import 'package:flutter/material.dart';
import 'package:patbond_flutter/core/theme/app_theme.dart';
import 'package:patbond_flutter/core/widgets/upload_progress_overlay.dart';
import 'package:patbond_flutter/features/community/media_uploader.dart';
import 'package:patbond_flutter/widgets/common.dart';

/// 图片九宫格展示态（05 号规范 §3.2）。
///
/// - 列数规则：2、4 图 → 2 列；3、5–9 图 → 3 列；全部 1:1 cover、
///   格间距 4、单格圆角 `sm`(12)，`RemoteImage` 复用（loading tint 块 /
///   失败图标兜底，缓存 key 已剥签名）。
/// - 超出折叠：最多显 9 格，[totalCount] 超过显示数时末格叠
///   `ink` 80% scrim + 白字「+N」20/w800（合成最亮白图 7.10:1；60% 档
///   3.88:1 不达标弃用，§5.1 精算）。
/// - 单图折叠形态：Feed 卡片契约只带封面 + mediaCount（FeedCard 裁剪），
///   [urls] 单元素而 [totalCount] > 1 时渲染 4:3 单格 + 右下「+N」角标
///   胶囊（同 80% scrim 精算）。
///
/// 编辑态（「＋」格 / 删除角标 / 进度覆盖层）见同文件 [PostMediaEditGrid]
/// （T3-17 发布页选图区）。
class PostMediaGrid extends StatelessWidget {
  const PostMediaGrid({
    required this.urls,
    super.key,
    this.totalCount,
    this.onCellTap,
  }) : assert(urls.length > 0, 'PostMediaGrid 至少一张图');

  /// 可展示的图片 URL（Feed 卡片仅封面一张；详情页全量）。
  final List<String> urls;

  /// 实际总张数（缺省 = urls.length）；大于可展示数时渲染「+N」。
  final int? totalCount;

  /// 格子点按（全屏浏览入口，T3-15 详情页接线）。
  final ValueChanged<int>? onCellTap;

  static const _maxCells = 9;
  static const _spacing = 4.0;

  int get _effectiveTotal => totalCount ?? urls.length;

  /// 列数规则（§3.2）：2、4 → 2 列；其余 → 3 列（1 图不走网格）。
  static int columnsFor(int cellCount) =>
      (cellCount == 2 || cellCount == 4) ? 2 : 3;

  @override
  Widget build(BuildContext context) {
    if (urls.length == 1) {
      return _CollapsedCover(
        url: urls.first,
        hiddenCount: _effectiveTotal - 1,
        onTap: onCellTap == null ? null : () => onCellTap!(0),
      );
    }

    final cellCount = urls.length > _maxCells ? _maxCells : urls.length;
    final overflow = _effectiveTotal - cellCount;
    final columns = columnsFor(cellCount);
    return GridView.builder(
      shrinkWrap: true,
      physics: const NeverScrollableScrollPhysics(),
      gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
        crossAxisCount: columns,
        mainAxisSpacing: _spacing,
        crossAxisSpacing: _spacing,
      ),
      itemCount: cellCount,
      itemBuilder: (context, index) {
        final isOverflowCell = overflow > 0 && index == cellCount - 1;
        Widget cell = RemoteImage(
          url: urls[index],
          borderRadius: BorderRadius.circular(AppRadius.sm),
        );
        if (isOverflowCell) {
          cell = Stack(
            fit: StackFit.expand,
            children: [
              cell,
              DecoratedBox(
                decoration: BoxDecoration(
                  color: AppColors.ink.withAlpha(204),
                  borderRadius: BorderRadius.circular(AppRadius.sm),
                ),
                child: Center(
                  child: Text(
                    '+$overflow',
                    style: const TextStyle(
                      color: Colors.white,
                      fontSize: 20,
                      fontWeight: FontWeight.w800,
                    ),
                  ),
                ),
              ),
            ],
          );
        }
        if (onCellTap != null) {
          cell = InkWell(
            onTap: () => onCellTap!(index),
            borderRadius: BorderRadius.circular(AppRadius.sm),
            child: cell,
          );
        }
        return cell;
      },
    );
  }
}

