Melo/lib/settings/equalizer_screen.dart

import 'dart:math' as math;

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

import '../player/audio_effects.dart';
import '../shared/theme.dart';

/// Equalizer-Bildschirm: Klangprofile, manuelle Bänder und die beiden
/// Drehregler für Bass und Immersives Audio.
class EqualizerScreen extends StatelessWidget {
  const EqualizerScreen({super.key});

  @override
  Widget build(BuildContext context) {
    final effects = context.watch<AudioEffects>();
    return Scaffold(
      appBar: AppBar(
        title: const Text('Equalizer'),
        actions: [
          Padding(
            padding: const EdgeInsets.only(right: 12),
            child: Switch(
              value: effects.enabled,
              onChanged: effects.available ? effects.setEnabled : null,
            ),
          ),
        ],
      ),
      body: !effects.available
          ? _NotAvailable(error: effects.error)
          : Opacity(
              opacity: effects.enabled ? 1 : 0.4,
              child: IgnorePointer(
                ignoring: !effects.enabled,
                child: ListView(
                  padding: const EdgeInsets.fromLTRB(16, 8, 16, 32),
                  children: [
                    _Presets(effects: effects),
                    const SizedBox(height: 24),
                    const _SectionTitle('Manuelle Anpassung'),
                    const SizedBox(height: 8),
                    _Bands(effects: effects),
                    const SizedBox(height: 28),
                    const _SectionTitle('Sound verbessern'),
                    const Padding(
                      padding: EdgeInsets.only(top: 4, bottom: 12),
                      child: Row(
                        children: [
                          Icon(Icons.headphones, size: 14, color: Colors.white38),
                          SizedBox(width: 6),
                          Expanded(
                            child: Text(
                              'Kopfhörer aufsetzen, bevor du die Soundeffekte '
                              'einstellst',
                              style: TextStyle(
                                  color: Colors.white38, fontSize: 12),
                            ),
                          ),
                        ],
                      ),
                    ),
                    _Enhancers(effects: effects),
                  ],
                ),
              ),
            ),
    );
  }
}

class _NotAvailable extends StatelessWidget {
  const _NotAvailable({this.error});
  final String? error;

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Padding(
        padding: const EdgeInsets.symmetric(horizontal: 32),
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            const Icon(Icons.graphic_eq, size: 64, color: Colors.white24),
            const SizedBox(height: 12),
            const Text(
              'Der Equalizer ist erst verfügbar, wenn Musik läuft',
              textAlign: TextAlign.center,
              style: TextStyle(color: Colors.white54),
            ),
            if (error != null) ...[
              const SizedBox(height: 8),
              Text(error!,
                  textAlign: TextAlign.center,
                  style: const TextStyle(color: Colors.white24, fontSize: 12)),
            ],
          ],
        ),
      ),
    );
  }
}

class _SectionTitle extends StatelessWidget {
  const _SectionTitle(this.text);
  final String text;

  @override
  Widget build(BuildContext context) {
    return Text(text,
        style: const TextStyle(fontSize: 20, fontWeight: FontWeight.w700));
  }
}

class _Presets extends StatelessWidget {
  const _Presets({required this.effects});
  final AudioEffects effects;

  @override
  Widget build(BuildContext context) {
    return Wrap(
      spacing: 10,
      runSpacing: 10,
      children: [
        for (var i = 0; i < effects.presets.length; i++)
          SizedBox(
            width: (MediaQuery.of(context).size.width - 32 - 20) / 3,
            height: 64,
            child: Material(
              color: MeloTheme.surfaceHigh,
              borderRadius: BorderRadius.circular(10),
              child: InkWell(
                borderRadius: BorderRadius.circular(10),
                onTap: () => effects.usePreset(i),
                child: Center(
                  child: Text(effects.presets[i],
                      textAlign: TextAlign.center,
                      maxLines: 2,
                      overflow: TextOverflow.ellipsis),
                ),
              ),
            ),
          ),
      ],
    );
  }
}

class _Bands extends StatelessWidget {
  const _Bands({required this.effects});
  final AudioEffects effects;

