wcwidth.ts

import combining from "./combining.ts";

export type Defaults = {
  nul?: number;
  control?: number;
};

/*
 *  The following functions define the column width of an ISO 10646
 *  character as follows:
 *  - The null character (U+0000) has a column width of 0.
 *  - Other C0/C1 control characters and DEL will lead to a return value
 *    of -1.
 *  - Non-spacing and enclosing combining characters (general category
 *    code Mn or Me in the
 *    Unicode database) have a column width of 0.
 *  - SOFT HYPHEN (U+00AD) has a column width of 1.
 *  - Other format characters (general category code Cf in the Unicode
 *    database) and ZERO WIDTH
 *    SPACE (U+200B) have a column width of 0.
 *  - Hangul Jamo medial vowels and final consonants (U+1160-U+11FF)
 *    have a column width of 0.
 *  - Spacing characters in the East Asian Wide (W) or East Asian
 *    Full-width (F) category as
 *    defined in Unicode Technical Report #11 have a column width of 2.
 *  - All remaining characters (including all printable ISO 8859-1 and
 *    WGL4 characters, Unicode control characters, etc.) have a column
 *    width of 1.
 *  This implementation assumes that characters are encoded in ISO 10646.
 */
export function wcswidth(
  str: string,
  { nul = 0, control = 0 }: Defaults = {},
): number {
  const opts = { nul, control };
  if (typeof str !== "string") return wcwidth(str, opts);

  let s = 0;
  for (let i = 0; i < str.length; i++) {
    const n = wcwidth(str.charCodeAt(i), opts);
    if (n < 0) return -1;
    s += n;
  }

  return s;
}

function wcwidth(ucs: number, { nul = 0, control = 0 }: Defaults = {}): number {
  // test for 8-bit control characters
  if (ucs === 0) return nul;
  if (ucs < 32 || (ucs >= 0x7f && ucs < 0xa0)) return control;

  // binary search in table of non-spacing characters
  if (bisearch(ucs)) return 0;

  // if we arrive here, ucs is not a combining or C0/C1 control character
  return (
    1 +
    (ucs >= 0x1100 &&
        (ucs <= 0x115f || // Hangul Jamo init. consonants
          ucs == 0x2329 ||
          ucs == 0x232a ||
          (ucs >= 0x2e80 && ucs <= 0xa4cf && ucs != 0x303f) || // CJK ... Yi
          (ucs >= 0xac00 && ucs <= 0xd7a3) || // Hangul Syllables
          (ucs >= 0xf900 && ucs <= 0xfaff) || // CJK Compatibility Ideographs
          (ucs >= 0xfe10 && ucs <= 0xfe19) || // Vertical forms
          (ucs >= 0xfe30 && ucs <= 0xfe6f) || // CJK Compatibility Forms
          (ucs >= 0xff00 && ucs <= 0xff60) || // Fullwidth Forms
          (ucs >= 0xffe0 && ucs <= 0xffe6) ||
          (ucs >= 0x20000 && ucs <= 0x2fffd) ||
          (ucs >= 0x30000 && ucs <= 0x3fffd))
      ? 1
      : 0)
  );
}

function bisearch(ucs: number): boolean {
  let min = 0;
  let max = combining.length - 1;
  let mid;

  if (ucs < combining[0][0] || ucs > combining[max][1]) return false;

  while (max >= min) {
    mid = Math.floor((min + max) / 2);
    if (ucs > combining[mid][1]) min = mid + 1;
    else if (ucs < combining[mid][0]) max = mid - 1;
    else return true;
  }

  return false;
}