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.
///
/// ── What the 2026-09-22 pass changed ──
///
/// **The pill stopped glowing.** It carried [DmShadow.liftSm] — a 65% crimson
/// shadow built for the committing button on a screen — which on a bar resting
/// against the bottom edge read as a smear under the tab rather than as lift.
/// It is a quarter of that strength now and sits closer to the shape.
///
/// **The glyph arrives.** The icon pops to 1.14 and settles as the pill lands
/// under it, on the same overshoot curve the pill travels on, so the two read
/// as one gesture instead of a moving rectangle and an icon that recolours when
/// it happens to be covered.
///
/// **A tab gives way when pressed.** The whole column scales to 0.9 under the
/// finger. Without it the only feedback for a tap was the pill starting to
/// move, which on the tab you are already on is no feedback at all.
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;

  /// The pill's own lift. Not [DmShadow.liftSm]: that is the glow under a
  /// committing action, and at the bottom edge of the screen it read as dirt
  /// under the tab.
  static const _pillShadow = [
    BoxShadow(
      color: Color(0x2E8F0F06),
      blurRadius: 10,
      spreadRadius: -2,
      offset: Offset(0, 4),
    ),
  ];

  @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: _pillShadow,
                        ),
                      ),
                    ),
                    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 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) {
    return Semantics(
      button: true,
      selected: widget.selected,
      child: GestureDetector(
        behavior: HitTestBehavior.opaque,
        onTapDown: (_) => setState(() => _down = true),
        onTapUp: (_) => setState(() => _down = false),
        onTapCancel: () => setState(() => _down = false),
        onTap: widget.onTap,
        child: AnimatedScale(
          // The whole column, including the label: a press that only moved the
          // glyph would read as the icon coming loose from its own tab.
          scale: _down ? 0.9 : 1,
          duration: DmMotion.fast,
          curve: DmMotion.ease,
          child: Column(
            mainAxisAlignment: MainAxisAlignment.start,
            children: [
              SizedBox(
                height: _TabBar._pillHeight,
                child: Center(
                  child: AnimatedScale(
                    // Lands with the pill, on the pill's own curve. The
                    // overshoot is what ties the two together — the glyph is
                    // reacting to the thing arriving under it.
                    scale: widget.selected ? 1.14 : 1,
                    duration: DmMotion.slow,
                    curve: DmMotion.glide,
                    child: AnimatedSwitcher(
                      duration: DmMotion.base,
                      child: Icon(
                        widget.icon,
                        key: ValueKey(widget.selected),
                        size: 21,
                        color: widget.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: widget.selected ? DmColors.brand : DmColors.ink3,
                  fontWeight:
                      widget.selected ? FontWeight.w700 : FontWeight.w600,
                ),
                child: Text(
                  widget.label,
                  maxLines: 1,
                  overflow: TextOverflow.ellipsis,
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}