const Browser = (() => {
  let selectedDirId = null;  // used as upload context
  let expandedDirs = new Set();
  let dirContents = {};  // 'root' | dirId -> { dirs, tracks }
  let dirMeta = {};      // dirId -> { id, name, parentId }
  let dragTrackId = null;
  let dragTrackName = null;
  let allDirs = [];  // flat list for move dialog

  async function init() {
    document.getElementById('new-dir-btn').addEventListener('click', createDirPrompt);
    document.getElementById('upload-btn').addEventListener('click', () => {
      document.getElementById('file-input').click();
    });
    document.getElementById('file-input').addEventListener('change', handleFileUpload);
    setupDropZone();
    await reload();
  }

  async function reload() {
    const prevExpanded = new Set(expandedDirs);
    dirContents = {};
    dirMeta = {};

    await loadRootContents();

    // Re-fetch previously expanded dirs to restore tree state
    for (const dirId of prevExpanded) {
      try {
        const data = await API.getDir(dirId);
        dirMeta[data.id] = { id: data.id, name: data.name, parentId: data.parentId };
        dirContents[dirId] = { dirs: data.children || [], tracks: data.tracks || [] };
        (data.children || []).forEach(d => {
          dirMeta[d.id] = { id: d.id, name: d.name, parentId: dirId };
        });
      } catch (e) {
        expandedDirs.delete(dirId);
      }
    }

    renderBreadcrumb();
    renderTree();
  }

  async function loadRootContents() {
    const [dirs, tracks] = await Promise.all([
      API.getDirs(),
      API.getTracks('')
    ]);
    dirContents['root'] = { dirs, tracks };
    dirs.forEach(d => { dirMeta[d.id] = { id: d.id, name: d.name, parentId: null }; });
  }

  // ===== Breadcrumb =====

  function renderBreadcrumb() {
    const bc = document.getElementById('breadcrumb');
    const path = buildPath(selectedDirId);
    let html = '<span class="bc-item" data-id="null">Root</span>';
    for (const item of path) {
      html += ' <span class="bc-sep">›</span> ';
      html += `<span class="bc-item" data-id="${item.id}">${escHtml(item.name)}</span>`;
    }
    bc.innerHTML = html;
    bc.querySelectorAll('.bc-item').forEach(el => {
      el.addEventListener('click', () => {
        selectedDirId = el.dataset.id === 'null' ? null : parseInt(el.dataset.id);
        renderBreadcrumb();
        renderTree();
      });
    });
  }

  function buildPath(dirId) {
    if (dirId === null) return [];
    const result = [];
    let current = dirId;
    const seen = new Set();
    while (current !== null && current !== undefined && !seen.has(current)) {
      seen.add(current);
      const meta = dirMeta[current];
      if (!meta) break;
      result.unshift({ id: meta.id, name: meta.name });
      current = meta.parentId;
    }
    return result;
  }

  // ===== Tree Rendering =====

  function renderTree() {
    const list = document.getElementById('browser-list');
    const root = dirContents['root'];
    if (!root) {
      list.innerHTML = '<div class="loading">Loading...</div>';
      return;
    }
    let html = buildTreeHtml(root.dirs, root.tracks, 0);
    if (!html.trim()) {
      html = '<div class="empty-list">No files here. Upload a GPX or create a folder.</div>';
    }
    list.innerHTML = html;
    bindEvents(list);
  }

  function buildTreeHtml(dirs, tracks, depth) {
    let html = '';
    const baseIndent = depth * 16;

    for (const dir of dirs) {
      const isExpanded = expandedDirs.has(dir.id);
      const isSelected = selectedDirId === dir.id;
      html += `<div class="tree-item dir-item${isSelected ? ' selected' : ''}"
        data-id="${dir.id}" data-name="${escAttr(dir.name)}"
        style="padding-left:${12 + baseIndent}px" data-drop-target="true">
        <span class="expand-btn${isExpanded ? ' expanded' : ''}" data-expand="${dir.id}"></span>
        <span class="item-icon">📁</span>
        <span class="item-name">${escHtml(dir.name)}</span>
        <span class="item-date">${formatDate(dir.updatedAt)}</span>
        <span class="item-actions">
          <button class="item-btn rename-dir-btn" data-id="${dir.id}" data-name="${escAttr(dir.name)}" title="Rename">✏️</button>
          <button class="item-btn delete-dir-btn" data-id="${dir.id}" data-name="${escAttr(dir.name)}" title="Delete">🗑️</button>
        </span>
      </div>`;

