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

import '../models/fuel_entry.dart';
import '../services/app_state.dart';
import '../widgets/receipt_thumbnail.dart';

/// Lets the user correct the *data* logged about a receipt (date, gallons,
/// price/gal, total cost) — not the receipt photo itself, which is shown
/// read-only up top (tap it to view full-screen, same as everywhere else
/// it's shown) and can't be replaced from here.
class EditFuelEntryScreen extends StatefulWidget {
  final FuelEntry entry;

  const EditFuelEntryScreen({super.key, required this.entry});

  @override
  State<EditFuelEntryScreen> createState() => _EditFuelEntryScreenState();
}

class _EditFuelEntryScreenState extends State<EditFuelEntryScreen> {
  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();
    _date = widget.entry.date;
    _gallonsController = TextEditingController(text: widget.entry.gallons.toStringAsFixed(3));
    _priceController = TextEditingController(text: widget.entry.pricePerGallon.toStringAsFixed(3));
    _totalController = TextEditingController(text: widget.entry.totalCost.toStringAsFixed(2));
  }

  @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 it's already
    // 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 {
      await context.read<AppState>().updateFuelEntry(
            entryId: widget.entry.id,
            date: _date,
            gallons: double.parse(_gallonsController.text),
            pricePerGallon: double.parse(_priceController.text),
            totalCost: double.parse(_totalController.text),
          );
      if (mounted) Navigator.of(context).pop();
    } 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();

    return Scaffold(
      appBar: AppBar(title: const Text('Edit Fuel Entry')),
      body: Form(
        key: _formKey,
        child: ListView(
          padding: const EdgeInsets.all(16),
          children: [
            Center(
              child: ReceiptThumbnail(entry: widget.entry, size: 180),
            ),
            const SizedBox(height: 8),
            Text(
              'Tap the photo to view it full-screen. The photo itself can\'t '
              "be changed here — only the data below can.",
              style: Theme.of(context).textTheme.bodySmall,
              textAlign: TextAlign.center,
            ),
            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 Changes'),
            ),
          ],
        ),
      ),
    );
  }
}