/// 相册列表页签：游标加载更多、下拉刷新、整图封面卡（UI-03 §4 页面 05）。
///
/// 卡片为 16:9 全幅封面（无封面同尺寸中性占位），标题（白，≤2 行，语言
/// 回退链）/时间场地（white70 单行）/公开与上传状态小徽章叠加在底部暗色
/// 渐变上——文字区域高于基准时卡片增高，不截掉徽章。手机单列；可用宽度
/// > 600 双列（行内卡片等高）。publicToken 与四开关堆叠不在主卡片（完整
/// 配置在详情设置）。
library;

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

import '../core/error_l10n.dart';
import '../features/albums/album_format.dart';
import '../features/albums/models.dart';
import '../features/albums/providers.dart';
import '../l10n/app_localizations.dart';
import '../ui/components/empty_state.dart';
import '../ui/components/error_state.dart';
import '../ui/components/photo_thumbnail.dart';
import '../ui/tokens.dart';
import 'album_detail_page.dart';
import 'album_form_page.dart';

/// 双列布局的可用宽度阈值（方案 §4.1「平板按可用宽度使用两列」）。
const double kAlbumTwoColumnMinWidth = 600;

/// 首页「相册」页签（UI-03 页面 05）：标题 + 副标题，右上「新建」圆形
/// 入口；空态 CTA 与之共用 [AlbumsTab.openCreate]。
class AlbumsTab extends ConsumerWidget {
  const AlbumsTab({super.key});

  /// 打开创建表单；成功后刷新列表（空态 CTA 与右上入口共用）。
  static Future<void> openCreate(BuildContext context, WidgetRef ref) async {
    final changed = await Navigator.of(context).push<bool>(
      MaterialPageRoute<bool>(builder: (_) => const AlbumFormPage()),
    );
    if (changed == true) {
      ref.read(albumListProvider.notifier).refresh();
    }
  }

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final l10n = AppLocalizations.of(context);
    final theme = Theme.of(context);
    final state = ref.watch(albumListProvider);
    return Scaffold(
      appBar: AppBar(
        title: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          mainAxisSize: MainAxisSize.min,
          children: [
            Text(l10n.albums),
            Text(
              l10n.albumsSubtitle,
              style: theme.textTheme.bodySmall?.copyWith(
                color: theme.colorScheme.onSurfaceVariant,
              ),
            ),
          ],
        ),
        actions: [
          Padding(
            padding: const EdgeInsets.only(right: kSpace16),
            child: IconButton.filled(
              tooltip: l10n.albumCreate,
              onPressed: () => openCreate(context, ref),
              icon: const Icon(Icons.add),
            ),
          ),
        ],
      ),
      body: AlbumListBody(state: state),
    );
  }
}

/// 列表主体：按状态分发 加载/错误/空/列表（含加载更多页脚）。
///
/// 空态带「新建相册」入口；错误态带重试。列表按可用宽度切换单/双列，
/// 行结构 [ListView.builder]（行 = 1-2 张卡片），保证下拉刷新与游标
/// 加载更多行为与旧版一致。
class AlbumListBody extends ConsumerWidget {
  const AlbumListBody({required this.state, super.key});

  final AlbumListState state;

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final l10n = AppLocalizations.of(context);
    final notifier = ref.read(albumListProvider.notifier);

    if (state.loading) {
      return const Center(child: CircularProgressIndicator());
    }
    if (state.items.isEmpty) {
      if (state.errorCode != null) {
        return ErrorState(
          message: l10n.messageForErrorCode(state.errorCode!),
          onRetry: notifier.refresh,
        );
      }
      // 空态也保留下拉刷新（被拉进相册后可手动刷新看到，2026-09-23 用户报告）。
      return RefreshIndicator(
        onRefresh: notifier.refresh,
        child: ListView(
          physics: const AlwaysScrollableScrollPhysics(),
          children: [
            SizedBox(
              height: MediaQuery.of(context).size.height * 0.5,
              child: EmptyState(
                icon: Icons.photo_library_outlined,
                title: l10n.albumsEmpty,
                actionLabel: l10n.albumCreate,
                onAction: () => AlbumsTab.openCreate(context, ref),
              ),
            ),
          ],
        ),
      );
    }

