import 'dart:async';
import 'dart:io';

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

import '../services/app_state.dart';
import '../services/receipt_parser.dart';
import '../widgets/backup_reminder.dart';
import 'receipt_image_screen.dart';

/// Shown right after a receipt photo is captured and OCR'd. Pre-fills
/// whatever the parser found and lets the user review/correct every field
/// before it's written to the data file, since OCR on a printed receipt is
/// usually good but not perfect.
class ConfirmFuelEntryScreen extends StatefulWidget {
  final String vehicleId;
  final File imageFile;
  final ParsedReceipt parsed;

  const ConfirmFuelEntryScreen({
    super.key,
    required this.vehicleId,
    required this.imageFile,
    required this.parsed,
  });

  @override
  State<ConfirmFuelEntryScreen> createState() => _ConfirmFuelEntryScreenState();
}

class _ConfirmFuelEntryScreenState extends State<ConfirmFuelEntryScreen> {
  final _formKey = GlobalKey<FormState>();
  late final TextEditingController _gallonsController;
  late final TextEditingController _priceController;
  late final TextEditingController _totalController;
  late DateTime _date;
  bool _saving = false;

  @override
  void initState() {
    super.initState();
    // Prefer the date/time printed on the receipt; fall back to now, same
    // as before, when it couldn't be parsed — the date picker below is
    // always available either way for manual entry/correction.
    _date = widget.parsed.date ?? DateTime.now();
    _gallonsController = TextEditingController(
      text: widget.parsed.gallons?.toStringAsFixed(3) ?? '',
    );
    _priceController = TextEditingController(
      text: widget.parsed.pricePerGallon?.toStringAsFixed(3) ?? '',
    );
    _totalController = TextEditingController(
      text: widget.parsed.totalCost?.toStringAsFixed(2) ?? '',
    );
    // So an ad is ready by the time _save() finishes without delaying it.
    context.read<AppState>().preloadFuelSaveAd();
  }

  @override
  void dispose() {
    _gallonsController.dispose();
    _priceController.dispose();
    _totalController.dispose();
    super.dispose();
  }

  void _calculateTotal() {
    final gallons = double.tryParse(_gallonsController.text);
    final price = double.tryParse(_priceController.text);
    if (gallons != null && price != null) {
      setState(() {
        _totalController.text = (gallons * price).toStringAsFixed(2);
      });
    }
  }

  Future<void> _pickDate() async {
    // initialDate must fall within [firstDate, lastDate] or the picker
    // throws — widen the bounds to cover _date in case a misread date from
    // the receipt landed outside the normal 5-years-back-to-today window.
    final today = DateTime.now();
    final firstDate = _date.isBefore(today.subtract(const Duration(days: 365 * 5)))
        ? _date
        : today.subtract(const Duration(days: 365 * 5));
    final lastDate = _date.isAfter(today) ? _date : today;

    final pickedDate = await showDatePicker(
      context: context,
      initialDate: _date,
      firstDate: firstDate,
      lastDate: lastDate,
    );
    if (pickedDate == null || !mounted) return;

    final pickedTime = await showTimePicker(
      context: context,
      initialTime: TimeOfDay.fromDateTime(_date),
    );
    if (pickedTime == null) return;

    setState(() {
      _date = DateTime(
        pickedDate.year,
        pickedDate.month,
        pickedDate.day,
        pickedTime.hour,
        pickedTime.minute,
      );
    });
  }

  Future<void> _save() async {
    if (!_formKey.currentState!.validate()) return;

    setState(() => _saving = true);
    try {
      final appState = context.read<AppState>();
      await appState.addFuelEntry(
            vehicleId: widget.vehicleId,
            date: _date,
            gallons: double.parse(_gallonsController.text),
            pricePerGallon: double.parse(_priceController.text),
            totalCost: double.parse(_totalController.text),
            receiptImage: widget.imageFile,
          );
      if (!mounted) return;

      // The entry is already committed by this point, so the ad isn't
      // gating the save — it just fills the moment between saving and
      // landing back on the list. Awaited rather than fired off, so the
      // two don't race and the ad can't end up drawn over the Receipts
      // tab after this screen has gone.
      final adShown = await appState.maybeShowFuelSaveAd();
      if (!mounted) return;