  @override
  Widget build(BuildContext context) {
    return Row(
      crossAxisAlignment: CrossAxisAlignment.end,
      children: [
        for (final band in effects.bands)
          Expanded(
            child: Column(
              children: [
                SizedBox(
                  height: 200,
                  child: RotatedBox(
                    quarterTurns: 3,
                    child: Slider(
                      value: band.level
                          .clamp(effects.minLevel, effects.maxLevel)
                          .toDouble(),
                      min: effects.minLevel.toDouble(),
                      max: effects.maxLevel.toDouble(),
                      onChanged: (v) =>
                          effects.setBandLevel(band.index, v.round()),
                    ),
                  ),
                ),
                Text(band.label,
                    style:
                        const TextStyle(color: Colors.white54, fontSize: 11)),
                Text('${(band.level / 100).round()}',
                    style:
                        const TextStyle(color: Colors.white38, fontSize: 11)),
              ],
            ),
          ),
      ],
    );
  }
}

class _Enhancers extends StatelessWidget {
  const _Enhancers({required this.effects});
  final AudioEffects effects;

  @override
  Widget build(BuildContext context) {
    return Row(
      mainAxisAlignment: MainAxisAlignment.spaceEvenly,
      children: [
        Knob(
          label: 'Bass',
          value: effects.bass / 1000,
          enabled: effects.bassSupported,
          onChanged: (v) => effects.setBass((v * 1000).round()),
        ),
        Knob(
          label: 'Immersives Audio',
          value: effects.virtualizer / 1000,
          enabled: effects.virtualizerSupported,
          onChanged: (v) => effects.setVirtualizer((v * 1000).round()),
        ),
      ],
    );
  }
}

/// Drehregler wie in der Vorlage: senkrecht wischen regelt von 0 bis 1.
class Knob extends StatelessWidget {
  const Knob({
    super.key,
    required this.label,
    required this.value,
    required this.onChanged,
    this.enabled = true,
  });

  final String label;
  final double value;
  final ValueChanged<double> onChanged;
  final bool enabled;

  static const _size = 120.0;

  @override
  Widget build(BuildContext context) {
    return Opacity(
      opacity: enabled ? 1 : 0.4,
      child: Column(
        children: [
          GestureDetector(
            onVerticalDragUpdate: enabled
                // Ein voller Ausschlag entspricht ~200 Pixel Wischweg.
                ? (d) => onChanged((value - d.delta.dy / 200).clamp(0.0, 1.0))
                : null,
            child: CustomPaint(
              size: const Size(_size, _size),
              painter: _KnobPainter(value),
            ),
          ),
          const SizedBox(height: 8),
          Text(label,
              style: const TextStyle(color: Colors.white54, fontSize: 12)),
          Text('${(value * 100).round()}',
              style: const TextStyle(color: Colors.white38, fontSize: 11)),
        ],
      ),
    );
  }
}

class _KnobPainter extends CustomPainter {
  _KnobPainter(this.value);
  final double value;

  /// Der Regelbereich läuft von unten links (135°) über 270° nach unten rechts.
  static const _start = math.pi * 0.75;
  static const _sweep = math.pi * 1.5;
  static const _dots = 24;

  @override
  void paint(Canvas canvas, Size size) {
    final center = Offset(size.width / 2, size.height / 2);
    final radius = size.width / 2;

    for (var i = 0; i < _dots; i++) {
      final t = i / (_dots - 1);
      final angle = _start + _sweep * t;
      final active = t <= value;
      canvas.drawCircle(
        center + Offset(math.cos(angle), math.sin(angle)) * (radius - 5),
        active ? 3.5 : 2.5,
        Paint()..color = active ? MeloTheme.red : Colors.white24,
      );
    }

    canvas.drawCircle(
      center,
      radius - 16,
      Paint()..color = MeloTheme.surfaceHigh,
    );
    canvas.drawCircle(
      center,
      radius - 16,
      Paint()
        ..style = PaintingStyle.stroke
        ..strokeWidth = 1
        ..color = Colors.white12,
    );

    final pointer = _start + _sweep * value;
    canvas.drawLine(
      center + Offset(math.cos(pointer), math.sin(pointer)) * (radius - 46),
      center + Offset(math.cos(pointer), math.sin(pointer)) * (radius - 22),
      Paint()
        ..color = Colors.white
        ..strokeWidth = 2
        ..strokeCap = StrokeCap.round,
    );
  }

  @override
  bool shouldRepaint(_KnobPainter oldDelegate) => oldDelegate.value != value;
}