// widgets/ds/ds_switch.dart — 原型 atoms.css .switch 的 Flutter 对照（2026-07-07 登记）。
// 38×22 pill 轨道 + 18px 圆点滑块：on=primary / off=border / disabled 45% 透明。
// 用于布尔即时生效场景（库存⇄在售挂售切换）；不同于 Material Switch 的尺寸与配色。
import 'package:flutter/material.dart';

import '../../core/theme/context_tokens.dart';

class DsSwitch extends StatelessWidget {
  final bool value;
  final ValueChanged<bool>? onChanged; // null = disabled
  const DsSwitch({super.key, required this.value, this.onChanged});

  @override
  Widget build(BuildContext context) {
    final t = context.tokens;
    final enabled = onChanged != null;
    return Semantics(
      toggled: value,
      button: true,
      child: GestureDetector(
        onTap: enabled ? () => onChanged!(!value) : null,
        child: Opacity(
          opacity: enabled ? 1 : .45,
          child: AnimatedContainer(
            duration: const Duration(milliseconds: 180),
            width: 38,
            height: 22,
            padding: const EdgeInsets.all(2),
            decoration: BoxDecoration(
              color: value ? t.primary : t.border,
              borderRadius: BorderRadius.circular(999),
            ),
            child: AnimatedAlign(
              duration: const Duration(milliseconds: 180),
              curve: Curves.easeOut,
              alignment: value ? Alignment.centerRight : Alignment.centerLeft,
              child: Container(
                width: 18,
                height: 18,
                decoration: BoxDecoration(
                  color: t.surface,
                  shape: BoxShape.circle,
                  boxShadow: [
                    BoxShadow(
                        color: t.shadow, blurRadius: 3, offset: const Offset(0, 1)),
                  ],
                ),
              ),
            ),
          ),
        ),
      ),
    );
  }
}