      // Ask while this screen (and its context) is still fully alive,
      // before popping — simpler than trying to show a dialog against a
      // context whose widget is mid-removal. Held back when an ad just
      // ran: one full-screen surface per save, and the reminder comes
      // back around on the next save anyway.
      var wantsBackupSetup = false;
      if (!adShown && !appState.hasCloudBackupConfigured) {
        wantsBackupSetup = await showBackupReminderDialog(context);
        if (!mounted) return;
      }

      Navigator.of(context).pop();
      if (wantsBackupSetup) {
        unawaited(openCloudBackupSetup(context));
      }
    } finally {
      if (mounted) setState(() => _saving = false);
    }
  }

  String? _requiredDecimal(String? value) {
    if (value == null || value.trim().isEmpty) return 'Required';
    if (double.tryParse(value) == null) return 'Enter a valid number';
    return null;
  }

  @override
  Widget build(BuildContext context) {
    final dateFormat = DateFormat.yMMMd().add_jm();
    final nothingParsed = widget.parsed.gallons == null &&
        widget.parsed.pricePerGallon == null &&
        widget.parsed.totalCost == null;

    return Scaffold(
      appBar: AppBar(title: const Text('Confirm Fuel Entry')),
      body: Form(
        key: _formKey,
        child: ListView(
          padding: const EdgeInsets.all(16),
          children: [
            GestureDetector(
              onTap: () => Navigator.of(context).push(
                MaterialPageRoute(
                  builder: (_) => ReceiptImageScreen(localImagePath: widget.imageFile.path),
                ),
              ),
              child: ClipRRect(
                borderRadius: BorderRadius.circular(8),
                child: Image.file(widget.imageFile, height: 180, fit: BoxFit.cover, width: double.infinity),
              ),
            ),
            const SizedBox(height: 8),
            Text(
              'Tap the photo to view it full-screen.',
              style: Theme.of(context).textTheme.bodySmall,
              textAlign: TextAlign.center,
            ),
            if (nothingParsed) ...[
              const SizedBox(height: 16),
              Container(
                padding: const EdgeInsets.all(12),
                decoration: BoxDecoration(
                  color: Theme.of(context).colorScheme.errorContainer,
                  borderRadius: BorderRadius.circular(8),
                ),
                child: Row(
                  children: [
                    Icon(Icons.warning_amber_rounded, color: Theme.of(context).colorScheme.onErrorContainer),
                    const SizedBox(width: 8),
                    Expanded(
                      child: Text(
                        "Couldn't automatically read this receipt. Please enter the values manually.",
                        style: TextStyle(color: Theme.of(context).colorScheme.onErrorContainer),
                      ),
                    ),
                  ],
                ),
              ),
            ],
            const SizedBox(height: 16),
            ListTile(
              contentPadding: EdgeInsets.zero,
              title: const Text('Date & time'),
              subtitle: Text(dateFormat.format(_date)),
              trailing: const Icon(Icons.edit_calendar_outlined),
              onTap: _pickDate,
            ),
            const SizedBox(height: 8),
            TextFormField(
              controller: _gallonsController,
              decoration: const InputDecoration(labelText: 'Gallons', suffixText: 'gal'),
              keyboardType: const TextInputType.numberWithOptions(decimal: true),
              validator: _requiredDecimal,
            ),
            const SizedBox(height: 12),
            TextFormField(
              controller: _priceController,
              decoration: const InputDecoration(labelText: 'Price per gallon', prefixText: '\$'),
              keyboardType: const TextInputType.numberWithOptions(decimal: true),
              validator: _requiredDecimal,
            ),
            const SizedBox(height: 12),
            TextFormField(
              controller: _totalController,
              decoration: InputDecoration(
                labelText: 'Total cost',
                prefixText: '\$',
                suffixIcon: IconButton(
                  icon: const Icon(Icons.calculate_outlined),
                  tooltip: 'Calculate from gallons × price',
                  onPressed: _calculateTotal,
                ),
              ),
              keyboardType: const TextInputType.numberWithOptions(decimal: true),
              validator: _requiredDecimal,
            ),
            const SizedBox(height: 24),
            FilledButton(
              onPressed: _saving ? null : _save,
              child: _saving
                  ? const SizedBox(height: 20, width: 20, child: CircularProgressIndicator(strokeWidth: 2))
                  : const Text('Save Entry'),
            ),
          ],
        ),
      ),
    );
  }
}