import { randomUUID } from "node:crypto";
import { closeSync, existsSync, fsyncSync, mkdirSync, openSync, readFileSync, renameSync, unlinkSync, writeFileSync } from "node:fs";
import { dirname } from "node:path";

export function readJsonFile(file: string): unknown | null {
  if (!existsSync(file)) return null;
  return JSON.parse(readFileSync(file, "utf-8"));
}

export function readJsonObject(
  file: string,
  onError?: (err: unknown) => void,
): Record<string, unknown> | null {
  try {
    const parsed = readJsonFile(file);
    return parsed !== null && typeof parsed === "object" && !Array.isArray(parsed)
      ? (parsed as Record<string, unknown>)
      : null;
  } catch (err) {
    onError?.(err);
    return null;
  }
}

function tryFsync(path: string): void {
  try {
    const fd = openSync(path, "r");
    try {
      fsyncSync(fd);
    } finally {
      closeSync(fd);
    }
  } catch {}
}

export function writeJsonAtomic(file: string, value: unknown): void {
  const tmp = `${file}.tmp.${process.pid}.${randomUUID()}`;
  try {
    mkdirSync(dirname(file), { recursive: true });
    writeFileSync(tmp, JSON.stringify(value, null, 2), "utf-8");
    tryFsync(tmp);
    renameSync(tmp, file);
    tryFsync(dirname(file));
  } catch (err) {
    try {
      unlinkSync(tmp);
    } catch {}
    throw err;
  }
}

export function compareNumericKeys(a: string, b: string): number {
  const na = Number(a);
  const nb = Number(b);
  if (Number.isNaN(na) && Number.isNaN(nb)) return a.localeCompare(b);
  if (Number.isNaN(na)) return 1;
  if (Number.isNaN(nb)) return -1;
  return na - nb;
}

export function sortedByNumericKeys<T>(obj: Record<string, T>): Record<string, T> {
  return Object.fromEntries(Object.entries(obj).sort(([a], [b]) => compareNumericKeys(a, b))) as Record<string, T>;
}