import 'package:flutter/material.dart';

import '../api.dart';
import '../session.dart';
import '../theme.dart';
import '../widgets.dart';

/// Email-code sign-in. Codes are only sent to existing accounts, and only admins get in.
class SignInScreen extends StatefulWidget {
  const SignInScreen({super.key});

  @override
  State<SignInScreen> createState() => _SignInScreenState();
}

class _SignInScreenState extends State<SignInScreen> {
  final _email = TextEditingController();
  final _code = TextEditingController();
  bool _codeSent = false;
  bool _busy = false;
  String? _error;

  @override
  void dispose() {
    _email.dispose();
    _code.dispose();
    super.dispose();
  }

  String get _emailText => _email.text.trim().toLowerCase();

  Future<void> _run(Future<void> Function() job) async {
    setState(() {
      _busy = true;
      _error = null;
    });
    try {
      await job();
    } catch (e) {
      _error = errorText(e);
    } finally {
      if (mounted) setState(() => _busy = false);
    }
  }

  void _sendCode() {
    if (!_emailText.contains('@')) {
      setState(() => _error = 'Enter your admin email address.');
      return;
    }
    _run(() async {
      await AdminApi.sendCode(_emailText);
      _codeSent = true;
      _code.clear();
    });
  }

  void _verify() {
    if (_code.text.trim().length < 6) {
      setState(() => _error = 'Enter the 6-digit code from the email.');
      return;
    }
    _run(() => AdminApi.verifyCode(_emailText, _code.text.trim()));
  }

  @override
  Widget build(BuildContext context) {
    final session = AdminSession.instance;
    return Scaffold(
      body: ListenableBuilder(
        listenable: session,
        builder: (context, _) {
          if (session.state == SessionState.checking) return const Center(child: CircularProgressIndicator());
          final message = _error ?? session.refusal;
          return Center(
            child: SingleChildScrollView(
              padding: const EdgeInsets.all(24),
              child: ConstrainedBox(
                constraints: const BoxConstraints(maxWidth: 400),
                child: Card(
                  child: Padding(
                    padding: const EdgeInsets.all(28),
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.stretch,
                      children: [
                        Container(
                          width: 56,
                          height: 56,
                          alignment: Alignment.center,
                          decoration: const BoxDecoration(color: NkColors.sun, shape: BoxShape.circle),
                          child: const Text('NK',
                              style: TextStyle(color: NkColors.ground, fontWeight: FontWeight.w900, fontSize: 20)),
                        ),
                        const SizedBox(height: 20),
                        Text('Nanga Kathai Admin', style: Theme.of(context).textTheme.headlineSmall),
                        const SizedBox(height: 6),
                        Text(
                          _codeSent
                              ? 'We emailed a 6-digit code to $_emailText.'
                              : 'Sign in with your admin email. We\'ll send you a code.',
                          style: Theme.of(context).textTheme.bodySmall,
                        ),
                        const SizedBox(height: 24),
                        if (!_codeSent)
                          TextField(
                            controller: _email,
                            autofocus: true,
                            keyboardType: TextInputType.emailAddress,
                            autofillHints: const [AutofillHints.email],
                            decoration: const InputDecoration(labelText: 'Email'),
                            onSubmitted: (_) => _sendCode(),
                          )
                        else
                          TextField(
                            controller: _code,
                            autofocus: true,
                            keyboardType: TextInputType.number,
                            autofillHints: const [AutofillHints.oneTimeCode],
                            maxLength: 6,
                            style: const TextStyle(fontSize: 22, letterSpacing: 8, fontWeight: FontWeight.w700),
                            decoration: const InputDecoration(labelText: 'Code', counterText: ''),
                            onSubmitted: (_) => _verify(),
                          ),
                        if (message != null) ...[
                          const SizedBox(height: 12),
                          Text(message, style: const TextStyle(color: NkColors.roofRed)),
                        ],
                        const SizedBox(height: 20),
                        FilledButton(
                          onPressed: _busy ? null : (_codeSent ? _verify : _sendCode),
                          child: _busy
                              ? const SizedBox.square(
                                  dimension: 20, child: CircularProgressIndicator(strokeWidth: 2))
                              : Text(_codeSent ? 'