const state = { stations: [], query: '', searchText: '', locationFilter: { province: '', city: '', district: '' }, suggestions: [], activeSuggestion: -1, searchDebounce: null, stationFilter: 'all', selected: null, userLocation: null, map: null, markers: [], userMarker: null, pitch: true };

document.addEventListener('DOMContentLoaded', () => { initClock(); initMap(); loadStations(); });
document.addEventListener('pointerdown', event => { if (!event.target?.closest?.('.map-explore-toolbar')) closeStationSearchSuggestions(); });

async function loadStations() {
  setStatus('正在同步加氢站数据…');
  try {
    const response = await fetch('/api/stations', { headers: { Accept: 'application/json' } });
    const payload = await response.json();
    if (!response.ok || payload.status !== 'ok') throw new Error(payload.message || `HTTP ${response.status}`);
    state.stations = payload.stations.filter(hasCoordinates);
    updateSummary(payload.summary);
    setStatus(`站点数据已同步 · ${formatNumber(payload.summary.totalStations)} 座加氢站 · ${payload.asOf}`);
    render();
  } catch (error) {
    console.error('station directory refresh failed', error);
    setStatus('站点数据同步失败 · 将自动重试', true);
  }
}

function initMap() {
  if (typeof AMap === 'undefined') { setStatus('地图组件加载失败', true); return; }
  state.map = new AMap.Map('amapContainer', { zoom: 4.8, center: [108.948024, 34.263161], viewMode: '3D', pitch: 30, mapStyle: 'amap://styles/light', showBuildingBlock: false, showLabel: true });
  state.map.on('complete', render);
  state.map.on('zoomend', render);
  state.map.on('moveend', render);
}

function updateSummary(summary) {
  const total = Number(summary.totalStations || 0), partner = Number(summary.cooperativeStations || 0), external = Math.max(0, total - partner);
  setHTML('kpiTotal', `${formatNumber(total)} <small>座</small>`); setHTML('kpiPartner', `${formatNumber(partner)} <small>座</small>`);
  setHTML('statusTotal', `${formatNumber(total)} <small>座</small>`); setHTML('statusPartner', `${formatNumber(partner)} <small>座</small>`); setHTML('statusExternal', `${formatNumber(external)} <small>座</small>`);
  document.getElementById('partnerSegment').style.width = `${total ? partner * 100 / total : 0}%`;
  document.getElementById('externalSegment').style.width = `${total ? external * 100 / total : 0}%`;
}

function stationMatchesQuery(station, query = state.query) { const needle = normalize(query); return !needle || [station.name, station.shortName, station.address].some(value => normalize(value).includes(needle)); }
function stationMatchesLocation(station) { const filter = state.locationFilter; return (!filter.province || station.province === filter.province) && (!filter.city || station.city === filter.city) && (!filter.district || stationDistrictName(station) === filter.district); }
function stationTypeScope() { return state.stations.filter(station => state.stationFilter !== 'partner' || station.cooperative); }
function filteredStations() { return stationTypeScope().filter(station => stationMatchesLocation(station) && stationMatchesQuery(station)); }
function stationSearchScore(station, query) {
  const fields = [station.name, station.shortName, station.province, station.city, station.district, station.address].filter(Boolean);
  for (const value of fields) { const text = normalize(value); if (text.includes(query)) return 3; const pinyin = toPinyin(value); if (pinyin.includes(query) || initials(pinyin).includes(query)) return 2; }
  return 0;
}
function toPinyin(value) { const converter = globalThis.pinyinPro?.pinyin; return converter ? normalize(converter(String(value), { toneType: 'none', separator: ' ' })) : ''; }
function initials(value) { return String(value).split(/\s+/).map(word => word[0] || '').join(''); }
function normalize(value) { return String(value || '').trim().toLocaleLowerCase(); }
function hasCoordinates(station) { return Number.isFinite(Number(station.longitude)) && Number.isFinite(Number(station.latitude)); }
function coords(station) { return [Number(station.longitude), Number(station.latitude)]; }
function stationDistrictName(station) { if (station?.district) return String(station.district).trim(); let address = String(station?.address || '').trim(); for (const prefix of [station?.province, station?.city]) { const normalized = String(prefix || '').trim(); if (normalized) address = address.split(normalized).join(''); } return address.match(/^(.{2,10}?(?:区|县|旗|市))/)?.[1] || ''; }

