src/viNumberFix.js

/**
 * Vietnamese text processing for both display and TTS.
 *
 * DESIGN: 
 * - Display text (chat & subtitles): numbers stay as digits for clean visual display
 * - TTS audio: numbers are converted to Vietnamese words for proper pronunciation
 * - Source links in greetings: rendered as clickable popup links
 */

// Vietnamese number words
const DIGITS = [
  "không", "một", "hai", "ba", "bốn", "năm", "sáu", "bảy", "tám", "chín",
];

function numberToVietnamese(n) {
  if (n === 0) return "không";
  if (n < 0) return "âm " + numberToVietnamese(-n);

  const units = ["", "nghìn", "triệu", "tỷ"];
  const groups = [];
  let temp = n;
  while (temp > 0) {
    groups.push(temp % 1000);
    temp = Math.floor(temp / 1000);
  }
  if (groups.length === 0) groups.push(0);

  const readGroup = (g) => {
    if (g === 0) return "";
    const h = Math.floor(g / 100);
    const r = g % 100;
    let s = "";
    if (h > 0) s += DIGITS[h] + " trăm ";
    else if (groups.length > 1) s += "không trăm ";
    if (r === 0) return s.trim();
    if (r < 10) {
      s += (h > 0 && r === 5) ? "lẻ năm" : "lẻ " + DIGITS[r];
    } else if (r < 20) {
      s += "mười" + (r === 10 ? "" : (r === 15 ? " lăm" : " " + DIGITS[r % 10]));
    } else {
      const t = Math.floor(r / 10);
      const o = r % 10;
      s += ["", "", "hai mươi", "ba mươi", "bốn mươi", "năm mươi",
            "sáu mươi", "bảy mươi", "tám mươi", "chín mươi"][t];
      if (o === 1) s += " mốt";
      else if (o === 5) s += " lăm";
      else if (o > 0) s += " " + DIGITS[o];
    }
    return s.replace(/\s+/g, " ").trim();
  };

  let result = "";
  for (let i = groups.length - 1; i >= 0; i--) {
    const g = groups[i];
    if (g === 0) continue;
    result += readGroup(g);
    if (i > 0) result += " " + units[i] + " ";
  }
  return result.replace(/\s+/g, " ").trim();
}

/**
 * Normalize Vietnamese text for display.
 * Numbers remain as digits for clean visual display.
 */
export function normalizeVietnameseText(text) {
  if (!text || typeof text !== "string") return text;
  return text.replace(/\s+/g, " ").trim();
}

/**
 * Check if text contains Vietnamese characters.
 */
export function containsVietnamese(text) {
  return /[àáạảãâầấậẩẫăằắặẳẵèéẹẻẽêềếệểễìíịỉĩòóọỏõôồốộổỗơờớợởỡùúụủũưừứựửữỳýỵỷỹđ]/i.test(text);
}

/**
 * Convert Arabic numerals to Vietnamese words for TTS.
 * Display texts keep the original digits.
 */
export function numbersToVietnameseWords(text) {
  if (!text || typeof text !== "string") return text;
  
  const units = ["", "nghìn", "triệu", "tỷ"];
  
  const numberToVietnameseLocal = (n) => {
    if (n === 0) return "không";
    if (n < 0) return "âm " + numberToVietnameseLocal(-n);
    
    const groups = [];
    let temp = n;
    while (temp > 0) {
      groups.push(temp % 1000);
      temp = Math.floor(temp / 1000);
    }
    if (groups.length === 0) groups.push(0);
    
    const readGroup = (g) => {
      if (g === 0) return "";
      const h = Math.floor(g / 100);
      const r = g % 100;
      let s = "";
      if (h > 0) s += DIGITS[h] + " trăm ";
      else if (groups.length > 1) s += "không trăm ";
      if (r === 0) return s.trim();
      if (r < 10) {
        s += (h > 0 && r === 5) ? "lẻ năm" : "lẻ " + DIGITS[r];
      } else if (r < 20) {
        s += "mười" + (r === 10 ? "" : (r === 15 ? " lăm" : " " + DIGITS[r % 10]));
      } else {
        const t = Math.floor(r / 10);
        const o = r % 10;
        s += ["", "", "hai mươi", "ba mươi", "bốn mươi", "năm mươi",
              "sáu mươi", "bảy mươi", "tám mươi", "chín mươi"][t];
        if (o === 1) s += " mốt";
        else if (o === 5) s += " lăm";
        else if (o > 0) s += " " + DIGITS[o];
      }
      return s.replace(/\s+/g, " ").trim();
    };
    
    let result = "";
    for (let i = groups.length - 1; i >= 0; i--) {
      const g = groups[i];
      if (g === 0) continue;
      result += readGroup(g);
      if (i > 0) result += " " + units[i] + " ";
    }
    return result.replace(/\s+/g, " ").trim();
  };
  
  // Match integers (including negative) - convert to Vietnamese words
  return text.replace(/\b-?\d+\b/g, (match) => {
    const num = parseInt(match);
    return numberToVietnameseLocal(num);
  });
}

/**
 * Smart normalizer: only run on Vietnamese text, only on final transcripts.
 */
export function smartNormalize(text, partial = false) {
  if (!text || partial) return text;
  if (containsVietnamese(text)) {
    return normalizeVietnameseText(text);
  }
  return text;
}

/**
 * Convert text for TTS: Vietnamese numbers to words for proper pronunciation.
 * Call this before sending text to TTS synthesis.
 */
export function prepareForTTS(text) {
  if (!text || typeof text !== "string") return text;
  if (containsVietnamese(text)) {
    return numbersToVietnameseWords(text);
  }
  return text;
}