import 'dart:math' as math;
import 'dart:ui' as ui;

import 'package:flutter/material.dart';
import 'package:flutter/physics.dart';

import 'glass_refraction.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> with TickerProviderStateMixin {
  static const _width = 264.0, _height = 68.0, _inset = 3.0, _travel = 86.0;
  static const _blue = Color(0xFF007AFF);
  static const _selectedInk = Color(0xFF62666C);
  late final AnimationController _motion = AnimationController.unbounded(
    vsync: this,
    value: widget.selectedIndex.toDouble(),
  );
  late final AnimationController _press = AnimationController.unbounded(
    vsync: this,
    value: 0,
  );
  bool _reduceMotion = false;
  double get _pressure => _press.value.clamp(0.0, 1.18);
  void _pressTo(double target) {
    if (_reduceMotion) {
      _press.value = target;
      return;
    }
    _press.animateWith(
      SpringSimulation(
        const SpringDescription(mass: 1, stiffness: 440, damping: 20),
        _press.value,
        target,
        _press.velocity,
      ),
    );
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    _reduceMotion = MediaQuery.disableAnimationsOf(context);
  }

  double? _drag;
  double _dragSpeed = 0;
  double get _position => _drag ?? _motion.value.clamp(-0.12, 2.12);
  void _spring(int index, [double velocity = 0]) {
    if (_reduceMotion) {
      _motion.value = index.toDouble();
      return;
    }
    _motion.animateWith(
      SpringSimulation(
        const SpringDescription(mass: 1, stiffness: 380, damping: 23),
        _position,
        index.toDouble(),
        velocity.clamp(-8, 8),
      ),
    );
  }

  void _select(int index, [double velocity = 0]) {
    final position = _position;
    setState(() => _drag = null);
    _motion.value = position;
    _spring(index, velocity);
    _pressTo(0);
    widget.onSelected(index);
  }

  @override
  void didUpdateWidget(GlassDock oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (oldWidget.selectedIndex != widget.selectedIndex && _drag == null) {
      _spring(widget.selectedIndex);
    }
  }

  @override
  void dispose() {
    _motion.dispose();
    _press.dispose();
    super.dispose();
  }

  Widget _glass({required Widget child, bool lens = false}) {
    final pressure = _pressure.clamp(0.0, 1.0);
    final content = CustomPaint(
      foregroundPainter: _GlassRimPainter(lens: lens),
      child: DecoratedBox(
        decoration: BoxDecoration(
          gradient: LinearGradient(
            begin: Alignment.topLeft,
            end: Alignment.bottomRight,
            colors: lens
                ? [
                    const Color(0xFFD8DBE0)
                        .withValues(alpha: 0.72 * (1 - pressure * 0.91)),
                    const Color(0xFFC3C7CE)
                        .withValues(alpha: 0.60 * (1 - pressure * 0.93)),
                    const Color(0xFFE5E7EB)
                        .withValues(alpha: 0.72 * (1 - pressure * 0.90)),
                  ]
                : [
                    Colors.white.withValues(alpha: 0.028),
                    _blue.withValues(alpha: 0.005),
                    Colors.white.withValues(alpha: 0.012),
                  ],
          ),
        ),
        child: child,
      ),
    );
    return ClipRRect(
      borderRadius: BorderRadius.circular(40),
      child: lens
          ? GlassRefraction(strength: 0.25 + pressure * 0.95, child: content)
          : BackdropFilter(
              filter: ui.ImageFilter.blur(sigmaX: 1.0, sigmaY: 1.0),
              child: content,
            ),
    );
  }

