import 'dart:io';
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'package:photo_manager/photo_manager.dart';
import 'package:photo_manager_image_provider/photo_manager_image_provider.dart';
import 'package:provider/provider.dart';
import '../controllers/upload_controller.dart';
import '../core/app_theme.dart';

class GalleryScreen extends StatefulWidget {
  const GalleryScreen({super.key, required this.folderId});
  final String? folderId;
  @override
  State<GalleryScreen> createState() => _GalleryScreenState();
}

class _GalleryScreenState extends State<GalleryScreen> {
  final _scroll = ScrollController();
  final List<AssetEntity> _assets = [];
  final Set<String> _selected = {};
  AssetPathEntity? _album;
  int _page = 0;
  bool _loading = true;
  bool _more = true;
  bool _queueing = false;
  String? _error;

  @override
  void initState() {
    super.initState();
    _scroll.addListener(() {
      if (_scroll.position.extentAfter < 800) _loadMore();
    });
    _initialize();
  }

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

  Future<void> _initialize() async {
    final permission = await PhotoManager.requestPermissionExtend();
    if (!permission.hasAccess) {
      setState(() {
        _loading = false;
        _error = 'Gallery access is required to choose your media.';
      });
      return;
    }
    final albums = await PhotoManager.getAssetPathList(
      type: RequestType.common,
      onlyAll: true,
    );
    if (albums.isEmpty) {
      setState(() {
        _loading = false;
        _error = 'No photos or videos were found.';
      });
      return;
    }
    _album = albums.first;
    await _loadMore();
  }

  Future<void> _loadMore() async {
    if (!_more ||
        (_loading && _assets.isNotEmpty) ||
        _album == null && !_loading) {
      return;
    }
    final album = _album;
    if (album == null) return;
    if (_assets.isNotEmpty) setState(() => _loading = true);
    final page = await album.getAssetListPaged(page: _page, size: 80);
    if (!mounted) return;
    setState(() {
      _assets.addAll(page);
      _page++;
      _more = page.length == 80;
      _loading = false;
    });
  }

  Future<void> _queueUploads() async {
    if (_selected.isEmpty) return;
    setState(() => _queueing = true);
    var queued = 0;
    try {
      final support = await getApplicationSupportDirectory();
      final queue = Directory(
        '${support.path}${Platform.pathSeparator}upload_queue',
      );
      await queue.create(recursive: true);
      final chosen = _assets
          .where((asset) => _selected.contains(asset.id))
          .toList();
      for (var index = 0; index < chosen.length; index++) {
        final asset = chosen[index];
        final source = await asset.originFile;
        if (source == null) continue;
        final original = (asset.title ?? source.uri.pathSegments.last)
            .replaceAll(RegExp(r'[\\/:*?"<>|]'), '_');
        final stagedName =
            '${DateTime.now().microsecondsSinceEpoch}_$index-$original';
        await source.copy('${queue.path}${Platform.pathSeparator}$stagedName');
        if (!mounted) return;
        await context.read<UploadController>().enqueue(
          filename: stagedName,
          displayName: original,
          folderId: widget.folderId,
        );
        queued++;
      }
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(
            content: Text(
              '$queued file${queued == 1 ? '' : 's'} added to the background upload queue.',
            ),
          ),
        );
        Navigator.pop(context, true);
      }
    } catch (error) {
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(content: Text('Could not queue all files: $error')),
        );
      }
    } finally {
      if (mounted) setState(() => _queueing = false);
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Choose from gallery'),
        actions: [
          if (_selected.isNotEmpty)
            TextButton(
              onPressed: () => setState(_selected.clear),
              child: const Text('Clear'),
            ),
        ],
      ),
      body: _error != null
          ? Center(
              child: Padding(
                padding: const EdgeInsets.all(32),
                child: Column(
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    const Icon(
                      Icons.photo_library_outlined,
                      size: 62,
                      color: AppTheme.blue,
                    ),
                    const SizedBox(height: 14),
                    Text(_error!, textAlign: TextAlign.center),
                    const SizedBox(height: 14),
                    OutlinedButton(
                      onPressed: PhotoManager.openSetting,
                      child: const Text('Open settings'),
                    ),
                  ],
                ),
              ),
            )
          : _assets.isEmpty && _loading
          ? const Center(child: CircularProgressIndicator())
          : GridView.builder(
              controller: _scroll,
              padding: const EdgeInsets.fromLTRB(3, 3, 3, 110),
              gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
                crossAxisCount: 3,
                mainAxisSpacing: 3,
                crossAxisSpacing: 3,
              ),
              itemCount: _assets.length + (_loading ? 1 : 0),
              itemBuilder: (context, index) {
                if (index >= _assets.length) {
                  return const Center(
                    child: CircularProgressIndicator(strokeWidth: 2),
                  );
                }
                final asset = _assets[index];
                final selected = _selected.contains(asset.id);
                return GestureDetector(
                  onTap: () => setState(
                    () => selected
                        ? _selected.remove(asset.id)
                        : _selected.add(asset.id),
                  ),
                  child: Stack(
                    fit: StackFit.expand,
                    children: [
                      AssetEntityImage(
                        asset,
                        isOriginal: false,
                        thumbnailSize: const ThumbnailSize.square(350),
                        fit: BoxFit.cover,
                      ),
                      if (selected)
                        Container(color: AppTheme.blue.withValues(alpha: .30)),
                      if (asset.type == AssetType.video)
                        const Positioned(
                          left: 7,
                          bottom: 7,
                          child: Icon(
                            Icons.videocam_rounded,
                            color: Colors.white,
                          ),
                        ),
                      Positioned(
                        right: 7,
                        top: 7,
                        child: AnimatedContainer(
                          duration: const Duration(milliseconds: 150),
                          width: 25,
                          height: 25,
                          decoration: BoxDecoration(
                            shape: BoxShape.circle,
                            color: selected ? AppTheme.blue : Colors.black38,
                            border: Border.all(color: Colors.white, width: 2),
                          ),
                          child: selected
                              ? const Icon(
                                  Icons.check,
                                  color: Colors.white,
                                  size: 17,
                                )
                              : null,
                        ),
                      ),
                    ],
                  ),
                );
              },
            ),
      bottomNavigationBar: SafeArea(
        child: Padding(
          padding: const EdgeInsets.all(14),
          child: FilledButton.icon(
            onPressed: _selected.isEmpty || _queueing ? null : _queueUploads,
            icon: _queueing
                ? const SizedBox.square(
                    dimension: 20,
                    child: CircularProgressIndicator(
                      strokeWidth: 2,
                      color: Colors.white,
                    ),
                  )
                : const Icon(Icons.cloud_upload_outlined),
            label: Text(
              _selected.isEmpty
                  ? 'Select photos or videos'
                  : 'Upload ${_selected.length} selected',
            ),
          ),
        ),
      ),
    );
  }
}