Implement PdfPageLabels

@@ -4,6 +4,7 @@
 
 - Update xml dependency range
 - Implement PointDataSet for Chart
+- Implement PdfPageLabels
 
 ## 3.7.4
 

@@ -33,6 +33,7 @@ export 'src/pdf/obj/info.dart';
 export 'src/pdf/obj/metadata.dart';
 export 'src/pdf/obj/outline.dart';
 export 'src/pdf/obj/page.dart';
+export 'src/pdf/obj/page_label.dart';
 export 'src/pdf/obj/pattern.dart';
 export 'src/pdf/obj/shading.dart';
 export 'src/pdf/obj/signature.dart';

@@ -30,6 +30,7 @@ import 'obj/names.dart';
 import 'obj/object.dart';
 import 'obj/outline.dart';
 import 'obj/page.dart';
+import 'obj/page_label.dart';
 import 'obj/page_list.dart';
 import 'obj/signature.dart';
 import 'output.dart';
@@ -83,10 +84,8 @@ class PdfDocument {
   })  : deflate = compress ? (deflate ?? defaultDeflate) : null,
         prev = null,
         _objser = 1 {
-    // Now create some standard objects
-    pdfPageList = PdfPageList(this);
-    pdfNames = PdfNames(this);
-    catalog = PdfCatalog(this, pdfPageList, pageMode, pdfNames);
+    // create the catalog
+    catalog = PdfCatalog(this, PdfPageList(this), pageMode);
   }
 
   PdfDocument.load(
@@ -99,9 +98,7 @@ class PdfDocument {
         _objser = prev!.size,
         version = prev.version {
     // Now create some standard objects
-    pdfPageList = PdfPageList(this);
-    pdfNames = PdfNames(this);
-    catalog = PdfCatalog(this, pdfPageList, pageMode, pdfNames);
+    catalog = PdfCatalog(this, PdfPageList(this), pageMode);
 
     // Import the existing document
     prev!.mergeDocument(this);
@@ -118,7 +115,7 @@ class PdfDocument {
   final Set<PdfObject> objects = <PdfObject>{};
 
   /// This is the Catalog object, which is required by each Pdf Document
-  late PdfCatalog catalog;
+  late final PdfCatalog catalog;
 
   /// PDF version to generate
   final PdfVersion version;
@@ -129,13 +126,13 @@ class PdfDocument {
   PdfInfo? info;
 
   /// This is the Pages object, which is required by each Pdf Document
-  late PdfPageList pdfPageList;
-
-  /// The name dictionary
-  late PdfNames pdfNames;
+  PdfPageList get pdfPageList => catalog.pdfPageList;
 
-  /// This is the Outline object, which is optional
-  PdfOutline? _outline;
+  /// The anchor names dictionary
+  PdfNames get pdfNames {
+    catalog.names ??= PdfNames(this);
+    return catalog.names!;
+  }
 
   /// This holds a [PdfObject] describing the default border for annotations.
   /// It's only used when the document is being written.
@@ -191,11 +188,14 @@ class PdfDocument {
 
   /// The root outline
   PdfOutline get outline {
-    if (_outline == null) {
-      _outline = PdfOutline(this);
-      catalog.outlines = _outline;
-    }
-    return _outline!;
+    catalog.outlines ??= PdfOutline(this);
+    return catalog.outlines!;
+  }
+
+  /// The root page labels
+  PdfPageLabels get pageLabels {
+    catalog.pageLabels ??= PdfPageLabels(this);
+    return catalog.pageLabels!;
   }
 
   /// Graphic states for opacity and transfer modes

@@ -21,6 +21,7 @@ import 'metadata.dart';
 import 'names.dart';
 import 'object_dict.dart';
 import 'outline.dart';
+import 'page_label.dart';
 import 'page_list.dart';
 
 /// Pdf Catalog object
@@ -30,7 +31,6 @@ class PdfCatalog extends PdfObjectDict {
     PdfDocument pdfDocument,
     this.pdfPageList,
     this.pageMode,
-    this.names,
   ) : super(pdfDocument, type: '/Catalog');
 
   /// The pages of the document
@@ -45,8 +45,11 @@ class PdfCatalog extends PdfObjectDict {
   /// The initial page mode
   final PdfPageMode pageMode;
 
-  /// The initial page mode
-  final PdfNames names;
+  /// The anchor names
+  PdfNames? names;
+
+  /// The page labels of the document
+  PdfPageLabels? pageLabels;
 
   /// These map the page modes just defined to the pagemodes setting of Pdf.
   static const List<String> _pdfPageModes = <String>[
@@ -75,7 +78,14 @@ class PdfCatalog extends PdfObjectDict {
     }
 
     // the Names object
-    params['/Names'] = names.ref();
+    if (names != null) {
+      params['/Names'] = names!.ref();
+    }
+
+    // the PageLabels object
+    if (pageLabels != null && pageLabels!.labels.isNotEmpty) {
+      params['/PageLabels'] = pageLabels!.ref();
+    }
 
