jiu/client/lib/screens/auth/auth_shared.dart

// screens/auth/auth_shared.dart — 登录/注册两屏共用的原型 1:1 骨架。
// 对应 login.html / register.html 的公共部分：
//   body：--page 底、居中、pad 24；
//   主题切换：主界面同款小衣服 ThemePickerPill（onSurface 浅色变体），
//     放表单面板右上角（2026-07-03 用户拍板，替代原型的 A/B/C 圆钮）；
//   .auth：两栏卡片（surface / 1px border / r-xl / sh-3，overflow hidden）；
//   .brand：左侧品牌渐变面板 linear-gradient(150deg, side-bg, side-active-bg)。
// 窄屏（≤ context.isMobile）折叠为单列，隐藏 pts/steps（原型 @media 760px 同构，
// 断点遵项目规则统一走 isMobile）。
import 'package:flutter/material.dart';

import '../../core/responsive/responsive.dart';
import '../../core/theme/app_dims.g.dart';
import '../../core/theme/context_tokens.dart';
import '../../widgets/theme_picker_pill.dart';

/// 整页骨架：page 底 + 居中滚动 + 两栏卡片 + 右上角主题切换器。
/// [brand]/[form] 为两栏内容；宽屏按 [brandWidth]/[formWidth] 定宽
/// （其一为 null 表示该栏弹性 1fr），窄屏纵向堆叠。
class AuthPageScaffold extends StatelessWidget {
  final Widget brand;
  final Widget form;
  final double maxWidth;
  final double narrowMaxWidth;
  final double? brandWidth; // null = 弹性栏
  final double? formWidth; // null = 弹性栏
  const AuthPageScaffold({
    super.key,
    required this.brand,
    required this.form,
    required this.maxWidth,
    required this.narrowMaxWidth,
    this.brandWidth,
    this.formWidth,
  });

  @override
  Widget build(BuildContext context) {
    final t = context.tokens;
    final narrow = context.isMobile;
    // 表单面板右上角叠主题小衣服（宽/窄屏都落在白底表单区上）
    final formWithPill = Stack(
      children: [
        form,
        const Positioned(
            top: 14, right: 16, child: ThemePickerPill(onSurface: true)),
      ],
    );
    final card = Container(
      clipBehavior: Clip.antiAlias,
      decoration: BoxDecoration(
        color: t.surface,
        border: Border.all(color: t.border),
        borderRadius: BorderRadius.circular(AppDims.rXl),
        boxShadow: [
          BoxShadow(
              color: t.shadow, offset: const Offset(0, 12), blurRadius: 34),
        ],
      ),
      child: narrow
          ? Column(
              mainAxisSize: MainAxisSize.min, children: [brand, formWithPill])
          : IntrinsicHeight(
              child: Row(
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: [
                  if (brandWidth != null)
                    SizedBox(width: brandWidth, child: brand)
                  else
                    Expanded(child: brand),
                  if (formWidth != null)
                    SizedBox(width: formWidth, child: formWithPill)
                  else
                    Expanded(child: formWithPill),
                ],
              ),
            ),
    );
    return Scaffold(
      backgroundColor: t.page,
      body: SingleChildScrollView(
        padding: const EdgeInsets.all(24),
        child: ConstrainedBox(
          constraints: BoxConstraints(
              minHeight: MediaQuery.of(context).size.height - 48),
          child: Center(
            child: ConstrainedBox(
              constraints:
                  BoxConstraints(maxWidth: narrow ? narrowMaxWidth : maxWidth),
              child: card,
            ),
          ),
        ),
      ),
    );
  }
}

/// 品牌渐变面板容器（.brand）：linear-gradient(150deg, side-bg, side-active-bg)。
class AuthBrandPanel extends StatelessWidget {
  final EdgeInsets padding;
  final double? minHeight;
  final Widget child;
  const AuthBrandPanel(
      {super.key, required this.padding, this.minHeight, required this.child});

  @override
  Widget build(BuildContext context) {
    final t = context.tokens;
    return Container(
      constraints:
          minHeight != null ? BoxConstraints(minHeight: minHeight!) : null,
      padding: padding,
      decoration: BoxDecoration(
        // 150deg ≈ 从左上偏上往右下（CSS 角度顺时针自 12 点起）
        gradient: LinearGradient(
          begin: const Alignment(-0.5, -1),
          end: const Alignment(0.5, 1),
          colors: [t.sideBg, t.sideActiveBg],
        ),
      ),
      child: child,
    );
  }
}