import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import 'package:lucide_icons_flutter/lucide_icons.dart';

import '../state/timecards_controller.dart';
import '../widgets/krow_nav_bar.dart';

/// The five primary tabs. Each keeps its own navigation stack.
class HomeShell extends ConsumerWidget {
  const HomeShell({super.key, required this.navigationShell});

  final StatefulNavigationShell navigationShell;

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final needsReview = ref.watch(timecardsNeedingReviewProvider).isNotEmpty;

    return Scaffold(
      body: _TabTransition(
        index: navigationShell.currentIndex,
        child: navigationShell,
      ),
      bottomNavigationBar: KrowNavBar(
        currentIndex: navigationShell.currentIndex,
        onSelect: (i) => navigationShell.goBranch(
          i,
          initialLocation: i == navigationShell.currentIndex,
        ),
        // Must stay in the same order as the shell branches in the router.
        items: [
          const KrowNavItem(icon: LucideIcons.briefcase, label: 'Shifts'),
          const KrowNavItem(icon: LucideIcons.wallet, label: 'Pay'),
          const KrowNavItem(icon: LucideIcons.house, label: 'Today'),
          KrowNavItem(
            icon: LucideIcons.clock,
            label: 'Clock',
            showDot: needsReview,
          ),
          const KrowNavItem(icon: LucideIcons.user, label: 'Profile'),
        ],
      ),
    );
  }
}

/// Fades and lifts the tab content each time the tab changes.
///
/// Deliberately not an AnimatedSwitcher: that would hold two copies of the
/// shell in the tree at once, and the branch navigators are keyed by
/// GlobalKey, so duplicating them would throw. This keeps one subtree — the
/// branches stay alive and keep their scroll positions — and animates it in
/// place when the index changes.
class _TabTransition extends StatefulWidget {
  const _TabTransition({required this.index, required this.child});

  final int index;
  final Widget child;

  @override
  State<_TabTransition> createState() => _TabTransitionState();
}

class _TabTransitionState extends State<_TabTransition>
    with SingleTickerProviderStateMixin {
  late final AnimationController _controller = AnimationController(
    vsync: this,
    duration: const Duration(milliseconds: 260),
    value: 1,
  );

  late final Animation<double> _curve = CurvedAnimation(
    parent: _controller,
    curve: Curves.easeOutCubic,
  );

  @override
  void didUpdateWidget(_TabTransition oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (oldWidget.index != widget.index) _controller.forward(from: 0);
  }

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

  @override
  Widget build(BuildContext context) {
    return AnimatedBuilder(
      animation: _curve,
      // The shell is passed through untouched so it is never rebuilt.
      child: widget.child,
      builder: (context, child) {
        final t = _curve.value;
        return Opacity(
          // Never fully transparent: a tab that blinks out reads as a glitch.
          opacity: 0.35 + 0.65 * t,
          child: Transform.translate(
            offset: Offset(0, (1 - t) * 10),
            child: child,
          ),
        );
      },
    );
  }
}