SpotiFLAC-Mobile/lib/widgets/selection_bottom_bar.dart

import 'package:flutter/material.dart';
import 'package:spotiflac_android/theme/app_tokens.dart';
import 'package:spotiflac_android/widgets/app_bottom_sheet.dart';
import 'package:spotiflac_android/l10n/l10n.dart';

/// Hosts selection bars above the shell navigation while keeping modal routes
/// above the bar. A raw entry in the root [Overlay] stays above routes pushed
/// later, which made download pickers appear behind the selection toolbar.
class SelectionOverlayHost extends StatefulWidget {
  const SelectionOverlayHost({super.key, required this.child});

  final Widget child;

  static _SelectionOverlayHostState? _maybeOf(BuildContext context) =>
      context.findAncestorStateOfType<_SelectionOverlayHostState>();

  @override
  State<SelectionOverlayHost> createState() => _SelectionOverlayHostState();
}

class _SelectionOverlayHostState extends State<SelectionOverlayHost> {
  SelectionOverlayController? _owner;
  WidgetBuilder? _builder;

  bool owns(SelectionOverlayController owner) =>
      _owner == owner && _builder != null;

  void show(SelectionOverlayController owner, WidgetBuilder builder) {
    if (!mounted) return;
    setState(() {
      _owner = owner;
      _builder = builder;
    });
  }

  void hide(SelectionOverlayController owner) {
    if (!mounted || _owner != owner) return;
    setState(() {
      _owner = null;
      _builder = null;
    });
  }

  @override
  Widget build(BuildContext context) {
    final owner = _owner;
    final builder = _builder;
    // A root modal makes the shell route non-current. Removing the toolbar
    // while that route is covered both prevents visual overlap and avoids the
    // hidden toolbar intercepting taps during the modal transition. The stored
    // builder is kept so the selection returns if the modal is dismissed.
    final routeIsCurrent = ModalRoute.of(context)?.isCurrent ?? true;
    return Stack(
      fit: StackFit.expand,
      children: [
        widget.child,
        if (routeIsCurrent && owner != null && builder != null)
          Positioned(
            left: 0,
            right: 0,
            bottom: 0,
            child: KeyedSubtree(
              key: ObjectKey(owner),
              child: AnimatedSelectionBottomBar(
                child: Material(
                  color: Colors.transparent,
                  child: Builder(builder: builder),
                ),
              ),
            ),
          ),
      ],
    );
  }
}

/// Mounts a selection bar in [SelectionOverlayHost]. Screens rendered outside
/// the main shell (including isolated widget tests) retain a root-overlay
/// fallback.
class SelectionOverlayController {
  OverlayEntry? _entry;
  _SelectionOverlayHostState? _host;
  WidgetBuilder? _builder;

  bool get isVisible => _entry != null || (_host?.owns(this) ?? false);

  /// Shows the bar, or rebuilds it in place when already visible so the
  /// entrance animation does not replay on every selection change.
  void show(BuildContext context, WidgetBuilder builder) {
    if (!TickerMode.valuesOf(context).enabled) {
      hide();
      return;
    }

    _builder = builder;
    final host = SelectionOverlayHost._maybeOf(context);
    if (host != null) {
      _entry?.remove();
      _entry = null;
      if (_host != null && _host != host) {
        _host!.hide(this);
      }
      _host = host;
      host.show(this, builder);
      return;
    }

    _host?.hide(this);
    _host = null;
    if (_entry != null) {
      _entry!.markNeedsBuild();
      return;
    }
    _entry = OverlayEntry(
      builder: (overlayContext) => Positioned(
        left: 0,
        right: 0,
        bottom: 0,
        child: AnimatedSelectionBottomBar(
          child: Material(
            color: Colors.transparent,
            child: _builder!(overlayContext),
          ),
        ),
      ),
    );
    Overlay.of(context, rootOverlay: true).insert(_entry!);
  }

  void hide() {
    _host?.hide(this);
    _host = null;
    _entry?.remove();
    _entry = null;
    _builder = null;
  }

  /// Call from the host `State.dispose`; an entry left in the root overlay
  /// outlives the screen that created it.
  void dispose() => hide();
}

/// Entrance animation shared by selection bars mounted in the root overlay.
class AnimatedSelectionBottomBar extends StatefulWidget {
  const AnimatedSelectionBottomBar({super.key, required this.child});

  final Widget child;