/// 编辑态九宫格（05 号规范 §3.2 编辑态；T3-17 发布页选图区）。
///
/// 与展示态 [PostMediaGrid] 同文件成组，但**独立成类**：展示态以
/// 「至少一张图 + URL 列表」为前提（构造断言），编辑态的常态却是
/// 「零张图 + 一个『＋』格」，共用一个构造签名只会让两边都别扭。
///
/// - 固定 3 列（九宫格语义），格间距 4、圆角 `sm`(12)、1:1 `cover`;
///   缩略图直接渲染选图原始字节（[MediaUploadItem.previewBytes]，
///   不落磁盘、不走网络；解码失败回落 surfaceTint 块 + pets 图标）。
/// - 每格叠 [UploadProgressOverlay]（六态映射四视觉态）；可重试失败格
///   整格点按重试，终态失败不给重试通栏。
/// - 删除角标：右上 22 圆 `ink` 80% 实底 + 白 close 14，触控热区 32。
/// - 「＋」格：虚线 1.5px 圆角 12 + `add_photo_alternate_outlined` 24
///   `inkSoft`；[canAdd] 为 false（满 9 张）时隐藏。
/// - 长按拖拽排序未做（05 §6 D9 可选项）：删格即整组重排，position 由
///   [MediaUploader.buildAttachRequests] 按当前列表序重发号。
class PostMediaEditGrid extends StatelessWidget {
  const PostMediaEditGrid({
    required this.items,
    super.key,
    this.canAdd = true,
    this.onAdd,
    this.onRemove,
    this.onRetry,
  });

  /// 当前上传项快照（顺序 = position 语义）。
  final List<MediaUploadItem> items;

  /// 是否渲染「＋」格（剩余槽位 > 0）。
  final bool canAdd;

  final VoidCallback? onAdd;

  /// 删格回调，参数为 [MediaUploadItem.localId]。
  final ValueChanged<int>? onRemove;

  /// 重试回调（仅可重试失败格触发），参数为 localId。
  final ValueChanged<int>? onRetry;

  static const _spacing = 4.0;
  static const _columns = 3;

  @override
  Widget build(BuildContext context) {
    final cellCount = items.length + (canAdd ? 1 : 0);
    if (cellCount == 0) return const SizedBox.shrink();
    return GridView.builder(
      shrinkWrap: true,
      physics: const NeverScrollableScrollPhysics(),
      gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
        crossAxisCount: _columns,
        mainAxisSpacing: _spacing,
        crossAxisSpacing: _spacing,
      ),
      itemCount: cellCount,
      itemBuilder: (context, index) {
        if (index == items.length) return _AddCell(onTap: onAdd);
        return _EditCell(
          item: items[index],
          onRemove: onRemove == null
              ? null
              : () => onRemove!(items[index].localId),
          onRetry: onRetry == null || !items[index].retryable
              ? null
              : () => onRetry!(items[index].localId),
        );
      },
    );
  }
}

class _EditCell extends StatelessWidget {
  const _EditCell({required this.item, this.onRemove, this.onRetry});

  final MediaUploadItem item;
  final VoidCallback? onRemove;
  final VoidCallback? onRetry;