      if (isExpanded) {
        const cached = dirContents[dir.id];
        if (cached) {
          html += buildTreeHtml(cached.dirs, cached.tracks, depth + 1);
        } else {
          html += `<div class="loading tree-loading" style="padding-left:${28 + baseIndent}px">Loading...</div>`;
        }
      }
    }

    for (const track of tracks) {
      const dist = track.totalDistance ? formatDistance(track.totalDistance) : '';
      html += `<div class="tree-item track-item" data-id="${track.id}" draggable="true"
        data-name="${escAttr(track.name)}" style="padding-left:${28 + baseIndent}px">
        <span class="item-icon">🗺️</span>
        <span class="item-name">${escHtml(track.name)}</span>
        <span class="item-meta">${dist}</span>
        <span class="item-date">${formatDate(track.trackDate || track.uploadDate)}</span>
        <span class="item-actions">
          <button class="item-btn view-track-btn" data-id="${track.id}" title="View on map">👁️</button>
          <button class="item-btn share-track-btn" data-id="${track.id}" title="Share">🔗</button>
          <button class="item-btn move-track-btn" data-id="${track.id}" data-name="${escAttr(track.name)}" title="Move">📂</button>
          <button class="item-btn delete-track-btn" data-id="${track.id}" data-name="${escAttr(track.name)}" title="Delete">🗑️</button>
        </span>
      </div>`;
    }

    return html;
  }

  // ===== Event Binding =====

  function bindEvents(container) {
    // Expand/collapse triangle
    container.querySelectorAll('.expand-btn[data-expand]').forEach(btn => {
      btn.addEventListener('click', async (e) => {
        e.stopPropagation();
        await toggleExpand(parseInt(btn.dataset.expand));
      });
    });

    // Dir click → select + zoom map to folder tracks
    container.querySelectorAll('.dir-item').forEach(el => {
      el.addEventListener('click', async (e) => {
        if (e.target.closest('.item-actions') || e.target.classList.contains('expand-btn')) return;
        await selectDir(parseInt(el.dataset.id));
      });
    });

    container.querySelectorAll('.rename-dir-btn').forEach(btn => {
      btn.addEventListener('click', (e) => {
        e.stopPropagation();
        renameDir(parseInt(btn.dataset.id), btn.dataset.name);
      });
    });

    container.querySelectorAll('.delete-dir-btn').forEach(btn => {
      btn.addEventListener('click', (e) => {
        e.stopPropagation();
        confirmDelete('directory', btn.dataset.name, () => deleteDir(parseInt(btn.dataset.id)));
      });
    });

    // Track click → open on map
    container.querySelectorAll('.track-item').forEach(el => {
      el.addEventListener('click', (e) => {
        if (e.target.closest('.item-actions')) return;
        openTrack(parseInt(el.dataset.id));
      });
    });

    container.querySelectorAll('.view-track-btn').forEach(btn => {
      btn.addEventListener('click', (e) => { e.stopPropagation(); openTrack(parseInt(btn.dataset.id)); });
    });

    container.querySelectorAll('.share-track-btn').forEach(btn => {
      btn.addEventListener('click', (e) => { e.stopPropagation(); shareTrack(parseInt(btn.dataset.id)); });
    });

    container.querySelectorAll('.move-track-btn').forEach(btn => {
      btn.addEventListener('click', (e) => {
        e.stopPropagation();
        showMoveDialog(parseInt(btn.dataset.id), btn.dataset.name);
      });
    });

    container.querySelectorAll('.delete-track-btn').forEach(btn => {
      btn.addEventListener('click', (e) => {
        e.stopPropagation();
        confirmDelete('track', btn.dataset.name, () => deleteTrack(parseInt(btn.dataset.id)));
      });
    });

    // Drag tracks
    container.querySelectorAll('.track-item[draggable="true"]').forEach(el => {
      el.addEventListener('dragstart', (e) => {
        dragTrackId = parseInt(el.dataset.id);
        dragTrackName = el.dataset.name;
        e.dataTransfer.effectAllowed = 'move';
        e.dataTransfer.setData('text/plain', String(dragTrackId));
        el.classList.add('dragging');
      });
      el.addEventListener('dragend', () => {
        el.classList.remove('dragging');
        container.querySelectorAll('.drag-target').forEach(d => d.classList.remove('drag-target'));
        dragTrackId = null;
        dragTrackName = null;
      });
    });