     // the /PageMode setting
     params['/PageMode'] = PdfName(_pdfPageModes[pageMode.index]);

@@ -58,7 +58,7 @@ class PdfOutline extends PdfObjectDict {
     this.color,
     this.destMode = PdfOutlineMode.fitPage,
     this.style = PdfOutlineStyle.normal,
-    int? page,
+    String? page,
   })  : assert(anchor == null || (dest == null && rect == null)),
         _page = page,
         super(pdfDocument);
@@ -76,10 +76,12 @@ class PdfOutline extends PdfObjectDict {
   PdfPage? dest;
 
   /// Page number
-  int? get page =>
+  String? get page =>
       _page ??
-      (dest != null ? pdfDocument.pdfPageList.pages.indexOf(dest!) + 1 : null);
-  final int? _page;
+      (dest != null
+          ? (pdfDocument.pdfPageList.pages.indexOf(dest!) + 1).toString()
+          : null);
+  final String? _page;
 
   /// The region on the destination page
   final PdfRect? rect;

+import '../../priv.dart';
+import '../document.dart';
+import 'object_dict.dart';
+
+enum PdfPageLabelStyle {
+  arabic,
+  romanUpper,
+  romanLower,
+  lettersUpper,
+  lettersLower
+}
+
+class PdfPageLabel {
+  PdfPageLabel(this.prefix, {this.style, this.subsequent});
+
+  PdfPageLabel.arabic({this.prefix, this.subsequent})
+      : style = PdfPageLabelStyle.arabic;
+
+  PdfPageLabel.romanUpper({this.prefix, this.subsequent})
+      : style = PdfPageLabelStyle.romanUpper;
+
+  PdfPageLabel.romanLower({this.prefix, this.subsequent})
+      : style = PdfPageLabelStyle.romanLower;
+
+  PdfPageLabel.lettersUpper({this.prefix, this.subsequent})
+      : style = PdfPageLabelStyle.lettersUpper;
+
+  PdfPageLabel.lettersLower({this.prefix, this.subsequent})
+      : style = PdfPageLabelStyle.lettersLower;
+
+  final PdfPageLabelStyle? style;
+  final String? prefix;
+  final int? subsequent;
+
+  PdfDict toDict(PdfObject obj) {
+    final PdfName? s;
+    switch (style) {
+      case PdfPageLabelStyle.arabic:
+        s = const PdfName('/D');
+        break;
+      case PdfPageLabelStyle.romanUpper:
+        s = const PdfName('/R');
+        break;
+      case PdfPageLabelStyle.romanLower:
+        s = const PdfName('/r');
+        break;
+      case PdfPageLabelStyle.lettersUpper:
+        s = const PdfName('/A');
+        break;
+      case PdfPageLabelStyle.lettersLower:
+        s = const PdfName('/a');
+        break;
+      case null:
+        s = null;
+    }
+    return PdfDict({
+      if (s != null) '/S': s,
+      if (prefix != null && prefix!.isNotEmpty)
+        '/P': PdfSecString.fromString(obj, prefix!),
+      if (subsequent != null) '/St': PdfNum(subsequent!)
+    });
+  }
+
+  String _toRoman(int decimal) {
+    const dictionary = {
+      1000: 'M',
+      900: 'CM',
+      500: 'D',
+      400: 'CD,',
+      100: 'C',
+      90: 'XC',
+      50: 'L',
+      40: 'XL',
+      10: 'X',
+      9: 'IX',
+      5: 'V',
+      4: 'IV',
+      1: 'I'
+    };
+
+    assert(decimal > 0 && decimal < 3999,
+        'Roman numerals are limited to the inclusive range of 1 to 3999.');
+
+    var result = '';
+    dictionary.forEach((k, v) {
+      while (decimal >= k) {
+        decimal -= k;
+        result += v;
+      }
+    });
+    return result;
+  }
+
+  String _toLetters(int decimal) {
+    final n = String.fromCharCode(0x41 + decimal % 26);
+    final r = decimal ~/ 26 + 1;
+    return n * r;
+  }
+
+  String asString([int index = 0]) {
+    final i = subsequent == null ? index : index + subsequent!;
+
+    final String suffix;
+    switch (style) {
+      case PdfPageLabelStyle.arabic:
+        suffix = (i + 1).toString();
+        break;
+      case PdfPageLabelStyle.romanUpper:
+        suffix = _toRoman(i + 1);
+        break;
+      case PdfPageLabelStyle.romanLower:
+        suffix = _toRoman(i + 1).toLowerCase();
+        break;
+      case PdfPageLabelStyle.lettersUpper:
+        suffix = _toLetters(i);
+        break;
+      case PdfPageLabelStyle.lettersLower:
+        suffix = _toLetters(i).toLowerCase();
+        break;
+      case null:
+        suffix = '';
+    }
+    return '${prefix ?? ''}$suffix';
+  }
+}
+
+/// Pdf PageLabels object
+class PdfPageLabels extends PdfObjectDict {
+  /// Constructs a Pdf PageLabels object.
+  PdfPageLabels(PdfDocument pdfDocument) : super(pdfDocument);
+
+  final labels = <int, PdfPageLabel>{};
+
+  String pageLabel(int index) {
+    final n = labels.keys.toList()..sort();
+    var current = PdfPageLabel.arabic();
+    var s = 0;
+    for (final i in n) {
+      if (index >= i) {
+        current = labels[i]!;
+        s = i;
+      }
+    }
+
+    return current.asString(index - s);
+  }
+
+  Iterable<String> get names sync* {
+    final n = labels.keys.toList()..sort();
+    var l = PdfPageLabel.arabic();
+    final len = pdfDocument.pdfPageList.pages.length;
+    var c = 0;
+    var b = c < n.length ? n[c] : len;
+    var s = 0;
+    for (var i = 0; i < len; i++) {
+      if (i >= b) {
+        l = labels[b]!;
+        c++;
+        b = c < n.length ? n[c] : len;
+        s = i;
+      }
+      yield l.asString(i - s);
+    }
+  }
+
+  @override
+  void prepare() {
+    super.prepare();
+
+    final nums = PdfArray();
+    for (final entry in labels.entries) {
+      nums.add(PdfNum(entry.key));
+      nums.add(entry.value.toDict(this));
+    }
+
+    params['/Nums'] = nums;
+  }
+}

