const Stats = (() => {
  const ALL_TYPES = ['hiking', 'running', 'cycling', 'driving', 'train', 'other', 'none'];
  const TYPE_LABELS = {
    hiking: '🥾 Hiking', running: '🏃 Running', cycling: '🚴 Cycling',
    driving: '🚗 Driving', train: '🚆 Train', other: '📍 Other', none: '— Untyped'
  };

  // null = all; otherwise Set of selected type strings
  let selectedTypes = null;

  async function init() {
    await loadStats();
  }

  async function loadStats() {
    const content = document.getElementById('stats-content');
    content.innerHTML = '<div class="loading">Loading stats...</div>';

    try {
      const types = selectedTypes ? [...selectedTypes] : [];
      const stats = await API.getStats(types);
      renderStats(stats);
    } catch (e) {
      content.innerHTML = '<div class="error-msg">Error loading stats: ' + escHtml(e.message) + '</div>';
    }
  }

  function renderFilterBar() {
    const allSelected = selectedTypes === null;
    let html = '<div class="stats-filter">';
    html += `<button class="stats-type-btn${allSelected ? ' active' : ''}" data-type="all">All</button>`;
    for (const t of ALL_TYPES) {
      const active = !allSelected && selectedTypes.has(t);
      html += `<button class="stats-type-btn${active ? ' active' : ''}" data-type="${escAttr(t)}">${TYPE_LABELS[t]}</button>`;
    }
    html += '</div>';
    return html;
  }

  function renderStats(stats) {
    const content = document.getElementById('stats-content');
    let html = renderFilterBar();

    // Summary totals
    if (stats.total !== undefined || stats.totalDistance !== undefined) {
      const totalDist = stats.total?.distance || stats.totalDistance || 0;
      const totalTracks = stats.total?.count || stats.trackCount || 0;
      html += `<div class="stats-section">
        <h3>Total</h3>
        <div class="stat-row">
          <span class="stat-label">Tracks</span>
          <div class="stat-bar-wrap"><div class="stat-bar" style="width:100%"></div></div>
          <span class="stat-value">${totalTracks}</span>
        </div>
        <div class="stat-row">
          <span class="stat-label">Distance</span>
          <div class="stat-bar-wrap"><div class="stat-bar" style="width:100%"></div></div>
          <span class="stat-value">${formatDistance(totalDist)}</span>
        </div>
      </div>`;
    }

    // By year
    if (stats.byYear && stats.byYear.length > 0) {
      const maxDist = Math.max(...stats.byYear.map(s => s.distance || 0));
      html += '<div class="stats-section"><h3>By Year</h3>';
      for (const s of stats.byYear) {
        const pct = maxDist > 0 ? ((s.distance || 0) / maxDist * 100) : 0;
        html += `<div class="stat-row">
          <span class="stat-label">${s.year}</span>
          <div class="stat-bar-wrap"><div class="stat-bar" style="width:${pct.toFixed(1)}%"></div></div>
          <span class="stat-value">${formatDistance(s.distance)}</span>
        </div>`;
      }
      html += '</div>';
    }

    // By month (last 24 months)
    if (stats.byMonth && stats.byMonth.length > 0) {
      const recent = stats.byMonth.slice(-24);
      const maxDist = Math.max(...recent.map(s => s.distance || 0));
      html += '<div class="stats-section"><h3>By Month (last 24)</h3>';
      for (const s of recent) {
        const pct = maxDist > 0 ? ((s.distance || 0) / maxDist * 100) : 0;
        const label = `${s.year}-${String(s.month).padStart(2, '0')}`;
        html += `<div class="stat-row">
          <span class="stat-label">${label}</span>
          <div class="stat-bar-wrap"><div class="stat-bar" style="width:${pct.toFixed(1)}%"></div></div>
          <span class="stat-value">${formatDistance(s.distance)}</span>
        </div>`;
      }
      html += '</div>';
    }

    // By week (last 52 weeks)
    if (stats.byWeek && stats.byWeek.length > 0) {
      const recent = stats.byWeek.slice(-52);
      const maxDist = Math.max(...recent.map(s => s.distance || 0));
      html += '<div class="stats-section"><h3>By Week (last 52)</h3>';
      for (const s of recent) {
        const pct = maxDist > 0 ? ((s.distance || 0) / maxDist * 100) : 0;
        const label = `${s.year}-W${String(s.week).padStart(2, '0')}`;
        html += `<div class="stat-row">
          <span class="stat-label">${label}</span>
          <div class="stat-bar-wrap"><div class="stat-bar" style="width:${pct.toFixed(1)}%"></div></div>
          <span class="stat-value">${formatDistance(s.distance)}</span>
        </div>`;
      }
      html += '</div>';
    }

    if (!html.includes('stats-section')) {
      html += '<div class="empty-list">No tracks match the current filter.</div>';
    }

    content.innerHTML = html;

    // Bind filter button events
    content.querySelectorAll('.stats-type-btn').forEach(btn => {
      btn.addEventListener('click', () => {
        const t = btn.dataset.type;
        if (t === 'all') {
          selectedTypes = null;
        } else {
          if (selectedTypes === null) {
            selectedTypes = new Set([t]);
          } else if (selectedTypes.has(t)) {
            selectedTypes.delete(t);
            if (selectedTypes.size === 0) selectedTypes = null;
          } else {
            selectedTypes.add(t);
          }
        }
        loadStats();
      });
    });
  }

  return { init, loadStats };
})();