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

import 'package:flutter/material.dart';
import 'package:flutter/physics.dart';
import 'package:flutter/scheduler.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: 620),
  );
  late final AnimationController _sway = AnimationController.unbounded(
    vsync: this,
  );
  late final AnimationController _ripple = AnimationController(
    vsync: this,
    duration: const Duration(milliseconds: 620),
  );
  void _wakeRipple() {
    if (!_reduceMotion && !_ripple.isAnimating) _ripple.forward(from: 0);
  }

  double _swayTarget = 0, _swayVelocity = 0, _dragTarget = 0, _dragVelocity = 0;
  Duration? _elasticLastTick;
  late final Ticker _elasticTicker = createTicker(_tickElastic);
  void _startElastic() {
    if (!_elasticTicker.isActive) {
      _elasticLastTick = null;
      _elasticTicker.start();
    }
  }

  // Keep one clock alive while input changes its targets. Restarting a spring
  // on every pointer event repeatedly paints t=0 under continuous dragging.
  void _tickElastic(Duration elapsed) {
    final seconds = _elasticLastTick == null
        ? 1 / 60
        : ((elapsed - _elasticLastTick!).inMicroseconds / 1000000).clamp(
            0.0,
            0.25,
          );
    _elasticLastTick = elapsed;
    if (_drag == null) {
      _swayTarget = _tap.isAnimating
          ? (_motion.velocity / 14).clamp(-0.85, 0.85)
          : 0;
    }
    final sway = _advanceSpring(
      _sway.value,
      _swayVelocity,
      _swayTarget,
      220,
      18,
      seconds,
    );
    final drag = _advanceSpring(
      _dragFollow.value,
      _dragVelocity,
      _dragTarget,
      680,
      28,
      seconds,
    );
    _swayVelocity = sway.$2;
    _dragVelocity = drag.$2;
    _sway.value = sway.$1;
    _dragFollow.value = drag.$1;
    if (!_tap.isAnimating &&
        (_sway.value - _swayTarget).abs() < 0.0005 &&
        _swayVelocity.abs() < 0.005 &&
        (_dragFollow.value - _dragTarget).abs() < 0.0005 &&
        _dragVelocity.abs() < 0.005) {
      _sway.value = _swayTarget;
      _dragFollow.value = _dragTarget;
      _swayVelocity = _dragVelocity = 0;
      _elasticTicker.stop();
      _elasticLastTick = null;
    }
  }

  (double, double) _advanceSpring(
    double value,
    double velocity,
    double target,
    double stiffness,
    double damping,
    double seconds,
  ) {
    final steps = math.max(1, (seconds * 120).ceil());
    final step = seconds / steps;
    for (var i = 0; i < steps; i++) {
      velocity += (stiffness * (target - value) - damping * velocity) * step;
      value += velocity * step;
    }
    return (value, velocity);
  }

  void _swayTo(double target) {
    _swayTarget = _reduceMotion ? 0 : target;
    if (_reduceMotion) {
      _sway.value = 0;
      _swayVelocity = 0;
      return;
    }
    _startElastic();
  }

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

  double get _pressure => _press.value.clamp(0.0, 1.18);
  double get _tapBloom {
    if (_reduceMotion) return 0;
    final t = _tap.value;
    final tail = t <= 0.5
        ? 1.0
        : Curves.easeInOut.transform((2 * (1 - t)).clamp(0.0, 1.0));
    return math.sin(math.pi * t) * tail;
  }

  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;
      _ripple.value = 0;
      _elasticTicker.stop();
      _elasticLastTick = null;
      _swayTarget = _swayVelocity = _dragVelocity = 0;
      _dragTarget = _drag ?? widget.selectedIndex.toDouble();
      _dragFollow.value = _drag ?? widget.selectedIndex.toDouble();
      _sway.value = 0;
    }
  }

  late final AnimationController _dragFollow = AnimationController.unbounded(
    vsync: this,
    value: widget.selectedIndex.toDouble(),
  );
  void _followDragTo(double target) {
    _dragTarget = target;
    if (_reduceMotion) {
      _dragFollow.value = target;
      _dragVelocity = 0;
      return;
    }
    _startElastic();
  }

  double? _drag;
  double _dragSpeed = 0;
  double get _position =>
      (_drag != null ? _dragFollow.value : _motion.value).clamp(-0.12, 2.12);
  void _moveTo(int index, {double velocity = 0, bool springyTap = false}) {
    _targetIndex = index;
    if (_reduceMotion) {
      _motion.value = index.toDouble();
      return;
    }
    _motion.animateWith(
      SpringSimulation(
        springyTap
            ? const SpringDescription(mass: 1, stiffness: 350, damping: 20)
            : 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, springyTap: !elastic);
    // 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() {
    _elasticTicker.dispose();
    _motion.dispose();
    _press.dispose();
    _tap.dispose();
    _sway.dispose();
    _ripple.dispose();
    _dragFollow.dispose();
    super.dispose();
  }

