// Guest-mode local GPX viewer — no backend, no auth required.
const LocalViewer = (() => {
  let tracks = {};   // id → { data: {segments,meta}, visible: bool }
  let nextId = 0;
  let currentId = null;   // track shown in info panel / elevation chart

  // ===== Public =====

  function init() {
    setupSidebar();
    setupMapDrop();
  }

  // ===== Sidebar =====

  function setupSidebar() {
    // Replace logged-in actions with a simple "Open GPX" button
    document.getElementById('browser-actions').innerHTML = `
      <button id="local-open-btn" class="action-btn">Open GPX</button>
      <input type="file" id="local-file-input" accept=".gpx" multiple style="display:none">
    `;
    document.getElementById('local-open-btn').addEventListener('click', () => {
      document.getElementById('local-file-input').click();
    });
    document.getElementById('local-file-input').addEventListener('change', (e) => {
      handleFiles(Array.from(e.target.files));
      e.target.value = '';
    });

    // Clear breadcrumb — not relevant in guest mode
    document.getElementById('breadcrumb').innerHTML =
      '<span style="color:var(--color-text-lighter);font-size:12px">Local viewer</span>';

    renderList();
  }

  // ===== Map drop zone =====

  function setupMapDrop() {
    const mc = document.getElementById('map-container');
    mc.addEventListener('dragover', (e) => {
      if (e.dataTransfer.types.includes('Files')) {
        e.preventDefault();
        mc.classList.add('drag-over');
      }
    });
    mc.addEventListener('dragleave', (e) => {
      if (!mc.contains(e.relatedTarget)) mc.classList.remove('drag-over');
    });
    mc.addEventListener('drop', (e) => {
      e.preventDefault();
      mc.classList.remove('drag-over');
      const files = Array.from(e.dataTransfer.files)
        .filter(f => f.name.toLowerCase().endsWith('.gpx'));
      if (files.length) handleFiles(files);
    });
  }

  // ===== File loading =====

  async function handleFiles(files) {
    for (const file of files) {
      try {
        const text = await file.text();
        const data = parseGPX(text, file.name);
        const id = 'local_' + (nextId++);
        tracks[id] = { data, visible: false };
        toggleTrack(id);    // open immediately
      } catch (e) {
        showToast('Error reading ' + file.name + ': ' + e.message, 'error');
      }
    }
  }

  // ===== Track toggling =====

  function toggleTrack(id) {
    const entry = tracks[id];
    if (!entry) return;

    if (entry.visible) {
      MapView.removeTrack(id);
      entry.visible = false;
      if (currentId === id) {
        currentId = null;
        MapView.setCurrentTrack(null);
        document.getElementById('track-info-panel').style.display = 'none';
        if (typeof Elevation !== 'undefined') Elevation.clear();
      }
    } else {
      MapView.addTrack(entry.data, id);
      MapView.fitTrack(id);
      MapView.setCurrentTrack(id);
      entry.visible = true;
      currentId = id;
      showTrackInfo(entry.data.meta);
      if (typeof Elevation !== 'undefined') {
        const pts = MapView.getTrackPoints(id);
        if (pts) Elevation.setTrack(pts);
      }
    }
    renderList();
  }

  function removeTrack(id) {
    if (tracks[id]?.visible) MapView.removeTrack(id);
    if (currentId === id) {
      currentId = null;
      MapView.setCurrentTrack(null);
      document.getElementById('track-info-panel').style.display = 'none';
      if (typeof Elevation !== 'undefined') Elevation.clear();
    }
    delete tracks[id];
    renderList();
  }

  // ===== Rendering =====

  function renderList() {
    const list = document.getElementById('browser-list');
    const ids = Object.keys(tracks);

    if (ids.length === 0) {
      list.innerHTML = '<div class="empty-list">Open a GPX file or drop it onto the map.</div>';
      return;
    }

    let html = '';
    for (const id of ids) {
      const { data, visible } = tracks[id];
      const meta = data.meta;
      const dist = meta.totalDistance ? formatDistance(meta.totalDistance) : '';
      html += `<div class="tree-item track-item${visible ? ' local-active' : ''}"
        data-id="${escAttr(id)}" style="padding-left:12px">
        <span class="item-icon">🗺️</span>
        <span class="item-name">${escHtml(meta.name)}</span>
        <span class="item-meta">${dist}</span>
        <span class="item-actions">
          <button class="item-btn local-remove-btn" data-id="${escAttr(id)}" title="Remove">🗑️</button>
        </span>
      </div>`;
    }
    list.innerHTML = html;

