querya_desktop/core/export/svg_png.dart';
+import 'package:querya_desktop/core/storage/app_settings.dart';
+import 'package:querya_desktop/features/erd/erd_export.dart';
+import 'package:querya_desktop/shared/widgets/app_toast.dart';
+import 'package:querya_desktop/features/erd/widgets/erd_export_menu.dart';
+
+/// What the exporter needs from the diagram view (#1362): its data, the
+/// colours it draws with, and the canvas it captures.
+abstract interface class ErdExportSource {
+  /// For toasts; only used while [exportMounted].
+  material.BuildContext get exportContext;
+  bool get exportMounted;
+
+  /// `<database>-erd`, or `erd` when the database name is unknown.
+  String get fileStem;
+
+  Future<void> saveFile(String name, Uint8List bytes);
+
+  List<ErdRoute> get routes;
+  List<ErdGroup> get groups;
+  List<ErdNote> get notes;
+
+  /// Header colour slot of each table the user (or the schema) tinted.
+  Map<String, String> get headerColorSlots;
+  material.Color slotColor(String slot);
+
+  material.Size canvasSize(ErdLayout layout);
+
+  /// Colours of the current theme for the SVG export.
+  ErdSvgColors currentThemeColors();
+  Map<String, String> headerFills(ErdSchema schema, String cardHex);
+  List<ErdSvgGroup> svgGroups(ErdLayout layout, String backgroundHex);
+  List<ErdSvgNote> svgNotes(ErdSvgColors colors);
+
+  /// The repaint boundary of the canvas, or null when it is not built.
+  RenderRepaintBoundary? get canvasBoundary;
+
+  /// Runs [capture] with the screen-only state (the pick, a picked relation,
+  /// the marks for a group, the hover) hidden, and puts it back after.
+  Future<void> withCleanCanvas(Future<void> Function() capture);
+}
+
+/// The diagram's export flows: Mermaid, DBML, SVG, PNG and PDF, and the
+/// setting that picks the light palette or the current theme.
+class ErdExporter {
+  ErdExporter(this._source);
+
+  final ErdExportSource _source;
+
+  void export(ErdExportAction action, ErdSchema schema, ErdLayout layout) {
+    final stem = _source.fileStem;
+    switch (action) {
+      case ErdExportAction.mermaid:
+        unawaited(_source.saveFile(
+            '$stem.mmd', Uint8List.fromList(utf8.encode(ErdExport.toMermaid(schema)))));
+      case ErdExportAction.svg:
+        unawaited(_exportSvg(schema, layout));
+      case ErdExportAction.png:
+        unawaited(_exportPng(schema, layout));
+      case ErdExportAction.pdfA4:
+        unawaited(_exportPdf(schema, layout, PdfPaper.a4));
+      case ErdExportAction.pdfA3:
+        unawaited(_exportPdf(schema, layout, PdfPaper.a3));
+      case ErdExportAction.dbml:
+        unawaited(_source.saveFile(
+            '$stem.dbml', Uint8List.fromList(utf8.encode(dbml(schema)))));
+      case ErdExportAction.copyDbml:
+        Clipboard.setData(ClipboardData(text: dbml(schema)));
+        showAppToast(
+          context: _source.exportContext,
+          message: 'DBML copied to the clipboard',
+        );
+      case ErdExportAction.toggleTheme:
+        unawaited(_toggleExportTheme());
+      case ErdExportAction.copyMermaid:
+        Clipboard.setData(ClipboardData(text: ErdExport.toMermaid(schema)));
+        showAppToast(
+          context: _source.exportContext,
+          message: 'Mermaid copied to the clipboard',
+        );
+    }
+  }
+
+  /// The DBML of what the diagram shows: its groups and notes, and the
+  /// header colours it draws.
+  String dbml(ErdSchema schema) {
+    final shown = {for (final t in schema.tables) t.name};
+    return ErdExport.toDbml(
+      schema,
+      groups: [
+        for (final g in _source.groups)
+          if (g.tables.any(shown.contains)) g,
+      ],
+      notes: List.of(_source.notes),
+      headerColors: {
+        for (final t in schema.tables)
+          if (erdHeaderSlot(t.name, _source.headerColorSlots) case final slot?)
