/* ---- 拖线 / 拖卡 / 平移（mousedown 分流 + document 跟随；bindContactsUI 统一绑定） ---- */
let dragLine = null, dragCard = null, panning = null;
function startDragLine(e, fromId, dir) {
  const path = document.createElementNS('http://www.w3.org/2000/svg', 'path');
  path.setAttribute('class', 'edge-line edge-pending'); path.setAttribute('fill', 'none');
  edgeSvg.appendChild(path);
  dragLine = { from: fromId, dir: dir || 'down', path: path };
  updateDragLine(e);
}
function updateDragLine(e) {
  const p = posOf(dragLine.from);
  if (!p) return;
  const sy = dragLine.dir === 'up' ? p.y : p.y + CARD_H;
  const pt = toCanvas(e.clientX, e.clientY);
  dragLine.path.setAttribute('d', 'M ' + (p.x + CARD_W / 2) + ' ' + sy + ' L ' + pt.x + ' ' + pt.y);
  canvasInner.querySelectorAll('.gcard.link-target').forEach(el => el.classList.remove('link-target'));
  const t = document.elementFromPoint(e.clientX, e.clientY);
  const card = t && t.closest ? t.closest('.gcard') : null;
  if (card && !card.classList.contains('company') && card.dataset.id && card.dataset.id !== dragLine.from) card.classList.add('link-target');
}
function tryConnect(aId, bId) {
  if (aId === bId) { toast('不允许连接自身(' + cname(aId) + ')', 'err'); return; }
  if (aId === COMPANY_ID || bId === COMPANY_ID) { toast('不允许为公司节点新增或删除关系', 'err'); return; }
  if (hasPair(effectiveEdges(), aId, bId) || hasPair(effectiveEdges(), bId, aId)) {
    toast('已存在连线:' + cname(aId) + ' ↔ ' + cname(bId) + '（蓝色实线即是），换一对联系人试试', 'err'); return;
  }
  const a = byId(aId), b = byId(bId);
  if (!a || !b) return;
  if (a.level == null || b.level == null) {
    toast('「' + cname(a.level == null ? aId : bId) + '」未设置等级，请先将其拖入等级格子完成定级再连线'); return;
  }
  commitDirectionalEdge(aId, bId);
}
/* 两端层级已齐：按层级自动定方向（高者为上级；同级不连）+ 单父约束 → 落 pending */
function commitDirectionalEdge(aId, bId) {
  const a = byId(aId), b = byId(bId);
  if (!a || !b) return false;
  if (a.level === b.level) { toast('同级（层级相同）之间不建立上下级连线', 'err'); return false; }
  const parentId = a.level > b.level ? aId : bId, childId = a.level > b.level ? bId : aId;
  const exParent = effectiveEdges().find(e => e.child === childId);
  if (exParent) { toast(cname(childId) + ' 已有上级(' + cname(exParent.parent) + ')，一个节点最多一个上级，请先删除原连线', 'err'); return false; }
  commitPendingEdge(parentId, childId);
  return true;
}
function commitPendingEdge(parentId, childId) {
  G.pendingAdds.push({ parent: parentId, child: childId });
  G.cycleHighlight = null;
  addLog('关系', '新增连线(未保存):' + cname(parentId) + ' → ' + cname(childId));
  renderGraph(); renderGraphState();
}
function graphMouseDown(e) {
  if (e.button !== 0) return;
  const dot = e.target.closest('.dot');
  if (dot && G.editing) {
    const gc = dot.closest('.gcard');
    if (!gc) return;
    if (dot.classList.contains('dot-bottom')) { e.preventDefault(); startDragLine(e, gc.dataset.id, 'down'); return; }
    if (dot.classList.contains('dot-top')) { e.preventDefault(); startDragLine(e, gc.dataset.id, 'up'); return; }
  }
  const card = e.target.closest('.gcard');
  if (card && G.editing && !card.classList.contains('company') && card.dataset.id) {
    const pt = toCanvas(e.clientX, e.clientY), p = G.cardPos[card.dataset.id];
    if (!p) return;
    dragCard = { id: card.dataset.id, dx: pt.x - p.x, dy: pt.y - p.y };
    e.preventDefault();
    return;
  }
  if (!card) {
    panning = { x: e.clientX, y: e.clientY, px: G.view.panX, py: G.view.panY };
    wrap.classList.add('panning');
  }
}
function graphMouseMove(e) {
  if (dragLine) { updateDragLine(e); return; }
  if (dragCard) {
    const pt = toCanvas(e.clientX, e.clientY);
    const p = G.cardPos[dragCard.id];
    if (!p) return;
    p.x = Math.max(0, Math.min(2400 - CARD_W, pt.x - dragCard.dx));
    p.y = Math.max(0, Math.min(1400 - CARD_H, pt.y - dragCard.dy));
    const el = canvasInner.querySelector('.gcard[data-id="' + dragCard.id + '"]');
    if (el) { el.style.left = p.x + 'px'; el.style.top = p.y + 'px'; }
    canvasInner.querySelectorAll('.lv-row.drop-target').forEach(x => x.classList.remove('drop-target'));
    if (G.editing) {
      const t = rowAt(pt.x, pt.y);
      if (t.kind === 'lv') { const row = canvasInner.querySelector('.lv-row[data-lv="' + t.lv + '"]'); if (row) row.classList.add('drop-target'); }
    }
    renderEdgesOnly();
    return;
  }
  if (panning) {
    G.view.panX = panning.px + (e.clientX - panning.x);
    G.view.panY = panning.py + (e.clientY - panning.y);
    applyTransform();
  }
}
function graphMouseUp(e) {
  if (dragLine) {
    const t = document.elementFromPoint(e.clientX, e.clientY);
    const card = t && t.closest ? t.closest('.gcard') : null;
    if (card && card.classList.contains('company')) toast('不允许为公司节点新增或删除关系', 'err');
    else if (card && card.dataset.id && card.dataset.id !== dragLine.from) tryConnect(dragLine.from, card.dataset.id);
    dragLine.path.remove();
    dragLine = null;
    canvasInner.querySelectorAll('.gcard.link-target').forEach(el => el.classList.remove('link-target'));
  }
  if (dragCard) {
    const pt = toCanvas(e.clientX, e.clientY);
    const t = rowAt(pt.x, pt.y);
    if (t.kind === 'lv' || t.kind === 'unrec') tryLevelDrop(dragCard.id, t);
    else if (t.kind === 'company') toast('公司行不可放置联系人卡片');
    canvasInner.querySelectorAll('.lv-row.drop-target').forEach(x => x.classList.remove('drop-target'));
  }
  dragCard = null;
  if (panning) { panning = null; wrap.classList.remove('panning'); }
}
function graphWheel(e) { e.preventDefault(); zoomAt(e.deltaY < 0 ? 1.12 : 0.9, e.clientX, e.clientY); }