import 'dart:typed_data';

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

import '../../core/api/api_config.dart';
import '../../core/api/services/image_api.dart';
import '../../core/auth/auth_service.dart';
import '../../core/theme/app_colors.dart';
import '../../core/theme/app_spacing.dart';
import '../../shared/widgets/top_nav_bar.dart';

import 'models/gallery_task_item.dart';
import 'video_thumbnail_cache.dart';

/// Gallery screen - matches Pencil hpwBg
class GalleryScreen extends StatefulWidget {
  const GalleryScreen({super.key, required this.isActive});

  final bool isActive;

  @override
  State<GalleryScreen> createState() => _GalleryScreenState();
}

class _GalleryScreenState extends State<GalleryScreen> {
  List<GalleryTaskItem> _tasks = [];
  bool _loading = true;
  bool _loadingMore = false;
  String? _error;
  int _currentPage = 1;
  bool _hasNext = false;
  bool _hasLoadedOnce = false;
  final ScrollController _scrollController = ScrollController();
  static const int _pageSize = 20;

  @override
  void initState() {
    super.initState();
    _scrollController.addListener(_onScroll);
    if (widget.isActive) _loadTasks(refresh: true);
  }

  @override
  void didUpdateWidget(covariant GalleryScreen oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (widget.isActive && !oldWidget.isActive && !_hasLoadedOnce) {
      _loadTasks(refresh: true);
    }
  }

  @override
  void dispose() {
    _scrollController.dispose();
    super.dispose();
  }

  void _onScroll() {
    if (_loadingMore || !_hasNext || _tasks.isEmpty) return;
    final pos = _scrollController.position;
    if (pos.pixels >= pos.maxScrollExtent - 200) {
      _loadTasks(refresh: false);
    }
  }

  Future<void> _loadTasks({bool refresh = true}) async {
    if (refresh) {
      setState(() {
        _loading = true;
        _error = null;
        _currentPage = 1;
      });
    } else {
      if (_loadingMore || !_hasNext) return;
      setState(() => _loadingMore = true);
    }

    try {
      await AuthService.loginComplete;
      final page = refresh ? 1 : _currentPage;
      final res = await ImageApi.getMyTasks(
        sentinel: ApiConfig.appId,
        trophy: page.toString(),
        heatmap: _pageSize.toString(),
      );
      if (!mounted) return;
      if (res.isSuccess && res.data != null) {
        final data = res.data as Map<String, dynamic>?;
        final intensify = data?['intensify'] as List<dynamic>? ?? [];

        final list = intensify
            .whereType<Map<String, dynamic>>()
            .map((e) => GalleryTaskItem.fromJson(e))
            .toList();
        final hasNext = data?['manifest'] as bool? ?? false;

        setState(() {
          if (refresh) {
            _tasks = list;
          } else {
            _tasks = [..._tasks, ...list];
          }
          _currentPage = page + 1;
          _hasNext = hasNext;
          _loading = false;
          _loadingMore = false;
          _hasLoadedOnce = true;
        });
      } else {
        setState(() {
          if (refresh) _tasks = [];
          _loading = false;
          _loadingMore = false;
          _error = res.msg.isNotEmpty ? res.msg : 'Failed to load';
        });
      }
    } catch (e) {
      if (mounted) {
        setState(() {
          if (refresh) _tasks = [];
          _loading = false;
          _loadingMore = false;
          _error = e.toString();
        });
      }
    }
  }