  Widget _glass({required Widget child, bool lens = false}) {
    final pressure = math.max(_pressure.clamp(0.0, 1.0), _tapBloom * 0.85);
    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: 0.28),
                      const Color(0xFFD8DBE0).withValues(alpha: 0.0252),
                      pressure,
                    )!,
                    Color.lerp(
                      const Color(0xFF8E939B).withValues(alpha: 0.21),
                      const Color(0xFFC3C7CE).withValues(alpha: 0.0144),
                      pressure,
                    )!,
                    Color.lerp(
                      const Color(0xFFB4B7BC).withValues(alpha: 0.26),
                      const Color(0xFFE5E7EB).withValues(alpha: 0.0216),
                      pressure,
                    )!,
                  ]
                : [
                    Colors.white.withValues(alpha: 0.29),
                    const Color(0xFFFDFEFF).withValues(alpha: 0.17),
                    Colors.white.withValues(alpha: 0.23),
                  ],
          ),
        ),
        child: child,
      ),
    );
    return ClipRRect(
      borderRadius: BorderRadius.circular(40),
      child: GlassRefraction(
        strength: lens ? 0.78 + pressure * 0.70 : 0.98,
        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,
      );
      final viewport = MediaQuery.sizeOf(context).width;
      final availableWidth = math.min(
        viewport > 0 ? viewport : constraints.maxWidth,
        constraints.maxWidth,
      );
      final edgeAllowance = math.max(0.0, (availableWidth - _width) / 2 - 8);
      return AnimatedBuilder(
        animation: Listenable.merge([
          _motion,
          _press,
          _tap,
          _sway,
          _ripple,
          _dragFollow,
        ]),
        builder: (context, _) {
          final press = _pressure;
          final pulse = _reduceMotion ? 0.0 : math.sin(math.pi * _tap.value);
          // Travel stretches horizontally; landing squeezes then rebounds
          // vertically. Endpoints are zero so quick retargets remain continuous.
          final tapWave = _reduceMotion
              ? 0.0
              : math.sin(2 * math.pi * _tap.value);
          final tapStretch = tapWave >= 0 ? tapWave * 0.24 : tapWave * 0.08;
          final tapRise = tapWave >= 0 ? -tapWave * 0.045 : -tapWave * 0.15;
          // Pointer movement wakes a finite ripple; pauses do not start idle loops.
          final dragWave = _reduceMotion
              ? 0.0
              : math.sin(2 * math.pi * _ripple.value) * press.clamp(0.0, 1.0);
          final dragStretch = dragWave * (dragWave >= 0 ? 0.10 : 0.06);
          final tapInflate = _tapBloom * 0.30;
          final speed = _reduceMotion
              ? 0.0
              : (_drag != null ? _dragSpeed : _motion.velocity).abs();
          final stretch =
              (speed / 80).clamp(0.0, 0.08) +
              tapStretch +
              tapInflate +
              press * 0.30 +
              dragStretch;
          final lensWidth = _travel * (1 + stretch);
          final lensHeight =
              (_height - _inset * 2) *
              (1 +
                  press * 0.31 +
                  tapRise +
                  tapInflate -
                  dragWave * 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 * 7 + sway.abs() * 4;
          final bodyHeight = _height + press * 5 + pulse * 3 - sway.abs() * 0.8;
          final dockShift = sway * 8;
          final leadingPull = sway * 6;
          return SizedBox(
            width: _width,
            height: _height,
            child: Stack(
              clipBehavior: Clip.none,
              children: [
                Positioned(
                  left: dockShift,
                  top: 0,
                  width: _width,
                  height: _height,
                  child: DecoratedBox(
                    decoration: BoxDecoration(
                      borderRadius: BorderRadius.circular(40),
                      boxShadow: [
                        BoxShadow(
                          color: const Color(0xFF4C6078)
                              .withValues(alpha: 0.05),
                          blurRadius: 14,
                          offset: const Offset(0, 4),
                        ),
                      ],
                    ),
                    child: Stack(
                      clipBehavior: Clip.none,
                      children: [
                        Positioned(
                          left: -bodyGrowth / 2 + math.min(leadingPull, 0),
                          top: (_height - bodyHeight) / 2,
                          width: _width + bodyGrowth + leadingPull.abs(),
                          height: bodyHeight,
                          child: _glass(child: const SizedBox.expand()),
                        ),
                        Positioned(
                          left:
                              (_inset +
                                      _position * _travel -
                                      (lensWidth - _travel) / 2)
                                  .clamp(
                                    -edgeAllowance - dockShift,
                                    _width +
                                        edgeAllowance -
                                        dockShift -
                                        lensWidth,
                                  ),
                          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(
            // Selection must not replace the symbol's active animation state.
            key: ValueKey('dock-item-$index'),
            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);
                    _dragFollow.value = start;
                    _dragTarget = start;
                    _dragVelocity = _motion.velocity;
                    _motion.stop();
                    _wakeRipple();
                    _pressTo(_reduceMotion ? 0 : 1);
                    setState(() {
                      _drag = start;
                      _dragSpeed = 0;
                    });
                  }
                : null,
            onHorizontalDragUpdate: index == widget.selectedIndex
                ? (details) => setState(() {
                    _dragSpeed = details.delta.dx / _travel * 60;
                    _wakeRipple();
                    _swayTo((_dragSpeed / 8).clamp(-1.0, 1.0));
                    _drag = (_drag! + details.delta.dx / _travel).clamp(
                      0.0,
                      2.0,
                    );
                    _followDragTo(_drag!);
                  })
                : null,
            onHorizontalDragEnd: index == widget.selectedIndex
                ? (details) => _select(
                    (_drag ?? _position).round().clamp(0, 2),
                    elastic: true,
                    velocity: _dragVelocity,
                  )
                : null,
            onHorizontalDragCancel: index == widget.selectedIndex
                ? () {
                    if (!mounted) return;
                    final position = _position;
                    setState(() => _drag = null);
                    _motion.value = position;
                    _moveTo(widget.selectedIndex, velocity: _dragVelocity);
                    _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: _DockSymbol(
                      active: (_position - index).abs() < 0.28,
                      reduceMotion: _reduceMotion,
                      child: Icon(
                        icon,
                        key: index == widget.selectedIndex
                            ? const Key('dock-cursor')
                            : null,
                        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),
                        ),
                      ),
                    ),
                  ),
                ],
              ),
            ),
          ),
        ),
      );
}

