import { existsSync, readFileSync } from 'node:fs';
import { rename, writeFile } from 'node:fs/promises';
import { join } from 'node:path';

import {
  BACKUP_STATUS_FILE,
  RESTORE_STATUS_FILE,
  type BackupStatus,
  type RestoreStatus,
} from '@dorfteich/shared';

/**
 * File I/O for `status.json` on the backups volume. The shape itself is a
 * shared contract (`@dorfteich/shared` backup-status.ts) because the api's
 * readiness check (#85) and admin panel (#86) read what this sidecar writes.
 */

export type { BackupRun, BackupSizes, BackupStatus } from '@dorfteich/shared';
export { BACKUP_STATUS_FILE as STATUS_FILE } from '@dorfteich/shared';

/** Reads the previous status; a missing or torn file is simply "no status". */
export function readStatus(backupsDir: string): BackupStatus | null {
  const path = join(backupsDir, BACKUP_STATUS_FILE);
  if (!existsSync(path)) return null;
  try {
    return JSON.parse(readFileSync(path, 'utf8')) as BackupStatus;
  } catch {
    return null;
  }
}

/** Atomic write (staging + rename) so readers never see a torn file. */
export async function writeStatus(backupsDir: string, status: BackupStatus): Promise<void> {
  await writeJsonAtomic(join(backupsDir, BACKUP_STATUS_FILE), status);
}

/** The in-app restore progress file (issue #103) — same contract discipline
 * as status.json: the api's maintenance gate and admin card read it. */
export function readRestoreStatus(backupsDir: string): RestoreStatus | null {
  const path = join(backupsDir, RESTORE_STATUS_FILE);
  if (!existsSync(path)) return null;
  try {
    return JSON.parse(readFileSync(path, 'utf8')) as RestoreStatus;
  } catch {
    return null;
  }
}

export async function writeRestoreStatus(backupsDir: string, status: RestoreStatus): Promise<void> {
  await writeJsonAtomic(join(backupsDir, RESTORE_STATUS_FILE), status);
}

async function writeJsonAtomic(path: string, value: unknown): Promise<void> {
  const staging = `${path}.tmp-${process.pid}`;
  await writeFile(staging, JSON.stringify(value, null, 2) + '\n');
  await rename(staging, path);
}