import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter/foundation.dart';
import 'package:camera/camera.dart';
import 'package:file_picker/file_picker.dart';
import 'package:file_selector/file_selector.dart' as fsel;
import 'package:votianlt_app/services/developer.dart' as developer;
import '../l10n/app_localizations.dart';
import '../models/tasks/photo_task.dart';
import '../widgets/offline_banner.dart';

class PhotoCaptureScreen extends StatefulWidget {
  final PhotoTask task;
  final Function(List<Uint8List>) onPhotosCompleted;

  const PhotoCaptureScreen({
    super.key,
    required this.task,
    required this.onPhotosCompleted,
  });

  @override
  State<PhotoCaptureScreen> createState() => _PhotoCaptureScreenState();
}

class _PhotoCaptureScreenState extends State<PhotoCaptureScreen> {
  CameraController? _cameraController; // Android/iOS/Web
  List<CameraDescription>? _cameras;
  final List<Uint8List> _capturedPhotos = [];
  final PageController _pageController = PageController();
  int _currentPhotoIndex = 0;
  bool _isCameraInitialized = false;
  bool _isCameraSupportedOnThisPlatform = false;
  bool _useFilePickerMode = false; // desktop fallback

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

  @override
  void dispose() {
    _cameraController?.dispose();
    _pageController.dispose();
    super.dispose();
  }

  void _detectPlatformSupportAndInit() {
    // Requirement: Desktop (macOS/Windows/Linux) uses file picker; Android/iOS uses camera.
    if (kIsWeb) {
      // Keep web behavior using camera if available
      _isCameraSupportedOnThisPlatform = true;
      _initializeCamera();
      return;
    }
    switch (defaultTargetPlatform) {
      case TargetPlatform.android:
      case TargetPlatform.iOS:
        _isCameraSupportedOnThisPlatform = true; // enable capture button
        _useFilePickerMode = false;
        _initializeCamera();
        return;
      case TargetPlatform.macOS:
      case TargetPlatform.windows:
      case TargetPlatform.linux:
        // Desktop → use file picker instead of camera
        _isCameraSupportedOnThisPlatform = true; // enable button
        _useFilePickerMode = true;
        return;
      default:
        _isCameraSupportedOnThisPlatform = false;
    }
  }

  Future<void> _initializeCamera() async {
    try {
      // Android/iOS/Web camera initialization
      _cameras = await availableCameras();
      if (_cameras != null && _cameras!.isNotEmpty) {
        _cameraController = CameraController(
          _cameras![0],
          ResolutionPreset.medium,
        );
        await _cameraController!.initialize();
        if (mounted) {
          setState(() {
            _isCameraInitialized = true;
          });
        }
      }
    } catch (e, stackTrace) {
      developer.log('Error initializing camera: $e', name: 'PhotoCaptureScreen');
      developer.log('Stack trace: $stackTrace', name: 'PhotoCaptureScreen');
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(content: Text('${AppLocalizations.of(context).cameraError}: $e')),
        );
      }
    }
  }

  Future<void> _capturePhoto() async {
    try {
      // Camera plugin path (Android/iOS/Web)
      if (_cameraController != null && _isCameraInitialized) {
        final XFile photo = await _cameraController!.takePicture();
        final Uint8List photoBytes = await photo.readAsBytes();

        setState(() {
          _capturedPhotos.add(photoBytes);
        });

        // Navigate to the newly added photo (even if it's the first one). If the
        // PageView is not attached yet, _showPhotoAt will schedule a post-frame jump.
        _showPhotoAt(_capturedPhotos.length - 1);
      } else {
        if (mounted) {
          ScaffoldMessenger.of(context).showSnackBar(
            SnackBar(content: Text(AppLocalizations.of(context).cameraNotReady)),
          );
        }
      }
    } catch (e, stackTrace) {
      developer.log('Error capturing photo: $e', name: 'PhotoCaptureScreen');
      developer.log('Stack trace: $stackTrace', name: 'PhotoCaptureScreen');
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(content: Text('${AppLocalizations.of(context).photoError}: $e')),
        );
      }
    }
  }

