feat: add LanguageExtractor interface and shared base utilities

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

understand-anything-plugin/packages/core/src/plugins/extractors/base-extractor.ts

@@ -0,0 +1,52 @@
+import type { TreeSitterNode } from "./types.js";
+
+/** Recursively traverse an AST tree, calling the visitor for each node. */
+export function traverse(
+  node: TreeSitterNode,
+  visitor: (node: TreeSitterNode) => void,
+): void {
+  visitor(node);
+  for (let i = 0; i < node.childCount; i++) {
+    const child = node.child(i);
+    if (child) traverse(child, visitor);
+  }
+}
+
+/** Extract the unquoted string value from a string-like node. */
+export function getStringValue(node: TreeSitterNode): string {
+  for (let i = 0; i < node.childCount; i++) {
+    const child = node.child(i);
+    if (child && child.type === "string_fragment") {
+      return child.text;
+    }
+  }
+  return node.text.replace(/^['"`]|['"`]$/g, "");
+}
+
+/** Find the first child matching a type. */
+export function findChild(node: TreeSitterNode, type: string): TreeSitterNode | null {
+  for (let i = 0; i < node.childCount; i++) {
+    const child = node.child(i);
+    if (child && child.type === type) return child;
+  }
+  return null;
+}
+
+/** Find all children matching a type. */
+export function findChildren(node: TreeSitterNode, type: string): TreeSitterNode[] {
+  const result: TreeSitterNode[] = [];
+  for (let i = 0; i < node.childCount; i++) {
+    const child = node.child(i);
+    if (child && child.type === type) result.push(child);
+  }
+  return result;
+}
+
+/** Check if a node has a child of the given type (used for export/visibility checks). */
+export function hasChildOfType(node: TreeSitterNode, type: string): boolean {
+  for (let i = 0; i < node.childCount; i++) {
+    const child = node.child(i);
+    if (child && child.type === type) return true;
+  }
+  return false;
+}

understand-anything-plugin/packages/core/src/plugins/extractors/types.ts

@@ -0,0 +1,19 @@
+import type { StructuralAnalysis, CallGraphEntry } from "../../types.js";
+
+// Re-export the tree-sitter Node type for use by extractors
+export type TreeSitterNode = import("web-tree-sitter").Node;
+
+/**
+ * Language-specific extractor that maps a tree-sitter AST
+ * to the common StructuralAnalysis / CallGraphEntry types.
+ */
+export interface LanguageExtractor {
+  /** Language IDs this extractor handles (must match LanguageConfig.id) */
+  languageIds: string[];
+
+  /** Extract functions, classes, imports, exports from the root AST node */
+  extractStructure(rootNode: TreeSitterNode): StructuralAnalysis;
+
+  /** Extract caller→callee relationships from the root AST node */
+  extractCallGraph(rootNode: TreeSitterNode): CallGraphEntry[];
+}