+            t.name: ErdSvgColors.hex(_source.slotColor(slot).toARGB32()),
+      },
+    );
+  }
+
+  Future<void> _exportPng(ErdSchema schema, ErdLayout layout) async {
+    final currentTheme = await AppSettings.instance.getExportCurrentTheme();
+    if (!_source.exportMounted) return;
+    final stem = _source.fileStem;
+    if (!currentTheme) {
+      final scale = ErdExport.pngPixelRatio(_source.canvasSize(layout));
+      const light = ErdSvgColors();
+      final svg = ErdExport.toSvg(schema, layout,
+          routes: _source.routes,
+          headerFills: _source.headerFills(schema, light.card),
+          groups: _source.svgGroups(layout, light.background),
+          notes: _source.svgNotes(light));
+      await _source.saveFile('$stem.png', await svgToPng(svg, scale: scale));
+      return;
+    }
+    final boundary = _source.canvasBoundary;
+    if (boundary == null) return;
+    await _source.withCleanCanvas(() async {
+      if (!_source.exportMounted) return;
+      final context = _source.exportContext;
+      try {
+        final ratio = ErdExport.pngPixelRatio(boundary.size);
+        if (ratio < 1) {
+          showAppToast(
+            context: context,
+            message: 'The diagram is larger than '
+                '${ErdExport.pngMaxSide} px per side, so the PNG is at '
+                '${(ratio * 100).round()}% resolution. The SVG export keeps full detail.',
+          );
+        }
+        final image = await boundary.toImage(pixelRatio: ratio);
+        final data = await image.toByteData(format: ui.ImageByteFormat.png);
+        image.dispose();
+        if (data == null) throw StateError('no image data');
+        await _source.saveFile('$stem.png', data.buffer.asUint8List());
+      } catch (e) {
+        final failed = _source.exportContext;
+        if (failed.mounted) {
+          showAppToast(
+            context: failed,
+            variant: AppToastVariant.error,
+            message: 'Could not render the PNG ($e). '
+                'Export SVG instead: it has no size limit.',
+          );
+        }
+      }
+    });
+  }
+
+  /// The diagram as SVG text, in the export palette: light for documents,
+  /// unless the setting asks for the current theme.
+  Future<String?> _svgText(ErdSchema schema, ErdLayout layout) async {
+    final currentTheme = await AppSettings.instance.getExportCurrentTheme();
+    if (!_source.exportMounted) return null;
+    final colors =
+        currentTheme ? _source.currentThemeColors() : const ErdSvgColors();
+    return ErdExport.toSvg(schema, layout,
+        routes: _source.routes,
+        colors: colors,
+        headerFills: _source.headerFills(schema, colors.card),
+        groups: _source.svgGroups(layout, colors.background),
+        notes: _source.svgNotes(colors));
+  }
+
+  Future<void> _exportSvg(ErdSchema schema, ErdLayout layout) async {
+    final svg = await _svgText(schema, layout);
+    if (svg == null) return;
+    await _source.saveFile(
+        '${_source.fileStem}.svg', Uint8List.fromList(utf8.encode(svg)));
+  }
+
+  /// The PDF export: the SVG fitted on one page of [paper].
+  Future<void> _exportPdf(
+      ErdSchema schema, ErdLayout layout, PdfPaper paper) async {
+    final svg = await _svgText(schema, layout);
+    if (svg == null) return;
+    try {
+      await _source.saveFile(
+          '${_source.fileStem}.pdf', await svgToPdf(svg, paper: paper));
+    } catch (e) {
+      final failed = _source.exportContext;
+      if (failed.mounted) {
+        showAppToast(
+          context: failed,
+          variant: AppToastVariant.error,
+          message: 'Could not render the PDF ($e). Export SVG instead.',
+        );
+      }
+    }
+  }
+
+  /// Flips between the light export palette and the current theme.
+  Future<void> _toggleExportTheme() async {
+    final now = !await AppSettings.instance.getExportCurrentTheme();
+    await AppSettings.instance.setExportCurrentTheme(now);
+    final context = _source.exportContext;
+    if (!context.mounted) return;
+    showAppToast(
+      context: context,
+      message: now
+          ? 'Exports use the current theme'
+          : 'Exports use the light palette for documents',
+    );
+  }
+}