  Future<void> _pickPhotoFromFile() async {
    try {
      // Use file_selector for desktop and web for robust platform support
      final bool useFileSelector = kIsWeb ||
          defaultTargetPlatform == TargetPlatform.macOS ||
          defaultTargetPlatform == TargetPlatform.windows ||
          defaultTargetPlatform == TargetPlatform.linux;

      if (useFileSelector) {
        final typeGroup = fsel.XTypeGroup(
          label: 'images',
          extensions: ['jpg', 'jpeg', 'png', 'heic', 'bmp', 'gif', 'webp'],
        );
        final fsel.XFile? picked = await fsel.openFile(acceptedTypeGroups: [typeGroup]);
        if (picked != null) {
          final data = await picked.readAsBytes();
          setState(() {
            _capturedPhotos.add(data);
          });

          _showPhotoAt(_capturedPhotos.length - 1);
        }
      } else {
        // On Android/iOS, use file_picker which integrates with platform pickers
        final result = await FilePicker.platform.pickFiles(
          allowMultiple: false,
          type: FileType.image,
          withData: true,
        );
        if (result != null && result.files.isNotEmpty) {
          final file = result.files.first;
          final bytes = file.bytes;
          if (bytes != null) {
            setState(() {
              _capturedPhotos.add(bytes);
            });

            _showPhotoAt(_capturedPhotos.length - 1);
          } else {
            // On some platforms, bytes may be null if withData was false; try path
            final path = file.path;
            if (path != null) {
              final data = await XFile(path).readAsBytes();
              setState(() {
                _capturedPhotos.add(data);
              });
              if (_capturedPhotos.length > 1) {
                _showPhotoAt(_capturedPhotos.length - 1);
              }
            }
          }
        }
      }
    } catch (e, stackTrace) {
      developer.log('Error picking photo from file: $e', name: 'PhotoCaptureScreen');
      developer.log('Stack trace: $stackTrace', name: 'PhotoCaptureScreen');
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(content: Text('${AppLocalizations.of(context).photoError}: $e')),
        );
      }
    }
  }

  void _deletePhoto(int index) {
    showDialog(
      context: context,
      builder: (BuildContext context) {
        return AlertDialog(
          title: Text(AppLocalizations.of(context).deletePhoto),
          content: Text(AppLocalizations.of(context).deletePhotoConfirm),
          actions: [
            TextButton(
              onPressed: () => Navigator.of(context).pop(),
              child: Text(AppLocalizations.of(context).cancel),
            ),
            ElevatedButton(
              onPressed: () {
                Navigator.of(context).pop();
                // Remove and navigate to a valid photo if any remain
                int targetIndex = _currentPhotoIndex;
                setState(() {
                  _capturedPhotos.removeAt(index);
                  if (_capturedPhotos.isEmpty) {
                    _currentPhotoIndex = 0;
                  } else {
                    if (targetIndex >= _capturedPhotos.length) {
                      targetIndex = _capturedPhotos.length - 1;
                    }
                    _currentPhotoIndex = targetIndex;
                  }
                });
                if (_capturedPhotos.isNotEmpty) {
                  _showPhotoAt(_currentPhotoIndex);
                }
              },
              style: ElevatedButton.styleFrom(backgroundColor: Colors.red),
              child: Text(AppLocalizations.of(context).delete, style: const TextStyle(color: Colors.white)),
            ),
          ],
        );
      },
    );
  }

  bool get _canComplete {
    return _capturedPhotos.length >= widget.task.minPhotoCount &&
           _capturedPhotos.length <= widget.task.maxPhotoCount;
  }

  bool get _canTakeMore {
    return _capturedPhotos.length < widget.task.maxPhotoCount;
  }

  bool get _isDesktopPlatform {
    if (kIsWeb) return false;
    switch (defaultTargetPlatform) {
      case TargetPlatform.macOS:
      case TargetPlatform.windows:
      case TargetPlatform.linux:
        return true;
      default:
        return false;
    }
  }

  void _showPhotoAt(int index) {
    if (_capturedPhotos.isEmpty) return;
    final int clamped = index.clamp(0, _capturedPhotos.length - 1);
    if (!mounted) return;