  @override
  Widget build(BuildContext context) {
    return Stack(
      fit: StackFit.expand,
      children: [
        ClipRRect(
          borderRadius: BorderRadius.circular(AppRadius.sm),
          child: Image.memory(
            item.previewBytes,
            fit: BoxFit.cover,
            gaplessPlayback: true,
            // 选图字节无法解码时的兜底（RemoteImage 同款形态）。
            errorBuilder: (context, _, _) => const ColoredBox(
              color: AppColors.surfaceTint,
              child: Center(
                child: Icon(Icons.pets, color: AppColors.muted, size: 20),
              ),
            ),
          ),
        ),
        ClipRRect(
          borderRadius: BorderRadius.circular(AppRadius.sm),
          child: UploadProgressOverlay(
            phase: item.phase,
            progress: item.progress,
            onRetry: onRetry,
          ),
        ),
        Positioned(
          right: 0,
          top: 0,
          child: GestureDetector(
            onTap: onRemove,
            behavior: HitTestBehavior.opaque,
            child: const Padding(
              // 22 圆角标 + padding 撑到 32 触控热区。
              padding: EdgeInsets.all(5),
              child: DecoratedBox(
                decoration: BoxDecoration(
                  shape: BoxShape.circle,
                  color: Color(0xCC3E2A1F),
                ),
                child: SizedBox(
                  width: 22,
                  height: 22,
                  child: Center(
                    child: Icon(Icons.close, size: 14, color: Colors.white),
                  ),
                ),
              ),
            ),
          ),
        ),
      ],
    );
  }
}

class _AddCell extends StatelessWidget {
  const _AddCell({this.onTap});

  final VoidCallback? onTap;

  @override
  Widget build(BuildContext context) {
    return InkWell(
      onTap: onTap,
      borderRadius: BorderRadius.circular(AppRadius.sm),
      child: CustomPaint(
        painter: const _DashedBorderPainter(),
        child: const Center(
          child: Icon(
            Icons.add_photo_alternate_outlined,
            size: 24,
            color: AppColors.inkSoft,
          ),
        ),
      ),
    );
  }
}

/// 「＋」格的虚线圆角边框（Flutter 无内置虚线边框，按规范 1.5px 自绘）。
class _DashedBorderPainter extends CustomPainter {
  const _DashedBorderPainter();

  @override
  void paint(Canvas canvas, Size size) {
    final paint = Paint()
      ..color = AppColors.border
      ..strokeWidth = 1.5
      ..style = PaintingStyle.stroke;
    final path = Path()
      ..addRRect(
        RRect.fromRectAndRadius(
          Offset.zero & size,
          const Radius.circular(AppRadius.sm),
        ),
      );
    const dash = 5.0;
    const gap = 4.0;
    for (final metric in path.computeMetrics()) {
      var distance = 0.0;
      while (distance < metric.length) {
        final next = distance + dash;
        canvas.drawPath(
          metric.extractPath(
            distance,
            next > metric.length ? metric.length : next,
          ),
          paint,
        );
        distance = next + gap;
      }
    }
  }

  @override
  bool shouldRepaint(_DashedBorderPainter oldDelegate) => false;
}

/// 单图折叠形态：4:3 圆角封面 + 右下「+N」胶囊角标。
class _CollapsedCover extends StatelessWidget {
  const _CollapsedCover({
    required this.url,
    required this.hiddenCount,
    this.onTap,
  });

  final String url;
  final int hiddenCount;
  final VoidCallback? onTap;

  @override
  Widget build(BuildContext context) {
    Widget cover = AspectRatio(
      aspectRatio: 4 / 3,
      child: Stack(
        fit: StackFit.expand,
        children: [
          RemoteImage(
            url: url,
            borderRadius: BorderRadius.circular(AppRadius.sm),
          ),
          if (hiddenCount > 0)
            Positioned(
              right: 8,
              bottom: 8,
              child: Container(
                padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 3),
                decoration: BoxDecoration(
                  color: AppColors.ink.withAlpha(204),
                  borderRadius: BorderRadius.circular(AppRadius.pill),
                ),
                child: Text(
                  '+$hiddenCount',
                  style: const TextStyle(
                    color: Colors.white,
                    fontSize: 12,
                    fontWeight: FontWeight.w700,
                  ),
                ),
              ),
            ),
        ],
      ),
    );
    if (onTap != null) {
      cover = InkWell(
        onTap: onTap,
        borderRadius: BorderRadius.circular(AppRadius.sm),
        child: cover,
      );
    }
    return cover;
  }
}