/// 登录页（UI-03 页面 01 重设计，图01）。
///
/// 结构：摄影拼贴顶部（渐变占位）→ 品牌 → 主标题（l10n `loginTitle`）
/// → 简短说明 → 账号/密码（显示/隐藏切换）→ Sign in → 管理员提供账号
/// 说明；右上角语言选择（复用 [showLanguageSheet]）。
///
/// 拼贴高度随可用高度自适应（正常 25%-32%；短屏/键盘开启时压缩），
/// 整页可滚动；提交期间禁用防重复，失败在表单附近以 StateBadge 展示
/// 错误码本地化文案。无注册/飞书/找回密码入口。
library;

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

import '../core/api_client.dart';
import '../core/app_exception.dart';
import '../core/error_l10n.dart';
import '../features/uploads/engine_scope.dart';
import '../l10n/app_localizations.dart';
import '../ui/components/language_sheet.dart';
import '../ui/components/state_badge.dart';
import '../ui/tokens.dart';

/// 登录页。
class LoginPage extends ConsumerStatefulWidget {
  const LoginPage({super.key});

  @override
  ConsumerState<LoginPage> createState() => _LoginPageState();
}

class _LoginPageState extends ConsumerState<LoginPage> {
  final _formKey = GlobalKey<FormState>();
  final _accountController = TextEditingController();
  final _passwordController = TextEditingController();

  bool _submitting = false;
  bool _obscurePassword = true;

  /// 最近一次提交失败文案（内联 StateBadge 展示；null = 无错误）。
  String? _errorText;

  @override
  void dispose() {
    _accountController.dispose();
    _passwordController.dispose();
    super.dispose();
  }

  Future<void> _submit() async {
    if (!_formKey.currentState!.validate()) return;
    setState(() {
      _submitting = true;
      _errorText = null;
    });
    final l10n = AppLocalizations.of(context);
    final navigator = Navigator.of(context);
    try {
      await ref.read(apiClientProvider).login(
            _accountController.text.trim(),
            _passwordController.text,
          );
      // 登录成功：刷新会话账号 → 引擎以新账号 scope start（Task 9 接线）。
      await ref.read(sessionAccountProvider.notifier).refresh();
      navigator.pushReplacementNamed('/home');
    } on AppException catch (error) {
      // 429（AUTH_RATE_LIMITED）等文案经错误码映射；登录页的
      // AUTH_INVALID_CREDENTIALS 即「账号或密码错误」。
      if (mounted) setState(() => _errorText = l10n.messageForError(error));
    } on Object {
      if (mounted) setState(() => _errorText = l10n.errorGeneric);
    } finally {
      if (mounted) setState(() => _submitting = false);
    }
  }

