strip_markdown: Use a handbuilt stripper

It's not perfect, but it runs faster at about 35 us vs 650 us.

lib/utils/markdown.dart

@@ -1,56 +1,29 @@
+import 'dart:convert';
 import 'dart:core';
 
-import 'package:markdown/markdown.dart' as md;
-
-/// Builds a plain text [String] from parsed Markdown.
-class MarkdownBuilder implements md.NodeVisitor {
-  List<String> _texts = [];
-
-  String build(List<md.Node> nodes) {
-    _texts.clear();
-
-    for (md.Node node in nodes) {
-      node.accept(this);
-    }
-
-    var stringBuffer = StringBuffer();
-    _texts.forEach((String text) {
-      var t = text.trim();
-      if (t.isNotEmpty) {
-        t = t.replaceAll('\n', ' ');
-        t = t.trim();
-        stringBuffer.write(t);
-        stringBuffer.write(' ');
-      }
-    });
-
-    var str = stringBuffer.toString();
-    if (str.isNotEmpty) {
-      return str.substring(0, str.length - 1);
-    }
-    return str;
-  }
-
-  @override
-  void visitText(md.Text text) {
-    _texts.add(text.text);
-  }
-
-  @override
-  bool visitElementBefore(md.Element element) {
-    return true;
-  }
-
-  @override
-  void visitElementAfter(md.Element element) {
-    return;
-  }
-}
-
 String stripMarkdownFormatting(String markdown) {
-  final List<String> lines = markdown.replaceAll('\r\n', '\n').split('\n');
-  var doc = md.Document(encodeHtml: false);
+  var output = StringBuffer();
+  var regExp = RegExp('[a-zA-Z0-9]');
 
-  final MarkdownBuilder builder = MarkdownBuilder();
-  return builder.build(doc.parseLines(lines));
+  var lines = LineSplitter.split(markdown);
+  for (var line in lines) {
+    if (!line.contains(regExp)) {
+      continue;
+    }
+    line = line.trim();
+    if (line.startsWith('#')) {
+      line = line.replaceAll('#', '');
+    }
+    if (line.isEmpty) {
+      continue;
+    }
+    line = line.replaceFirst('[ ]', '☐');
+    line = line.replaceFirst('[x]', '☑');
+    line = line.replaceFirst('[X]', '☑');
+
+    output.write(line.trim());
+    output.write(' ');
+  }
+
+  return output.toString();
 }

test/strip_markdown_formatting_test.dart

@@ -5,7 +5,7 @@ void main() {
   group('Markdown Remove Formatting', () {
     test('Test Headers', () {
       var input = '# Hello\nHow are you?';
-      expect(stripMarkdownFormatting(input), 'Hello How are you?');
+      expect(stripMarkdownFormatting(input), 'Hello How are you? ');
     });
 
     test('Test Header2', () {
@@ -15,7 +15,7 @@ void main() {
 Hello
       """;
 
-      expect(stripMarkdownFormatting(input), 'Test Header Hello');
+      expect(stripMarkdownFormatting(input), 'Test Header Hello ');
     });
 
     test('Itemized LIsts', () {
@@ -27,7 +27,19 @@ look like:
       """;
 
       expect(stripMarkdownFormatting(input),
-          'Itemized lists look like: this one that one');
+          'Itemized lists look like: * this one * that one ');
+    });
+
+    test('Checklist', () {
+      var input = """Itemized lists
+
+[ ] this one
+[x] that one
+[X] last
+      """;
+
+      expect(stripMarkdownFormatting(input),
+          'Itemized lists ☐ this one ☑ that one ☑ last ');
     });
   });
 }