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

export function copyArtifactAtomically(source, destination, copy = fs.copyFileSync) {
  let lastError;
  for (let attempt = 0; attempt < 3; attempt += 1) {
    const temporary = `${destination}.${process.pid}.${crypto.randomUUID()}.tmp`;
    try {
      const before = fs.statSync(source, { bigint: true });
      copy(source, temporary);
      const after = fs.statSync(source, { bigint: true });
      if (before.size !== after.size || before.mtimeNs !== after.mtimeNs || before.ino !== after.ino)
        throw new Error(`Artifact changed while copying; wait for its build to finish: ${source}`);
      if (destination.endsWith(".wasm") && !WebAssembly.validate(fs.readFileSync(temporary)))
        throw new Error(`Incomplete or invalid WASM; previous published file retained: ${source}`);
      fs.renameSync(temporary, destination);
      return;
    } catch (error) {
      lastError = error;
    } finally {
      fs.rmSync(temporary, { force: true });
    }
  }
  throw lastError;
}

export function missingArtifactPair(source) {
  const match = path.basename(source).match(/^(FreeCADWeb[A-Za-z0-9]+)\.(?:js|wasm|data|worker\.js)$/);
  if (!match) return [];
  const stem = path.join(path.dirname(source), match[1]);
  return [stem + ".js", stem + ".wasm"].filter(file => !fs.existsSync(file));
}

export function pthreadSidecar(source, destination) {
  if (!source.endsWith(".js") || source.endsWith(".worker.js")) return null;
  const worker = source.slice(0, -3) + ".worker.js";
  return fs.existsSync(worker) ? [worker, destination.slice(0, -3) + ".worker.js"] : null;
}

export function artifactRevision(hashes) {
  return crypto.createHash("sha256").update(JSON.stringify(hashes)).digest("hex").slice(0, 16);
}

export function writeManifestIfChanged(file, manifest) {
  const stable = value => {
    const copy = { ...value };
    delete copy.generatedAt;
    return JSON.stringify(copy);
  };
  try {
    if (stable(JSON.parse(fs.readFileSync(file, "utf8"))) === stable(manifest)) return false;
  } catch {
    // Missing or incomplete manifests are replaced below.
  }
  const temporary = file + ".tmp";
  fs.writeFileSync(temporary, JSON.stringify(manifest, null, 2) + "\n");
  fs.renameSync(temporary, file);
  return true;
}