function render() { renderMarkers(); renderList(); }
function renderMarkers() {
  if (!state.map || typeof AMap === 'undefined') return;
  state.markers.forEach(marker => marker.remove()); state.markers = [];
  const nodes = stationNodes(true);
  nodes.forEach(node => {
    const point = node.kind === 'station', content = document.createElement('div');
    content.className = 'province-info-badge-wrap';
    const label = point ? (node.cooperative ? 'H₂ · 合作' : '') : `${formatNumber(node.count)} 座`;
    const subline = point ? node.adminPath : '';
    content.innerHTML = `<div class="province-info-card${point ? ` is-station-point${node.cooperative ? '' : ' is-external'}${state.selected?.id === node.station.id ? ' is-selected' : ''}` : ''}"><div class="p-head"><span class="p-name">${escapeHTML(node.name)}</span>${label ? `<span class="p-total">${escapeHTML(label)}</span>` : ''}</div>${subline ? `<div class="p-sub">${escapeHTML(subline)}</div>` : ''}</div>`;
    const marker = new AMap.Marker({ position: node.lnglat, content, offset: new AMap.Pixel(-30, -12), title: node.name, zIndex: point ? 20 : 10 });
    marker.on('click', () => { if (point) selectStation(node.station, true); else state.map.setZoomAndCenter(nextZoomForLevel(node.level), node.lnglat); }); marker.setMap(state.map); state.markers.push(marker);
  });
  renderUserMarker();
}
function stationHierarchyLevel(zoom = state.map?.getZoom?.() || 0) {
  if (normalize(state.query)) return 'station';
  if (zoom < 7) return 'province';
  if (zoom < 11) return 'city';
  return 'station';
}
function stationGroupName(station, level) {
  const raw = (level === 'province' ? station.province : station.city) || '未标注区域';
  return level === 'province' ? String(raw).replace(/(壮族|回族|维吾尔)?自治区$|特别行政区$|省$|市$/, '') : String(raw).replace(/自治州$|地区$|林区$|[盟区县市]$/, '');
}
function buildStationNodes(stations = filteredStations(), level = stationHierarchyLevel()) {
  if (level === 'station') return stations.map(station => ({ id: `station-${station.id}`, kind: 'station', level, name: station.name || station.shortName || '未命名站点', lnglat: coords(station), station, count: 1, online: station.cooperative ? 1 : 0, adminPath: stationRegion(station), detail: [stationRegion(station), station.address].filter(Boolean).join(' · '), cooperative: Boolean(station.cooperative) }));
  const grouped = new Map();
  for (const station of stations) {
    const key = (level === 'province' ? station.province : `${station.province || ''}/${station.city || ''}`) || 'UNSPECIFIED';
    const group = grouped.get(key) || { kind: level === 'province' ? 'stationProvince' : 'stationCity', level, name: stationGroupName(station, level), lng: 0, lat: 0, count: 0, online: 0, stations: [] };
    group.lng += Number(station.longitude); group.lat += Number(station.latitude); group.count += 1; group.online += station.cooperative ? 1 : 0; group.stations.push(station); grouped.set(key, group);
  }
  return [...grouped.values()].map((group, index) => ({ ...group, id: `station-${level}-${index}`, lnglat: [group.lng / group.count, group.lat / group.count], detail: group.stations.slice(0, 5).map(station => station.name).join('、') }));
}
function currentMapBounds() { const bounds = state.map?.getBounds?.(), sw = bounds?.getSouthWest?.(), ne = bounds?.getNorthEast?.(); if (!sw || !ne) return null; return { west: sw.getLng(), south: sw.getLat(), east: ne.getLng(), north: ne.getLat() }; }
function nodesInsideCurrentMapBounds(nodes) { const bounds = currentMapBounds(); if (!bounds) return nodes; return nodes.filter(node => node.lnglat[0] >= bounds.west && node.lnglat[0] <= bounds.east && node.lnglat[1] >= bounds.south && node.lnglat[1] <= bounds.north); }
function stationNodes(visibleOnly = false) { const nodes = buildStationNodes(); return visibleOnly && !normalize(state.query) ? nodesInsideCurrentMapBounds(nodes) : nodes; }
function stationViewportSummary() { const level = stationHierarchyLevel(), allNodes = stationNodes(false), visibleNodes = normalize(state.query) ? allNodes : nodesInsideCurrentMapBounds(allNodes); return { level, allNodes, visibleNodes }; }
