/* lightbox.js — 图片查看器：缩放、拖拽、键盘操作 */

(function() {
  function openLightbox(src, alt) {
    var existing = document.querySelector('.lightbox-overlay');
    if (existing) existing.remove();

    var overlay = document.createElement('div');
    overlay.className = 'lightbox-overlay';

    var img = document.createElement('img');
    img.src = src;
    img.alt = alt || '';
    img.draggable = false;

    // 工具栏
    var toolbar = document.createElement('div');
    toolbar.className = 'lightbox-toolbar';
    toolbar.innerHTML =
      '<button title="缩小">−</button>' +
      '<button title="放大">+</button>' +
      '<button title="适合窗口">⊡</button>' +
      '<button title="原始大小">1:1</button>' +
      '<button title="关闭">✕</button>';

    overlay.appendChild(img);
    overlay.appendChild(toolbar);
    document.body.appendChild(overlay);

    // 视图状态
    var scale = 1, tx = 0, ty = 0;
    var baseW = 0, baseH = 0;
    var dragging = false, dragStartX = 0, dragStartY = 0, startTx = 0, startTy = 0;

    function apply() {
      img.style.transform = 'translate(' + tx + 'px,' + ty + 'px) scale(' + scale + ')';
    }

    function fitToScreen() {
      if (!baseW) return;
      var sw = window.innerWidth, sh = window.innerHeight;
      scale = Math.min(sw * 0.9 / baseW, sh * 0.9 / baseH, 1);
      tx = (sw - baseW * scale) / 2;
      ty = (sh - baseH * scale) / 2;
      apply();
    }

    function resetOrigin() {
      scale = 1;
      tx = (window.innerWidth - baseW) / 2;
      ty = (window.innerHeight - baseH) / 2;
      apply();
    }

    function zoomAt(factor, cx, cy) {
      var newScale = Math.max(0.1, Math.min(scale * factor, 20));
      tx = cx - (cx - tx) * (newScale / scale);
      ty = cy - (cy - ty) * (newScale / scale);
      scale = newScale;
      apply();
    }

    function zoomCenter(factor) {
      var cx = window.innerWidth / 2;
      var cy = window.innerHeight / 2;
      var newScale = Math.max(0.1, Math.min(scale * factor, 20));
      tx = cx - (cx - tx) * (newScale / scale);
      ty = cy - (cy - ty) * (newScale / scale);
      scale = newScale;
      apply();
    }

    // 图片加载后初始化
    img.onload = function() {
      baseW = img.naturalWidth;
      baseH = img.naturalHeight;
      fitToScreen();
    };
    // 如果已缓存
    if (img.complete && img.naturalWidth) {
      baseW = img.naturalWidth;
      baseH = img.naturalHeight;
      fitToScreen();
    }

    // 工具栏按钮（缩小 / 放大 / 适合 / 原始 / 关闭）
    var btns = toolbar.querySelectorAll('button');
    btns[0].onclick = function(e) { e.stopPropagation(); zoomCenter(0.7); };
    btns[1].onclick = function(e) { e.stopPropagation(); zoomCenter(1.4); };
    btns[2].onclick = function(e) { e.stopPropagation(); fitToScreen(); };
    btns[3].onclick = function(e) { e.stopPropagation(); resetOrigin(); };
    btns[4].onclick = function(e) { e.stopPropagation(); close(); };

    // 滚轮缩放（以鼠标为中心）
    overlay.addEventListener('wheel', function(e) {
      e.preventDefault();
      var factor = e.deltaY < 0 ? 1.15 : 0.87;
      var rect = overlay.getBoundingClientRect();
      var cx = e.clientX - rect.left;
      var cy = e.clientY - rect.top;
      var newScale = Math.max(0.1, Math.min(scale * factor, 20));
      tx = cx - (cx - tx) * (newScale / scale);
      ty = cy - (cy - ty) * (newScale / scale);
      scale = newScale;
      apply();
    }, { passive: false });

    // 拖拽平移
    overlay.addEventListener('pointerdown', function(e) {
      if (e.target.closest('.lightbox-toolbar')) return;
      dragging = true;
      dragStartX = e.clientX;
      dragStartY = e.clientY;
      startTx = tx;
      startTy = ty;
      img.classList.add('dragging');
      overlay.setPointerCapture(e.pointerId);
    });
    overlay.addEventListener('pointermove', function(e) {
      if (!dragging) return;
      tx = startTx + (e.clientX - dragStartX);
      ty = startTy + (e.clientY - dragStartY);
      apply();
    });
    overlay.addEventListener('pointerup', function() {
      dragging = false;
      img.classList.remove('dragging');
    });

    // ESC 关闭
    function onKey(e) {
      if (e.key === 'Escape') { close(); }
      else if (e.key === '+' || e.key === '=') { zoomCenter(1.4); }
      else if (e.key === '-') { zoomCenter(0.7); }
      else if (e.key === '0') { fitToScreen(); }
    }

    function close() {
      overlay.remove();
      document.removeEventListener('keydown', onKey);
    }

    document.addEventListener('keydown', onKey);

    // 激活动画
    requestAnimationFrame(function() {
      overlay.classList.add('active');
    });
  }

  document.addEventListener('click', function(e) {
    var img = e.target;
    if (img.tagName !== 'IMG') return;
    if (!img.closest('.inline-figure') && !img.closest('.gallery-item')) return;
    if (img.closest('.lightbox-overlay')) return;
    e.preventDefault();
    openLightbox(img.src, img.alt);
  });
})();