structure.js

const { parseTraversal } = require("./syntax");

function summarize(children, groupDepth) {
  const pointerCount = children.reduce(
    (total, child) => total + (child.kind === "pointer" ? 1 : child.pointerCount),
    0
  );
  const groupCount = children.reduce(
    (total, child) => total + (child.kind === "group" ? 1 + child.groupCount : 0),
    0
  );
  const depth = children.reduce(
    (maximum, child) => Math.max(maximum, child.kind === "group" ? child.depth : groupDepth),
    groupDepth
  );
  return { pointerCount, groupCount, depth };
}

/**
 * Build a stable, source-linked tree projection of one traversal expression.
 * This is deliberately a structural projection, not recursive graph expansion.
 */
function buildTraversalStructure(
  compilation,
  source,
  context = {},
  options = {}
) {
  const baseOffset = options.baseOffset ?? 0;
  const layers = options.layers ?? ["document", "profile"];
  const traversal = parseTraversal(source, { baseOffset });

  function buildItems(items, path, groupDepth) {
    return items.map((item, ordinal) => {
      const itemPath = [...path, ordinal];
      if (item.kind === "pointer") {
        const bound = compilation.resolve(
          item.id,
          { ...context, offset: item.span.start },
          { layers }
        );
        return {
          kind: "pointer",
          path: itemPath,
          span: item.span,
          wrapperSpan: item.wrapperSpan,
          pointer: item.id,
          title: bound?.declaration.title ?? "",
          resolved: Boolean(bound),
          provenance: bound?.provenance,
          declarationIdentity: bound?.declaration.identity
        };
      }

      const children = buildItems(item.items, itemPath, groupDepth + 1);
      return {
        kind: "group",
        path: itemPath,
        span: item.span,
        children,
        ...summarize(children, groupDepth + 1)
      };
    });
  }

  const children = buildItems(traversal.items, [], 0);
  return {
    kind: "traversal-structure",
    span: traversal.span,
    children,
    ...summarize(children, 0)
  };
}

module.exports = { buildTraversalStructure };