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 _height = 58.0, _inset = 3.0;
  double _width = 264;
  double get _travel => (_width - _inset * 2) / 3;
  static const _blue = Color(0xFF007AFF);
  late final AnimationController _motion = AnimationController.unbounded(
    vsync: this,
    value: widget.selectedIndex.toDouble(),
  );
  late final AnimationController _press = AnimationController.unbounded(
    vsync: this,
    value: 0,
  );
  late final AnimationController _tap = AnimationController(
    vsync: this,
    duration: const Duration(milliseconds: 460),
  );
  late final AnimationController _sway = AnimationController.unbounded(
    vsync: this,
  );
  void _swayTo(double target) {
    if (_reduceMotion) {
      _sway.value = 0;
      return;
    }
    _sway.animateWith(
      SpringSimulation(
        const SpringDescription(mass: 1, stiffness: 220, damping: 18),
        _sway.value,
        target,
        _sway.velocity.clamp(-12, 12),
      ),
    );
  }

  bool _reduceMotion = false;
  late int _targetIndex;
  @override
  void initState() {
    super.initState();
    _targetIndex = widget.selectedIndex;
  }

  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: 17),
        _press.value,
        target,
        _press.velocity,
      ),
    );
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    _reduceMotion = MediaQuery.disableAnimationsOf(context);
    if (_reduceMotion) {
      _motion.value = widget.selectedIndex.toDouble();
      _press.value = 0;
      _tap.value = 0;
      _sway.value = 0;
    }
  }

  double? _drag;
  double _dragSpeed = 0;
  double get _position => _drag ?? _motion.value.clamp(-0.12, 2.12);
  void _moveTo(int index, {double velocity = 0}) {
    _targetIndex = index;
    if (_reduceMotion) {
      _motion.value = index.toDouble();
      return;
    }
    _motion.animateWith(
      SpringSimulation(
        const SpringDescription(mass: 1, stiffness: 360, damping: 26),
        _position,
        index.toDouble(),
        velocity,
      ),
    );
  }

  void _select(int index, {bool elastic = false, double velocity = 0}) {
    final position = _position;
    final releaseVelocity = elastic
        ? velocity.clamp(-8.0, 8.0)
        : _motion.velocity;
    setState(() => _drag = null);
    _motion.value = position;
    _moveTo(index, velocity: releaseVelocity);
    // Retarget the position spring without resetting an in-flight size pulse.
    // Restarting that pulse at its peak made the glass edges jump on quick taps.
    if (!elastic && !_reduceMotion && !_tap.isAnimating) {
      _tap.forward(from: 0);
    }
    _pressTo(0);
    _swayTo(0);
    widget.onSelected(index);
  }

  @override
  void didUpdateWidget(GlassDock oldWidget) {
    super.didUpdateWidget(oldWidget);
    // The parent acknowledges onSelected with a rebuild. Restarting here used
    // to erase the release velocity and start a second spring for the same tab.
    if (widget.selectedIndex != _targetIndex && _drag == null) {
      _moveTo(widget.selectedIndex, velocity: _motion.velocity);
    }
  }

  @override
  void dispose() {
    _motion.dispose();
    _press.dispose();
    _tap.dispose();
    _sway.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, pressure: pressure),
      child: DecoratedBox(
        decoration: BoxDecoration(
          gradient: LinearGradient(
            begin: Alignment.topLeft,
            end: Alignment.bottomRight,
            colors: lens
                ? [
                    Color.lerp(
                      const Color(0xFFA1A4AA).withValues(alpha: 0.34),
                      const Color(0xFFD8DBE0).withValues(alpha: 0.0252),
                      pressure,
                    )!,
                    Color.lerp(
                      const Color(0xFF8E939B).withValues(alpha: 0.26),
                      const Color(0xFFC3C7CE).withValues(alpha: 0.0144),
                      pressure,
                    )!,
                    Color.lerp(
                      const Color(0xFFB4B7BC).withValues(alpha: 0.32),
                      const Color(0xFFE5E7EB).withValues(alpha: 0.0216),
                      pressure,
                    )!,
                  ]
                : [
                    Colors.white.withValues(alpha: 0.24),
                    const Color(0xFFF9FBFF).withValues(alpha: 0.12),
                    Colors.white.withValues(alpha: 0.18),
                  ],
          ),
        ),
        child: child,
      ),
    );
    return ClipRRect(
      borderRadius: BorderRadius.circular(40),
      child: GlassRefraction(
        strength: lens ? 0.78 + pressure * 0.70 : 1.05,
        blurSigma: lens ? 1.6 - pressure * 0.6 : 1.5,
        child: content,
      ),
    );
  }

