Function convertEdgePattern

packages/graph/src/astToSteps.ts:1642–1694

* Convert an edge pattern to steps, handling quantifiers for variable-length paths.

(edgePattern: EdgePattern, destNode?: NodePattern)

 * Convert an edge pattern to steps, handling quantifiers for variable-length paths.
 */
function convertEdgePattern(edgePattern: EdgePattern, destNode?: NodePattern): Step<any>[] {
  // No quantifier - single edge traversal + destination vertex
  if (!edgePattern.quantifier) {
    const baseStep = new EdgeStep({
      direction: edgePattern.direction,
      edgeLabels: edgePattern.labels,
      stepLabels: edgePattern.variable ? [edgePattern.variable] : undefined,
    });

    const steps: Step<any>[] = [baseStep];

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

    // Add VertexStep with "other" direction to traverse to the destination vertex
    if (destNode) {
      steps.push(
        new VertexStep({
          direction: "other",
          edgeLabels: [],
          stepLabels: destNode.variable ? [destNode.variable] : undefined,
        }),
      );
    }

    return steps;
  }

  // With quantifier - wrap in RepeatStep with destination node label
  const baseStep = new EdgeStep({
    direction: edgePattern.direction,
    edgeLabels: edgePattern.labels,
    stepLabels: edgePattern.variable ? [edgePattern.variable] : undefined,
  });

  const repeatStep = convertQuantifiedEdge(
    baseStep,
    edgePattern.quantifier,
    destNode?.variable,
    edgePattern.properties,
  );

  return [repeatStep];
}

/**
 * Convert a quantified edge pattern to a RepeatStep.