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

import '../wallet/address_script.dart';
import '../wallet/tx_builder.dart';
import '../wallet/wallet_controller.dart';

/// Send tab: enter a destination address + amount, then build, sign (on-device)
/// and broadcast. Validates the address against the current network before
/// enabling send.
class SendScreen extends StatefulWidget {
  const SendScreen({super.key});

  @override
  State<SendScreen> createState() => _SendScreenState();
}

class _SendScreenState extends State<SendScreen> {
  final _addressController = TextEditingController();
  final _amountController = TextEditingController();
  String? _addressError;
  String? _amountError;

  @override
  void dispose() {
    _addressController.dispose();
    _amountController.dispose();
    super.dispose();
  }

  bool _validate(WalletController wallet) {
    String? addrErr;
    String? amtErr;

    final addr = _addressController.text.trim();
    if (addr.isEmpty) {
      addrErr = 'Enter a destination address';
    } else {
      try {
        AddressScript.forAddress(addr, wallet.network);
      } catch (_) {
        addrErr = 'Not a valid ${wallet.network.id} address';
      }
    }

    final amount = double.tryParse(_amountController.text.trim());
    if (amount == null || amount <= 0) {
      amtErr = 'Enter a positive amount';
    }

    setState(() {
      _addressError = addrErr;
      _amountError = amtErr;
    });
    return addrErr == null && amtErr == null;
  }

  Future<void> _send(WalletController wallet) async {
    if (!_validate(wallet)) return;
    final amount = double.parse(_amountController.text.trim());
    final to = _addressController.text.trim();

    // Build (and sign) the tx locally first so the confirmation shows the REAL
    // fee and total. This also surfaces an implausible node-quoted fee rate
    // (ExcessiveFeeRateException) before the user commits to anything.
    final SignedTx preview;
    try {
      preview = await wallet.previewSpend(toAddress: to, amountBig: amount);
    } catch (e) {
      if (!mounted) return;
      _showError(e);
      return;
    }
    final feeBig = preview.feeSats / 1e8;
    final totalBig = (preview.amountSats + preview.feeSats) / 1e8;

    if (!mounted) return;
    final confirmed = await showDialog<bool>(
      context: context,
      builder: (_) => AlertDialog(
        title: const Text('Confirm send'),
        content: Text(
          'Send ${amount.toStringAsFixed(8)} BIG to:\n\n$to\n\n'
          'Network fee: ${feeBig.toStringAsFixed(8)} BIG\n'
          'Total debited: ${totalBig.toStringAsFixed(8)} BIG\n\n'
          'On ${wallet.network.id}.',
        ),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(context, false),
            child: const Text('Cancel'),
          ),
          FilledButton(
            onPressed: () => Navigator.pop(context, true),
            child: const Text('Send'),
          ),
        ],
      ),
    );
    if (confirmed != true) return;

    try {
      final txid = await wallet.send(toAddress: to, amountBig: amount);
      if (!mounted) return;
      _addressController.clear();
      _amountController.clear();
      showDialog<void>(
        context: context,
        builder: (_) => AlertDialog(
          title: const Text('Sent'),
          content: SelectableText('Transaction broadcast:\n\n$txid'),
          actions: [
            TextButton(
              onPressed: () => Navigator.pop(context),
              child: const Text('OK'),
            ),
          ],
        ),
      );
    } catch (e) {
      if (!mounted) return;
      _showError(e);
    }
  }

  void _showError(Object e) {
    final String message;
    if (e is InsufficientFundsException) {
      message = 'Insufficient funds for this amount + fee.';
    } else if (e is ExcessiveFeeRateException) {
      message = 'The network fee quoted is implausibly high; refusing to send.';
    } else {
      message = e.toString();
    }
    ScaffoldMessenger.of(context)
        .showSnackBar(SnackBar(content: Text(message)));
  }

  @override
  Widget build(BuildContext context) {
    final wallet = context.watch<WalletController>();
    final available = wallet.balance?.total;

    return Scaffold(
      appBar: AppBar(title: const Text('Send')),
      body: Padding(
        padding: const EdgeInsets.all(20),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            if (available != null)
              Text('Available: ${available.toStringAsFixed(8)} BIG',
                  style: const TextStyle(color: Colors.white54)),
            const SizedBox(height: 16),
            TextField(
              controller: _addressController,
              autocorrect: false,
              enableSuggestions: false,
              decoration: InputDecoration(
                labelText: 'Destination address',
                hintText: wallet.network.addressPrefixHint,
                border: const OutlineInputBorder(),
                errorText: _addressError,
              ),
            ),
            const SizedBox(height: 16),
            TextField(
              controller: _amountController,
              keyboardType:
                  const TextInputType.numberWithOptions(decimal: true),
              decoration: InputDecoration(
                labelText: 'Amount (BIG)',
                border: const OutlineInputBorder(),
                errorText: _amountError,
              ),
            ),
            const SizedBox(height: 24),
            FilledButton.icon(
              icon: wallet.busy
                  ? const SizedBox(
                      height: 18,
                      width: 18,
                      child: CircularProgressIndicator(strokeWidth: 2))
                  : const Icon(Icons.send),
              label: Text(wallet.busy ? 'Sending…' : 'Send'),
              onPressed: wallet.busy ? null : () => _send(wallet),
            ),
            const SizedBox(height: 16),
            const Text(
              'The transaction is built and signed on this device. Only the '
              'signed result is sent to the network.',
              style: TextStyle(color: Colors.white38, fontSize: 12),
            ),
          ],
        ),
      ),
    );
  }
}