/// Shared pick → crop → OCR → parse flow for adding a receipt to a trip.
library;

import 'dart:io';
import 'dart:ui' as ui;

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 '../crop_receipt_screen.dart';
import '../models/line_item.dart';
import 'receipt_parser.dart';

class CapturedReceiptParse {
  const CapturedReceiptParse({
    required this.items,
    required this.rawText,
    this.imagePath,
    this.needsReview = false,
    this.detectedStore,
  });

  final List<LineItem> items;
  final String rawText;
  final String? imagePath;
  final bool needsReview;
  final String? detectedStore;
}

/// Asks camera vs gallery, crops, runs OCR, and returns parsed items.
///
/// Returns null if the user cancels at any step.
Future<CapturedReceiptParse?> captureAndParseReceipt(
  BuildContext context, {
  ImagePicker? picker,
}) async {
  final source = await showModalBottomSheet<ImageSource>(
    context: context,
    showDragHandle: true,
    builder: (context) {
      return SafeArea(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            ListTile(
              leading: const Icon(Icons.photo_camera_outlined),
              title: const Text('Take photo'),
              onTap: () => Navigator.pop(context, ImageSource.camera),
            ),
            ListTile(
              leading: const Icon(Icons.photo_library_outlined),
              title: const Text('Pick from gallery'),
              onTap: () => Navigator.pop(context, ImageSource.gallery),
            ),
          ],
        ),
      );
    },
  );
  if (source == null || !context.mounted) return null;

  final imagePicker = picker ?? ImagePicker();
  final file = await imagePicker.pickImage(source: source, imageQuality: 95);
  if (file == null || !context.mounted) return null;

  final croppedPath = await Navigator.of(context).push<String>(
    MaterialPageRoute(
      fullscreenDialog: true,
      builder: (_) => CropReceiptScreen(imagePath: file.path),
    ),
  );
  if (croppedPath == null || !context.mounted) return null;

  return _runOcrAndParse(context, croppedPath);
}

Future<CapturedReceiptParse?> _runOcrAndParse(
  BuildContext context,
  String imagePath,
) async {
  showDialog<void>(
    context: context,
    barrierDismissible: false,
    builder: (context) {
      return const PopScope(
        canPop: false,
        child: Center(
          child: Card(
            child: Padding(
              padding: EdgeInsets.all(24),
              child: Column(
                mainAxisSize: MainAxisSize.min,
                children: [
                  CircularProgressIndicator(),
                  SizedBox(height: 16),
                  Text('Reading receipt…'),
                ],
              ),
            ),
          ),
        ),
      );
    },
  );

  final recognizer = TextRecognizer(script: TextRecognitionScript.latin);
  try {
    final bytes = await File(imagePath).readAsBytes();
    final codec = await ui.instantiateImageCodec(bytes);
    final frame = await codec.getNextFrame();
    final imageWidth = frame.image.width.toDouble();
    final imageHeight = frame.image.height.toDouble();
    frame.image.dispose();

    final recognized = await recognizer.processImage(
      InputImage.fromFilePath(imagePath),
    );
    final rawText = recognized.text.trim();
    if (rawText.isEmpty) {
      if (context.mounted) {
        Navigator.of(context, rootNavigator: true).pop();
        ScaffoldMessenger.of(context).showSnackBar(
          const SnackBar(content: Text('No text found in this image.')),
        );
      }
      return null;
    }

    final parsed = ReceiptParser.parseRecognizedText(
      recognized,
      imageWidth: imageWidth,
      imageHeight: imageHeight,
    );

    if (context.mounted) {
      Navigator.of(context, rootNavigator: true).pop();
    }

    if (parsed.items.isEmpty) {
      if (context.mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          const SnackBar(content: Text('No products found on this receipt.')),
        );
      }
      return null;
    }

    // Fresh ids so merged trips never collide with existing item keys.
    final stamp = DateTime.now().microsecondsSinceEpoch;
    final items = [
      for (var i = 0; i < parsed.items.length; i++)
        parsed.items[i].copyWith(id: 'merged-$stamp-$i'),
    ];

    return CapturedReceiptParse(
      items: items,
      rawText: rawText,
      imagePath: imagePath,
      needsReview: !parsed.validationPassed,
      detectedStore: parsed.store,
    );
  } on PlatformException catch (error) {
    if (context.mounted) {
      Navigator.of(context, rootNavigator: true).pop();
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(
          content: Text(
            'Could not read text from this image.'
            '${error.message == null || error.message!.isEmpty ? '' : '\n${error.message}'}',
          ),
        ),
      );
    }
    return null;
  } catch (error) {
    if (context.mounted) {
      Navigator.of(context, rootNavigator: true).pop();
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text('Could not read text from this image.\n$error')),
      );
    }
    return null;
  } finally {
    await recognizer.close();
  }
}