    // Always schedule navigation after the current frame so that
    // PageView has rebuilt with the latest itemCount before we jump/animate.
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (!mounted) return;
      if (_pageController.hasClients) {
        try {
          _pageController.animateToPage(
            clamped,
            duration: const Duration(milliseconds: 250),
            curve: Curves.easeInOut,
          );
        } catch (e, stackTrace) {
          developer.log('Error animating to page: $e', name: 'PhotoCaptureScreen');
          developer.log('Stack trace: $stackTrace', name: 'PhotoCaptureScreen');
          _pageController.jumpToPage(clamped);
        }
        setState(() {
          _currentPhotoIndex = clamped;
        });
      }
    });
  }

  void _goToPreviousPhoto() {
    if (_currentPhotoIndex > 0) {
      _showPhotoAt(_currentPhotoIndex - 1);
    }
  }

  void _goToNextPhoto() {
    if (_currentPhotoIndex < _capturedPhotos.length - 1) {
      _showPhotoAt(_currentPhotoIndex + 1);
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(AppLocalizations.of(context).photoCapture),
        backgroundColor: Colors.blue,
        foregroundColor: Colors.white,
        actions: [
          if (_canComplete)
            TextButton(
              onPressed: () {
                widget.onPhotosCompleted(_capturedPhotos);
                Navigator.of(context).pop();
              },
              child: Text(
                AppLocalizations.of(context).finish,
                style: TextStyle(color: Colors.white, fontWeight: FontWeight.bold),
              ),
            ),
        ],
      ),
      body: Column(
        children: [
          OfflineBanner(),
          // Task info header
          Container(
            width: double.infinity,
            padding: EdgeInsets.all(16),
            color: Colors.grey[100],
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                Text(
                  '${AppLocalizations.of(context).requiredPhotos}: ${widget.task.minPhotoCount}-${widget.task.maxPhotoCount}',
                  style: TextStyle(fontSize: 16, fontWeight: FontWeight.bold),
                ),
                Text(
                  '${AppLocalizations.of(context).photosTaken}: ${_capturedPhotos.length}',
                  style: TextStyle(fontSize: 14, color: Colors.grey[600]),
                ),
              ],
            ),
          ),

          // Camera preview, photo gallery or empty state
          Expanded(
            child: _capturedPhotos.isEmpty
                ? _buildCameraOrEmptyState()
                : _buildPhotoGallery(),
          ),

          // Bottom controls
          Container(
            padding: EdgeInsets.all(16),
            decoration: BoxDecoration(
              color: Colors.white,
              boxShadow: [
                BoxShadow(
                  color: Colors.grey.withValues(alpha: 0.3),
                  spreadRadius: 1,
                  blurRadius: 5,
                  offset: Offset(0, -3),
                ),
              ],
            ),
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.stretch,
              children: [
                Row(
                  children: [
                    // Camera or file select button
                    Expanded(
                      child: ElevatedButton.icon(
                        onPressed: _canTakeMore && _isCameraSupportedOnThisPlatform
                            ? (_useFilePickerMode
                                ? _pickPhotoFromFile
                                : (_isCameraInitialized ? _capturePhoto : null))
                            : null,
                        icon: Icon(_useFilePickerMode ? Icons.photo_library : Icons.camera_alt),
                        label: Text(
                          !_isCameraSupportedOnThisPlatform
                              ? AppLocalizations.of(context).cameraNotSupportedOnPlatform
                              : (!_canTakeMore
                                  ? AppLocalizations.of(context).maxPhotosReached
                                  : (_useFilePickerMode
                                      ? AppLocalizations.of(context).selectPhoto
                                      : (_isCameraInitialized ? AppLocalizations.of(context).takePhoto : (defaultTargetPlatform == TargetPlatform.macOS ? AppLocalizations.of(context).cameraReadyNoPreview : AppLocalizations.of(context).cameraLoading)))),
                        ),
                        style: ElevatedButton.styleFrom(
                          backgroundColor: _canTakeMore && (_useFilePickerMode || _isCameraInitialized) ? Colors.blue : Colors.grey,
                          foregroundColor: Colors.white,
                          padding: EdgeInsets.symmetric(vertical: 12),
                        ),
                      ),
                    ),

