/**
 * CSV 다운로드 유틸리티
 * 참조: mda-react-front/src/widgets/rightMenu/ui/RightMenu.tsx (512-579)
 */
import { Polygon } from 'ol/geom';
import { shipTypeMap } from '../assets/data/shiptype';
import { SHIP_KIND_LABELS, SIGNAL_SOURCE_LABELS } from '../types/constants';

// 해구도 데이터 캐시 (첫 호출 시만 로딩)
let trenchCache = null;

/**
 * 해구도 폴리곤 데이터 로딩 (동적 import, 캐시)
 */
async function loadTrenchData() {
  if (trenchCache) return trenchCache;
  const data = await import('../assets/data/largeTrench.json');
  const geojson = data.default || data;
  trenchCache = geojson.features.map((f) => ({
    zoneName: f.properties.zone_name,
    polygon: new Polygon(f.geometry.coordinates),
  }));
  return trenchCache;
}

/**
 * 선박 좌표 → 해구도 번호 일괄 조회
 * @param {Array} ships - 선박 배열 (longitude, latitude 필드 필요)
 * @returns {Map<number, string>} index → zone_name 매핑
 */
async function lookupTrenchNumbers(ships) {
  const trenchData = await loadTrenchData();
  const result = new Map();

  ships.forEach((ship, idx) => {
    const lon = parseFloat(ship.longitude);
    const lat = parseFloat(ship.latitude);
    if (isNaN(lon) || isNaN(lat)) {
      result.set(idx, 'X');
      return;
    }

    let found = false;
    for (const { zoneName, polygon } of trenchData) {
      if (polygon.intersectsCoordinate([lon, lat])) {
        result.set(idx, zoneName);
        found = true;
        break;
      }
    }
    if (!found) {
      result.set(idx, 'X');
    }
  });

  return result;
}

/**
 * 수신시간 포맷 변환
 * "YYYYMMDDHHmmss" → "YYYY-MM-DD HH:mm:ss"
 */
function formatRecvDateTime(raw) {
  if (!raw || raw.length < 14) return raw || '';
  return `${raw.slice(0, 4)}-${raw.slice(4, 6)}-${raw.slice(6, 8)} ${raw.slice(8, 10)}:${raw.slice(10, 12)}:${raw.slice(12, 14)}`;
}

/**
 * CSV 안전 필드 (쌍따옴표 감싸기)
 */
function csvField(val) {
  const str = val == null ? '' : String(val);
  return `"${str.replace(/"/g, '""')}"`;
}

/**
 * CSV 문자열 생성
 * @param {Array} ships - 선박 배열
 * @param {Map} trenchMap - index → zone_name 매핑
 * @returns {string} CSV 문자열 (BOM 포함)
 */
function buildCsvString(ships, trenchMap) {
  const BOM = '\uFEFF';
  const headers = [
    '타겟ID', '선박명', '선종/기종', '선종/기종-유형', '신호',
    'SOG', 'COG', '경도', '위도', '흘수', '수신시간', '해구도',
  ];

  const rows = ships.map((ship, idx) => {
    const fields = [
      csvField(ship.downloadTargetId),
      csvField(ship.shipName),
      csvField(SHIP_KIND_LABELS[ship.signalKindCode] || ship.signalKindCode),
      csvField(shipTypeMap.get(String(ship.shipType)) || ship.shipType),
      csvField(SIGNAL_SOURCE_LABELS[ship.signalSourceCode] || ship.signalSourceCode),
      csvField(ship.sog),
      csvField(ship.cog),
      csvField(ship.longitude),
      csvField(ship.latitude),
      csvField(ship.draught),
      csvField(formatRecvDateTime(ship.receivedTime)),
      csvField(trenchMap.get(idx) || 'X'),
    ];
    return fields.join(',');
  });

  return BOM + headers.map(csvField).join(',') + '\n' + rows.join('\n');
}

/**
 * CSV 다운로드 트리거
 * @param {Array} ships - getDownloadShips()에서 반환된 선박 배열
 */
export async function downloadShipCsv(ships) {
  const trenchMap = await lookupTrenchNumbers(ships);
  const csvString = buildCsvString(ships, trenchMap);

  const blob = new Blob([csvString], { type: 'text/csv;charset=utf-8;' });
  const url = URL.createObjectURL(blob);

  const now = new Date();
  const pad = (n) => String(n).padStart(2, '0');
  const fileName = `ship_download_${now.getFullYear()}${pad(now.getMonth() + 1)}${pad(now.getDate())}_${pad(now.getHours())}${pad(now.getMinutes())}${pad(now.getSeconds())}.csv`;

  const link = document.createElement('a');
  link.href = url;
  link.download = fileName;
  document.body.appendChild(link);
  link.click();
  document.body.removeChild(link);
  URL.revokeObjectURL(url);
}