// Adapted from https://github.com/mathiasbynens/he/blob/36afe179392226cf1b6ccdb16ebbb7a5a844d93a/src/he.js#L106-L134

const decodeMap = new Map([
	[0, 65_533],
	// C1 Unicode control character reference replacements
	[128, 8364],
	[130, 8218],
	[131, 402],
	[132, 8222],
	[133, 8230],
	[134, 8224],
	[135, 8225],
	[136, 710],
	[137, 8240],
	[138, 352],
	[139, 8249],
	[140, 338],
	[142, 381],
	[145, 8216],
	[146, 8217],
	[147, 8220],
	[148, 8221],
	[149, 8226],
	[150, 8211],
	[151, 8212],
	[152, 732],
	[153, 8482],
	[154, 353],
	[155, 8250],
	[156, 339],
	[158, 382],
	[159, 376],
]);

/**
 * Polyfill for `String.fromCodePoint`. It is used to create a string from a Unicode code point.
 */
export const fromCodePoint: (...codePoints: number[]) => string =
	// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition, n/no-unsupported-features/es-builtins
	String.fromCodePoint ??
	((codePoint: number): string => {
		let output = '';

		if (codePoint > 0xff_ff) {
			codePoint -= 0x1_00_00;
			output += String.fromCharCode(((codePoint >>> 10) & 0x3_ff) | 0xd8_00);
			codePoint = 0xdc_00 | (codePoint & 0x3_ff);
		}

		output += String.fromCharCode(codePoint);
		return output;
	});

/**
 * Replace the given code point with a replacement character if it is a
 * surrogate or is outside the valid range. Otherwise return the code
 * point unchanged.
 */
export function replaceCodePoint(codePoint: number): number {
	if ((codePoint >= 0xd8_00 && codePoint <= 0xdf_ff) || codePoint > 0x10_ff_ff) {
		return 0xff_fd;
	}

	return decodeMap.get(codePoint) ?? codePoint;
}

/**
 * Replace the code point if relevant, then convert it to a string.
 *
 * @deprecated Use `fromCodePoint(replaceCodePoint(codePoint))` instead.
 * @param codePoint The code point to decode.
 * @returns The decoded code point.
 */
export function decodeCodePoint(codePoint: number): string {
	return fromCodePoint(replaceCodePoint(codePoint));
}
