scroll/src/common/strings.ts

/**
 * Split a string by graphemes, not just bytes
 * @param s - the string to split into 'characters'
 */
export function chars(s: string): string[] {
	return s.split(/(?:)/u);
}

/**
 * Get the 'character length' of a string, not its UTF16 byte count
 * @param s - the string to check
 */
export function strlen(s: string): number {
	return chars(s).length;
}

/**
 * Is the character part of ascii?
 *
 * @param char - a one character string to check
 */
export function is_ascii(char: string): boolean {
	return chars(char).every((char) => {
		const point = char.codePointAt(0);
		if (point === undefined) {
			return false;
		}

		return point < 0x80;
	});
}

/**
 * Is the one char in the string an ascii control character?
 *
 * @param char - a one character string to check
 */
export function is_control(char: string): boolean {
	const code = char.codePointAt(0);
	if (code === undefined) {
		return false;
	}

	return is_ascii(char) && (code === 0x7f || code < 0x20);
}

/**
 * Get the key code for a ctrl chord
 * @param char - a one character string
 */
export function ctrl_key(char: string): string {
	// This is the normal use case, of course
	if (is_ascii(char)) {
		const point = char.codePointAt(0);
		if (point === undefined) {
			return char;
		}

		return String.fromCodePoint(point & 0x1f);
	}

	// If it's not ascii, just return the input key code
	return char;
}

/**
 * Trim a string to a max number of characters
 * @param s
 * @param maxLen
 */
export function truncate(s: string, maxLen: number): string {
	const chin = chars(s);
	if (maxLen >= chin.length) {
		return s;
	}

	return chin.slice(0, maxLen).join('');
}