minstrel/flutter_client/lib/shared/delayed_loading.dart

import 'dart:async';
import 'package:flutter/widgets.dart';

/// Renders [whileDelayed] only after [isLoading] has been true
/// continuously for [delay], then renders [whenReady] once loading
/// completes. Mirrors the web `useDelayed` hook: a brief loading flash
/// doesn't trigger a skeleton; sustained loading does.
///
/// Once [isLoading] flips back to false, the timer resets.
class DelayedLoading extends StatefulWidget {
  const DelayedLoading({
    super.key,
    required this.isLoading,
    required this.whileDelayed,
    required this.whenReady,
    this.delay = const Duration(milliseconds: 200),
  });

  final bool isLoading;
  final Widget whileDelayed;
  final Widget whenReady;
  final Duration delay;

  @override
  State<DelayedLoading> createState() => _DelayedLoadingState();
}

class _DelayedLoadingState extends State<DelayedLoading> {
  Timer? _timer;
  bool _delayPassed = false;

  @override
  void initState() {
    super.initState();
    _maybeStart();
  }

  @override
  void didUpdateWidget(DelayedLoading old) {
    super.didUpdateWidget(old);
    if (widget.isLoading != old.isLoading) {
      _timer?.cancel();
      _delayPassed = false;
      _maybeStart();
    }
  }

  void _maybeStart() {
    if (!widget.isLoading) return;
    _timer = Timer(widget.delay, () {
      if (mounted) setState(() => _delayPassed = true);
    });
  }

  @override
  void dispose() {
    _timer?.cancel();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    if (!widget.isLoading) return widget.whenReady;
    return _delayPassed ? widget.whileDelayed : const SizedBox.shrink();
  }
}