Function convertShortestPathPattern

packages/graph/src/astToSteps.ts:1175–1286

* Convert a ShortestPathPattern into a sequence of steps. * Uses ShortestPathStep with BFS/Dijkstra algorithm. * * TODO: The pattern.all field (for allShortestPaths) currently throws an error. * Only a single shortest path is supported. Implement support for finding * all shortest paths when pa

(
  pattern: ShortestPathPattern,
  whereClause?: WhereClause,
)

 * @throws {Error} When pattern.all is true (allShortestPaths not implemented)
 */
function convertShortestPathPattern(
  pattern: ShortestPathPattern,
  whereClause?: WhereClause,
): Step<any>[] {
  // Check if allShortestPaths is requested - not yet implemented
  if (pattern.all === true) {
    throw new Error(
      "allShortestPaths() is not yet implemented. Use shortestPath() to find a single shortest path.",
    );
  }

  const steps: Step<any>[] = [];
  const { source, target, edge, variable } = pattern;

  // Build the source vertex fetch step
  const sourceStepLabels = source.variable ? [source.variable] : undefined;
  steps.push(
    new FetchVerticesStep({
      vertexLabels: source.labels.length > 0 ? source.labels : undefined,
      stepLabels: sourceStepLabels,
    }),
  );

  // Apply WHERE conditions that reference the source variable
  let targetCondition: StepCondition | undefined;

  if (whereClause && source.variable) {
    const { early, late } = splitASTConditionByVariables(whereClause.condition, [source.variable]);

    // Apply early conditions to filter source vertices
    if (early) {
      steps.push(new FilterElementsStep({ condition: convertCondition(early) }));
    }

    // Extract target conditions from late conditions
    if (late && target.variable) {
      const targetVarConditions = extractConditionsForVariable(late, target.variable);
      if (targetVarConditions) {
        // Use direct property access for shortestPath target conditions
        // since the target vertex hasn't been bound to a variable yet
        targetCondition = convertCondition(targetVarConditions, true);
      }
    }
  }

  // Build target condition from target node labels and properties
  const targetConditions: StepCondition[] = [];

  // Add label conditions for target
  if (target.labels.length > 0) {
    if (target.labels.length === 1) {
      targetConditions.push(["=", "@label", target.labels[0]!] as StepCondition);
    } else {
      targetConditions.push([
        "or",
        ...target.labels.map((label) => ["=", "@label", label] as StepCondition),
      ] as StepCondition);
    }