Function convertQuantifiedEdge

packages/graph/src/astToSteps.ts:1700–1762

* Convert a quantified edge pattern to a RepeatStep. * For variable-length paths, we need to repeat both the edge traversal and vertex traversal.

(
  baseStep: EdgeStep,
  quantifier: Quantifier,
  destNodeVariable?: string,
  edgeProperties?: { [key: string]: any },
)

 * For variable-length paths, we need to repeat both the edge traversal and vertex traversal.
 */
function convertQuantifiedEdge(
  baseStep: EdgeStep,
  quantifier: Quantifier,
  destNodeVariable?: string,
  edgeProperties?: { [key: string]: any },
): RepeatStep<Step<any>[]> {
  const { min, max } = quantifier;

  // Build the steps for each iteration
  const iterationSteps: Step<any>[] = [baseStep];

  // Add filter for edge properties if specified
  if (edgeProperties && Object.keys(edgeProperties).length > 0) {
    const propertyConditions = Object.entries(edgeProperties).map(
      ([key, value]) => ["=", key, value] as StepCondition,
    );
    const condition: StepCondition =
      propertyConditions.length === 1
        ? propertyConditions[0]!
        : (["and", ...propertyConditions] as StepCondition);
    iterationSteps.push(new FilterElementsStep({ condition }));
  }

  // For variable-length paths, we need to traverse edge -> vertex repeatedly
  // The vertex step should use the same direction as the edge step to continue in that direction
  const vertexStep = new VertexStep({
    direction: baseStep.config.direction,
    edgeLabels: [],
  });
  iterationSteps.push(vertexStep);

  const stepLabels = destNodeVariable ? [destNodeVariable] : undefined;

  // Handle zero-min case: {0,n} or {0} includes the starting node
  const emitInput = min === 0;
  // emitStart is 1-indexed (iteration 1 = 1 hop), so set it to min (but at least 1)
  const effectiveMin = min ?? 1;
  const emitStart = effectiveMin > 0 ? effectiveMin : 1;

  // Exact count: *2 or {2} means exactly 2 hops
  if (max !== undefined && effectiveMin === max) {
    // For exact count with zero min, we need emit to also get the input
    if (emitInput) {
      return new RepeatStep({ times: max, stepLabels, emitInput }, iterationSteps);
    }
    return new RepeatStep({ times: max, stepLabels }, iterationSteps);
  }

  // Range: *1..3 or {1,3} means 1 to 3 hops (with emitStart respecting min)
  if (max !== undefined) {
    return new RepeatStep(
      { times: max, emit: true, emitStart, emitInput, stepLabels },
      iterationSteps,
    );
  }

  // Open-ended: *2.. or {2,} means 2 or more hops
  // Use a large number for open-ended paths