import 'dart:typed_data';

import 'package:flutter/foundation.dart'
    show defaultTargetPlatform, kIsWeb, TargetPlatform;
import 'package:flutter/material.dart';
import 'package:flutter_lucide/flutter_lucide.dart';
import 'package:photo_manager/photo_manager.dart';

import '../../../core/theme/app_colors.dart';
import '../../../core/theme/app_spacing.dart';

/// [showModalBottomSheet] 返回此值时由**外层页面**调系统相机，避免 BottomSheet 与相机 Activity 叠放导致返回后黑屏/卡死。
const String kAlbumPickerRequestCamera = '__album_picker_camera__';

/// 底部弹层：首格为拍照，其余为相册图片（与常见 App 一致）
class AlbumPickerSheet extends StatefulWidget {
  const AlbumPickerSheet({super.key});

  @override
  State<AlbumPickerSheet> createState() => _AlbumPickerSheetState();
}

class _AlbumPickerSheetState extends State<AlbumPickerSheet> {
  /// 首屏少一点，减轻同时解码缩略图的压力
  static const int _pageSize = 36;

  final ScrollController _scrollController = ScrollController();

  bool _busy = true;
  String? _error;
  AssetPathEntity? _recentAlbum;
  final List<AssetEntity> _assets = [];
  int _loadedPage = -1;
  int _totalCount = 0;
  bool _loadingMore = false;
  /// 最近一次权限结果（用于「仅部分照片」等说明）
  PermissionState _permissionState = PermissionState.notDetermined;

  @override
  void initState() {
    super.initState();
    _scrollController.addListener(_maybeLoadMore);
    // 等弹层完成首帧布局后再跑权限/读库，避免与 ModalRoute 争主线程；也方便 ScrollController 晚一点 attach
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (mounted) _init();
    });
  }

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

  Future<void> _init() async {
    setState(() {
      _busy = true;
      _error = null;
    });

    final state = await PhotoManager.requestPermissionExtend();
    if (!mounted) return;
    _permissionState = state;

    if (!state.hasAccess) {
      setState(() {
        _busy = false;
        _error = state == PermissionState.denied
            ? 'Photo library access is required. Tap below to open Settings.'
            : 'Cannot access photo library.';
      });
      return;
    }

    final paths = await PhotoManager.getAssetPathList(
      type: RequestType.image,
      onlyAll: true,
      hasAll: true,
    );
    if (!mounted) return;

    if (paths.isEmpty) {
      setState(() {
        _busy = false;
        _recentAlbum = null;
        _totalCount = 0;
        _assets.clear();
        _loadedPage = -1;
      });
      return;
    }

    _recentAlbum = paths.first;
    _totalCount = await _recentAlbum!.assetCountAsync;
    if (!mounted) return;

    if (_totalCount == 0) {
      setState(() {
        _assets.clear();
        _loadedPage = -1;
        _busy = false;
      });
      return;
    }

    final first = await _recentAlbum!.getAssetListPaged(page: 0, size: _pageSize);
    if (!mounted) return;

    setState(() {
      _assets
        ..clear()
        ..addAll(first);
      _loadedPage = 0;
      _busy = false;
    });
  }

  /// iOS：系统「补充照片」面板；Android 等：打开系统设置改权限
  Future<void> _openManagePhotoAccess() async {
    if (!kIsWeb && defaultTargetPlatform == TargetPlatform.iOS) {
      try {
        await PhotoManager.presentLimited();
      } catch (_) {
        await PhotoManager.openSetting();
        return;
      }
    } else {
      await PhotoManager.openSetting();
      return;
    }
    if (mounted) await _init();
  }

  void _maybeLoadMore() {
    if (_loadingMore || _busy || _recentAlbum == null) return;
    if (_assets.length >= _totalCount) return;
    // 未 attach 时访问 .position 会抛错，导致点击 Generate 后卡死/闪退
    if (!_scrollController.hasClients) return;
    final pos = _scrollController.position;
    final maxExtent = pos.maxScrollExtent;
    if (!maxExtent.isFinite || maxExtent <= 0) return;
    if (pos.pixels < maxExtent - 380) return;
    _loadMore();
  }

  Future<void> _loadMore() async {
    final album = _recentAlbum;
    if (album == null || _loadingMore) return;
    if (_assets.length >= _totalCount) return;

    setState(() => _loadingMore = true);
    try {
      final nextPage = _loadedPage + 1;
      final list =
          await album.getAssetListPaged(page: nextPage, size: _pageSize);
      if (!mounted) return;
      if (list.isNotEmpty) {
        setState(() {
          _assets.addAll(list);
          _loadedPage = nextPage;
        });
      }
    } finally {
      if (mounted) setState(() => _loadingMore = false);
    }
  }

  Future<void> _onCamera() async {
    if (!mounted) return;
    // 不在弹层内调 pickImage：BottomSheet 与相机 Activity 叠加时，返回后 Surface 有概率无法恢复（全黑）。
    Navigator.of(context).pop<String>(kAlbumPickerRequestCamera);
  }