  @override
  Widget build(BuildContext context) => LayoutBuilder(
    builder: (context, constraints) {
      _width = math.min(
        constraints.maxWidth,
        MediaQuery.sizeOf(context).width >= 600 ? 300.0 : 264.0,
      );
      return AnimatedBuilder(
        animation: Listenable.merge([_motion, _press, _tap, _sway]),
        builder: (context, _) {
          final press = _pressure;
          final pulse = _reduceMotion ? 0.0 : math.sin(math.pi * _tap.value);
          final speed = _reduceMotion
              ? 0.0
              : (_drag != null ? _dragSpeed : _motion.velocity).abs();
          final stretch =
              (speed / 80).clamp(0.0, 0.08) + pulse * 0.10 + press * 0.30;
          final lensWidth = _travel * (1 + stretch);
          final lensHeight =
              (_height - _inset * 2) *
              (1 +
                  press * 0.31 +
                  pulse * 0.08 -
                  (speed / 180).clamp(0.0, 0.035));
          // Resize real glass bounds: sampling stays aligned without scaling text.
          final sway = _reduceMotion ? 0.0 : _sway.value.clamp(-1.2, 1.2);
          final bodyGrowth = press * 12 + pulse * 3 + sway.abs() * 4;
          final bodyHeight =
              _height + press * 5 + pulse * 1.5 - sway.abs() * 0.8;
          final bodyShift =
              (_position - 1).clamp(-1.0, 1.0) * press * 2 + sway * 2.5;
          return SizedBox(
            width: _width,
            height: _height,
            child: DecoratedBox(
              decoration: BoxDecoration(
                borderRadius: BorderRadius.circular(40),
                boxShadow: [
                  BoxShadow(
                    color: const Color(0xFF4C6078).withValues(alpha: 0.075),
                    blurRadius: 18,
                    offset: const Offset(0, 6),
                  ),
                ],
              ),
              child: Stack(
                clipBehavior: Clip.none,
                children: [
                  Positioned(
                    left: -bodyGrowth / 2 + bodyShift,
                    top: (_height - bodyHeight) / 2,
                    width: _width + bodyGrowth,
                    height: bodyHeight,
                    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_rounded, '考试'),
                        _item(2, Icons.person_rounded, '个人设置', caption: '我的'),
                      ],
                    ),
                  ),
                ],
              ),
            ),
          );
        },
      );
    },
  );
  Widget _item(int index, IconData icon, String label, {String? caption}) =>
      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: index == widget.selectedIndex
                ? (_) => _pressTo(_reduceMotion ? 0 : 1)
                : null,
            onTapCancel: () {
              if (_drag == null) _pressTo(0);
            },
            onTap: () => _select(index),
            onHorizontalDragStart: index == widget.selectedIndex
                ? (_) {
                    final start = _position.clamp(0.0, 2.0);
                    _motion.stop();
                    _pressTo(_reduceMotion ? 0 : 1);
                    setState(() {
                      _drag = start;
                      _dragSpeed = 0;
                    });
                  }
                : null,
            onHorizontalDragUpdate: index == widget.selectedIndex
                ? (details) => setState(() {
                    _dragSpeed = details.delta.dx / _travel * 60;
                    _swayTo((_dragSpeed / 8).clamp(-1.0, 1.0));
                    _drag = (_position + details.delta.dx / _travel).clamp(
                      0.0,
                      2.0,
                    );
                  })
                : null,
            onHorizontalDragEnd: index == widget.selectedIndex
                ? (details) => _select(
                    _position.round().clamp(0, 2),
                    elastic: true,
                    velocity: details.velocity.pixelsPerSecond.dx / _travel,
                  )
                : null,
            onHorizontalDragCancel: index == widget.selectedIndex
                ? () {
                    if (!mounted) return;
                    final position = _position;
                    setState(() => _drag = null);
                    _motion.value = position;
                    _moveTo(widget.selectedIndex);
                    _pressTo(0);
                    _swayTo(0);
                  }
                : null,
            child: Center(
              child: Column(
                mainAxisSize: MainAxisSize.min,
                children: [
                  AnimatedScale(
                    scale: index == _position.round().clamp(0, 2)
                        ? 1 + _pressure * 0.08
                        : 1,
                    duration: const Duration(milliseconds: 130),
                    child: Icon(
                      icon,
                      size: 25,
                      color: index == _position.round().clamp(0, 2)
                          ? _blue
                          : _blue.withValues(alpha: 0.72),
                      shadows: [
                        Shadow(
                          color: Colors.white.withValues(
                            alpha: index == _position.round().clamp(0, 2)
                                ? 0.60
                                : 0.38,
                          ),
                          blurRadius: 8,
                        ),
                        Shadow(
                          color: Colors.white.withValues(
                            alpha: index == _position.round().clamp(0, 2)
                                ? 0.95
                                : 0.85,
                          ),
                          blurRadius: 2.8,
                        ),
                        Shadow(
                          color: Colors.white.withValues(
                            alpha: index == _position.round().clamp(0, 2)
                                ? 0.34
                                : 0.22,
                          ),
                          blurRadius: 1.4,
                        ),
                      ],
                    ),
                  ),
                  const SizedBox(height: 2),
                  Flexible(
                    child: FittedBox(
                      fit: BoxFit.scaleDown,
                      child: Text(
                        caption ?? label,
                        maxLines: 1,
                        style: TextStyle(
                          fontSize: 11,
                          height: 1.1,
                          fontWeight: FontWeight.w600,
                          color: index == _position.round().clamp(0, 2)
                              ? _blue
                              : _blue.withValues(alpha: 0.62),
                        ),
                      ),
                    ),
                  ),
                ],
              ),
            ),
          ),
        ),
      );
}