  @override
  State<AnimatedSelectionBottomBar> createState() =>
      _AnimatedSelectionBottomBarState();
}

class _AnimatedSelectionBottomBarState extends State<AnimatedSelectionBottomBar>
    with SingleTickerProviderStateMixin {
  late final AnimationController _controller;
  late final Animation<Offset> _slideAnimation;
  late final Animation<double> _fadeAnimation;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      vsync: this,
      duration: const Duration(milliseconds: 240),
    );
    final curve = CurvedAnimation(
      parent: _controller,
      curve: Curves.easeOutCubic,
    );
    _slideAnimation = Tween<Offset>(
      begin: const Offset(0, 0.08),
      end: Offset.zero,
    ).animate(curve);
    _fadeAnimation = Tween<double>(begin: 0, end: 1).animate(curve);
    _controller.forward();
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return FadeTransition(
      opacity: _fadeAnimation,
      child: SlideTransition(position: _slideAnimation, child: widget.child),
    );
  }
}

/// Shared chrome for the multi-select bottom bar: rounded surface, drag
/// handle, close button, "N selected" header and select-all toggle.
/// The screen-specific action buttons go in [children].
class SelectionBottomBar extends StatelessWidget {
  const SelectionBottomBar({
    super.key,
    required this.selectedCount,
    required this.allSelected,
    required this.onClose,
    required this.onToggleSelectAll,
    required this.bottomPadding,
    required this.children,
    this.allSelectedLabel,
    this.tapToSelectLabel,
  });

  final int selectedCount;
  final bool allSelected;
  final VoidCallback onClose;
  final VoidCallback onToggleSelectAll;
  final double bottomPadding;
  final List<Widget> children;

  /// Overrides the default "All tracks selected" subtitle.
  final String? allSelectedLabel;

  /// Overrides the default "Tap tracks to select" subtitle.
  final String? tapToSelectLabel;

  @override
  Widget build(BuildContext context) {
    final tokens = context.tokens;
    final colorScheme = Theme.of(context).colorScheme;

    return Container(
      decoration: BoxDecoration(
        color: colorScheme.surfaceContainerHigh,
        borderRadius: BorderRadius.vertical(
          top: Radius.circular(tokens.radiusSheet),
        ),
        boxShadow: [
          BoxShadow(
            color: colorScheme.shadow.withValues(alpha: 0.15),
            blurRadius: 12,
            offset: const Offset(0, -4),
          ),
        ],
      ),
      child: SafeArea(
        top: false,
        child: Padding(
          padding: EdgeInsets.fromLTRB(16, 16, 16, bottomPadding > 0 ? 8 : 16),
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              const AppSheetHandle(),

              Row(
                children: [
                  IconButton.filledTonal(
                    onPressed: onClose,
                    tooltip: MaterialLocalizations.of(
                      context,
                    ).closeButtonTooltip,
                    icon: const Icon(Icons.close),
                    style: IconButton.styleFrom(
                      backgroundColor: colorScheme.surfaceContainerHighest,
                    ),
                  ),
                  const SizedBox(width: 12),

                  Expanded(
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.start,
                      children: [
                        Text(
                          context.l10n.selectionSelected(selectedCount),
                          style: Theme.of(context).textTheme.titleMedium
                              ?.copyWith(fontWeight: FontWeight.bold),
                        ),
                        Text(
                          allSelected
                              ? allSelectedLabel ??
                                    context.l10n.selectionAllSelected
                              : tapToSelectLabel ??
                                    context.l10n.downloadedAlbumTapToSelect,
                          style: Theme.of(context).textTheme.bodySmall
                              ?.copyWith(color: colorScheme.onSurfaceVariant),
                        ),
                      ],
                    ),
                  ),

                  TextButton.icon(
                    onPressed: onToggleSelectAll,
                    icon: Icon(
                      allSelected ? Icons.deselect : Icons.select_all,
                      size: 20,
                    ),
                    label: Text(
                      allSelected
                          ? context.l10n.actionDeselect
                          : context.l10n.actionSelectAll,
                    ),
                    style: TextButton.styleFrom(
                      foregroundColor: colorScheme.primary,
                    ),
                  ),
                ],
              ),

              const SizedBox(height: 12),

              ...children,
            ],
          ),
        ),
      ),
    );
  }
}