normalizePrefix function
Normalizes one path segment into '' or /segment form.
Empty input, '/', and '//' all collapse to '' so that joining is
associative and a controller mounted at the root does not gain a trailing
slash.
Implementation
String normalizePrefix(String value) {
var normalized = value.trim();
if (normalized.isEmpty) return '';
if (!normalized.startsWith('/')) normalized = '/$normalized';
while (normalized.length > 1 && normalized.endsWith('/')) {
normalized = normalized.substring(0, normalized.length - 1);
}
normalized = normalized.replaceAll(RegExp('/+'), '/');
return normalized == '/' ? '' : normalized;
}