Select Graphic Rendition (SGR)

sgr.js

/**
 * Applies Select Graphic Rendition (SGR) parameters to a given message for
 * styling in terminal environments. This function allows for the dynamic
 * styling of text output using ANSI escape codes. It supports a variety of
 * modes such as color, brightness, and text decorations like bold or underline.
 * 
 * @param {string} message The message to be styled.
 * @param {...string} useModes A series of strings representing the desired
 * styling modes. Modes can include colors (e.g., 'red', 'blue'), brightness
 * ('bright'), foreground/background ('fg', 'bg'), and text decorations
 * ('bold', 'underline'). Modes can be combined in a single string using
 * commas or passed as separate arguments.
 * 
 * Colors:
 * ```
 * 'black', 'red', 'green', 'yellow', 'blue', 'magenta', 'cyan', 'white'
 * ```
 * Color Specifiers:
 * ```
 * 'fg' -> foreground   |  'bg' -> background  |  'bright' -> bright colors
 * ```
 * 
 * Modes:
 * ```
 * 'blink' or 'k' | 'conceal' or 'c' | 'italics' or 'i'  | 'strike' or 's'
 * 'bold' or 'b'  | 'dim' or 'd'     | 'negative' or 'n' | 'underline' or 'u'
 * ```
 * 
 * Examples:
 * - `sgr('Hello', 'red')` applies red color to 'Hello'.
 * - `sgr('World', 'green,bold')` applies green color and bold styling 
 *   to 'World'.
 * - `sgr('Example', 'bluebgbright')` applies bright blue 
 *   background color.
 * 
 * Short hand syntax is also allowed:
 * - `sgr('hello', 'biu')` applies bold, italics and underline
 * - `sgr('hello', 'bi,redfg')` applies bold, italics and red foreground
 * 
 * As a bonus, there is a secret getter applied to the return string that
 * allows you to invoke `sgr(...).show` to automatically log the output to
 * `console.log`. This is done by wrapping the output string in `Object()`
 * to make it a `String` instance and then adding the property descriptor. 
 * A custom `Symbol` is applied to make it evaluate in nodejs as though it 
 * were a normal string. To strip the extras, wrap the output in `String()`
 * 
 * @returns {string} The message wrapped in ANSI escape codes corresponding
 * to the specified modes. The returned string, when printed to a terminal,
 * displays the styled message. Additional properties are attached to the
 * result for utility purposes, such as 'show' for immediate console output.
 */
function sgr(message, ...useModes) {
  const colors = Object.assign(
    ['black', 'red', 'green', 'yellow', 'blue', 'magenta', 'cyan', 'white'],
    {
      isBG: a => !!/bg/i.exec(a),
      isBright: a => !!/bright/i.exec(a),
      isColor: a => {
        let color = colors.find(c => new RegExp(c, 'i').exec(a));
        return [!!color, colors.indexOf(color)];
      },
    }
  );

  const arrayifyString = s => {
    if (Array.isArray(s)) {
      let results = [];

      for (const i of s) {
        results = [ ...results, ...arrayifyString(i) ];
      }

      return results.flat().filter(i => i.length);
    }

    if (!s || typeof s !== 'string') {
      return [''];
    }
    else if (s.includes(',')) {
      return arrayifyString(s.split(','));
    }
    else {
      if (!colors.isColor(s)[0] && s.length > 1) {
        return [...s];
      } 
      else return [s];
    }
  }

  let modes = arrayifyString(useModes)

  const sgrModes = {
    blink: ['\x1b[5m', '\x1b[25m', 'k'],
    bold: ['\x1b[1m', '\x1b[22m', 'b'],
    conceal: ['\x1b[8m', '\x1b[28m', 'c'],
    dim: ['\x1b[2m', '\x1b[22m', 'd'],
    italics: ['\x1b[3m', '\x1b[23m', 'i'],
    negative: ['\x1b[7m', '\x1b[27m', 'n'],
    strike: ['\x1b[9m', '\x1b[29m', 's'], 
    underline: ['\x1b[4m', '\x1b[24m', 'u'],
  };
  
  Object.values(sgrModes).forEach(mode => sgrModes[mode[2]] = mode);

  const codes = a => {
    let open = '', close = '', mode = String(a).toLowerCase(); 
    let [_isColor, colorIndex] = colors.isColor(mode);

    if (_isColor) {
      open = colors.isBG(mode) 
        ? `\x1b[${colors.isBright(mode) ? 10 : 4}${colorIndex}m`
        : `\x1b[${colors.isBright(mode) ? 9 : 3}${colorIndex}m`;
      close = colors.isBG(mode) ? '\x1b[49m' : `\x1b[39m`;
    }
    else if (sgrModes[mode]) {
      open = sgrModes[mode][0];
      close = sgrModes[mode][1];
    }

    return [open, close];
  };

  const onOrder = modes.map(key => codes(key)[0]).join('');
  const offOrder = modes.map(key => codes(key)[1]).reverse().join('');

  let result = Object(`${onOrder}${message}${offOrder}`)
  Object.defineProperties(result, {
    show: { 
      get() { console.log(String(this)); return this }, 
      enumerable: false,
    },
    [Symbol.for('nodejs.util.inspect.custom')]: {
      value(depth, options, inspect) { 
        return inspect(String(this), options) 
      },
      enumerable: false,
    },
  })

  return result
}