  @override
  Widget build(BuildContext context) => AnimatedBuilder(
    animation: Listenable.merge([_motion, _press]),
    builder: (context, _) {
      final press = _pressure;
      final speed = (_drag != null ? _dragSpeed : _motion.velocity).abs();
      final stretch = (speed / 16).clamp(0.0, 0.12) + press * 0.18;
      final lensWidth = _travel * (1 + stretch);
      final lensHeight =
          (_height - _inset * 2) *
          (1 + press * 0.19 - (speed / 16).clamp(0.0, 0.07));
      return SizedBox(
        width: _width,
        height: _height,
        child: DecoratedBox(
          decoration: BoxDecoration(
            borderRadius: BorderRadius.circular(40),
            boxShadow: [
              BoxShadow(
                color: _blue.withValues(alpha: 0.035),
                blurRadius: 12,
                offset: const Offset(0, 5),
              ),
            ],
          ),
          child: Stack(
            clipBehavior: Clip.none,
            children: [
              Positioned.fill(child: _glass(child: const SizedBox.expand())),
              Positioned(
                left: (_inset + _position * _travel - (lensWidth - _travel) / 2)
                    .clamp(1.0, _width - lensWidth - 1),
                top: (_height - lensHeight) / 2,
                width: lensWidth,
                height: lensHeight,
                child: IgnorePointer(
                  child: _glass(lens: true, child: const SizedBox.expand()),
                ),
              ),
              Positioned(
                left: _inset,
                right: _inset,
                top: _inset,
                bottom: _inset,
                child: Row(
                  children: [
                    _item(0, Icons.calendar_month_rounded, '课表'),
                    _item(1, Icons.assignment_outlined, '考试'),
                    _item(2, Icons.person_rounded, '个人设置'),
                  ],
                ),
              ),
            ],
          ),
        ),
      );
    },
  );
  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,
        onTapDown: (_) => _pressTo(1),
        onTapCancel: () {
          if (_drag == null) _pressTo(0);
        },
        onTap: () => _select(index),
        onHorizontalDragStart: index == widget.selectedIndex
            ? (_) {
                final start = _position.clamp(0.0, 2.0);
                _motion.stop();
                _pressTo(1);
                setState(() {
                  _drag = start;
                  _dragSpeed = 0;
                });
              }
            : null,
        onHorizontalDragUpdate: index == widget.selectedIndex
            ? (details) => setState(() {
                _dragSpeed = details.delta.dx / _travel * 60;
                _drag = (_position + details.delta.dx / _travel).clamp(
                  0.0,
                  2.0,
                );
              })
            : null,
        onHorizontalDragEnd: index == widget.selectedIndex
            ? (details) => _select(
                _position.round().clamp(0, 2),
                details.velocity.pixelsPerSecond.dx / _travel,
              )
            : null,
        onHorizontalDragCancel: index == widget.selectedIndex
            ? () {
                if (!mounted) return;
                final position = _position;
                setState(() => _drag = null);
                _motion.value = position;
                _spring(widget.selectedIndex);
                _pressTo(0);
              }
            : null,
        child: Center(
          child: AnimatedScale(
            scale: index == _position.round().clamp(0, 2)
                ? 1 + _pressure * 0.08
                : 1,
            duration: const Duration(milliseconds: 130),
            child: Icon(
              icon,
              size: 27,
              color: index == _position.round().clamp(0, 2)
                  ? _selectedInk
                  : _blue.withValues(alpha: 0.48),
            ),
          ),
        ),
      ),
    ),
  );
}

/// Thin paired rims and directional glints suggest rounded optical thickness.
/// All strong highlights stay on the edge; the centre remains clear.
class _GlassRimPainter extends CustomPainter {
  const _GlassRimPainter({required this.lens});
  final bool lens;
  static const _blue = Color(0xFF007AFF);
  @override
  void paint(Canvas canvas, Size size) {
    final edge = lens ? const Color(0xFF7B838F) : _blue;
    final bounds = Offset.zero & size;
    final outer = RRect.fromRectAndRadius(
      bounds.deflate(0.7),
      Radius.circular(size.height / 2),
    );
    final inner = RRect.fromRectAndRadius(
      bounds.deflate(2.2),
      Radius.circular(size.height / 2 - 1.5),
    );
    canvas.drawRRect(
      outer,
      Paint()
        ..style = PaintingStyle.stroke
        ..strokeWidth = lens ? 1.25 : 1.1
        ..shader = ui.Gradient.sweep(
          bounds.center,
          [
            Colors.white.withValues(alpha: 0.90),
            edge.withValues(alpha: lens ? 0.30 : 0.15),
            Colors.white.withValues(alpha: 0.10),
            Colors.white.withValues(alpha: 0.86),
            edge.withValues(alpha: 0.12),
            Colors.white.withValues(alpha: 0.90),
          ],
          [0.0, 0.18, 0.38, 0.60, 0.80, 1.0],
          TileMode.clamp,
          -math.pi / 2,
          math.pi * 1.5,
        ),
    );
    canvas.drawRRect(
      inner,
      Paint()
        ..style = PaintingStyle.stroke
        ..strokeWidth = 0.7
        ..shader = ui.Gradient.linear(
          bounds.topLeft,
          bounds.bottomRight,
          [
            Colors.white.withValues(alpha: 0.30),
            edge.withValues(alpha: lens ? 0.13 : 0.07),
            Colors.white.withValues(alpha: 0.40),
          ],
          [0.0, 0.5, 1.0],
        ),
    );
    final shine = Path()
      ..moveTo(size.height * 0.32, 4)
      ..quadraticBezierTo(
        size.width * 0.5,
        1.8,
        size.width - size.height * 0.35,
        4,
      );
    canvas.drawPath(
      shine,
      Paint()
        ..style = PaintingStyle.stroke
        ..strokeCap = StrokeCap.round
        ..strokeWidth = 0.8
        ..shader = ui.Gradient.linear(
          Offset.zero,
          Offset(size.width, 0),
          [
            Colors.white.withValues(alpha: 0),
            Colors.white.withValues(alpha: 0.65),
            Colors.white.withValues(alpha: 0),
          ],
          [0.0, 0.5, 1.0],
        ),
    );
  }

  @override
  bool shouldRepaint(_GlassRimPainter oldDelegate) => oldDelegate.lens != lens;
}