function nextZoomForLevel(level) { return level === 'province' ? 7.2 : level === 'city' ? 11.2 : 14; }

function renderList() {
  const box = document.getElementById('stationList'); if (!box) return;
  const { level, allNodes, visibleNodes } = stationViewportSummary();
  const display = [...visibleNodes].sort(compareNodes);
  document.getElementById('resultMeta').textContent = `视野 ${formatNumber(visibleNodes.reduce((sum, node) => sum + node.count, 0))} / ${formatNumber(filteredStations().length)}`;
  document.getElementById('rankViewportMeta').textContent = `当前视野 ${formatNumber(visibleNodes.length)} · 全部 ${formatNumber(allNodes.length)}`;
  document.getElementById('panelRankTitle').textContent = state.userLocation && level === 'station' ? `附近${state.stationFilter === 'partner' ? '合作' : ''}加氢站` : level === 'province' ? '加氢站省份 TOP 排名' : level === 'city' ? '加氢站城市 TOP 排名' : '加氢站 TOP 排名';
  if (!display.length) { box.innerHTML = '<div class="rank-empty">未找到匹配站点<br>请尝试名称、地址、城市或拼音首字母</div>'; return; }
  box.innerHTML = display.slice(0, 100).map((node, index) => { const distance = node.kind === 'station' ? stationDistance(node.station) : Number.POSITIVE_INFINITY, partnerTag = node.kind === 'station' && node.cooperative ? '<span class="station-list-partner-tag">合作</span>' : ''; return `<button type="button" class="rank-glass-row${node.kind === 'station' && state.selected?.id === node.station.id ? ' is-selected' : ''}" data-node-id="${escapeAttribute(node.id)}"><span class="r-badge ${index < 3 ? `r-top${index + 1}` : ''}">${index + 1}</span><span class="r-name">${partnerTag}<span class="station-list-name">${escapeHTML(node.name)}</span></span><span class="r-val">${Number.isFinite(distance) ? `${formatNumber(distance, 1)} km` : `${formatNumber(node.count)} 座`}</span></button>`; }).join('');
  box.querySelectorAll('[data-node-id]').forEach(button => button.addEventListener('click', () => { const node = display.find(item => item.id === button.dataset.nodeId); if (node?.kind === 'station') selectStation(node.station, true); else if (node) state.map?.setZoomAndCenter(nextZoomForLevel(node.level), node.lnglat); }));
}
function compareNodes(left, right) { if (state.userLocation && left.kind === 'station' && right.kind === 'station') return stationDistance(left.station) - stationDistance(right.station); return right.count - left.count || String(left.name || '').localeCompare(String(right.name || ''), 'zh-CN'); }

function fuzzySearchScore(value, query) {
  const needle = normalize(query); if (!needle) return 4;
  const text = normalize(value); if (text === needle) return 0; if (text.startsWith(needle)) return 1; if (text.includes(needle)) return 2;
  const pinyin = toPinyin(value); if (pinyin === needle || pinyin.startsWith(needle) || initials(pinyin).startsWith(needle)) return 3;
  return pinyin.includes(needle) || initials(pinyin).includes(needle) ? 4 : Number.POSITIVE_INFINITY;
}
function compactPath(parts) { return parts.filter(Boolean).join(' · '); }
function stationLocationOptions() {
  const groups = new Map();
  const add = (level, station) => {
    const province = station.province || '', city = station.city || '', district = station.district || '';
    const key = level === 'province' ? `province|${province}` : level === 'city' ? `city|${province}|${city}` : `district|${province}|${city}|${district}`;
    if (!groups.has(key)) groups.set(key, { type: 'location', level, province, city, district, stations: [] });
    groups.get(key).stations.push(station);
  };
  for (const station of stationTypeScope()) { const district = stationDistrictName(station); if (station.province) add('province', station); if (station.province && station.city) add('city', station); if (station.province && station.city && district) add('district', { ...station, district }); }
  return [...groups.values()].map(option => {
    const target = option.level === 'province' ? option.province : option.level === 'city' ? option.city : option.district;
    const longitude = option.stations.reduce((sum, station) => sum + Number(station.longitude), 0) / option.stations.length;
    const latitude = option.stations.reduce((sum, station) => sum + Number(station.latitude), 0) / option.stations.length;
    return { ...option, label: stationGroupName({ province: target, city: target }, option.level === 'province' ? 'province' : 'city'), path: compactPath([option.province, option.city, option.district]), lnglat: [longitude, latitude] };