/// A white, rounded bevel catches light around a translucent milky body.
/// Highlights stay at the edge; the backdrop remains visible beneath the glass.
class _GlassRimPainter extends CustomPainter {
  const _GlassRimPainter({required this.lens, required this.pressure});
  final bool lens;
  final double pressure;
  @override
  void paint(Canvas canvas, Size size) {
    final edge = lens ? const Color(0xFF7B838F) : const Color(0xFF9CAABD);
    // A quiet grey selection at rest; the glossy lens rim returns on touch.
    final opacity = lens ? 0.25 + pressure * 0.75 : 1.0;
    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 ? 1.8 : 2.8
        ..maskFilter = MaskFilter.blur(BlurStyle.normal, lens ? 0.9 : 0.65)
        ..shader = ui.Gradient.linear(
          bounds.topLeft,
          bounds.bottomRight,
          [
            Colors.white.withValues(alpha: (lens ? 0.24 : 0.42) * opacity),
            edge.withValues(alpha: 0.04 * opacity),
            Colors.white.withValues(alpha: (lens ? 0.14 : 0.30) * opacity),
          ],
          [0.0, 0.55, 1.0],
        ),
    );
    canvas.drawRRect(
      outer,
      Paint()
        ..style = PaintingStyle.stroke
        ..strokeWidth = lens ? 1.25 : 1.1
        ..shader = ui.Gradient.sweep(
          bounds.center,
          [
            Colors.white.withValues(alpha: 0.96 * opacity),
            edge.withValues(alpha: (lens ? 0.30 : 0.15) * opacity),
            Colors.white.withValues(alpha: 0.10 * opacity),
            Colors.white.withValues(alpha: 0.94 * opacity),
            edge.withValues(alpha: 0.12 * opacity),
            Colors.white.withValues(alpha: 0.96 * opacity),
          ],
          [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: (lens ? 0.20 : 0.34) * opacity),
            edge.withValues(alpha: (lens ? 0.13 : 0.07) * opacity),
            Colors.white.withValues(alpha: (lens ? 0.28 : 0.40) * opacity),
          ],
          [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: 0.50 * opacity),
            Colors.white.withValues(alpha: 0),
          ],
          [0.0, 0.5, 1.0],
        ),
    );
  }

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