@@ -622,7 +622,7 @@ class Outline extends Anchor {
       anchor: name,
       color: color,
       style: style,
-      page: context.pageNumber,
+      page: context.pageLabel,
     )..effectiveLevel = level;
 
     final root = context.document.outline;

@@ -62,7 +62,16 @@ class Context {
 
   final PdfDocument document;
 
-  int get pageNumber => document.pdfPageList.pages.indexOf(page) + 1;
+  int get _pageNumber => document.pdfPageList.pages.indexOf(page);
+
+  int get pageNumber => _pageNumber + 1;
+
+  String get pageLabel => document.catalog.pageLabels == null
+      ? pageNumber.toString()
+      : document.pageLabels.pageLabel(_pageNumber);
+
+  set pageLabel(String value) =>
+      document.pageLabels.labels[_pageNumber] = PdfPageLabel(value);
 
   /// Number of pages in the document.
   /// This value is not available in a MultiPage body and will be equal to pageNumber.

+/*
+ * Copyright (C) 2017, David PHAM-VAN <dev.nfet.net@gmail.com>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import 'package:pdf/pdf.dart';
+import 'package:test/test.dart';
+
+void main() {
+  test('Page label', () async {
+    final pdf = PdfDocument();
+
+    for (var i = 0; i < 5; i++) {
+      PdfPage(pdf);
+    }
+
+    pdf.pageLabels.labels[0] = PdfPageLabel('Hello');
+    pdf.pageLabels.labels[1] = PdfPageLabel.lettersUpper();
+    pdf.pageLabels.labels[3] = PdfPageLabel.romanLower(prefix: 'appendix ');
+
+    expect(pdf.pageLabels.pageLabel(0), 'Hello');
+    expect(pdf.pageLabels.pageLabel(1), 'A');
+    expect(pdf.pageLabels.pageLabel(2), 'B');
+    expect(pdf.pageLabels.pageLabel(3), 'appendix i');
+    expect(pdf.pageLabels.pageLabel(4), 'appendix ii');
+  });
+
+  test('Roman labels', () async {
+    final pdf = PdfDocument();
+
+    for (var i = 0; i < 500; i++) {
+      PdfPage(pdf);
+    }
+
+    pdf.pageLabels.labels[3] = PdfPageLabel.romanLower();
+
+    expect(pdf.pageLabels.pageLabel(0), '1');
+    expect(pdf.pageLabels.pageLabel(300), 'ccxcviii');
+    expect(pdf.pageLabels.names.toList()[300], 'ccxcviii');
+  });
+
+  test('No of labels', () async {
+    final pdf = PdfDocument();
+
+    for (var i = 0; i < 500; i++) {
+      PdfPage(pdf);
+    }
+
+    expect(pdf.pageLabels.pageLabel(0), '1');
+    expect(pdf.pageLabels.pageLabel(300), '301');
+    expect(pdf.pageLabels.names.toList()[300], '301');
+  });
+
+  test('Letter labels', () async {
+    final pdf = PdfDocument();
+
+    for (var i = 0; i < 500; i++) {
+      PdfPage(pdf);
+    }
+
+    pdf.pageLabels.labels[30] = PdfPageLabel.lettersLower();
+
+    expect(pdf.pageLabels.pageLabel(0), '1');
+    expect(pdf.pageLabels.pageLabel(30), 'a');
+    expect(pdf.pageLabels.names.toList()[30], 'a');
+    expect(pdf.pageLabels.pageLabel(40), 'k');
+    expect(pdf.pageLabels.names.toList()[40], 'k');
+    expect(pdf.pageLabels.pageLabel(60), 'ee');
+    expect(pdf.pageLabels.names.toList()[60], 'ee');
+  });
+}