import 'dart:io' show Platform;

import 'package:flutter/foundation.dart' show kIsWeb;
import 'package:flutter/material.dart';
import 'package:zxing_barcode_scanner/zxing_barcode_scanner.dart';

import '../data/species_repository.dart';
import '../data/variety_repository.dart';
import '../i18n/strings.g.dart';
import '../services/camera_availability.dart';
import '../services/seed_label_scan.dart';

/// Whether this platform can open the camera scanner. Mobile-only for now
/// (pure-ZXing platform views; no Google Play Services) — elsewhere the scan
/// button simply isn't offered, same pattern as the OCR capture. On Android it
/// also requires an actual camera, so camera-less devices (Chromebooks,
/// Automotive, some TVs) don't get a scan button that can't open — see
/// [deviceHasCamera].
bool get qrScanSupported =>
    !kIsWeb && ((Platform.isAndroid && deviceHasCamera) || Platform.isIOS);

/// Opens the full-screen camera scanner and returns the first decoded QR
/// payload, or null if the person backed out. (Ğ1nkgo's scanner pattern on
/// the same pure-ZXing stack.)
Future<String?> scanSeedLabelQr(BuildContext context) {
  return Navigator.of(context).push<String>(
    MaterialPageRoute<String>(builder: (_) => const _ScannerScreen()),
  );
}

/// Acts on a scanned payload: a known seed opens its record (via
/// [openVariety]); an unknown seed label asks before adding anything; anything
/// else says so and moves on. Navigation is injected so the flow is
/// widget-testable without a camera or a router.
Future<void> handleScannedPayload(
  BuildContext context, {
  required VarietyRepository repository,
  required SpeciesRepository species,
  required String payload,
  required void Function(String varietyId) openVariety,
}) async {
  final t = context.t;
  final messenger = ScaffoldMessenger.of(context);
  final result = await resolveScannedLabel(repository, payload);
  if (!context.mounted) return;

  if (result.varietyId case final id?) {
    openVariety(id);
    return;
  }
  final data = result.data;
  if (data == null) {
    messenger.showSnackBar(SnackBar(content: Text(t.scan.notALabel)));
    return;
  }

  final add = await showDialog<bool>(
    context: context,
    builder: (context) => AlertDialog(
      key: const Key('scan.addPrompt'),
      title: Text(t.scan.addTitle),
      content: Text(t.scan.addBody(label: data.varietyLabel)),
      actions: [
        TextButton(
          key: const Key('scan.cancel'),
          onPressed: () => Navigator.of(context).pop(false),
          child: Text(t.common.cancel),
        ),
        FilledButton(
          key: const Key('scan.add'),
          onPressed: () => Navigator.of(context).pop(true),
          child: Text(t.scan.add),
        ),
      ],
    ),
  );
  if (add != true) return;

  final varietyId = await importScannedLabel(
    repository: repository,
    species: species,
    data: data,
  );
  messenger.showSnackBar(SnackBar(content: Text(t.scan.added)));
  openVariety(varietyId);
}

class _ScannerScreen extends StatefulWidget {
  const _ScannerScreen();

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

class _ScannerScreenState extends State<_ScannerScreen> {
  bool _done = false;

  void _onScan(List<BarcodeResult> results) {
    if (_done || !mounted || results.isEmpty) return;
    final text = results.first.text;
    if (text == null || text.isEmpty) return;
    _done = true;
    // A beat so the camera view settles before popping (Ğ1nkgo does the same).
    Future<void>.delayed(const Duration(milliseconds: 150), () {
      if (mounted) Navigator.of(context).pop(text);
    });
  }

  @override
  Widget build(BuildContext context) {
    final t = context.t;
    return Scaffold(
      appBar: AppBar(title: Text(t.scan.title)),
      body: ZxingBarcodeScanner(
        onScan: _onScan,
        onError: (error) => Center(
          child: Padding(
            padding: const EdgeInsets.all(24),
            child: Text(error.message ?? t.common.offline),
          ),
        ),
      ),
    );
  }
}