    // Drop targets (folders)
    container.querySelectorAll('.dir-item[data-drop-target]').forEach(el => {
      el._dragCount = 0;
      el.addEventListener('dragenter', (e) => {
        if (dragTrackId === null) return;
        e.preventDefault();
        el._dragCount = (el._dragCount || 0) + 1;
        el.classList.add('drag-target');
      });
      el.addEventListener('dragleave', () => {
        if (dragTrackId === null) return;
        el._dragCount = (el._dragCount || 1) - 1;
        if (el._dragCount <= 0) {
          el._dragCount = 0;
          el.classList.remove('drag-target');
        }
      });
      el.addEventListener('dragover', (e) => {
        if (dragTrackId === null) return;
        e.preventDefault();
        e.dataTransfer.dropEffect = 'move';
      });
      el.addEventListener('drop', (e) => {
        e.preventDefault();
        e.stopPropagation();
        el._dragCount = 0;
        el.classList.remove('drag-target');
        if (dragTrackId === null) return;
        const targetDirId = parseInt(el.dataset.id);
        const targetDirName = el.dataset.name;
        const trackId = dragTrackId;
        const trackName = dragTrackName;
        dragTrackId = null;
        dragTrackName = null;
        confirmMoveTrack(trackId, trackName, targetDirId, targetDirName);
      });
    });
  }

  // ===== Expand / Select =====

  async function toggleExpand(dirId) {
    if (expandedDirs.has(dirId)) {
      expandedDirs.delete(dirId);
      renderTree();
    } else {
      expandedDirs.add(dirId);
      if (!dirContents[dirId]) {
        renderTree(); // show loading placeholder
        try {
          const data = await API.getDir(dirId);
          dirMeta[data.id] = { id: data.id, name: data.name, parentId: data.parentId };
          dirContents[dirId] = { dirs: data.children || [], tracks: data.tracks || [] };
          (data.children || []).forEach(d => {
            dirMeta[d.id] = { id: d.id, name: d.name, parentId: dirId };
          });
        } catch (e) {
          showToast('Error: ' + e.message, 'error');
          expandedDirs.delete(dirId);
        }
      }
      renderTree();
    }
  }

  async function selectDir(dirId) {
    selectedDirId = dirId;
    renderBreadcrumb();
    renderTree();

    // Ensure contents loaded
    if (!dirContents[dirId]) {
      try {
        const data = await API.getDir(dirId);
        dirMeta[data.id] = { id: data.id, name: data.name, parentId: data.parentId };
        dirContents[dirId] = { dirs: data.children || [], tracks: data.tracks || [] };
        (data.children || []).forEach(d => {
          dirMeta[d.id] = { id: d.id, name: d.name, parentId: dirId };
        });
      } catch (e) {
        showToast('Error loading folder: ' + e.message, 'error');
        return;
      }
    }

    // Load all tracks in this folder onto map and zoom
    const tracks = dirContents[dirId].tracks;
    if (tracks.length === 0) return;

    await Promise.all(tracks.map(async track => {
      if (!MapView.hasTrack(track.id)) {
        try {
          const data = await API.getTrackPoints(track.id);
          MapView.addTrack(data, track.id);
        } catch (e) { /* ignore individual errors */ }
      }
    }));
    MapView.fitAll();
  }

  // ===== Track Actions =====

  async function openTrack(trackId) {
    try {
      if (MapView.hasTrack(trackId)) {
        MapView.removeTrack(trackId);
        MapView.setCurrentTrack(null);
        document.getElementById('track-info-panel').style.display = 'none';
        return;
      }
      const data = await API.getTrackPoints(trackId);
      MapView.addTrack(data, trackId);
      MapView.fitTrack(trackId);
      MapView.setCurrentTrack(trackId);
      showTrackInfo(data.meta);
    } catch (e) {
      showToast('Error loading track: ' + e.message, 'error');
    }
  }

  function showTrackInfo(meta) {
    if (!meta) return;
    const panel = document.getElementById('track-info-panel');
    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>` : ''}
    `;
    panel.style.display = 'block';
    document.getElementById('track-info-close').onclick = () => { panel.style.display = 'none'; };
  }

  async function deleteTrack(id) {
    try {
      MapView.removeTrack(id);
      await API.deleteTrack(id);
      await reload();
    } catch (e) {
      showToast('Error: ' + e.message, 'error');
    }
  }

