import fs from "node:fs";
import path from "node:path";

/**
 * Reads a feature.manifest.ts file and extracts the manifest's `name` field
 * and `requiredCores` array via regex. Returns null if the file does not
 * exist or does not match the expected literal `as const` manifest shape.
 *
 * The repo's convention is that every feature.manifest.ts uses defineFeature
 * with literal `as const` syntax — this is enforced by the type-system
 * design (defineFeature has `<const M>` to preserve literal types). The
 * regex extraction is therefore safe; the AST path is overkill.
 *
 * Returns: { name: string, requiredCores: string[] } | null
 */
export function readManifestSource(manifestPath) {
  let src;
  try {
    src = fs.readFileSync(manifestPath, "utf8");
  } catch {
    return null;
  }
  const nameMatch = src.match(/name:\s*"([^"]+)"/);
  if (!nameMatch) return null;
  const coresMatch = src.match(/requiredCores:\s*\[([^\]]*)\]/);
  const cores = coresMatch
    ? coresMatch[1]
        .split(",")
        .map((s) => s.trim().replace(/^"/, "").replace(/"$/, ""))
        .filter((s) => s.length > 0)
    : [];
  return { name: nameMatch[1], requiredCores: cores };
}

/**
 * Canonical manifest path for a given feature package root.
 */
export function manifestPathForFeature(featureRoot) {
  return path.join(featureRoot, "src", "feature.manifest.ts");
}

/**
 * Given an absolute file path and the monorepo root, returns the feature
 * package root that contains the file (e.g. /repo/packages/auth). Returns
 * null when the file lives outside the packages/ tree.
 *
 * Assumes the conventional layout `packages/<feature>/src/...`.
 */
export function featureRootForFile(filepath, repoRoot) {
  const packagesDir = path.join(repoRoot, "packages");
  if (!filepath.startsWith(packagesDir + path.sep)) return null;
  const rel = filepath.slice(packagesDir.length + 1); // e.g. "auth/src/..."
  const slash = rel.indexOf(path.sep);
  if (slash === -1) return null;
  const featureName = rel.slice(0, slash);
  return path.join(packagesDir, featureName);
}