Function topoOrderIds

yaml-flow-editor/src/utils/layout.ts:415–443

* BFS order with "next" (main flow) edge first at each node. First column is strictly * Start → step1 → step2 → … along the main flow; no 4 above 3.

(nodes: FlowNode[], edges: FlowEdge[])

 * Start → step1 → step2 → … along the main flow; no 4 above 3.
 */
function topoOrderIds(nodes: FlowNode[], edges: FlowEdge[]): string[] {
  const { inEdges, outEdgesWithHandle } = buildGraph(nodes, edges);
  const sources = nodes.filter((n) => (inEdges.get(n.id)?.length ?? 0) === 0).map((n) => n.id);
  if (sources.length === 0) return nodes.map((n) => n.id);

  const inDeg = new Map<string, number>();
  nodes.forEach((n) => inDeg.set(n.id, inEdges.get(n.id)!.length));

  const order: string[] = [];
  const queue: string[] = [...sources];

  while (queue.length > 0) {
    const id = queue.shift()!;
    order.push(id);
    const out = (outEdgesWithHandle.get(id) ?? []).slice();
    out.sort((a, b) => {
      const p = nextFlowPriority(a.sourceHandle) - nextFlowPriority(b.sourceHandle);
      if (p !== 0) return p;
      return a.target.localeCompare(b.target, undefined, { numeric: true });
    });
    for (const { target: targetId } of out) {
      const d = (inDeg.get(targetId) ?? 0) - 1;
      inDeg.set(targetId, d);
      if (d === 0) queue.push(targetId);
    }
  }

  return order.length === nodes.length ? order : nodes.map((n) => n.id);
}

/**
 * Place nodes in columns using greedy bin-packing by height budget.