import { existsSync, readFileSync } from "node:fs";
import { join } from "node:path";

/**
 * Throws with a clear message if any required anchor is missing from the target
 * file. Generator actions call this in their prompt validator so the run aborts
 * cleanly before any partial output lands on disk.
 */
export function assertAnchors(
  repoRoot: string,
  relativePath: string,
  anchors: string[],
): void {
  const path = join(repoRoot, relativePath);
  if (!existsSync(path)) {
    throw new Error(`Required file does not exist: ${relativePath}`);
  }
  const content = readFileSync(path, "utf8");
  for (const anchor of anchors) {
    if (!content.includes(anchor)) {
      throw new Error(
        `Missing anchor "${anchor}" in ${relativePath}. Add it before running this generator.`,
      );
    }
  }
}