/// In-app browser for Enable Banking hosted auth.
///
/// Enable Banking only allows http(s) redirect URLs, so we keep
/// `http://localhost:8000/api/connect/callback` and capture `code` here
/// when the WebView navigates to that callback.
library;

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

/// Result popped from [BankAuthScreen] after bank login.
class BankAuthResult {
  const BankAuthResult({this.code, this.state, this.error});

  final String? code;
  final String? state;
  final String? error;

  bool get hasCode => code != null && code!.isNotEmpty;
}

class BankAuthScreen extends StatefulWidget {
  const BankAuthScreen({
    super.key,
    required this.authUrl,
    this.pendingState,
  });

  final String authUrl;
  final String? pendingState;

  @override
  State<BankAuthScreen> createState() => _BankAuthScreenState();
}

class _BankAuthScreenState extends State<BankAuthScreen> {
  late final WebViewController _controller;
  var _finishing = false;
  var _loading = true;

  @override
  void initState() {
    super.initState();
    _controller = WebViewController()
      ..setJavaScriptMode(JavaScriptMode.unrestricted)
      ..setNavigationDelegate(
        NavigationDelegate(
          onPageStarted: (url) {
            if (mounted) setState(() => _loading = true);
            _handleUrl(url);
          },
          onPageFinished: (_) {
            if (mounted) setState(() => _loading = false);
          },
          onNavigationRequest: (request) {
            if (_handleUrl(request.url)) {
              return NavigationDecision.prevent;
            }
            return NavigationDecision.navigate;
          },
          onWebResourceError: (error) {
            // Callback to localhost often fails to load on emulators; if we
            // already captured the code, ignore the load error.
            if (_finishing) return;
            debugPrint('Bank auth WebView error: ${error.description}');
          },
        ),
      )
      ..loadRequest(Uri.parse(widget.authUrl));
  }

  /// Returns true when [url] is the Enable Banking redirect callback.
  bool _handleUrl(String url) {
    final uri = Uri.tryParse(url);
    if (uri == null || _finishing) return false;
    if (!_isConnectCallback(uri)) return false;

    _finishing = true;
    final error = uri.queryParameters['error'];
    final code = uri.queryParameters['code'];
    final state = uri.queryParameters['state'] ?? widget.pendingState;

    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (!mounted) return;
      Navigator.of(context).pop(
        BankAuthResult(
          code: code,
          state: state,
          error: error,
        ),
      );
    });
    return true;
  }

  bool _isConnectCallback(Uri uri) {
    final path = uri.path;
    return path == '/api/connect/callback' ||
        path.endsWith('/api/connect/callback');
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Connect bank'),
        leading: IconButton(
          icon: const Icon(Icons.close),
          onPressed: () => Navigator.of(context).pop(),
        ),
      ),
      body: Stack(
        children: [
          WebViewWidget(controller: _controller),
          if (_loading)
            const Align(
              alignment: Alignment.topCenter,
              child: LinearProgressIndicator(minHeight: 2),
            ),
        ],
      ),
    );
  }
}