    return LayoutBuilder(
      builder: (context, constraints) {
        final twoColumns = constraints.maxWidth > kAlbumTwoColumnMinWidth;
        final rowCount = (state.items.length / (twoColumns ? 2 : 1)).ceil();
        final hasFooter = state.hasMore || state.loadMoreFailed;
        return RefreshIndicator(
          onRefresh: notifier.refresh,
          child: ListView.builder(
            physics: const AlwaysScrollableScrollPhysics(),
            padding: const EdgeInsets.fromLTRB(
              kSpace16,
              kSpace8,
              kSpace16,
              kSpace32,
            ),
            itemCount: rowCount + (hasFooter ? 1 : 0),
            itemBuilder: (context, index) {
              if (index >= rowCount) {
                if (state.loadMoreFailed) {
                  return ListTile(
                    contentPadding: EdgeInsets.zero,
                    leading: const Icon(Icons.error_outline),
                    title: Text(l10n.loadMoreFailed),
                    onTap: notifier.loadMore,
                  );
                }
                return const Padding(
                  padding: EdgeInsets.symmetric(vertical: kSpace16),
                  child: Center(
                    child: SizedBox(
                      height: 24,
                      width: 24,
                      child: CircularProgressIndicator(strokeWidth: 2),
                    ),
                  ),
                );
              }
              // 接近底部时预取下一页（loadMore 自带并发/末页守卫）。
              if (index >= rowCount - 2 &&
                  state.hasMore &&
                  !state.loadingMore) {
                WidgetsBinding.instance.addPostFrameCallback(
                  (_) => notifier.loadMore(),
                );
              }
              if (!twoColumns) {
                return AlbumCard(album: state.items[index]);
              }
              final first = index * 2;
              final hasSecond = first + 1 < state.items.length;
              // 双列并排：卡片高度由 16:9 封面主导、各自自撑（不用
              // IntrinsicHeight 等高——整图卡内含 LayoutBuilder 不支持
              // intrinsic 计算；文字区域高于基准的极端大字体下允许行内
              // 微小高度差）。
              return Row(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  Expanded(child: AlbumCard(album: state.items[first])),
                  if (hasSecond) ...[
                    const SizedBox(width: kSpace12),
                    Expanded(child: AlbumCard(album: state.items[first + 1])),
                  ],
                ],
              );
            },
          ),
        );
      },
    );
  }
}

/// 相册卡片（UI-03 §4 页面 05）：整卡 16:9 封面 + 底部暗色渐变叠层。
///
/// 图片铺满整卡（无封面/加载失败为同尺寸中性占位），标题/时间场地/状态
/// 徽章以白字叠加在渐变上；文字区域高于 16:9 基准时卡片增高（大字体下
/// 不截断徽章）。标题按「界面语言 → 相册默认语言 → 首个条目」回退；时间
/// 用相册时区；公开/上传分别显示（图标 + 文案，不只靠颜色）。publicToken
/// 与四开关堆叠已从主卡片移除（完整配置在详情设置）。
class AlbumCard extends StatelessWidget {
  const AlbumCard({required this.album, super.key});

  final AlbumSummary album;

  /// 底部渐变：透明 → black54，只压暗下半部（白字对比度）。
  /// UI06：app-preview .scrim——30% 起渐变到 #0C1728E8（只压暗下部）。
  static const LinearGradient _scrim = LinearGradient(
    begin: Alignment.topCenter,
    end: Alignment.bottomCenter,
    stops: [0.30, 1.0],
    colors: [Color(0x00000000), Color(0xE80C1728)],
  );