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final l10n = AppLocalizations.of(context);
    return Scaffold(
      // 顶部拼贴通到状态栏后（无 AppBar）；键盘由 Scaffold 默认压缩 body。
      body: SafeArea(
        top: false,
        child: LayoutBuilder(
          builder: (context, constraints) {
            final keyboardOpen =
                MediaQuery.of(context).viewInsets.bottom > 0;
            // 正常高度 28%（25%-32% 区间）；键盘/短屏压缩至 10%。
            final headerHeight = (constraints.maxHeight *
                    (keyboardOpen ? 0.10 : 0.28))
                .clamp(96.0, 320.0);
            return SingleChildScrollView(
              child: ConstrainedBox(
                constraints: BoxConstraints(
                  minHeight: constraints.maxHeight,
                ),
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.stretch,
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    _CollageHeader(height: headerHeight),
                    Padding(
                      padding: const EdgeInsets.fromLTRB(
                        kSpace24, kSpace24, kSpace24, kSpace24,
                      ),
                      child: ConstrainedBox(
                        constraints:
                            const BoxConstraints(maxWidth: 460),
                        child: Form(
                          key: _formKey,
                          autovalidateMode:
                              AutovalidateMode.onUserInteraction,
                          child: Column(
                            crossAxisAlignment:
                                CrossAxisAlignment.stretch,
                            children: [
                              _BrandRow(),
                              const SizedBox(height: kSpace16),
                              Text(
                                l10n.loginTitle,
                                // UI06：app-preview .login-content h1——27px/700。
                                style: theme.textTheme.titleLarge?.copyWith(
                                  fontSize: 27,
                                  fontWeight: FontWeight.w700,
                                  letterSpacing: -0.5,
                                ),
                              ),
                              const SizedBox(height: kSpace8),
                              Text(
                                l10n.loginSubtitle,
                                style: theme.textTheme.bodyMedium?.copyWith(
                                  color: theme.colorScheme.onSurfaceVariant,
                                ),
                              ),
                              const SizedBox(height: kSpace24),
                              TextFormField(
                                controller: _accountController,
                                autofillHints: const [
                                  AutofillHints.username,
                                ],
                                textInputAction: TextInputAction.next,
                                decoration: InputDecoration(
                                  labelText: l10n.username,
                                ),
                                validator: (value) => (value == null ||
                                        value.trim().isEmpty)
                                    ? l10n.fieldRequired
                                    : null,
                              ),
                              const SizedBox(height: kSpace16),
                              TextFormField(
                                controller: _passwordController,
                                obscureText: _obscurePassword,
                                enableSuggestions: false,
                                autocorrect: false,
                                autofillHints: const [
                                  AutofillHints.password,
                                ],
                                textInputAction: TextInputAction.done,
                                onFieldSubmitted: (_) =>
                                    _submitting ? null : _submit(),
                                decoration: InputDecoration(
                                  labelText: l10n.password,
                                  suffixIcon: Tooltip(
                                    message: _obscurePassword
                                        ? l10n.loginShowPassword
                                        : l10n.loginHidePassword,
                                    child: IconButton(
                                      onPressed: () => setState(
                                        () => _obscurePassword =
                                            !_obscurePassword,
                                      ),
                                      icon: Icon(
                                        _obscurePassword
                                            ? Icons.visibility_outlined
                                            : Icons
                                                .visibility_off_outlined,
                                        size: 24,
                                      ),
                                    ),
                                  ),
                                ),
                                validator: (value) => (value == null ||
                                        value.isEmpty)
                                    ? l10n.fieldRequired
                                    : null,
                              ),
                              if (_errorText != null) ...[
                                const SizedBox(height: kSpace16),
                                StateBadge(
                                  variant: BadgeVariant.error,
                                  label: _errorText!,
                                ),
                              ],
                              const SizedBox(height: kSpace24),
                              FilledButton(
                                onPressed: _submitting ? null : _submit,
                                child: _submitting
                                    ? const SizedBox(
                                        height: 20,
                                        width: 20,
                                        child: CircularProgressIndicator(
                                          strokeWidth: 2,
                                        ),
                                      )
                                    : Text(l10n.login),
                              ),
                              const SizedBox(height: kSpace12),
                              Text(
                                l10n.loginAskAdmin,
                                textAlign: TextAlign.center,
                                style: theme.textTheme.bodySmall?.copyWith(
                                  color:
                                      theme.colorScheme.onSurfaceVariant,
                                ),
                              ),
                            ],
                          ),
                        ),
                      ),
                    ),
                  ],
                ),
              ),
            );
          },
        ),
      ),
    );
  }
}

/// 摄影拼贴顶部（渐变 + 半透明照片色块占位）+ 右上语言选择入口。
///
/// TODO(brand-asset): 换用项目正式品牌/摄影素材（UI-03 §3.1：不得裁切
/// 设计板图片作背景；当前为可替换的中性渐变占位，不依赖远程图库）。
class _CollageHeader extends StatelessWidget {
  const _CollageHeader({required this.height});

  /// 占位高度（调用方按可用高度/键盘状态计算）。
  final double height;