    list.querySelectorAll('.track-item').forEach(el => {
      el.addEventListener('click', (e) => {
        if (e.target.closest('.item-actions')) return;
        toggleTrack(el.dataset.id);
      });
    });
    list.querySelectorAll('.local-remove-btn').forEach(btn => {
      btn.addEventListener('click', (e) => {
        e.stopPropagation();
        removeTrack(btn.dataset.id);
      });
    });
  }

  // ===== Track info panel =====

  function showTrackInfo(meta) {
    if (!meta) return;
    document.getElementById('track-info-content').innerHTML = `
      <h3>${escHtml(meta.name || 'Track')}</h3>
      <div class="info-row"><label>Distance</label><span>${formatDistance(meta.totalDistance)}</span></div>
      <div class="info-row"><label>Points</label><span>${meta.pointCount || 0}</span></div>
      ${meta.trackDate ? `<div class="info-row"><label>Date</label><span>${formatDate(meta.trackDate)}</span></div>` : ''}
    `;
    const panel = document.getElementById('track-info-panel');
    panel.style.display = 'block';
    document.getElementById('track-info-close').onclick = () => { panel.style.display = 'none'; };
  }

  // ===== GPX parsing =====

  function haversine(lat1, lon1, lat2, lon2) {
    const R = 6371000;
    const dLat = (lat2 - lat1) * Math.PI / 180;
    const dLon = (lon2 - lon1) * Math.PI / 180;
    const a = Math.sin(dLat / 2) ** 2 +
              Math.cos(lat1 * Math.PI / 180) * Math.cos(lat2 * Math.PI / 180) *
              Math.sin(dLon / 2) ** 2;
    return R * 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
  }

  function parseGPX(xmlText, filename) {
    const doc = new DOMParser().parseFromString(xmlText, 'application/xml');
    if (doc.querySelector('parsererror')) throw new Error('Invalid GPX XML');

    const nameNode = doc.querySelector('trk > name, rte > name, metadata > name');
    const name = nameNode ? nameNode.textContent.trim()
                          : filename.replace(/\.gpx$/i, '');

    const segments = [];
    let trackDate = null;

    // Standard tracks (trkseg/trkpt)
    for (const seg of doc.querySelectorAll('trkseg')) {
      const pts = parsePts(seg.querySelectorAll('trkpt'));
      if (pts.length) {
        if (!trackDate && pts[0][3]) trackDate = pts[0][3];
        segments.push(pts);
      }
    }

    // Routes as fallback (rte/rtept)
    if (segments.length === 0) {
      for (const rte of doc.querySelectorAll('rte')) {
        const pts = parsePts(rte.querySelectorAll('rtept'));
        if (pts.length) segments.push(pts);
      }
    }

    if (segments.length === 0) throw new Error('No track points found');

    // Compute totals
    let totalDistance = 0;
    let pointCount = 0;
    for (const seg of segments) {
      pointCount += seg.length;
      for (let i = 1; i < seg.length; i++) {
        totalDistance += haversine(seg[i - 1][0], seg[i - 1][1], seg[i][0], seg[i][1]);
      }
    }

    return { segments, meta: { name, totalDistance, pointCount, trackDate } };
  }

  function parsePts(nodeList) {
    const pts = [];
    for (const pt of nodeList) {
      const lat = parseFloat(pt.getAttribute('lat'));
      const lon = parseFloat(pt.getAttribute('lon'));
      if (isNaN(lat) || isNaN(lon)) continue;
      const eleNode  = pt.querySelector('ele');
      const timeNode = pt.querySelector('time');
      const ele  = eleNode  ? parseFloat(eleNode.textContent)  : null;
      const time = timeNode ? timeNode.textContent              : null;
      pts.push([lat, lon, (ele != null && !isNaN(ele)) ? ele : null, time]);
    }
    return pts;
  }

  return { init };
})();