  Future<void> _onAsset(AssetEntity e) async {
    final f = await e.file;
    if (!mounted) return;
    if (f != null) {
      Navigator.of(context).pop<String>(f.path);
    } else if (mounted) {
      final limited = _permissionState == PermissionState.limited;
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(
          content: Text(
            limited
                ? 'Cannot read this photo. It may not be included in your '
                    'current selection. Use "Manage photo access" or choose '
                    'another image.'
                : 'Could not open this photo. Try another.',
          ),
          behavior: SnackBarBehavior.floating,
        ),
      );
    }
  }

  bool get _showNoPhotosHelp =>
      !_busy && _error == null && _totalCount == 0;

  static const int _crossCount = 3;
  static const double _spacing = 3;

  @override
  Widget build(BuildContext context) {
    final bottomPad = MediaQuery.paddingOf(context).bottom;

    return Material(
      color: AppColors.surface,
      borderRadius: const BorderRadius.vertical(top: Radius.circular(16)),
      clipBehavior: Clip.antiAlias,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          Padding(
            padding: const EdgeInsets.fromLTRB(
              AppSpacing.sm,
              AppSpacing.sm,
              AppSpacing.sm,
              AppSpacing.md,
            ),
            child: Row(
              children: [
                IconButton(
                  onPressed: () => Navigator.of(context).pop<String?>(),
                  icon: const Icon(LucideIcons.x, color: AppColors.textPrimary),
                ),
                const Expanded(
                  child: Text(
                    'Choose photo',
                    textAlign: TextAlign.center,
                    style: TextStyle(
                      fontSize: 17,
                      fontWeight: FontWeight.w600,
                      color: AppColors.textPrimary,
                    ),
                  ),
                ),
                const SizedBox(width: 48),
              ],
            ),
          ),
          const Divider(height: 1, color: AppColors.border),
          Expanded(
            child: _busy
                ? const Center(
                    child: CircularProgressIndicator(color: AppColors.primary),
                  )
                : _error != null
                    ? Center(
                        child: Padding(
                          padding: const EdgeInsets.all(AppSpacing.xl),
                          child: Column(
                            mainAxisSize: MainAxisSize.min,
                            children: [
                              Text(
                                _error!,
                                textAlign: TextAlign.center,
                                style: const TextStyle(
                                  color: AppColors.textSecondary,
                                ),
                              ),
                              const SizedBox(height: AppSpacing.lg),
                              TextButton(
                                onPressed: () async {
                                  await PhotoManager.openSetting();
                                },
                                child: const Text('Open Settings'),
                              ),
                              TextButton(
                                onPressed: _init,
                                child: const Text('Try again'),
                              ),
                            ],
                          ),
                        ),
                      )
                    : _showNoPhotosHelp
                        ? _NoPhotosInLibraryPanel(
                            isLimitedAccess:
                                _permissionState == PermissionState.limited,
                            onManageAccess: _openManagePhotoAccess,
                            onOpenSettings: () async {
                              await PhotoManager.openSetting();
                            },
                            onRetry: _init,
                            onUseCamera: _onCamera,
                          )
                        : GridView.builder(
                        controller: _scrollController,
                        cacheExtent: 220,
                        padding: EdgeInsets.fromLTRB(
                          _spacing,
                          _spacing,
                          _spacing,
                          _spacing + bottomPad,
                        ),
                        gridDelegate:
                            const SliverGridDelegateWithFixedCrossAxisCount(
                          crossAxisCount: _crossCount,
                          mainAxisSpacing: _spacing,
                          crossAxisSpacing: _spacing,
                          childAspectRatio: 1,
                        ),
                        itemCount:
                            1 + _assets.length + (_loadingMore ? 1 : 0),
                        itemBuilder: (context, index) {
                          if (index == 0) {
                            return _CameraGridTile(onTap: _onCamera);
                          }
                          final ai = index - 1;
                          if (ai >= _assets.length) {
                            return const Center(
                              child: SizedBox(
                                width: 24,
                                height: 24,
                                child: CircularProgressIndicator(
                                  strokeWidth: 2,
                                  color: AppColors.primary,
                                ),
                              ),
                            );
                          }
                          final asset = _assets[ai];
                          return GestureDetector(
                            onTap: () => _onAsset(asset),
                            child: _AlbumThumbnail(asset: asset),
                          );
                        },
                      ),
          ),
        ],
      ),
    );
  }
}

/// 权限为「部分照片」或相册对本应用不可见时：引导补充选图或去设置，避免只显示相机无说明
class _NoPhotosInLibraryPanel extends StatelessWidget {
  const _NoPhotosInLibraryPanel({
    required this.isLimitedAccess,
    required this.onManageAccess,
    required this.onOpenSettings,
    required this.onRetry,
    required this.onUseCamera,
  });

  final bool isLimitedAccess;
  final Future<void> Function() onManageAccess;
  final Future<void> Function() onOpenSettings;
  final Future<void> Function() onRetry;
  final Future<void> Function() onUseCamera;

