/**
 * Korean name detection — heuristic based on top surnames.
 * Matches: top-100 Korean surname + 1-2 Hangul given name characters.
 */

import type { PIIDetection } from "@klawn/shared";

/** Top Korean surnames by frequency. */
const TOP_SURNAMES = [
  "김", "이", "박", "최", "정", "강", "조", "윤", "장", "임",
  "한", "오", "서", "신", "권", "황", "안", "송", "류", "전",
  "홍", "고", "문", "양", "손", "배", "백", "허", "유", "남",
  "심", "노", "하", "곽", "성", "차", "주", "우", "구", "민",
  "라", "지", "엄", "원", "천", "방", "공", "진", "감", "변",
];

/** Hangul Unicode range. */
function isHangul(char: string): boolean {
  const code = char.charCodeAt(0);
  return code >= 0xAC00 && code <= 0xD7A3;
}

/** Common Korean particles that follow names. */
const PARTICLES = "와|과|의|은|는|이|가|을|를|에|에게|한테|께|도|만|부터|까지|처럼|같이|보다|로|으로|랑|이랑";

/**
 * Build regex from surnames. Matches surname + 1-2 hangul chars.
 * Preceded by whitespace/start. Followed by particle, whitespace, delimiter, or end.
 */
function buildNameRegex(): RegExp {
  const surnames = TOP_SURNAMES.join("|");
  // Match surname + 1-2 Hangul given name chars, followed by particle or boundary
  return new RegExp(
    `(?<=^|[\\s,;:()\\[\\]{}])(?:${surnames})[가-힣]{1,2}(?=(?:${PARTICLES})|$|[\\s,;:()\\[\\]{}])`,
    "g",
  );
}

const NAME_REGEX = buildNameRegex();

/**
 * Common Korean words that start with surname chars but are NOT names.
 * Reduces false positives from the heuristic name detector.
 */
const COMMON_WORD_EXCLUSIONS = new Set([
  // 오 (surname)
  "오늘", "오전", "오후", "오른",
  // 전 (surname)
  "전화", "전체", "전부", "전달", "전자", "전국", "전문", "전혀",
  // 서 (surname)
  "서버", "서류", "서비", "서울",
  // 주 (surname)
  "주소", "주문", "주요", "주의", "주간", "주말",
  // 한 (surname)
  "한국", "한번", "한편",
  // 고 (surname)
  "고객",
  // 최 (surname)
  "최근", "최대", "최소", "최초",
  // 공 (surname)
  "공지", "공유", "공간",
  // 방 (surname)
  "방법", "방금", "방문",
  // 구 (surname)
  "구매",
  // 남 (surname)
  "남은", "남자",
  // 문 (surname)
  "문의", "문서", "문제",
  // 신 (surname)
  "신청", "신규",
  // 배 (surname)
  "배송",
  // 차 (surname)
  "차이",
  // 안 (surname)
  "안내", "안전",
  // 성 (surname)
  "성공",
  // 강 (surname)
  "강화",
  // 임 (surname)
  "임시",
  // 원 (surname)
  "원래",
]);

export function detectName(text: string): PIIDetection[] {
  const results: PIIDetection[] = [];
  let match: RegExpExecArray | null;

  NAME_REGEX.lastIndex = 0;
  while ((match = NAME_REGEX.exec(text)) !== null) {
    const name = match[0];
    // Validate all characters are Hangul
    if ([...name].every(isHangul) && name.length >= 2 && name.length <= 3) {
      // Skip common Korean words that are not names
      if (COMMON_WORD_EXCLUSIONS.has(name)) continue;

      results.push({
        type: "NAME",
        value: name,
        start: match.index,
        end: match.index + name.length,
        confidence: 0.6, // Heuristic — lower confidence
      });
    }
  }

  return results;
}