  });
}
function stationLocationSuggestions(query) {
  return stationLocationOptions().map(option => ({ ...option, score: Math.min(fuzzySearchScore(option.label, query), fuzzySearchScore(option.path, query)) }))
    .filter(option => Number.isFinite(option.score)).sort((left, right) => left.score - right.score || left.label.localeCompare(right.label, 'zh-CN')).slice(0, normalize(query) ? 8 : 6);
}
function stationEntitySuggestions(query) {
  if (!normalize(query)) return [];
  return filteredStations().map(station => ({ type: 'station', station, score: stationSearchScore(station, query) }))
    .filter(item => item.score > 0).sort((left, right) => right.score - left.score || String(left.station.name || '').localeCompare(String(right.station.name || ''), 'zh-CN')).slice(0, 5);
}
function renderStationSearchSuggestions() {
  const box = document.getElementById('stationSearchSuggestions'); if (!box || box.hidden) return;
  const locations = stationLocationSuggestions(state.searchText), stations = stationEntitySuggestions(state.searchText);
  state.suggestions = [...locations, ...stations]; state.activeSuggestion = Math.min(state.activeSuggestion, state.suggestions.length - 1);
  if (!state.suggestions.length) { box.innerHTML = '<span class="suggestion-empty">未找到匹配的位置或站点</span>'; return; }
  let html = '';
  if (locations.length) html += `<span class="suggestion-section-label">位置</span>${locations.map((item, index) => `<button type="button" class="explore-suggestion${index === state.activeSuggestion ? ' is-active' : ''}" role="option" onclick="selectStationSearchSuggestion(${index})"><span class="suggestion-symbol is-location">⌖</span><span class="suggestion-copy"><strong>${escapeHTML(item.label)}</strong><small>${escapeHTML(item.path)}</small></span><span class="suggestion-kind">地点</span></button>`).join('')}`;
  if (stations.length) html += `<span class="suggestion-section-label">加氢站</span>${stations.map((item, offset) => { const index = locations.length + offset, station = item.station; return `<button type="button" class="explore-suggestion${index === state.activeSuggestion ? ' is-active' : ''}" role="option" onclick="selectStationSearchSuggestion(${index})"><span class="suggestion-symbol">H₂</span><span class="suggestion-copy"><strong>${escapeHTML(station.name || station.shortName || '未命名站点')}</strong><small>${escapeHTML(stationRegion(station) || station.address || '')}</small></span><span class="suggestion-kind">加氢站</span></button>`; }).join('')}`;
  box.innerHTML = html;
}
function openStationSearchSuggestions() { const box = document.getElementById('stationSearchSuggestions'); if (!box) return; box.hidden = false; renderStationSearchSuggestions(); }
function closeStationSearchSuggestions() { const box = document.getElementById('stationSearchSuggestions'); if (box) box.hidden = true; state.activeSuggestion = -1; }
function focusSearchResults() {
  const stations = filteredStations(); if (!state.map || !stations.length) return;
  const longitudes = stations.map(station => Number(station.longitude)), latitudes = stations.map(station => Number(station.latitude));
  const center = [(Math.min(...longitudes) + Math.max(...longitudes)) / 2, (Math.min(...latitudes) + Math.max(...latitudes)) / 2];
  const span = Math.max(Math.max(...longitudes) - Math.min(...longitudes), Math.max(...latitudes) - Math.min(...latitudes));
  const zoom = stations.length === 1 ? 14 : span < .1 ? 13 : span < .35 ? 11.5 : span < 1 ? 9.5 : 7;
  state.map.setZoomAndCenter(zoom, center);
}
function handleStationSearchInput(value) { state.searchText = value; document.getElementById('clearSearch').hidden = !normalize(value); state.activeSuggestion = -1; openStationSearchSuggestions(); window.clearTimeout(state.searchDebounce); state.searchDebounce = window.setTimeout(() => { state.query = value; state.selected = null; closeDetail(); render(); if (normalize(value)) focusSearchResults(); }, 180); }
function selectStationSearchSuggestion(index) {
  const item = state.suggestions[index]; if (!item) return;
