import 'dart:async';
import 'dart:io';

import 'package:flutter/material.dart';

import '../../routing/app_routes.dart';
import '../../utils/downloads/download_job.dart';
import '../../utils/downloads/download_manager.dart';
import '../../utils/haptics.dart';
import '../confirm_dialog.dart';
import '../info_dialog.dart';

/// Verifies a finished download's cache file is still on disk before opening.
///
/// Downloads live in the app's temp dir, which Android may clear at any time
/// (storage pressure, "Cache leeren") — while completion notifications and
/// tray entries stay tappable indefinitely. Returns true when the file exists;
/// otherwise drops the stale job (incl. its notification) and offers a
/// re-download when the remote path is known (it isn't for notification taps
/// whose task metadata got lost).
bool ensureDownloadStillExists(BuildContext context, DownloadJob job) {
  final path = job.localPath;
  if (path == null || File(path).existsSync()) return true;

  DownloadManager.instance.markOpened(job);
  showFileGoneDialog(
    context,
    subject: 'Die heruntergeladene Datei',
    onRedownload: job.remotePath.isEmpty
        ? null
        : () => unawaited(DownloadManager.instance.retry(job)),
  );
  return false;
}

/// Opens a finished download in the viewer, unless its file vanished.
void openFinishedDownload(BuildContext context, DownloadJob job, String path) {
  if (!ensureDownloadStillExists(context, job)) return;
  DownloadManager.instance.markOpened(job);
  Haptics.success();
  AppRoutes.openFileViewer(context, path, remoteFile: job.remoteFile);
}

/// Tells the user that the system cleared a cached file ([subject], e.g.
/// "Die Datei") and offers a re-download when [onRedownload] is given.
void showFileGoneDialog(
  BuildContext context, {
  required String subject,
  VoidCallback? onRedownload,
}) {
  const title = 'Datei nicht mehr verfügbar';
  final gone = '$subject wurde vom System aus dem Zwischenspeicher entfernt.';
  if (onRedownload == null) {
    InfoDialog.show(
      context,
      '$gone Bitte lade sie erneut herunter.',
      title: title,
    );
    return;
  }
  ConfirmDialog(
    title: title,
    content: '$gone\nErneut herunterladen?',
    confirmButton: 'Herunterladen',
    onConfirm: onRedownload,
  ).asDialog(context);
}