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

import '../tokens.dart';
import 'account_screen.dart';
import 'home_screen.dart';
import 'orders_screen.dart';

/// Bottom-navigation shell: Home · Orders · Account.
///
/// Booking and tracking screens are pushed on top, so the tab bar only ever
/// shows on the three destinations that need it.
class ShellScreen extends StatefulWidget {
  const ShellScreen({super.key, this.initialTab = 0});

  final int initialTab;

  static ShellScreenState? of(BuildContext context) =>
      context.findAncestorStateOfType<ShellScreenState>();

  @override
  State<ShellScreen> createState() => ShellScreenState();
}

class ShellScreenState extends State<ShellScreen> {
  late int _index = widget.initialTab;

  void goToTab(int index) {
    if (index == _index) return;
    HapticFeedback.selectionClick();
    setState(() => _index = index);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: DmColors.canvas,
      body: IndexedStack(
        index: _index,
        children: const [HomeScreen(), OrdersScreen(), AccountScreen()],
      ),
      bottomNavigationBar: _TabBar(index: _index, onChanged: goToTab),
    );
  }
}

/// The tab bar, fixed to the bottom edge.
///
/// ── Why it is no longer a floating pill-shaped bar ──
///
/// It used to hover 10pt above the bottom with a 28pt radius and a shadow
/// under it, which put a second rounded surface between the content and the
/// gesture bar and made every screen end in two stacked edges. It now sits on
/// the edge with a single hairline above it, like the footers in the rest of
/// the app.
///
/// The indicator does the work instead: a crimson pill that travels to the tab
/// you pick, with the glyph turning white as it arrives. Selection reads as one
/// object moving rather than three tabs changing colour in place — and the
/// label under it stays crimson, so the tab is still identifiable in the
/// half-second the pill is in flight.
class _TabBar extends StatelessWidget {
  const _TabBar({required this.index, required this.onChanged});

  final int index;
  final ValueChanged<int> onChanged;

  /// Lucide, not Material. One 1.5px stroke family at one weight, so the three
  /// glyphs read as a set instead of three different drawing styles — and the
  /// same set the pushed screens use.
  static const _items = [
    (label: 'Home', icon: LucideIcons.house),
    (label: 'Orders', icon: LucideIcons.package),
    (label: 'Account', icon: LucideIcons.userRound),
  ];

  /// The travelling pill's size. Narrower than its slot so it reads as an
  /// object sitting in the row rather than as a selected cell.
  static const double _pillWidth = 62;
  static const double _pillHeight = 34;

  @override
  Widget build(BuildContext context) {
    return DecoratedBox(
      decoration: const BoxDecoration(
        color: DmColors.surface,
        border: Border(top: BorderSide(color: DmColors.border)),
      ),
      child: SafeArea(
        top: false,
        child: Padding(
          padding: const EdgeInsets.fromLTRB(6, 9, 6, 7),
          child: SizedBox(
            // The row is the pill plus the label, and the label is type: at
            // 1.8x accessibility text a fixed 58 clipped it by two points. The
            // bar gets taller instead, which is what a larger-text user asked
            // for.
            height: _pillHeight +
                5 +
                MediaQuery.textScalerOf(context).scale(11.5) * 1.3,
            child: LayoutBuilder(
              builder: (context, constraints) {
                final slot = constraints.maxWidth / _items.length;
                return Stack(
                  children: [
                    AnimatedPositioned(
                      duration: DmMotion.slow,
                      curve: DmMotion.glide,
                      left: slot * index + (slot - _pillWidth) / 2,
                      width: _pillWidth,
                      top: 0,
                      height: _pillHeight,
                      child: DecoratedBox(
                        decoration: BoxDecoration(
                          color: DmColors.brand,
                          borderRadius: DmRadius.all(DmRadius.pill),
                          boxShadow: DmShadow.liftSm,
                        ),
                      ),
                    ),
                    Row(
                      children: [
                        for (var i = 0; i < _items.length; i++)
                          Expanded(
                            child: _TabButton(
                              label: _items[i].label,
                              icon: _items[i].icon,
                              selected: index == i,
                              onTap: () => onChanged(i),
                            ),
                          ),
                      ],
                    ),
                  ],
                );
              },
            ),
          ),
        ),
      ),
    );
  }
}

class _TabButton extends StatelessWidget {
  const _TabButton({
    required this.label,
    required this.icon,
    required this.selected,
    required this.onTap,
  });

  final String label;
  final IconData icon;
  final bool selected;
  final VoidCallback onTap;

  @override
  Widget build(BuildContext context) {
    return Semantics(
      button: true,
      selected: selected,
      child: GestureDetector(
        behavior: HitTestBehavior.opaque,
        onTap: onTap,
        child: Column(
          mainAxisAlignment: MainAxisAlignment.start,
          children: [
            SizedBox(
              height: _TabBar._pillHeight,
              child: Center(
                child: AnimatedSwitcher(
                  duration: DmMotion.base,
                  child: Icon(
                    icon,
                    key: ValueKey(selected),
                    size: 22,
                    color: selected ? Colors.white : DmColors.ink3,
                  ),
                ),
              ),
            ),
            const SizedBox(height: 5),
            AnimatedDefaultTextStyle(
              duration: DmMotion.base,
              curve: DmMotion.ease,
              style: DmText.label.copyWith(
                fontSize: 11.5,
                height: 1.0,
                color: selected ? DmColors.brand : DmColors.ink3,
                fontWeight: selected ? FontWeight.w700 : FontWeight.w600,
              ),
              child: Text(label, maxLines: 1, overflow: TextOverflow.ellipsis),
            ),
          ],
        ),
      ),
    );
  }
}