  if (item.type === 'location') { state.locationFilter = { province: item.province, city: item.city, district: item.district }; state.query = ''; state.searchText = ''; document.getElementById('stationSearch').value = ''; document.getElementById('clearSearch').hidden = true; state.map?.setZoomAndCenter(item.level === 'province' ? 7.2 : item.level === 'city' ? 10.5 : 13, item.lnglat); document.getElementById('selectedRegionHint').textContent = `视角: ${item.path}`; closeStationSearchSuggestions(); render(); return; }
  closeStationSearchSuggestions(); selectStation(item.station, true);
}
function setStationFilter(filter) { if (!['all', 'partner'].includes(filter) || state.stationFilter === filter) return; state.stationFilter = filter; state.selected = null; closeDetail(); document.querySelectorAll('[data-station-filter]').forEach(button => button.classList.toggle('is-active', button.dataset.stationFilter === filter)); render(); renderStationSearchSuggestions(); }
function clearSearch() { window.clearTimeout(state.searchDebounce); document.getElementById('stationSearch').value = ''; state.query = ''; state.searchText = ''; state.locationFilter = { province: '', city: '', district: '' }; closeStationSearchSuggestions(); closeDetail(); resetMap(); render(); }
function handleSearchKeydown(event) { if (event.key === 'Escape') { closeStationSearchSuggestions(); event.currentTarget.blur(); return; } if (!['ArrowDown', 'ArrowUp', 'Enter'].includes(event.key)) return; const box = document.getElementById('stationSearchSuggestions'); if (box?.hidden) openStationSearchSuggestions(); if (event.key === 'Enter' && state.activeSuggestion >= 0) { event.preventDefault(); selectStationSearchSuggestion(state.activeSuggestion); return; } if (event.key !== 'Enter') { event.preventDefault(); const direction = event.key === 'ArrowDown' ? 1 : -1; state.activeSuggestion = (state.activeSuggestion + direction + state.suggestions.length) % Math.max(state.suggestions.length, 1); renderStationSearchSuggestions(); } }

function selectStation(station, fit = false) {
  if (!station) return; state.selected = station; if (fit) state.map?.setZoomAndCenter(14.5, coords(station));
  document.getElementById('detailName').textContent = station.name || station.shortName || '未命名站点'; document.getElementById('detailRegion').textContent = stationRegion(station);
  const cooperative = Boolean(station.cooperative), tag = document.getElementById('detailType'); tag.textContent = cooperative ? '合作站' : '外部站'; tag.classList.toggle('is-station', cooperative);
  const distance = stationDistance(station); document.getElementById('detailFields').innerHTML = `${detailField('站点状态', cooperative ? '合作站点' : '外部站点')}${detailField('行政区域', stationRegion(station))}${detailField('详细地址', station.address || '暂无详细地址', true)}${Number.isFinite(distance) ? detailField('距离我', `${formatNumber(distance, 1)} km`) : ''}`;
  document.getElementById('stationDetail').hidden = false; renderMarkers(); renderList();
}
function detailField(label, value, full = false) { return `<div class="detail-field${full ? ' is-full' : ''}"><dt>${escapeHTML(label)}</dt><dd>${escapeHTML(value)}</dd></div>`; }
function stationRegion(station) { return [station.province, station.city, stationDistrictName(station)].filter(value => value && value !== '[]').filter((value, index, list) => index === 0 || value !== list[index - 1]).join(' · '); }
function closeDetail() { const detail = document.getElementById('stationDetail'); if (detail) detail.hidden = true; }

function locateMe() { if (!navigator.geolocation) return locationFailed('当前设备不支持定位'); const button = document.getElementById('locateDeviceBtn'); button.disabled = true; button.classList.remove('is-error'); document.getElementById('locateDeviceLabel').textContent = '定位中'; navigator.geolocation.getCurrentPosition(position => { state.userLocation = wgs84ToGcj02(Number(position.coords.longitude), Number(position.coords.latitude)); button.disabled = false; button.classList.add('is-active'); document.getElementById('locateDeviceLabel').textContent = '已定位'; state.map?.setZoomAndCenter(13, state.userLocation); document.getElementById('selectedRegionHint').textContent = '视角: 我的位置附近'; render(); }, error => locationFailed(error?.code === 1 ? '请允许位置权限' : '定位失败'), { enableHighAccuracy: true, timeout: 10000, maximumAge: 30000 }); }
