import 'package:flutter/material.dart';
import 'package:qr_flutter/qr_flutter.dart';

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

  @override
  State<UpiScreen> createState() => _UpiScreenState();
}

class _UpiScreenState extends State<UpiScreen> {
  final TextEditingController accountCtrl = TextEditingController();
  final TextEditingController ifscCtrl = TextEditingController();
  final TextEditingController nameCtrl = TextEditingController();

  String? upiUri;

  /// Build UPI URI using Account Number + IFSC
  /// Follows NPCI UPI URI standards (upi://pay?pa=...&pn=...&cu=INR)
  /// Supported by UPI QR generators like Labnol which accept bank account + IFSC as payment address.
  String buildUpiUri({
    required String accountNumber,
    required String ifsc,
    required String name,
  }) {
    final upiAddress = "$accountNumber@apl";
    //const upiAddress = "asifarbaj-2@okaxis";

    final uri = Uri(
      scheme: "upi",
      host: "pay",
      queryParameters: {
        "pa": upiAddress,
        "pn": name,
        "cu": "INR",
      },
    );

    return uri.toString();
  }

  void generateQr() {
    final account = accountCtrl.text.trim();
    final ifsc = ifscCtrl.text.trim();
    final name = nameCtrl.text.trim();

    if (account.isEmpty || ifsc.isEmpty || name.isEmpty) {
      ScaffoldMessenger.of(context).showSnackBar(
        const SnackBar(content: Text("Please fill all fields")),
      );
      return;
    }

    setState(() {
      upiUri = buildUpiUri(
        accountNumber: account,
        ifsc: ifsc,
        name: name,
      );
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("Receive Money by UPI"),
        centerTitle: true,
      ),
      body: Padding(
        padding: const EdgeInsets.all(20),
        child: SingleChildScrollView(
          child: Column(
            children: [
              TextField(
                controller: accountCtrl,
                decoration: const InputDecoration(
                  labelText: "Account Number",
                  border: OutlineInputBorder(),
                ),
                keyboardType: TextInputType.number,
              ),
              const SizedBox(height: 15),

              TextField(
                controller: ifscCtrl,
                decoration: const InputDecoration(
                  labelText: "IFSC Code",
                  border: OutlineInputBorder(),
                ),
              ),
              const SizedBox(height: 15),

              TextField(
                controller: nameCtrl,
                decoration: const InputDecoration(
                  labelText: "Account Holder Name",
                  border: OutlineInputBorder(),
                ),
              ),
              const SizedBox(height: 25),

              ElevatedButton(
                onPressed: generateQr,
                child: const Text("Generate QR"),
              ),

              const SizedBox(height: 30),

              if (upiUri != null) ...[
                const Text(
                  "Your UPI QR Code:",
                  style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
                ),
                const SizedBox(height: 15),

                QrImageView(
                  data: upiUri!,
                  version: QrVersions.auto,
                  size: 260,
                  backgroundColor: Colors.white,
                ),

                const SizedBox(height: 10),

                SelectableText(
                  upiUri!,
                  textAlign: TextAlign.center,
                ),
              ],
            ],
          ),
        ),
      ),
    );
  }
}