  // ===== Dir Actions =====

  async function createDirPrompt() {
    const name = prompt('Folder name:');
    if (!name || !name.trim()) return;
    try {
      await API.createDir(name.trim(), selectedDirId);
      await reload();
    } catch (e) {
      showToast('Error: ' + e.message, 'error');
    }
  }

  async function renameDir(id, currentName) {
    const name = prompt('New name:', currentName);
    if (!name || !name.trim() || name.trim() === currentName) return;
    try {
      await API.renameDir(id, name.trim());
      await reload();
    } catch (e) {
      showToast('Error: ' + e.message, 'error');
    }
  }

  async function deleteDir(id) {
    try {
      await API.deleteDir(id);
      if (selectedDirId === id) selectedDirId = null;
      expandedDirs.delete(id);
      await reload();
    } catch (e) {
      showToast('Error: ' + e.message, 'error');
    }
  }

  // ===== Upload =====

  async function handleFileUpload(e) {
    const files = Array.from(e.target.files);
    if (files.length === 0) return;
    e.target.value = '';

    for (const file of files) {
      showUploadToast(`Uploading ${file.name}...`);
      try {
        await API.uploadTrack(file, selectedDirId, null);
        showToast(`Uploaded: ${file.name}`, 'success');
      } catch (err) {
        showToast(`Error uploading ${file.name}: ${err.message}`, 'error');
      }
    }
    hideUploadToast();
    await reload();
  }

  function setupDropZone() {
    const mapContainer = document.getElementById('map-container');
    mapContainer.addEventListener('dragover', (e) => {
      // Only handle file drops (not track drags)
      if (e.dataTransfer.types.includes('Files')) {
        e.preventDefault();
        mapContainer.classList.add('drag-over');
      }
    });
    mapContainer.addEventListener('dragleave', (e) => {
      if (!mapContainer.contains(e.relatedTarget)) {
        mapContainer.classList.remove('drag-over');
      }
    });
    mapContainer.addEventListener('drop', async (e) => {
      e.preventDefault();
      mapContainer.classList.remove('drag-over');
      const files = Array.from(e.dataTransfer.files).filter(f => f.name.toLowerCase().endsWith('.gpx'));
      if (files.length === 0) return;
      for (const file of files) {
        showUploadToast(`Uploading ${file.name}...`);
        try {
          await API.uploadTrack(file, selectedDirId, null);
          showToast(`Uploaded: ${file.name}`, 'success');
        } catch (err) {
          showToast(`Error: ${err.message}`, 'error');
        }
      }
      hideUploadToast();
      await reload();
    });
  }

  // ===== Move Track =====

  function confirmMoveTrack(trackId, trackName, targetDirId, targetDirName) {
    document.getElementById('confirm-title').textContent = 'Move Track';
    document.getElementById('confirm-message').textContent =
      `Move "${trackName}" to folder "${targetDirName}"?`;
    const modal = document.getElementById('confirm-modal');
    modal.style.display = 'flex';
    document.getElementById('confirm-ok-btn').onclick = async () => {
      modal.style.display = 'none';
      try {
        await API.updateTrack(trackId, { directoryId: targetDirId });
        await reload();
        showToast('Track moved', 'success');
      } catch (e) {
        showToast('Error: ' + e.message, 'error');
      }
    };
  }

  async function showMoveDialog(trackId, trackName) {
    try {
      allDirs = await loadAllDirs();
      const list = document.getElementById('move-dir-list');
      let html = '<div class="move-dir-item" data-id=""><span>📁</span> (Root)</div>';
      for (const dir of allDirs) {
        html += `<div class="move-dir-item" data-id="${dir.id}"><span>📁</span> ${escHtml(dir.path)}</div>`;
      }
      list.innerHTML = html;

      let selectedMoveId = null;
      list.querySelectorAll('.move-dir-item').forEach(el => {
        el.addEventListener('click', () => {
          list.querySelectorAll('.move-dir-item').forEach(e => e.classList.remove('selected'));
          el.classList.add('selected');
          selectedMoveId = el.dataset.id || null;
        });
      });

