/// Single screen: capture or pick a receipt photo, then show raw OCR text.
library;

import 'dart:io';

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:google_mlkit_text_recognition/google_mlkit_text_recognition.dart';
import 'package:image_picker/image_picker.dart';

import 'products_screen.dart';
import 'review_screen.dart';
import 'services/product_repository.dart';
import 'services/receipt_parser.dart';
import 'utils/constants.dart';

class ScanScreen extends StatefulWidget {
  const ScanScreen({super.key, required this.repository});

  final ProductRepository repository;

  @override
  State<ScanScreen> createState() => _ScanScreenState();
}

class _ScanScreenState extends State<ScanScreen> {
  final ImagePicker _picker = ImagePicker();

  String _extractedText = '';
  bool _busy = false;
  String? _error;

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

  /// Android may kill the activity while the camera app is open.
  Future<void> _recoverLostImage() async {
    try {
      final response = await _picker.retrieveLostData();
      if (!mounted || response.isEmpty) return;
      final file = response.file;
      if (file != null) {
        await _runOcr(file.path);
      }
    } on UnimplementedError {
      // Desktop / platforms that do not support lost-data recovery.
    }
  }

  Future<void> _capture(ImageSource source) async {
    final file = await _picker.pickImage(
      source: source,
      imageQuality: 95,
    );
    if (file == null || !mounted) return;
    await _runOcr(file.path);
  }

  Future<void> _scanSampleReceipt() async {
    try {
      final data = await rootBundle.load(kSampleReceiptAsset);
      final file = File(
        '${Directory.systemTemp.path}/receipity_sample_receipt.jpeg',
      );
      await file.writeAsBytes(data.buffer.asUint8List(), flush: true);
      if (!mounted) return;
      await _runOcr(file.path);
    } catch (_) {
      if (!mounted) return;
      setState(() {
        _error = 'Could not load the sample receipt.';
      });
    }
  }

  Future<void> _runOcr(String imagePath) async {
    setState(() {
      _busy = true;
      _error = null;
      _extractedText = '';
    });

    final recognizer = TextRecognizer(script: TextRecognitionScript.latin);
    try {
      final inputImage = InputImage.fromFilePath(imagePath);
      final recognized = await recognizer.processImage(inputImage);
      if (!mounted) return;
      setState(() {
        _extractedText = recognized.text.trim();
        if (_extractedText.isEmpty) {
          _error = 'No text found in this image.';
        }
      });
    } catch (error) {
      if (!mounted) return;
      setState(() {
        _error = 'Could not read text from this image.';
      });
    } finally {
      await recognizer.close();
      if (mounted) {
        setState(() => _busy = false);
      }
    }

    if (mounted && _extractedText.isNotEmpty) {
      await _openReview(_extractedText);
    }
  }

  Future<void> _openReview(String rawText) async {
    final items = ReceiptParser.parse(rawText);
    if (!mounted) return;
    await Navigator.of(context).push(
      MaterialPageRoute<void>(
        builder: (_) => ReviewScreen(
          items: items,
          rawText: rawText,
          repository: widget.repository,
        ),
      ),
    );
  }

  void _openProducts() {
    Navigator.of(context).push(
      MaterialPageRoute<void>(
        builder: (_) => ProductsScreen(repository: widget.repository),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);

    return Scaffold(
      appBar: AppBar(
        title: const Text(kAppName),
        actions: [
          IconButton(
            tooltip: 'Products',
            onPressed: _openProducts,
            icon: const Icon(Icons.inventory_2_outlined),
          ),
        ],
      ),
      body: SafeArea(
        child: Padding(
          padding: const EdgeInsets.all(16),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: [
              FilledButton.icon(
                onPressed: _busy ? null : () => _capture(ImageSource.camera),
                icon: const Icon(Icons.photo_camera_outlined),
                label: const Text('Take photo'),
              ),
              const SizedBox(height: 8),
              OutlinedButton.icon(
                onPressed: _busy ? null : () => _capture(ImageSource.gallery),
                icon: const Icon(Icons.photo_library_outlined),
                label: const Text('Pick from gallery'),
              ),
              const SizedBox(height: 8),
              TextButton.icon(
                onPressed: _busy ? null : _scanSampleReceipt,
                icon: const Icon(Icons.receipt_long_outlined),
                label: const Text('Use sample receipt'),
              ),
              if (_extractedText.isNotEmpty) ...[
                const SizedBox(height: 8),
                OutlinedButton(
                  onPressed: _busy ? null : () => _openReview(_extractedText),
                  child: const Text('Review items'),
                ),
              ],
              if (_busy) ...[
                const SizedBox(height: 16),
                const LinearProgressIndicator(),
                const SizedBox(height: 8),
                Text(
                  'Reading text…',
                  style: theme.textTheme.bodyMedium,
                ),
              ],
              const SizedBox(height: 16),
              Expanded(child: _ResultPane(text: _extractedText, error: _error)),
            ],
          ),
        ),
      ),
    );
  }
}

class _ResultPane extends StatelessWidget {
  const _ResultPane({required this.text, required this.error});

  final String text;
  final String? error;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);

    if (error != null && text.isEmpty) {
      return Center(
        child: Text(
          error!,
          textAlign: TextAlign.center,
          style: theme.textTheme.bodyLarge,
        ),
      );
    }

    if (text.isEmpty) {
      return Center(
        child: Text(
          'Take a photo of a shopping receipt, or pick one from the gallery.\n\nExtracted text will show up here.',
          textAlign: TextAlign.center,
          style: theme.textTheme.bodyLarge,
        ),
      );
    }

    return SingleChildScrollView(
      child: SelectableText(
        text,
        style: theme.textTheme.bodyLarge?.copyWith(
          color: theme.colorScheme.onSurface,
          height: 1.4,
        ),
      ),
    );
  }
}