function locationFailed(label) { const button = document.getElementById('locateDeviceBtn'); button.disabled = false; button.classList.add('is-error'); document.getElementById('locateDeviceLabel').textContent = label; window.setTimeout(() => { button.classList.remove('is-error'); document.getElementById('locateDeviceLabel').textContent = state.userLocation ? '已定位' : '定位'; }, 2600); }
function renderUserMarker() { if (!state.map || !state.userLocation || typeof AMap === 'undefined') return; if (state.userMarker) state.userMarker.remove(); const content = document.createElement('div'); content.className = 'user-location-marker'; state.userMarker = new AMap.Marker({ position: state.userLocation, content, offset: new AMap.Pixel(-9, -9), zIndex: 50 }); state.userMarker.setMap(state.map); }
function stationDistance(station) { return state.userLocation ? distanceKm(state.userLocation, coords(station)) : Number.POSITIVE_INFINITY; }
function distanceKm(origin, target) { const radians = value => value * Math.PI / 180, dLat = radians(target[1] - origin[1]), dLng = radians(target[0] - origin[0]), a = Math.sin(dLat / 2) ** 2 + Math.cos(radians(origin[1])) * Math.cos(radians(target[1])) * Math.sin(dLng / 2) ** 2; return 6371 * 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a)); }
function resetMap() { state.map?.setZoomAndCenter(4.8, [108.948024, 34.263161]); state.map?.setPitch(30); document.getElementById('selectedRegionHint').textContent = '视角: 全国加氢站网络'; }
function toggleMapPitch() { state.pitch = !state.pitch; state.map?.setPitch(state.pitch ? 30 : 0); }
function setTheme(theme) { document.body.className = theme; document.querySelectorAll('.bw-btn').forEach(button => button.classList.remove('active')); document.querySelector(theme === 'theme-white' ? '.theme-white-btn' : '.theme-dark-btn')?.classList.add('active'); state.map?.setMapStyle(theme === 'theme-white' ? 'amap://styles/light' : 'amap://styles/darkblue'); }
function navigateToStation() { if (!state.selected) return; const [lng, lat] = coords(state.selected), name = encodeURIComponent(state.selected.name || state.selected.shortName || '加氢站'); const overlay = document.getElementById('navigationOverlay'); overlay.hidden = false; window.setTimeout(() => window.location.assign(`https://uri.amap.com/navigation?to=${lng.toFixed(6)},${lat.toFixed(6)},${name}&mode=car&coordinate=gaode&callnative=1`), 140); }
function setStatus(text, error = false) { const status = document.getElementById('mapStatusText'); if (status) status.textContent = text; status?.parentElement?.classList.toggle('is-error', error); }
function setHTML(id, value) { const element = document.getElementById(id); if (element) element.innerHTML = value; }
function formatNumber(value, digits = 0) { return Number(value || 0).toLocaleString('zh-CN', { maximumFractionDigits: digits, minimumFractionDigits: digits }); }
function escapeHTML(value) { return String(value ?? '').replace(/[&<>'"]/g, char => ({ '&': '&amp;', '<': '&lt;', '>': '&gt;', "'": '&#39;', '"': '&quot;' }[char])); }
function escapeAttribute(value) { return escapeHTML(value).replace(/`/g, '&#96;'); }
function initClock() { const clock = document.getElementById('clockTime'), update = () => { if (clock) clock.textContent = new Date().toLocaleTimeString('zh-CN', { hour12: false }); }; update(); window.setInterval(update, 1000); }
function wgs84ToGcj02(lng, lat) { if (lng < 72.004 || lng > 137.8347 || lat < .8293 || lat > 55.8271) return [lng, lat]; const transformLat = (x, y) => -100 + 2*x + 3*y + .2*y*y + .1*x*y + .2*Math.sqrt(Math.abs(x)) + (20*Math.sin(6*x*Math.PI)+20*Math.sin(2*x*Math.PI))*2/3 + (20*Math.sin(y*Math.PI)+40*Math.sin(y/3*Math.PI))*2/3 + (160*Math.sin(y/12*Math.PI)+320*Math.sin(y*Math.PI/30))*2/3; const transformLng = (x, y) => 300 + x + 2*y + .1*x*x + .1*x*y + .1*Math.sqrt(Math.abs(x)) + (20*Math.sin(6*x*Math.PI)+20*Math.sin(2*x*Math.PI))*2/3 + (20*Math.sin(x*Math.PI)+40*Math.sin(x/3*Math.PI))*2/3 + (150*Math.sin(x/12*Math.PI)+300*Math.sin(x/30*Math.PI))*2/3; const a = 6378245, ee = .00669342162296594323; let dLat = transformLat(lng-105, lat-35), dLng = transformLng(lng-105, lat-35); const radLat = lat / 180 * Math.PI, magic = 1 - ee * Math.sin(radLat) ** 2, sqrtMagic = Math.sqrt(magic); dLat = dLat * 180 / ((a * (1-ee)) / (magic * sqrtMagic) * Math.PI); dLng = dLng * 180 / (a / sqrtMagic * Math.cos(radLat) * Math.PI); return [lng + dLng, lat + dLat]; }