      document.getElementById('move-confirm-btn').onclick = async () => {
        try {
          await API.updateTrack(trackId, { directoryId: selectedMoveId || null });
          document.getElementById('move-modal').style.display = 'none';
          await reload();
          showToast('Track moved', 'success');
        } catch (e) {
          showToast('Error: ' + e.message, 'error');
        }
      };

      document.getElementById('move-modal').style.display = 'flex';
    } catch (e) {
      showToast('Error: ' + e.message, 'error');
    }
  }

  async function loadAllDirs(parentId, prefix) {
    const result = [];
    let dirs;
    try {
      if (parentId !== undefined && parentId !== null) {
        const data = await API.getDir(parentId);
        dirs = data.children || [];
      } else {
        dirs = await API.getDirs();
      }
    } catch (e) {
      return result;
    }
    for (const d of dirs) {
      const path = (prefix ? prefix + ' / ' : '') + d.name;
      result.push({ id: d.id, name: d.name, path });
      const sub = await loadAllDirs(d.id, path);
      result.push(...sub);
    }
    return result;
  }

  // ===== Share =====

  async function shareTrack(trackId) {
    try {
      const track = await API.getTrack(trackId);
      const modal = document.getElementById('share-modal');
      const content = document.getElementById('share-content');

      const existingCode = track.ShareLink?.code || track.shareCode;

      if (existingCode) {
        const shareUrl = buildShareUrl(existingCode);
        content.innerHTML = `
          <p>Share link:</p>
          <div class="share-url-box">
            <input type="text" id="share-url-input" value="${escAttr(shareUrl)}" readonly>
            <button id="copy-share-btn">Copy</button>
          </div>
          <div style="margin-top:12px">
            <button id="share-revoke-btn" class="btn-danger">Revoke link</button>
          </div>
        `;
        content.querySelector('#copy-share-btn').addEventListener('click', () => {
          navigator.clipboard.writeText(shareUrl).then(() => showToast('Copied!', 'success')).catch(() => {
            document.getElementById('share-url-input').select();
            document.execCommand('copy');
            showToast('Copied!', 'success');
          });
        });
        content.querySelector('#share-revoke-btn').addEventListener('click', async () => {
          try {
            await API.deleteShare(trackId);
            modal.style.display = 'none';
            showToast('Share link revoked', 'success');
          } catch (err) {
            showToast('Error: ' + err.message, 'error');
          }
        });
      } else {
        content.innerHTML = `
          <p>No share link yet.</p>
          <button id="share-create-btn" class="btn-primary">Create share link</button>
        `;
        content.querySelector('#share-create-btn').addEventListener('click', async () => {
          try {
            const res = await API.createShare(trackId);
            const shareUrl = buildShareUrl(res.code);
            content.innerHTML = `
              <p>Share link created:</p>
              <div class="share-url-box">
                <input type="text" id="share-url-input-new" value="${escAttr(shareUrl)}" readonly>
                <button id="copy-share-new-btn">Copy</button>
              </div>
            `;
            content.querySelector('#copy-share-new-btn').addEventListener('click', () => {
              navigator.clipboard.writeText(shareUrl).then(() => showToast('Copied!', 'success')).catch(() => {
                document.getElementById('share-url-input-new').select();
                document.execCommand('copy');
                showToast('Copied!', 'success');
              });
            });
          } catch (err) {
            showToast('Error: ' + err.message, 'error');
          }
        });
      }

      modal.style.display = 'flex';
    } catch (e) {
      showToast('Error: ' + e.message, 'error');
    }
  }

  function buildShareUrl(code) {
    const base = window.location.origin + window.location.pathname;
    const appRoot = base.replace(/\/[^/]*$/, '/');
    return appRoot + 'share/' + code;
  }

  // ===== Confirm Delete =====

  function confirmDelete(type, name, onConfirm) {
    document.getElementById('confirm-title').textContent = `Delete ${type}`;
    document.getElementById('confirm-message').textContent = `Are you sure you want to delete "${name}"? This cannot be undone.`;
    const modal = document.getElementById('confirm-modal');
    modal.style.display = 'flex';
    document.getElementById('confirm-ok-btn').onclick = () => {
      modal.style.display = 'none';
      onConfirm();
    };
  }

  function getCurrentDirId() { return selectedDirId; }
  function refresh() { return reload(); }

  return { init, getCurrentDirId, refresh };
})();