calculadora_supermarket/lib/main.dart

import 'package:flutter/material.dart';

void main() {
  runApp(const SupermarketCalcApp());
}

class SupermarketCalcApp extends StatelessWidget {
  const SupermarketCalcApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Calc Margen',
      debugShowCheckedModeBanner: false,
      // Configuración Material You (M3)
      theme: ThemeData(
        useMaterial3: true,
        colorScheme: ColorScheme.fromSeed(
          seedColor: Colors.red,
          brightness: Brightness.light,
        ),
      ),
      home: const HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  const HomePage({super.key});

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  final _costController = TextEditingController(text: "1.50");
  final _marginController = TextEditingController(text: "40");
  
  double _exactPrice = 2.10;
  double _profit = 0.60;
  String _suggestedPrice = "2.50 €";

  @override
  void initState() {
    super.initState();
    _calculate();
  }

  void _calculate() {
    final double cost = double.tryParse(_costController.text) ?? 0;
    final double marginPercent = double.tryParse(_marginController.text) ?? 0;

    if (cost <= 0 || marginPercent <= 0) {
      setState(() {
        _suggestedPrice = "---";
      });
      return;
    }

    _profit = cost * (marginPercent / 100);
    _exactPrice = cost + _profit;

    // Lógica de Redondeo Psicológico (.50, .95, .99)
    int floorPrice = _exactPrice.floor();
    double finalVal;

    if (_exactPrice <= 1) {
      finalVal = (_exactPrice < 0.50) ? 0.99 : (_exactPrice.ceil() - 0.01);
    } else {
      if (_exactPrice <= floorPrice + 0.50) {
        finalVal = floorPrice + 0.50;
      } else if (_exactPrice <= floorPrice + 0.95) {
        finalVal = floorPrice + 0.95;
      } else {
        finalVal = floorPrice + 0.99;
      }
      
      if (finalVal < _exactPrice) {
        finalVal = _exactPrice.ceil() + 0.99;
      }
    }

    setState(() {
      _suggestedPrice = "${finalVal.toStringAsFixed(2)} €";
    });
  }

  @override
  Widget build(BuildContext context) {
    final colors = Theme.of(context).colorScheme;

    return Scaffold(
      backgroundColor: colors.surface,
      appBar: AppBar(
        title: const Text("Calculadora de Margen"),
        centerTitle: true,
        backgroundColor: colors.surface,
        elevation: 0,
      ),
      body: SingleChildScrollView(
        padding: const EdgeInsets.all(24.0),
        child: Column(
          children: [
            // Card de entrada de datos
            Card(
              elevation: 0,
              color: colors.surfaceContainerHighest.withOpacity(0.3),
              shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(24)),
              child: Padding(
                padding: const EdgeInsets.all(20.0),
                child: Column(
                  children: [
                    TextField(
                      controller: _costController,
                      keyboardType: const TextInputType.numberWithOptions(decimal: true),
                      onChanged: (_) => _calculate(),
                      decoration: InputDecoration(
                        labelText: "Costo Base",
                        prefixText: "€ ",
                        border: OutlineInputBorder(borderRadius: BorderRadius.circular(16)),
                        filled: true,
                        fillColor: colors.surface,
                      ),
                    ),
                    const SizedBox(height: 16),
                    TextField(
                      controller: _marginController,
                      keyboardType: TextInputType.number,
                      onChanged: (_) => _calculate(),
                      decoration: InputDecoration(
                        labelText: "Margen Deseado",
                        suffixText: "%",
                        border: OutlineInputBorder(borderRadius: BorderRadius.circular(16)),
                        filled: true,
                        fillColor: colors.surface,
                      ),
                    ),
                  ],
                ),
              ),
            ),
            const SizedBox(height: 24),
            
            // Resultados Intermedios
            Row(
              children: [
                _buildInfoTile("Precio Exacto", "${_exactPrice.toStringAsFixed(2)} €", colors),
                const SizedBox(width: 12),
                _buildInfoTile("Ganancia", "${_profit.toStringAsFixed(2)} €", colors),
              ],
            ),
            const SizedBox(height: 24),

            // Card de Resultado Final (Material You Hero)
            Container(
              width: double.infinity,
              padding: const EdgeInsets.symmetric(vertical: 32, horizontal: 16),
              decoration: BoxDecoration(
                color: colors.primaryContainer,
                borderRadius: BorderRadius.circular(28),
              ),
              child: Column(
                children: [
                  Text(
                    "PRECIO SUGERIDO",
                    style: TextStyle(
                      color: colors.onPrimaryContainer,
                      fontWeight: FontWeight.w900,
                      letterSpacing: 1.2,
                    ),
                  ),
                  const SizedBox(height: 8),
                  Text(
                    _suggestedPrice,
                    style: TextStyle(
                      fontSize: 56,
                      fontWeight: FontWeight.bold,
                      color: colors.onPrimaryContainer,
                    ),
                  ),
                  Icon(Icons.auto_awesome, color: colors.primary, size: 30),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildInfoTile(String label, String value, ColorScheme colors) {
    return Expanded(
      child: Container(
        padding: const EdgeInsets.all(16),
        decoration: BoxDecoration(
          border: Border.all(color: colors.outlineVariant),
          borderRadius: BorderRadius.circular(20),
        ),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(label, style: TextStyle(fontSize: 12, color: colors.secondary)),
            Text(value, style: const TextStyle(fontSize: 18, fontWeight: FontWeight.bold)),
          ],
        ),
      ),
    );
  }
}