import crypto from "node:crypto";
import fs from "node:fs";
import path from "node:path";
import { fileURLToPath } from "node:url";

export const root = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "../..");
const webRoot = path.join(root, "web");

function walk(directory, output) {
  if (!fs.existsSync(directory)) return;
  for (const entry of fs.readdirSync(directory, { withFileTypes: true })) {
    if (entry.name === "node_modules" || entry.name === "dist" || entry.name === ".cache" || entry.name === ".vite") continue;
    const file = path.join(directory, entry.name);
    if (entry.isDirectory()) walk(file, output);
    else if (entry.isFile()) output.push(file);
  }
}

export function inputFiles() {
  const files = [
    path.join(webRoot, "package.json"),
    path.join(webRoot, "package-lock.json"),
    path.join(webRoot, "tsconfig.json"),
    path.join(webRoot, "app/vite.config.ts"),
  ];
  walk(path.join(webRoot, "app/src"), files);
  walk(path.join(webRoot, "protocol"), files);
  walk(path.join(webRoot, "app/public"), files);
  return [...new Set(files)].filter((file) => fs.existsSync(file)).sort();
}

export function fingerprint() {
  const hash = crypto.createHash("sha256");
  for (const file of inputFiles()) {
    // Read nanosecond metadata as bigint. Without the explicit option
    // `mtimeNs` is undefined in Node, so same-sized edits can reuse stale
    // bundles indefinitely.
    const stat = fs.statSync(file, { bigint: true });
    hash.update(path.relative(root, file));
    hash.update("\0");
    hash.update(stat.size.toString());
    hash.update("\0");
    hash.update(stat.mtimeNs.toString());
    hash.update("\n");
  }
  return hash.digest("hex");
}

export function statePath(name) {
  return path.join(webRoot, ".cache", name);
}

export function readState(name) {
  try { return JSON.parse(fs.readFileSync(statePath(name), "utf8")); }
  catch { return null; }
}

export function writeState(name, value) {
  const file = statePath(name);
  fs.mkdirSync(path.dirname(file), { recursive: true });
  const temporary = `${file}.tmp-${process.pid}`;
  fs.writeFileSync(temporary, `${JSON.stringify(value, null, 2)}\n`);
  fs.renameSync(temporary, file);
}