  @override
  Widget build(BuildContext context) {
    final l10n = AppLocalizations.of(context);
    final theme = Theme.of(context);
    final venue = albumDisplayVenue(album, l10n.localeName);
    final meta = venue == null
        ? _timeRange(l10n)
        : '${_timeRange(l10n)} · $venue';
    return Card(
      margin: const EdgeInsets.symmetric(vertical: kSpace8),
      clipBehavior: Clip.antiAlias,
      child: InkWell(
        onTap: () => Navigator.of(context).push(
          MaterialPageRoute<void>(
            builder: (_) => AlbumDetailPage(albumId: album.id),
          ),
        ),
        child: LayoutBuilder(
          builder: (context, constraints) {
            // 16:9 基准高度；作为 Stack 首个子节点参与 IntrinsicHeight
            // 双列等高（RenderStack 的 intrinsic 只看首子节点）。
            final baseHeight = constraints.maxWidth * 9 / 16;
            return Stack(
              alignment: Alignment.bottomLeft,
              children: [
                SizedBox(width: double.infinity, height: baseHeight),
                Positioned.fill(
                  child: PhotoThumbnail(
                    url: album.cover?.url,
                    aspectRatio: 16 / 9,
                  ),
                ),
                const Positioned.fill(
                  child: DecoratedBox(
                    decoration: BoxDecoration(gradient: _scrim),
                  ),
                ),
                Padding(
                  padding: const EdgeInsets.fromLTRB(
                    kSpace16,
                    kSpace16,
                    kSpace16,
                    kSpace12,
                  ),
                  child: Column(
                    mainAxisSize: MainAxisSize.min,
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      Text(
                        albumDisplayTitle(album, l10n.localeName),
                        maxLines: 2,
                        overflow: TextOverflow.ellipsis,
                        style: theme.textTheme.titleMedium?.copyWith(
                          color: Colors.white,
                          fontWeight: FontWeight.w600,
                        ),
                      ),
                      const SizedBox(height: kSpace4),
                      Text(
                        meta,
                        maxLines: 1,
                        overflow: TextOverflow.ellipsis,
                        style: theme.textTheme.bodySmall?.copyWith(
                          color: Colors.white70,
                        ),
                      ),
                      const SizedBox(height: kSpace8),
                      Row(
                        children: [
                          _OverlayBadge(
                            icon: album.publicEnabled
                                ? Icons.info_outline
                                : Icons.remove_circle_outline,
                            color: album.publicEnabled
                                ? kColorInfoDark
                                : Colors.white70,
                            label: album.publicEnabled
                                ? l10n.tagPublic
                                : l10n.albumPublicOff,
                          ),
                          const SizedBox(width: kSpace8),
                          _OverlayBadge(
                            icon: album.uploadEnabled
                                ? Icons.check_circle
                                : Icons.remove_circle_outline,
                            color: album.uploadEnabled
                                ? kColorSuccessDark
                                : Colors.white70,
                            label: album.uploadEnabled
                                ? l10n.albumUploadsOn
                                : l10n.albumUploadsOff,
                          ),
                        ],
                      ),
                    ],
                  ),
                ),
              ],
            );
          },
        ),
      ),
    );
  }

  /// 相册时区的时间区间（结束未定显示「未定」占位）。
  String _timeRange(AppLocalizations l10n) {
    final locale = l10n.localeName;
    final start = formatAlbumDateTime(album.startAt, album.timezone, locale);
    final end = album.endAt == null
        ? l10n.notSet
        : formatAlbumDateTime(album.endAt!, album.timezone, locale);
    return '$start ~ $end';
  }
}

/// 图片叠层上的状态小徽章：半透明深色底 + 白字（语义色仅用于图标，
/// 提亮变体保证在照片上的对比度）。
class _OverlayBadge extends StatelessWidget {
  const _OverlayBadge({
    required this.icon,
    required this.color,
    required this.label,
  });

  final IconData icon;
  final Color color;
  final String label;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Container(
      padding: const EdgeInsets.symmetric(horizontal: kSpace8, vertical: 4),
      decoration: BoxDecoration(
        color: Colors.black.withValues(alpha: 0.35),
        borderRadius: BorderRadius.circular(kRadiusBadge),
      ),
      child: Row(
        mainAxisSize: MainAxisSize.min,
        children: [
          Icon(icon, size: 14, color: color),
          const SizedBox(width: kSpace4),
          Text(
            label,
            maxLines: 1,
            overflow: TextOverflow.ellipsis,
            style: theme.textTheme.labelSmall?.copyWith(
              color: Colors.white,
              fontWeight: FontWeight.w600,
            ),
          ),
        ],
      ),
    );
  }
}