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,
      // The bar floats, so it is stacked over the content rather than laid
      // out beneath it — and each root pads its own scroll view past it.
      extendBody: true,
      body: IndexedStack(
        index: _index,
        children: const [HomeScreen(), OrdersScreen(), AccountScreen()],
      ),
      bottomNavigationBar: _TabBar(index: _index, onChanged: goToTab),
    );
  }
}

/// The tab bar, fixed to the bottom edge.
///
/// ── A floating pill, after all ──
///
/// This bar has been three things. It hovered as a pill, then sat on the edge
/// with a hairline over it and a crimson indicator travelling along it, then
/// lost the indicator's edge. The reference the app is now drawn against puts
/// it back in the air — and the reason is better than the first time round.
///
/// The pill works *because* the screens above it stopped having edges. When
/// every card was outlined, a floating bar was a fourth rounded surface in a
/// stack of them. Now the content is white shapes lifted off a near-white
/// page, and the bar is one more of those: same radius language, same shadow,
/// read as the same kind of object.
///
/// The labels went with the edge. Three glyphs a customer has seen on every
/// app they own do not need naming, and without them the bar is 62pt instead
/// of 86 — which is the space the pill is floating in.
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),
  ];

  static const double _slot = 74;
  static const double _height = 62;

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      top: false,
      child: Padding(
        padding: const EdgeInsets.fromLTRB(DmSpace.pad, 0, DmSpace.pad, 10),
        // A Row, not a Center: `bottomNavigationBar` hands its child an
        // unbounded height, and a Center in that slot expands to fill the
        // whole screen with the pill floating in the middle of it.
        child: Row(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Container(
              height: _height,
              padding: const EdgeInsets.symmetric(horizontal: 6),
              decoration: BoxDecoration(
                color: DmColors.surface,
                borderRadius: DmRadius.all(DmRadius.pill),
                boxShadow: DmShadow.cardRaised,
              ),
              child: Row(
                mainAxisSize: MainAxisSize.min,
                children: [
                  for (var i = 0; i < _items.length; i++)
                    SizedBox(
                      width: _slot,
                      child: _TabButton(
                        label: _items[i].label,
                        icon: _items[i].icon,
                        selected: index == i,
                        onTap: () => onChanged(i),
                      ),
                    ),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }
}

class _TabButton extends StatefulWidget {
  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
  State<_TabButton> createState() => _TabButtonState();
}

class _TabButtonState extends State<_TabButton> {
  bool _down = false;

  @override
  Widget build(BuildContext context) {
    final selected = widget.selected;
    return Semantics(
      button: true,
      selected: selected,
      label: widget.label,
      child: GestureDetector(
        behavior: HitTestBehavior.opaque,
        onTapDown: (_) => setState(() => _down = true),
        onTapUp: (_) => setState(() => _down = false),
        onTapCancel: () => setState(() => _down = false),
        onTap: widget.onTap,
        child: AnimatedScale(
          scale: _down ? 0.88 : 1,
          duration: DmMotion.fast,
          curve: DmMotion.ease,
          child: Center(
            // ── Colour alone ──
            //
            // The glyph sat in a `brandSoft` rounded square, which made the
            // selected tab the only filled object in a bar whose whole job is
            // to recede. The reference marks it with the brand and nothing
            // else, and with three glyphs in a white pill that is unambiguous
            // — there is only one coloured thing on the bar.
            //
            // It arrives with a shade of overshoot, so the tab reacts to the
            // press rather than recolouring after it.
            child: AnimatedScale(
              scale: selected ? 1.08 : 1,
              duration: DmMotion.slow,
              curve: DmMotion.glide,
              child: AnimatedContainer(
                duration: DmMotion.base,
                curve: DmMotion.ease,
                child: Icon(
                  widget.icon,
                  size: 23,
                  color: selected ? DmColors.brand : DmColors.ink4,
                ),
              ),
            ),
          ),
        ),
      ),
    );
  }
}