import 'dart:ui';

import 'package:flutter/material.dart';

class GlassDock extends StatefulWidget {
  const GlassDock({
    super.key,
    required this.selectedIndex,
    required this.onSelected,
  });
  final int selectedIndex;
  final ValueChanged<int> onSelected;
  @override
  State<GlassDock> createState() => _GlassDockState();
}

class _GlassDockState extends State<GlassDock> {
  static const _width = 192.0, _travel = 88.0;
  double? _drag;
  double get _position => _drag ?? widget.selectedIndex.toDouble();
  void _select(int index) {
    setState(() => _drag = null);
    widget.onSelected(index);
  }

  @override
  Widget build(BuildContext context) => Container(
    width: _width,
    height: 70,
    decoration: BoxDecoration(
      borderRadius: BorderRadius.circular(40),
      boxShadow: [
        BoxShadow(
          color: const Color(0xFF10212E).withValues(alpha: 0.22),
          blurRadius: 28,
          offset: const Offset(0, 10),
        ),
        BoxShadow(
          color: Colors.white.withValues(alpha: 0.35),
          blurRadius: 1,
          spreadRadius: 1,
        ),
      ],
    ),
    child: ClipRRect(
      borderRadius: BorderRadius.circular(40),
      child: BackdropFilter(
        filter: ImageFilter.blur(sigmaX: 24, sigmaY: 24),
        child: DecoratedBox(
          decoration: BoxDecoration(
            borderRadius: BorderRadius.circular(40),
            gradient: LinearGradient(
              begin: Alignment.topLeft,
              end: Alignment.bottomRight,
              colors: [
                const Color(0xFFB9C0CA).withValues(alpha: 0.58),
                const Color(0xFF56616D).withValues(alpha: 0.34),
                const Color(0xFFA1ADB8).withValues(alpha: 0.42),
              ],
            ),
            border: Border.all(
              color: Colors.white.withValues(alpha: 0.55),
              width: 1.2,
            ),
          ),
          child: Stack(
            children: [
              Positioned(
                left: 18,
                right: 18,
                top: 1,
                child: Container(
                  height: 1.5,
                  decoration: BoxDecoration(
                    borderRadius: BorderRadius.circular(30),
                    gradient: LinearGradient(
                      colors: [
                        Colors.white.withValues(alpha: 0),
                        Colors.white.withValues(alpha: 0.8),
                        Colors.white.withValues(alpha: 0.08),
                      ],
                    ),
                  ),
                ),
              ),
              AnimatedPositioned(
                duration: Duration(milliseconds: _drag == null ? 260 : 0),
                curve: Curves.easeOutCubic,
                left: 7 + _position * _travel,
                top: _drag == null ? 7 : 5,
                width: _drag == null ? 90 : 94,
                height: _drag == null ? 56 : 60,
                child: IgnorePointer(
                  child: Container(
                    decoration: BoxDecoration(
                      borderRadius: BorderRadius.circular(36),
                      gradient: LinearGradient(
                        begin: Alignment.topLeft,
                        end: Alignment.bottomRight,
                        colors: [
                          const Color(0xFF24323F).withValues(alpha: 0.64),
                          const Color(0xFF101E2B).withValues(alpha: 0.8),
                          const Color(0xFF475866).withValues(alpha: 0.5),
                        ],
                      ),
                      border: Border.all(
                        color: Colors.white.withValues(alpha: 0.3),
                        width: 0.9,
                      ),
                      boxShadow: [
                        BoxShadow(
                          color: Colors.black.withValues(alpha: 0.18),
                          blurRadius: 7,
                          offset: const Offset(0, 3),
                        ),
                        BoxShadow(
                          color: Colors.white.withValues(alpha: 0.12),
                          blurRadius: 3,
                          spreadRadius: 0.5,
                        ),
                      ],
                    ),
                  ),
                ),
              ),
              Positioned(
                left: 8,
                right: 8,
                top: 7,
                bottom: 7,
                child: Row(
                  children: [
                    _item(0, Icons.calendar_month_rounded, '课表'),
                    _item(1, Icons.person_rounded, '我的'),
                  ],
                ),
              ),
              Positioned(
                left: 16,
                right: 16,
                bottom: 1,
                child: Container(
                  height: 1.3,
                  decoration: BoxDecoration(
                    gradient: LinearGradient(
                      colors: [
                        Colors.white.withValues(alpha: 0.05),
                        Colors.white.withValues(alpha: 0.5),
                        Colors.white.withValues(alpha: 0.05),
                      ],
                    ),
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    ),
  );
  Widget _item(int index, IconData icon, String label) => Expanded(
    child: Semantics(
      label: label,
      button: true,
      selected: index == widget.selectedIndex,
      excludeSemantics: true,
      onTap: () => _select(index),
      child: GestureDetector(
        key: index == widget.selectedIndex ? const Key('dock-cursor') : null,
        behavior: HitTestBehavior.opaque,
        onTap: () => _select(index),
        // Only the selected lens can start a drag. The pages have no swipe handlers.
        onHorizontalDragStart: index == widget.selectedIndex
            ? (_) => setState(() => _drag = widget.selectedIndex.toDouble())
            : null,
        onHorizontalDragUpdate: index == widget.selectedIndex
            ? (details) => setState(
                () => _drag = (_position + details.delta.dx / _travel).clamp(
                  0,
                  1,
                ),
              )
            : null,
        onHorizontalDragEnd: index == widget.selectedIndex
            ? (_) => _select(_position >= 0.5 ? 1 : 0)
            : null,
        onHorizontalDragCancel: index == widget.selectedIndex
            ? () => setState(() => _drag = null)
            : null,
        child: Center(
          child: Icon(
            icon,
            size: 27,
            color: index == (_position >= 0.5 ? 1 : 0)
                ? const Color(0xFF458BFF)
                : Colors.white.withValues(alpha: 0.85),
          ),
        ),
      ),
    ),
  );
}