plainText function

String plainText(String markdown)

Reduces markdown to searchable prose.

Implementation

String plainText(String markdown) {
  var text = markdown;

  // Component tags (<Info>, <CardGrid …>) and raw HTML carry no query terms.
  text = text.replaceAll(RegExp('<!--.*?-->', dotAll: true), ' ');
  text = text.replaceAll(RegExp(r'</?[A-Za-z][\w-]*(\s[^<>]*)?/?>'), ' ');

  text = text.replaceAllMapped(
    RegExp(r'!\[([^\]]*)\]\([^)]*\)'),
    (m) => m.group(1)!,
  );
  text = text.replaceAllMapped(
    RegExp(r'\[([^\]]+)\]\([^)]*\)'),
    (m) => m.group(1)!,
  );
  // Reference-style links: keep the label, drop the key.
  text = text.replaceAllMapped(
    RegExp(r'\[([^\]]+)\]\[[^\]]*\]'),
    (m) => m.group(1)!,
  );
  text = text.replaceAll(
    RegExp(r'^\[[^\]]+\]:\s*\S+\s*$', multiLine: true),
    '',
  );

  text = text.replaceAll(RegExp(r'^\s{0,3}>\s?', multiLine: true), '');
  text = text.replaceAll(RegExp(r'^\s*[-*+]\s+', multiLine: true), '');
  text = text.replaceAll(
    RegExp(
      r'^\s*\|?\s*:?-{3,}:?\s*(\|\s*:?-{3,}:?\s*)*\|?\s*$',
      multiLine: true,
    ),
    '',
  );
  text = text.replaceAll('|', ' ');
  // Underscores survive: `snake_case` identifiers and file names are exactly
  // what people search for, and `_emphasis_` is not a style docs prose uses.
  text = text.replaceAll(RegExp('[`*#]'), '');

  return text.replaceAll(RegExp(r'\s+'), ' ').trim();
}