  @override
  Widget build(BuildContext context) {
    final bottom = MediaQuery.paddingOf(context).bottom;
    return SingleChildScrollView(
      padding: EdgeInsets.fromLTRB(
        AppSpacing.xl,
        AppSpacing.lg,
        AppSpacing.xl,
        AppSpacing.xl + bottom,
      ),
      child: Column(
        children: [
          Icon(
            LucideIcons.folder_open,
            size: 48,
            color: AppColors.textSecondary.withValues(alpha: 0.9),
          ),
          const SizedBox(height: AppSpacing.lg),
          Text(
            isLimitedAccess
                ? 'No photos shared with this app'
                : 'No photos available',
            textAlign: TextAlign.center,
            style: const TextStyle(
              fontSize: 17,
              fontWeight: FontWeight.w600,
              color: AppColors.textPrimary,
            ),
          ),
          const SizedBox(height: AppSpacing.md),
          Text(
            isLimitedAccess
                ? 'You allowed access to only some photos, or none are '
                    'selected for this app. Add photos or change permission, '
                    'then try again.'
                : 'We could not load any images. Check photo access in '
                    'Settings or try again.',
            textAlign: TextAlign.center,
            style: const TextStyle(
              fontSize: 14,
              height: 1.4,
              color: AppColors.textSecondary,
            ),
          ),
          const SizedBox(height: AppSpacing.xl),
          SizedBox(
            width: double.infinity,
            child: ElevatedButton(
              style: ElevatedButton.styleFrom(
                backgroundColor: AppColors.primary,
                foregroundColor: AppColors.surface,
                minimumSize: const Size(double.infinity, 48),
                shape: RoundedRectangleBorder(
                  borderRadius: BorderRadius.circular(12),
                ),
              ),
              onPressed: () => onManageAccess(),
              child: Text(
                !kIsWeb && defaultTargetPlatform == TargetPlatform.iOS
                    ? 'Select photos'
                    : 'Manage photo access',
              ),
            ),
          ),
          const SizedBox(height: AppSpacing.sm),
          TextButton(
            onPressed: () => onOpenSettings(),
            child: const Text('Open Settings'),
          ),
          TextButton(
            onPressed: () => onRetry(),
            child: const Text('Try again'),
          ),
          const SizedBox(height: AppSpacing.md),
          TextButton.icon(
            onPressed: () => onUseCamera(),
            icon: const Icon(LucideIcons.camera, size: 20),
            label: const Text('Take photo with camera'),
          ),
        ],
      ),
    );
  }
}

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

  final VoidCallback onTap;

  @override
  Widget build(BuildContext context) {
    return Material(
      color: AppColors.surfaceAlt,
      child: InkWell(
        onTap: onTap,
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Icon(
              LucideIcons.camera,
              size: 32,
              color: AppColors.primary.withValues(alpha: 0.9),
            ),
            const SizedBox(height: AppSpacing.sm),
            Text(
              'Camera',
              style: TextStyle(
                fontSize: 12,
                fontWeight: FontWeight.w600,
                color: AppColors.textSecondary.withValues(alpha: 0.95),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

class _AlbumThumbnail extends StatefulWidget {
  const _AlbumThumbnail({required this.asset});

  final AssetEntity asset;

  @override
  State<_AlbumThumbnail> createState() => _AlbumThumbnailState();
}

class _AlbumThumbnailState extends State<_AlbumThumbnail> {
  Uint8List? _bytes;
  bool _loadFailed = false;

  @override
  void initState() {
    super.initState();
    _load();
  }

  @override
  void didUpdateWidget(covariant _AlbumThumbnail oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (oldWidget.asset.id != widget.asset.id) {
      _bytes = null;
      _loadFailed = false;
      _load();
    }
  }

  Future<void> _load() async {
    try {
      final data = await widget.asset.thumbnailDataWithSize(
        const ThumbnailSize.square(200),
      );
      if (mounted) {
        setState(() {
          _bytes = data;
          _loadFailed = data == null || data.isEmpty;
        });
      }
    } catch (_) {
      if (mounted) {
        setState(() {
          _bytes = null;
          _loadFailed = true;
        });
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    final b = _bytes;
    return ColoredBox(
      color: AppColors.surfaceAlt,
      child: b != null && b.isNotEmpty
          ? Image.memory(
              b,
              fit: BoxFit.cover,
              gaplessPlayback: true,
              filterQuality: FilterQuality.low,
            )
          : _loadFailed
              ? const Icon(
                  LucideIcons.image_off,
                  size: 28,
                  color: AppColors.textSecondary,
                )
              : const Center(
                  child: SizedBox(
                    width: 22,
                    height: 22,
                    child: CircularProgressIndicator(
                      strokeWidth: 2,
                      color: AppColors.primary,
                    ),
                  ),
                ),
    );
  }
}