  /// 拼贴占位（测试定位用）。
  static const Key collageKey = Key('login-collage');

  @override
  Widget build(BuildContext context) {
    final scheme = Theme.of(context).colorScheme;
    final soft = Color.lerp(scheme.primary, scheme.surface, 0.55);
    return SizedBox(
      height: height,
      child: Stack(
        children: [
          // 渐变拼贴占位（浅深色均由语义色派生，不硬编码白 token）。
          Container(
            key: collageKey,
            decoration: BoxDecoration(
              gradient: LinearGradient(
                begin: Alignment.topLeft,
                end: Alignment.bottomRight,
                colors: [scheme.primary, soft!],
              ),
            ),
          ),
          // 半透明「照片」色块（模拟拼贴节奏的装饰，可整体替换）。
          Positioned(
            left: 28,
            top: 24,
            child: _tile(120, 84, Colors.white.withValues(alpha: 0.16),
                rotate: -0.08),
          ),
          Positioned(
            right: 44,
            top: 40,
            child: _tile(132, 92, Colors.white.withValues(alpha: 0.12),
                rotate: 0.06),
          ),
          Positioned(
            left: 96,
            bottom: 18,
            child: _tile(150, 72, Colors.white.withValues(alpha: 0.10),
                rotate: -0.04),
          ),
          // 右上语言选择（浮于拼贴之上）。
          Positioned(
            top: MediaQuery.paddingOf(context).top + 8,
            right: kSpace12,
            child: const _LanguagePill(),
          ),
        ],
      ),
    );
  }

  Widget _tile(double width, double height, Color color,
      {double rotate = 0}) {
    return Transform.rotate(
      angle: rotate,
      child: Container(
        width: width,
        height: height,
        decoration: BoxDecoration(
          color: color,
          borderRadius: BorderRadius.circular(kRadiusInput),
        ),
      ),
    );
  }
}

/// 品牌行：小 logo 点 + 产品名（沿用现有 appName，不新增 slogan）。
class _BrandRow extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Row(
      children: [
        Container(
          width: 32,
          height: 32,
          decoration: BoxDecoration(
            color: theme.colorScheme.primary,
            borderRadius: BorderRadius.circular(10),
          ),
          child: Icon(
            Icons.photo_camera_outlined,
            size: 18,
            color: theme.colorScheme.onPrimary,
          ),
        ),
        const SizedBox(width: kSpace12),
        Text(
          AppLocalizations.of(context).appName,
          style: theme.textTheme.titleSmall?.copyWith(
            color: theme.colorScheme.onSurfaceVariant,
          ),
        ),
      ],
    );
  }
}

/// 语言选择胶囊（显示当前生效语言简称，点开共享语言面板）。
class _LanguagePill extends StatelessWidget {
  const _LanguagePill();

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final l10n = AppLocalizations.of(context);
    final isZh =
        Localizations.maybeLocaleOf(context)?.languageCode == 'zh';
    return Semantics(
      label: l10n.language,
      button: true,
      child: Material(
        color: theme.colorScheme.surface.withValues(alpha: 0.92),
        borderRadius: BorderRadius.circular(20),
        child: InkWell(
          onTap: () => showLanguageSheet(context),
          borderRadius: BorderRadius.circular(20),
          child: Padding(
            padding: const EdgeInsets.symmetric(
              horizontal: kSpace12,
              vertical: kSpace8,
            ),
            child: Row(
              mainAxisSize: MainAxisSize.min,
              children: [
                Icon(
                  Icons.language,
                  size: 18,
                  color: theme.colorScheme.onSurface,
                ),
                const SizedBox(width: kSpace4),
                Text(
                  isZh ? '中文' : 'EN',
                  style: theme.textTheme.labelMedium?.copyWith(
                    color: theme.colorScheme.onSurface,
                  ),
                ),
                Icon(
                  Icons.arrow_drop_down,
                  size: 18,
                  color: theme.colorScheme.onSurfaceVariant,
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}