dmc-codegen 0.2.3

/// HTML-escape text content per CommonMark reference output: `&`, `<`,
/// `>`, and `"` map to named entities. CM's spec runner encodes `"` in
/// text too so the diff stays clean.
pub fn escape_text(s: &str) -> String {
  let mut out = String::with_capacity(s.len());
  for ch in s.chars() {
    match ch {
      '&' => out.push_str("&amp;"),
      '<' => out.push_str("&lt;"),
      '>' => out.push_str("&gt;"),
      '"' => out.push_str("&quot;"),
      _ => out.push(ch),
    }
  }
  out
}

/// Percent-encode the bytes that CM's reference renderer escapes inside
/// link destinations. Keeps already-encoded sequences (`%5C`) intact and
/// preserves the unreserved + sub-delims set per RFC 3986.
pub fn escape_url(s: &str) -> String {
  let bytes = s.as_bytes();
  let mut out = String::with_capacity(bytes.len());
  let mut i = 0;
  while i < bytes.len() {
    let b = bytes[i];
    // Pass-through unreserved + sub-delims + reserved gen-delims that
    // CM treats as safe.
    let safe = b.is_ascii_alphanumeric()
      || matches!(
        b,
        b'-' | b'_' | b'.' | b'~' // unreserved
        | b'!' | b'$' | b'\''
        | b'(' | b')' | b'*'
        | b',' | b';' | b'='
        | b'+'
        | b':' | b'@' | b'/'
        | b'?' | b'#'
      );
    if b == b'%' && i + 2 < bytes.len() && bytes[i + 1].is_ascii_hexdigit() && bytes[i + 2].is_ascii_hexdigit() {
      // Already percent-encoded; pass through.
      out.push('%');
      out.push(bytes[i + 1] as char);
      out.push(bytes[i + 2] as char);
      i += 3;
      continue;
    }
    if b == b'&' {
      // Preserve HTML entity escape downstream. `&` becomes `&amp;`
      // when this output flows through `escape_attr`; here just keep
      // the literal byte.
      out.push('&');
    } else if safe {
      out.push(b as char);
    } else {
      out.push_str(&format!("%{:02X}", b));
    }
    i += 1;
  }
  out
}

/// HTML-escape an attribute value. Same as [`escape_text`] plus `"` -> `&quot;`
/// since attribute values are quoted.
pub fn escape_attr(s: &str) -> String {
  let mut out = String::with_capacity(s.len());
  for ch in s.chars() {
    match ch {
      '&' => out.push_str("&amp;"),
      '"' => out.push_str("&quot;"),
      '<' => out.push_str("&lt;"),
      '>' => out.push_str("&gt;"),
      _ => out.push(ch),
    }
  }
  out
}