                    if (_capturedPhotos.isNotEmpty) ...[
                      SizedBox(width: 16),
                      // Delete current photo button
                      ElevatedButton.icon(
                        onPressed: () => _deletePhoto(_currentPhotoIndex),
                        icon: Icon(Icons.delete),
                        label: Text(AppLocalizations.of(context).delete),
                        style: ElevatedButton.styleFrom(
                          backgroundColor: Colors.red,
                          foregroundColor: Colors.white,
                          padding: EdgeInsets.symmetric(vertical: 12, horizontal: 16),
                        ),
                      ),
                    ],
                  ],
                ),
                SizedBox(height: 12),
                // Bottom 'Fertig' button placed under the row
                SizedBox(
                  width: double.infinity,
                  child: ElevatedButton(
                    onPressed: _canComplete
                        ? () {
                            widget.onPhotosCompleted(_capturedPhotos);
                            Navigator.of(context).pop();
                          }
                        : null,
                    style: ElevatedButton.styleFrom(
                      backgroundColor: _canComplete ? Colors.green : Colors.grey,
                      foregroundColor: Colors.white,
                      padding: EdgeInsets.symmetric(vertical: 14),
                    ),
                    child: Text(AppLocalizations.of(context).finish, style: const TextStyle(fontWeight: FontWeight.bold)),
                  ),
                ),
              ],
            ),
          ),
        ],
      ),
    );
  }

  Widget _buildCameraOrEmptyState() {
    // If platform not supported, show informative message
    if (!_isCameraSupportedOnThisPlatform) {
      return Center(
        child: Padding(
          padding: EdgeInsets.all(24),
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Icon(Icons.desktop_windows, size: 80, color: Colors.grey[400]),
              SizedBox(height: 16),
              Text(
                AppLocalizations.of(context).cameraNotAvailable,
                style: TextStyle(fontSize: 18, fontWeight: FontWeight.w600, color: Colors.grey[700]),
              ),
              SizedBox(height: 8),
              Text(
                AppLocalizations.of(context).cameraNotSupportedMessage,
                textAlign: TextAlign.center,
                style: TextStyle(fontSize: 14, color: Colors.grey[600]),
              ),
            ],
          ),
        ),
      );
    }

    // macOS fallback: explain file selection
    if (_useFilePickerMode) {
      return Center(
        child: Padding(
          padding: EdgeInsets.all(24),
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Icon(Icons.photo_library, size: 80, color: Colors.grey[400]),
              SizedBox(height: 16),
              Text(
                AppLocalizations.of(context).addPhotos,
                style: TextStyle(fontSize: 18, fontWeight: FontWeight.w600, color: Colors.grey[700]),
              ),
              SizedBox(height: 8),
              Text(
                AppLocalizations.of(context).addPhotosInstruction,
                textAlign: TextAlign.center,
                style: TextStyle(fontSize: 14, color: Colors.grey[600]),
              ),
            ],
          ),
        ),
      );
    }

    // Show camera preview if available on any platform
    if (_isCameraInitialized && _cameraController != null) {
      return Container(
        margin: EdgeInsets.all(16),
        decoration: BoxDecoration(
          borderRadius: BorderRadius.circular(12),
          boxShadow: [
            BoxShadow(
              color: Colors.grey.withValues(alpha: 0.3),
              spreadRadius: 2,
              blurRadius: 8,
              offset: Offset(0, 4),
            ),
          ],
        ),
        child: ClipRRect(
          borderRadius: BorderRadius.circular(12),
          child: CameraPreview(_cameraController!),
        ),
      );
    }

