import 'dart:async';
import 'dart:js_interop';

import 'package:web/web.dart' as web;

/// Provided by the inline Firebase bootstrap in web/index.html. Returns an FCM
/// registration token, or null if push isn't configured / permission denied.
@JS('kcGetPushToken')
external JSPromise<JSString?> _kcGetPushToken();

Future<String?> getPushToken() async {
  try {
    final result = await _kcGetPushToken().toDart;
    return result?.toDart;
  } catch (_) {
    return null;
  }
}

/// Per-tab storage for the PKCE verifier + CSRF state (cleared when the tab
/// closes), and the little bit of `window` access the OIDC redirect needs.

void setSession(String key, String value) =>
    web.window.sessionStorage.setItem(key, value);

String? getSession(String key) => web.window.sessionStorage.getItem(key);

void removeSession(String key) => web.window.sessionStorage.removeItem(key);

void redirect(String url) => web.window.location.assign(url);

Map<String, String> currentQueryParameters() =>
    Uri.parse(web.window.location.href).queryParameters;

/// Drop the OIDC callback path + `?code=…&state=…` from the address bar
/// without reloading (back to the app root).
void clearQuery() {
  web.window.history.replaceState(null, '', '/');
}

/// Opens the OS file picker and reads the chosen file's bytes.
Future<({String name, List<int> bytes})?> pickFile() {
  final completer = Completer<({String name, List<int> bytes})?>();
  final input = web.HTMLInputElement()..type = 'file';
  input.onchange = ((web.Event _) {
    final files = input.files;
    if (files == null || files.length == 0) {
      completer.complete(null);
      return;
    }
    final file = files.item(0)!;
    final reader = web.FileReader();
    reader.onload = ((web.Event _) {
      final buffer = (reader.result as JSArrayBuffer).toDart;
      completer.complete((name: file.name, bytes: buffer.asUint8List()));
    }).toJS;
    reader.onerror = ((web.Event _) => completer.complete(null)).toJS;
    reader.readAsArrayBuffer(file);
  }).toJS;
  input.click();
  return completer.future;
}

/// Triggers a browser download of an in-memory string (e.g. the CSV export).
void downloadText(
  String filename,
  String content, {
  String mime = 'text/csv;charset=utf-8',
}) {
  final blob = web.Blob([content.toJS].toJS, web.BlobPropertyBag(type: mime));
  final url = web.URL.createObjectURL(blob);
  web.HTMLAnchorElement()
    ..href = url
    ..download = filename
    ..click();
  web.URL.revokeObjectURL(url);
}