Add a PoC for parsing markdown to a checklist

lib/main2.dart

@@ -0,0 +1,84 @@
+import 'package:markdown/markdown.dart';
+import 'package:markdown/markdown.dart' as md;
+
+var text = """# Title 1
+
+How are you doing?
+
+[ ] item 1
+[x] item 2
+[X] item 3
+[ ] item 4
+
+Booga Wooga""";
+
+void main() {
+  print(markdownToHtml(
+    text,
+    extensionSet: ExtensionSet.gitHubWeb,
+    inlineSyntaxes: [TaskListSyntax()],
+  ));
+
+  var doc = md.Document(
+    encodeHtml: false,
+    inlineSyntaxes: [TaskListSyntax()],
+    extensionSet: ExtensionSet.gitHubWeb,
+  );
+
+  final MarkdownBuilder builder = MarkdownBuilder();
+  builder.build(doc.parseInline(text));
+}
+
+/// Parse [task list items](https://github.github.com/gfm/#task-list-items-extension-).
+class TaskListSyntax extends md.InlineSyntax {
+  // FIXME: Waiting for dart-lang/markdown#269 to land
+  static final String _pattern = r'^ *\[([ xX])\] +';
+
+  TaskListSyntax() : super(_pattern);
+
+  @override
+  bool onMatch(md.InlineParser parser, Match match) {
+    md.Element el = md.Element.withTag('input');
+    el.attributes['type'] = 'checkbox';
+    el.attributes['disabled'] = 'true';
+    el.attributes['checked'] = '${match[1].trim().isNotEmpty}';
+    parser.addNode(el);
+    return true;
+  }
+}
+
+class MarkdownBuilder implements md.NodeVisitor {
+  @override
+  bool visitElementBefore(md.Element element) {
+    return true;
+  }
+
+  @override
+  void visitText(md.Text text) {
+    print("text: ${text.text}");
+  }
+
+  @override
+  void visitElementAfter(md.Element element) {
+    final String tag = element.tag;
+
+    print("Tag: $tag");
+    if (tag == 'input') {
+      var el = element;
+      if (el is md.Element && el.attributes['type'] == 'checkbox') {
+        bool val = el.attributes['checked'] != 'false';
+        print("VAL $val");
+      }
+    }
+  }
+
+  String build(List<md.Node> nodes) {
+    print("---build---");
+    for (md.Node node in nodes) {
+      node.accept(this);
+    }
+    print("---build---");
+
+    return "";
+  }
+}