/**

* Unicode escape / unescape utilities.

*

* - Escape: converts non-ASCII characters to \\uXXXX (BMP) or \\u{XXXXX} (supplementary)

* Also supports `escapeAll` mode that escapes ASCII control chars too.

* - Unescape: handles \\uXXXX, \\u{XXXXX}, \\xXX, surrogate pairs, and standard JSON-style

* escapes (\\n, \\t, \\r, \\b, \\f, \\", \\\\).

*

* All operations work on the UTF-8/UTF-16 view of the JS string (the JS engine already

* keeps strings as UTF-16 internally).

*/

export interface UnicodeEscapeOptions {

escapeAll?: boolean; // also escape control chars (\\n, \\t, \\r, \\b, \\f, \\0)

escapeASCII?: boolean; // also escape printable ASCII (rarely useful)

useES6Braces?: boolean; // use \u{XXXXX} form for supplementary plane chars (default true)

}

export function escapeUnicode(input: string, opts: UnicodeEscapeOptions = {}): string {

const {

escapeAll = true,

escapeASCII = false,

useES6Braces = true,

} = opts;

let out = '';

for (let i = 0; i < input.length; i++) {

const ch = input[i]!;

const code = ch.codePointAt(0)!;

// Surrogates for supplementary plane chars need to be paired.

if (code >= 0xD800 && code <= 0xDBFF && input[i + 1]) {

const next = input[i + 1]!.codePointAt(0)!;

if (next >= 0xDC00 && next <= 0xDFFF) {

const full = 0x10000 + ((code - 0xD800) << 10) + (next - 0xDC00);

out += useES6Braces ? `\\u{${full.toString(16)}}` : `\\u${((full >> 16) + 0xD800).toString(16)}\\u${((full & 0xFFFF) + 0xDC00).toString(16)}`;

i++;

continue;

}

}

if (escapeAll) {

switch (ch) {

case '\\n': out += '\\n'; continue;

case '\\t': out += '\\t'; continue;

case '\\r': out += '\\r'; continue;

case '\\b': out += '\\b'; continue;

case '\\f': out += '\\f'; continue;

case '\\0': out += '\\0'; continue;

}

}

if (ch === '\\') { out += '\\\\'; continue; }

if (code < 0x20) {

out += `\\u${code.toString(16).padStart(4, '0')}`;

} else if (code < 0x7F && !escapeASCII) {

out += ch;

} else if (code <= 0xFFFF) {

out += `\\u${code.toString(16).padStart(4, '0')}`;

} else {

out += useES6Braces ? `\\u{${code.toString(16)}}` : `\\u${((code - 0x10000) >> 16 & 0xFFFF).toString(16).padStart(4, '0')}\\u${((code - 0x10000) & 0xFFFF).toString(16).padStart(4, '0')}`;

}

}

return out;

}

const UNI_ESCAPE = /\\(?:u\{([0-9a-fA-F]+)\}|u([0-9a-fA-F]{4})|x([0-9a-fA-F]{2})|n|r|t|b|f|0|\\|")/g;

export function unescapeUnicode(input: string): { output?: string; error?: string } {

try {

const out = input.replace(UNI_ESCAPE, (full, braced, u4, x2) => {

if (braced !== undefined) return String.fromCodePoint(parseInt(braced, 16));

if (u4 !== undefined) return String.fromCharCode(parseInt(u4, 16));

if (x2 !== undefined) return String.fromCharCode(parseInt(x2, 16));

switch (full) {

case '\\n': return '\n';

case '\\r': return '\r';

case '\\t': return '\t';

case '\\b': return '\b';

case '\\f': return '\f';

case '\\0': return '\0';

case '\\\\': return '\\';

case '\\"': return '"';

default: return full;

}

});

return { output: out };

} catch (e) {

return { error: e instanceof Error ? e.message : 'Invalid Unicode escape sequence' };

}

}