/**
 * Deterministically reopen a resolved unknown node in a SituationGraph.
 *
 * Transition: node.status "resolved" → "unknown", and removes the node's ID
 * from resolvedNodeIds. This reverses canonical resolution so the question
 * reappears among Open Questions for further investigation.
 *
 * Idempotent — if the target is not a currently-resolved unknown, returns the
 * original graph unchanged (no mutation). Does NOT create nodes, delete edges,
 * or touch contributions/findings/historical evidence.
 */

export function reopenResolvedUnknown(situationGraph, nodeId) {
  if (!situationGraph || !nodeId) return situationGraph;

  const nodeIndex = situationGraph.nodes.findIndex((n) => n.id === nodeId);
  if (nodeIndex === -1) return situationGraph;

  const node = situationGraph.nodes[nodeIndex];
  if (node.kind !== "unknown" || node.status !== "resolved") return situationGraph;

  const newNode = { ...node, status: "unknown" };
  const newNodes = [...situationGraph.nodes];
  newNodes[nodeIndex] = newNode;

  const newResolvedNodeIds = [
    ...(situationGraph.resolvedNodeIds || []),
  ].filter((id) => id !== nodeId);

  return {
    ...situationGraph,
    nodes: newNodes,
    resolvedNodeIds: newResolvedNodeIds,
  };
}