import 'dart:io';

import 'package:flutter/material.dart';
import 'package:image_picker/image_picker.dart';
import 'package:provider/provider.dart';

import '../screens/confirm_fuel_entry_screen.dart';
import '../services/app_state.dart';
import '../services/ocr_service.dart';
import '../services/receipt_parser.dart';
import 'image_source_sheet.dart';

/// Long edge and JPEG quality a receipt photo is downscaled to unless
/// "keep max quality" is on — a receipt is a photo of small printed text,
/// not something that benefits from a multi-megapixel original, and this
/// keeps typical files in the low hundreds of KB instead of several MB.
const receiptImageMaxDimension = 1600.0;
const receiptImageQuality = 70;

/// Shared by [VehicleDetailScreen]'s "Log Fuel Receipt" button and the
/// Receipts tab's "+" action: pick a photo, OCR it, and — unless the
/// receipt looks like it's from outside Missouri, in which case the user
/// gets a chance to back out first — hand off to [ConfirmFuelEntryScreen]
/// for [vehicleId].
Future<void> captureReceiptForVehicle(BuildContext context, String vehicleId) async {
  final source = await chooseImageSource(context, heading: 'Receipt From');
  if (source == null || !context.mounted) return;

  final keepMaxQuality = context.read<AppState>().keepMaxQualityReceiptPhotos;
  final picker = ImagePicker();

  // Raised *before* the camera/gallery opens rather than after it returns.
  // [ImagePicker.pickImage] doesn't complete when the camera closes — it
  // also downscales the captured photo (several MB straight off the
  // sensor), which takes seconds on a busy device. With the progress
  // shown only afterward, that whole stretch left the user staring at an
  // unchanged Receipts list with no sign anything was happening, which
  // reads as "the capture did nothing" — and tapping away during it
  // genuinely does abandon the capture.
  var progressShowing = false;
  void showProgress() {
    if (progressShowing || !context.mounted) return;
    progressShowing = true;
    showDialog(
      context: context,
      barrierDismissible: false,
      builder: (_) => const _ReceiptProgressDialog(),
    );
  }

  void hideProgress() {
    if (!progressShowing || !context.mounted) return;
    progressShowing = false;
    Navigator.of(context).pop();
  }

  showProgress();

  XFile? photo;
  try {
    photo = await picker.pickImage(
      source: source,
      imageQuality: keepMaxQuality ? null : receiptImageQuality,
      maxWidth: keepMaxQuality ? null : receiptImageMaxDimension,
      maxHeight: keepMaxQuality ? null : receiptImageMaxDimension,
    );
  } catch (e) {
    hideProgress();
    if (context.mounted) {
      final sourceLabel = source == ImageSource.camera ? 'camera' : 'photo library';
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text('Could not open $sourceLabel: $e')),
      );
    }
    return;
  }
  // Cancelled (backed out of the camera, or didn't confirm the shot) —
  // nothing to say about that, it was deliberate.
  if (photo == null) {
    hideProgress();
    return;
  }

  final imageFile = File(photo.path);

  if (!context.mounted) return;

  final ocrService = OcrService();
  String recognizedText = '';
  try {
    recognizedText = await ocrService.recognizeText(imageFile);
  } catch (_) {
    recognizedText = '';
  } finally {
    ocrService.dispose();
  }

  final parsed = ReceiptParser.parse(recognizedText);

  if (!context.mounted) return;
  hideProgress();

  final state = parsed.state;
  if (state != null && state != 'MO') {
    final proceed = await _confirmNonMissouriPurchase(context, state);
    if (!proceed || !context.mounted) return;
  }

  if (context.mounted) {
    Navigator.of(context).push(
      MaterialPageRoute(
        builder: (_) => ConfirmFuelEntryScreen(
          vehicleId: vehicleId,
          imageFile: imageFile,
          parsed: parsed,
        ),
      ),
    );
  }
}

/// Shown from the moment the camera/gallery is opened until the parsed
/// receipt is ready to review. Deliberately says what's happening rather
/// than showing a bare spinner: the wait here is mostly downscaling and
/// reading the photo, which is long enough on a slow device that an
/// unexplained spinner invites tapping away mid-capture.
class _ReceiptProgressDialog extends StatelessWidget {
  const _ReceiptProgressDialog();

  @override
  Widget build(BuildContext context) {
    return PopScope(
      // Backing out here wouldn't cancel the underlying capture, it would
      // just hide it and strand the user.
      canPop: false,
      child: Dialog(
        child: Padding(
          padding: const EdgeInsets.symmetric(horizontal: 28, vertical: 32),
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              const CircularProgressIndicator(),
              const SizedBox(height: 20),
              Text('Reading your receipt…', style: Theme.of(context).textTheme.titleSmall),
              const SizedBox(height: 6),
              Text(
                'This can take a few seconds.',
                textAlign: TextAlign.center,
                style: Theme.of(context).textTheme.bodySmall?.copyWith(
                      color: Theme.of(context).colorScheme.onSurfaceVariant,
                    ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

/// Missouri's fuel tax refund only applies to fuel bought in Missouri —
/// warn if the receipt's address is somewhere else, and let the user
/// decide whether to log it anyway (e.g. it might still be worth tracking
/// for other reasons even if it won't qualify for a refund).
Future<bool> _confirmNonMissouriPurchase(BuildContext context, String stateCode) async {
  final stateName = usStateNames[stateCode] ?? stateCode;
  final proceed = await showDialog<bool>(
    context: context,
    builder: (context) => AlertDialog(
      title: const Text('Non-Missouri Purchase'),
      content: Text(
        'This receipt looks like it\'s from a gas station in $stateName. '
        'The Missouri fuel tax refund only applies to fuel purchased in '
        'Missouri.\n\nDo you still want to add this entry?',
      ),
      actions: [
        TextButton(onPressed: () => Navigator.of(context).pop(false), child: const Text('No')),
        FilledButton(onPressed: () => Navigator.of(context).pop(true), child: const Text('Yes')),
      ],
    ),
  );
  return proceed ?? false;
}