  List<GalleryMediaItem> get _gridItems {
    final items = <GalleryMediaItem>[];
    for (final task in _tasks) {
      items.addAll(task.mediaItems);
    }
    return items;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: AppColors.background,
      appBar: const PreferredSize(
        preferredSize: Size.fromHeight(56),
        child: TopNavBar(
          title: 'My Gallery',
        ),
      ),
      body: _loading
          ? const Center(child: CircularProgressIndicator())
          : _error != null
              ? Center(
                  child: Column(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: [
                      Text(
                        _error!,
                        textAlign: TextAlign.center,
                        style: const TextStyle(color: AppColors.textSecondary),
                      ),
                      const SizedBox(height: AppSpacing.lg),
                      TextButton(
                        onPressed: _loadTasks,
                        child: const Text('Retry'),
                      ),
                    ],
                  ),
                )
              : LayoutBuilder(
                  builder: (context, constraints) {
                    return Center(
                      child: ConstrainedBox(
                        constraints: const BoxConstraints(maxWidth: 390),
                        child: RefreshIndicator(
                          onRefresh: () => _loadTasks(refresh: true),
                          child: _gridItems.isEmpty && !_loading
                              ? SingleChildScrollView(
                                  physics:
                                      const AlwaysScrollableScrollPhysics(),
                                  child: SizedBox(
                                    height: constraints.maxHeight - 100,
                                    child: const Center(
                                      child: Text(
                                        'No images yet',
                                        style: TextStyle(
                                          color: AppColors.textSecondary,
                                        ),
                                      ),
                                    ),
                                  ),
                                )
                              : GridView.builder(
                                  physics:
                                      const AlwaysScrollableScrollPhysics(),
                                  controller: _scrollController,
                                  padding: EdgeInsets.fromLTRB(
                                    AppSpacing.screenPadding,
                                    AppSpacing.xl,
                                    AppSpacing.screenPadding,
                                    AppSpacing.screenPaddingLarge +
                                        (_loadingMore ? 48.0 : 0),
                                  ),
                                  gridDelegate:
                                      const SliverGridDelegateWithFixedCrossAxisCount(
                                    crossAxisCount: 2,
                                    childAspectRatio: 165 / 248,
                                    mainAxisSpacing: AppSpacing.xl,
                                    crossAxisSpacing: AppSpacing.xl,
                                  ),
                                  itemCount: _gridItems.length +
                                      (_loadingMore ? 1 : 0),
                                  itemBuilder: (context, index) {
                                    if (index >= _gridItems.length) {
                                      return const Center(
                                        child: Padding(
                                          padding: EdgeInsets.all(16),
                                          child: SizedBox(
                                            width: 24,
                                            height: 24,
                                            child: CircularProgressIndicator(
                                              strokeWidth: 2,
                                            ),
                                          ),
                                        ),
                                      );
                                    }
                                    return _GalleryCard(
                                      mediaItem: _gridItems[index],
                                      onTap: () {
                                        Navigator.of(context).pushNamed(
                                          '/result',
                                          arguments: _gridItems[index],
                                        );
                                      },
                                    );
                                  },
                                ),
                        ),
                      ),
                    );
                  },
                ),
    );
  }
}

class _GalleryCard extends StatelessWidget {
  const _GalleryCard({
    required this.mediaItem,
    required this.onTap,
  });

  final GalleryMediaItem mediaItem;
  final VoidCallback onTap;

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: onTap,
      child: LayoutBuilder(
        builder: (context, constraints) {
          return Container(
            width: constraints.maxWidth,
            height: constraints.maxHeight,
            decoration: BoxDecoration(
              color: AppColors.surfaceAlt,
              borderRadius: BorderRadius.circular(24),
              border: Border.all(color: AppColors.border, width: 1),
              boxShadow: const [
                BoxShadow(
                  color: AppColors.shadowMedium,
                  blurRadius: 12,
                  offset: Offset(0, 4),
                ),
              ],
            ),
            child: ClipRRect(
              borderRadius: BorderRadius.circular(24),
              child: mediaItem.isVideo
                  ? _VideoThumbnailCover(videoUrl: mediaItem.videoUrl!)
                  : (mediaItem.imageUrl != null &&
                          mediaItem.imageUrl!.isNotEmpty)
                      ? CachedNetworkImage(
                          imageUrl: mediaItem.imageUrl!,
                          fit: BoxFit.cover,
                          placeholder: (_, __) => Container(
                            color: AppColors.surfaceAlt,
                          ),
                          errorWidget: (_, __, ___) => Container(
                            color: AppColors.surfaceAlt,
                          ),
                        )
                      : Container(color: AppColors.surfaceAlt),
            ),
          );
        },
      ),
    );
  }
}

class _VideoThumbnailCover extends StatelessWidget {
  const _VideoThumbnailCover({required this.videoUrl});

  final String videoUrl;

  @override
  Widget build(BuildContext context) {
    return FutureBuilder<Uint8List?>(
      future: VideoThumbnailCache.instance.getThumbnail(videoUrl),
      builder: (context, snapshot) {
        if (snapshot.hasData && snapshot.data != null) {
          return Image.memory(
            snapshot.data!,
            fit: BoxFit.cover,
          );
        }
        return Container(
          color: AppColors.surfaceAlt,
          child: snapshot.connectionState == ConnectionState.waiting
              ? const Center(
                  child: SizedBox(
                    width: 24,
                    height: 24,
                    child: CircularProgressIndicator(strokeWidth: 2),
                  ),
                )
              : const SizedBox.shrink(),
        );
      },
    );
  }
}