    // When camera is not available, show empty state
    return Center(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Icon(
            Icons.camera_alt,
            size: 80,
            color: Colors.grey[400],
          ),
          SizedBox(height: 16),
          Text(
            AppLocalizations.of(context).cameraInitializing,
            style: TextStyle(
              fontSize: 18,
              color: Colors.grey[600],
              fontWeight: FontWeight.w500,
            ),
          ),
          SizedBox(height: 8),
          Text(
            AppLocalizations.of(context).cameraLoadingMessage,
            style: TextStyle(
              fontSize: 14,
              color: Colors.grey[500],
            ),
            textAlign: TextAlign.center,
          ),
        ],
      ),
    );
  }

  Widget _buildPhotoGallery() {
    return Column(
      children: [
        // Photo counter (if more than one photo)
        if (_capturedPhotos.length > 1)
          Container(
            padding: EdgeInsets.symmetric(vertical: 8),
            child: Text(
              '${_currentPhotoIndex + 1} ${AppLocalizations.of(context).photoOf} ${_capturedPhotos.length}',
              style: TextStyle(
                fontSize: 16,
                fontWeight: FontWeight.w500,
                color: Colors.grey[700],
              ),
            ),
          ),

        // Photo viewer with swipe gestures and navigation arrows
        Expanded(
          child: Stack(
            children: [
              PageView.builder(
                controller: _pageController,
                onPageChanged: (index) {
                  setState(() {
                    _currentPhotoIndex = index;
                  });
                },
                itemCount: _capturedPhotos.length,
                itemBuilder: (context, index) {
                  return Container(
                    margin: EdgeInsets.all(16),
                    decoration: BoxDecoration(
                      borderRadius: BorderRadius.circular(12),
                      boxShadow: [
                        BoxShadow(
                          color: Colors.grey.withValues(alpha: 0.3),
                          spreadRadius: 2,
                          blurRadius: 8,
                          offset: Offset(0, 4),
                        ),
                      ],
                    ),
                    child: ClipRRect(
                      borderRadius: BorderRadius.circular(12),
                      child: Image.memory(
                        _capturedPhotos[index],
                        fit: BoxFit.contain,
                        errorBuilder: (context, error, stackTrace) {
                          return Container(
                            color: Colors.grey[300],
                            child: Center(
                              child: Column(
                                mainAxisAlignment: MainAxisAlignment.center,
                                children: [
                                  Icon(Icons.error, size: 50, color: Colors.grey[600]),
                                  SizedBox(height: 8),
                                  Text(AppLocalizations.of(context).photoError),
                                ],
                              ),
                            ),
                          );
                        },
                      ),
                    ),
                  );
                },
              ),
              if (_capturedPhotos.length > 1 && _isDesktopPlatform)
                Positioned(
                  left: 8,
                  top: 0,
                  bottom: 0,
                  child: Center(
                    child: IconButton(
                      onPressed: _currentPhotoIndex > 0
                          ? _goToPreviousPhoto
                          : null,
                      icon: Icon(Icons.chevron_left, size: 36),
                      style: IconButton.styleFrom(
                        backgroundColor: Colors.white.withValues(alpha: 0.7),
                      ),
                    ),
                  ),
                ),
              if (_capturedPhotos.length > 1 && _isDesktopPlatform)
                Positioned(
                  right: 8,
                  top: 0,
                  bottom: 0,
                  child: Center(
                    child: IconButton(
                      onPressed: _currentPhotoIndex < _capturedPhotos.length - 1
                          ? _goToNextPhoto
                          : null,
                      icon: Icon(Icons.chevron_right, size: 36),
                      style: IconButton.styleFrom(
                        backgroundColor: Colors.white.withValues(alpha: 0.7),
                      ),
                    ),
                  ),
                ),
            ],
          ),
        ),

        // Photo indicators (if more than one photo)
        if (_capturedPhotos.length > 1)
          Container(
            padding: EdgeInsets.symmetric(vertical: 16),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.center,
              children: _capturedPhotos.asMap().entries.map((entry) {
                return Container(
                  width: 8,
                  height: 8,
                  margin: EdgeInsets.symmetric(horizontal: 4),
                  decoration: BoxDecoration(
                    shape: BoxShape.circle,
                    color: _currentPhotoIndex == entry.key
                        ? Colors.blue
                        : Colors.grey[400],
                  ),
                );
              }).toList(),
            ),
          ),
      ],
    );
  }
}