Add support for rendering wiki links

This way clicking on a wiki link also opens the corresponding note, if
it exists.

lib/widgets/note_viewer.dart

@@ -3,20 +3,23 @@ import 'dart:io';
 import 'package:cached_network_image/cached_network_image.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
+
 import 'package:flutter_markdown/flutter_markdown.dart';
+import 'package:markdown/markdown.dart' as md;
+
+import 'package:gitjournal/core/note.dart';
+import 'package:gitjournal/core/notes_folder_fs.dart';
 import 'package:gitjournal/folder_views/common.dart';
 import 'package:gitjournal/settings.dart';
 import 'package:gitjournal/utils.dart';
 import 'package:gitjournal/utils/logger.dart';
 import 'package:gitjournal/widgets/editor_scroll_view.dart';
 import 'package:gitjournal/widgets/notes_backlinks.dart';
+
 import 'package:provider/provider.dart';
 import 'package:url_launcher/url_launcher.dart';
 import 'package:path/path.dart' as p;
 
-import 'package:gitjournal/core/note.dart';
-import 'package:gitjournal/core/notes_folder_fs.dart';
-
 class NoteViewer extends StatelessWidget {
   final Note note;
   const NoteViewer({Key key, @required this.note}) : super(key: key);
@@ -50,6 +53,12 @@ class NoteViewer extends StatelessWidget {
       ),
     );
 
+    // It's important to add both these inline syntaxes before the other
+    // syntaxes as the LinkSyntax intefers with both of these
+    var markdownExtensions = md.ExtensionSet.gitHubFlavored;
+    markdownExtensions.inlineSyntaxes.insert(0, WikiLinkSyntax2());
+    markdownExtensions.inlineSyntaxes.insert(1, TaskListSyntax());
+
     final rootFolder = Provider.of<NotesFolderFS>(context);
     var view = EditorScrollView(
       child: Column(
@@ -63,6 +72,14 @@ class NoteViewer extends StatelessWidget {
               styleSheet: markdownStyleSheet,
               onTapLink: (String link) async {
                 var spec = link;
+
+                if (link.startsWith('[[') &&
+                    link.endsWith(']]') &&
+                    link.length > 4) {
+                  // FIXME: What if the case is different?
+                  spec = link.substring(2, link.length - 2) + ".md";
+                }
+
                 if (link.startsWith('./')) {
                   spec = link.substring(2);
                 }
@@ -97,6 +114,7 @@ class NoteViewer extends StatelessWidget {
               },
               imageBuilder: (url, title, alt) => kDefaultImageBuilder(
                   url, note.parent.folderPath + p.separator, null, null),
+              extensionSet: markdownExtensions,
             ),
           ),
           const SizedBox(height: 16.0),
@@ -208,3 +226,23 @@ Widget _handleDataSchemeUri(Uri uri, final double width, final double height) {
   }
   return const SizedBox();
 }
+
+/// Parse [[term]]
+class WikiLinkSyntax2 extends md.InlineSyntax {
+  static final String _pattern = r'\[\[([^\[\]]+)\]\]';
+
+  WikiLinkSyntax2() : super(_pattern);
+
+  @override
+  bool onMatch(md.InlineParser parser, Match match) {
+    // print("-------- WIKI LINK -------");
+    var term = match[1].trim();
+
+    var el = md.Element('a', [md.Text(term)]);
+    el.attributes['type'] = 'wiki';
+    el.attributes['href'] = '[[$term]]';
+
+    parser.addNode(el);
+    return true;
+  }
+}

pubspec.lock

@@ -477,12 +477,14 @@ packages:
     source: hosted
     version: "0.11.3+2"
   markdown:
-    dependency: transitive
+    dependency: "direct overridden"
     description:
-      name: markdown
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.1.3"
+      path: "."
+      ref: HEAD
+      resolved-ref: "2e87055c39b4b29939bb99ceff593880e2bcf20a"
+      url: "https://github.com/GitJournal/markdown.git"
+    source: git
+    version: "2.1.5"
   matcher:
     dependency: transitive
     description:

pubspec.yaml

@@ -72,6 +72,8 @@ dev_dependencies:
 dependency_overrides:
   intl:
     git: https://github.com/GitJournal/intl.git
+  markdown:
+    git: https://github.com/GitJournal/markdown.git
 
 flutter:
   uses-material-design: true