/**
 * Bidi embedding/override/isolate controls (U+202A–U+202E, U+2066–U+2069) can
 * visually reorder text ("evil" + U+202E + "txt.exe"); they are always removed.
 */
const BIDI_CONTROLS = /[\u202A-\u202E\u2066-\u2069]/g;
/** Marks and zero-width characters used for spoofing look-alike names. */
const INVISIBLES = /[\u200B-\u200F\u061C\u180E\u2060-\u2064\uFEFF\u034F\u115F\u1160\u3164\uFFA0]/g;
/** C0/C1 controls except tab and newline; lone surrogates. */
const CONTROLS = /[\u0000-\u0008\u000B-\u001F\u007F-\u009F]|[\uD800-\uDBFF](?![\uDC00-\uDFFF])|(?<![\uD800-\uDBFF])[\uDC00-\uDFFF]/g;

/** Normalises body text: strips controls and bidi overrides, keeps ZWJ (emoji sequences). */
export function neutralizeText(input: string): string {
  return input.replace(CONTROLS, "").replace(BIDI_CONTROLS, "").replace(/\r\n?/g, "\n");
}

/**
 * Display names, usernames, channel names: single line, no bidi or zero-width
 * characters at all, whitespace collapsed, length-capped.
 */
export function neutralizeDisplayName(input: string, maxLength = 100): string {
  const cleaned = input
    .normalize("NFC")
    .replace(CONTROLS, "")
    .replace(BIDI_CONTROLS, "")
    .replace(INVISIBLES, "")
    .replace(/\s+/g, " ")
    .trim();
  return truncateCodePoints(cleaned, maxLength);
}

export function truncateCodePoints(input: string, max: number): string {
  if (input.length <= max) return input;
  const chars = Array.from(input);
  return chars.length <= max ? input : chars.slice(0, max).join("") + "…";
}

const SCRIPT_RUNS: readonly [string, RegExp][] = [
  ["Latin", /\p{Script=Latin}/u],
  ["Cyrillic", /\p{Script=Cyrillic}/u],
  ["Greek", /\p{Script=Greek}/u],
  ["Armenian", /\p{Script=Armenian}/u],
  ["Cherokee", /\p{Script=Cherokee}/u],
];

/**
 * Homoglyph heuristic: true when a single word mixes Latin with a script that
 * has Latin look-alikes ("pаypal" with Cyrillic "а"). The UI should flag such
 * names rather than trust them; it is a warning, not a sanitiser.
 */
export function hasMixedScriptConfusables(input: string): boolean {
  for (const word of input.normalize("NFKC").split(/[\s\p{P}]+/u)) {
    let seen = 0;
    for (const [, re] of SCRIPT_RUNS) if (re.test(word)) seen++;
    if (seen > 1) return true;
  }
  return false;
}