/// Plays once on entry. Remaining over a symbol does not restart its animation.
class _DockSymbol extends StatefulWidget {
  const _DockSymbol({
    required this.active,
    required this.reduceMotion,
    required this.child,
  });
  final bool active, reduceMotion;
  final Widget child;
  @override
  State<_DockSymbol> createState() => _DockSymbolState();
}

class _DockSymbolState extends State<_DockSymbol>
    with SingleTickerProviderStateMixin {
  late final AnimationController _bounce = AnimationController(
    vsync: this,
    duration: const Duration(milliseconds: 440),
  );
  @override
  void didUpdateWidget(_DockSymbol oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (widget.reduceMotion || !widget.active) {
      _bounce.value = 0;
    } else if (!oldWidget.active) {
      _bounce.forward(from: 0);
    }
  }

  @override
  void dispose() {
    _bounce.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) => AnimatedBuilder(
    animation: _bounce,
    child: widget.child,
    builder: (context, child) {
      final lift = widget.reduceMotion
          ? 0.0
          : math.sin(math.pi * _bounce.value);
      return Transform.translate(
        offset: Offset(0, -3.5 * lift),
        child: Transform.scale(scale: 1 + lift * 0.16, child: child),
      );
    },
  );
}

/// 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 ? 1.2 : 1.6
        ..maskFilter = MaskFilter.blur(BlurStyle.normal, lens ? 1.05 : 1.0)
        ..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 ? 0.85 : 0.65
        ..shader = ui.Gradient.sweep(
          bounds.center,
          [
            Colors.white.withValues(alpha: 0.84 * opacity),
            edge.withValues(alpha: (lens ? 0.30 : 0.15) * opacity),
            Colors.white.withValues(alpha: 0.10 * opacity),
            Colors.white.withValues(alpha: 0.82 * opacity),
            edge.withValues(alpha: 0.12 * opacity),
            Colors.white.withValues(alpha: 0.84 * 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 = 0.35
        ..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;
}