import fs from "node:fs";

export function loadPatternListFile(filePath: string, label: string): string[] {
  const parsed = JSON.parse(fs.readFileSync(filePath, "utf8")) as unknown;
  if (!Array.isArray(parsed)) {
    throw new TypeError(`${label} must point to a JSON array: ${filePath}`);
  }
  return parsed.filter((value): value is string => typeof value === "string" && value.length > 0);
}

export function loadPatternListFromEnv(
  envKey: string,
  env: Record<string, string | undefined> = process.env,
): string[] | null {
  const filePath = env[envKey]?.trim();
  if (!filePath) {
    return null;
  }
  return loadPatternListFile(filePath, envKey);
}