import 'dart:io';

import 'package:flutter/material.dart';
import 'package:camera/camera.dart';
import 'package:google_mlkit_text_recognition/google_mlkit_text_recognition.dart';

/// Screen that uses the camera to scan text (OCR) from a Hot Wheels package
/// and extract the hw_id (e.g. "JKF21").
///
/// The detected ID is returned via Navigator.pop(context, hwId).
class ScannerScreen extends StatefulWidget {
  const ScannerScreen({super.key});

  @override
  State<ScannerScreen> createState() => _ScannerScreenState();
}

class _ScannerScreenState extends State<ScannerScreen> {
  CameraController? _cameraController;
  late final TextRecognizer _textRecognizer;
  bool _isBusy = false;
  bool _cameraReady = false;
  String? _lastDetected;

  // Matches typical Hot Wheels model IDs: 2–5 uppercase letters followed by
  // 2–4 digits, e.g. JKF21, HCV73, GRX33, FYD83.
  final _hwIdPattern = RegExp(r'\b([A-Z]{2,5}\d{2,4})\b');

  @override
  void initState() {
    super.initState();
    _textRecognizer = TextRecognizer();
    _initCamera();
  }

  Future<void> _initCamera() async {
    final cameras = await availableCameras();
    if (cameras.isEmpty) {
      if (!mounted) return;
      ScaffoldMessenger.of(context).showSnackBar(
        const SnackBar(content: Text('No camera available')),
      );
      return;
    }

    // Use the first back-facing camera.
    final backCamera = cameras.firstWhere(
      (c) => c.lensDirection == CameraLensDirection.back,
      orElse: () => cameras.first,
    );

    _cameraController = CameraController(
      backCamera,
      ResolutionPreset.high,
      enableAudio: false,
    );

    await _cameraController!.initialize();
    if (!mounted) return;
    setState(() => _cameraReady = true);
  }

  /// Capture a photo, run OCR, and look for a Hot Wheels ID.
  Future<void> _captureAndScan() async {
    if (_isBusy || _cameraController == null || !_cameraController!.value.isInitialized) return;

    setState(() => _isBusy = true);

    try {
      final xFile = await _cameraController!.takePicture();
      final inputImage = InputImage.fromFilePath(xFile.path);
      final recognized = await _textRecognizer.processImage(inputImage);

      // Search all recognized text blocks for something matching the HW ID pattern.
      String? found;
      for (final block in recognized.blocks) {
        for (final line in block.lines) {
          final match = _hwIdPattern.firstMatch(line.text.toUpperCase());
          if (match != null) {
            found = match.group(1);
            break;
          }
        }
        if (found != null) break;
      }

      // Clean up the temp image.
      try {
        await File(xFile.path).delete();
      } catch (_) {}

      if (!mounted) return;

      if (found != null) {
        setState(() => _lastDetected = found);
      } else {
        // Show all detected text so user knows what was seen.
        final allText = recognized.blocks.map((b) => b.text).join('\n');
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(
            content: Text(
              allText.isEmpty
                  ? 'No text detected — try again closer.'
                  : 'No HW ID found. Detected:\n$allText',
            ),
            duration: const Duration(seconds: 4),
          ),
        );
      }
    } catch (e) {
      if (!mounted) return;
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text('Scan error: $e'), backgroundColor: Colors.red),
      );
    } finally {
      if (mounted) setState(() => _isBusy = false);
    }
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Scan Hot Wheels ID')),
      body: Column(
        children: [
          // ── Camera preview ──
          Expanded(
            child: _cameraReady
                ? ClipRect(
                    child: SizedBox.expand(
                      child: FittedBox(
                        fit: BoxFit.cover,
                        child: SizedBox(
                          width: _cameraController!.value.previewSize!.height,
                          height: _cameraController!.value.previewSize!.width,
                          child: CameraPreview(_cameraController!),
                        ),
                      ),
                    ),
                  )
                : const Center(child: CircularProgressIndicator()),
          ),

          // ── Detected ID confirmation area ──
          if (_lastDetected != null)
            Container(
              width: double.infinity,
              color: Colors.green.shade50,
              padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
              child: Row(
                children: [
                  const Icon(Icons.check_circle, color: Colors.green),
                  const SizedBox(width: 12),
                  Expanded(
                    child: Text(
                      'Detected: $_lastDetected',
                      style: const TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
                    ),
                  ),
                  ElevatedButton(
                    onPressed: () => Navigator.of(context).pop(_lastDetected),
                    child: const Text('Use'),
                  ),
                ],
              ),
            ),

          // ── Bottom controls ──
          SafeArea(
            child: Padding(
              padding: const EdgeInsets.all(16),
              child: Row(
                children: [
                  // Manual entry button
                  Expanded(
                    child: OutlinedButton.icon(
                      icon: const Icon(Icons.keyboard),
                      label: const Text('Enter manually'),
                      onPressed: () => _showManualEntry(context),
                    ),
                  ),
                  const SizedBox(width: 12),
                  // Capture / scan button
                  Expanded(
                    child: ElevatedButton.icon(
                      icon: _isBusy
                          ? const SizedBox(
                              height: 18,
                              width: 18,
                              child: CircularProgressIndicator(strokeWidth: 2),
                            )
                          : const Icon(Icons.camera_alt),
                      label: Text(_isBusy ? 'Scanning...' : 'Scan'),
                      onPressed: _isBusy ? null : _captureAndScan,
                    ),
                  ),
                ],
              ),
            ),
          ),
        ],
      ),
    );
  }

  /// Fallback: let the user type the HW ID manually.
  Future<void> _showManualEntry(BuildContext context) async {
    final result = await showDialog<String>(
      context: context,
      builder: (_) => const _ManualEntryDialog(),
    );

    if (result != null && context.mounted) {
      Navigator.of(context).pop(result);
    }
  }
}

// ── Manual Entry Dialog ───────────────────────────────────────────────
class _ManualEntryDialog extends StatefulWidget {
  const _ManualEntryDialog();

  @override
  State<_ManualEntryDialog> createState() => _ManualEntryDialogState();
}

class _ManualEntryDialogState extends State<_ManualEntryDialog> {
  final _controller = TextEditingController();

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

  void _submit() {
    final value = _controller.text.trim().toUpperCase();
    if (value.isNotEmpty) Navigator.of(context).pop(value);
  }

  @override
  Widget build(BuildContext context) {
    return AlertDialog(
      title: const Text('Enter HW ID'),
      content: TextField(
        controller: _controller,
        autofocus: true,
        textCapitalization: TextCapitalization.characters,
        decoration: const InputDecoration(
          hintText: 'e.g. JKF21',
          border: OutlineInputBorder(),
        ),
        onSubmitted: (_) => _submit(),
      ),
      actions: [
        TextButton(
          onPressed: () => Navigator.of(context).pop(),
          child: const Text('Cancel'),
        ),
        ElevatedButton(
          onPressed: _submit,
          child: const Text('OK'),
        ),
      ],
    );
  }
}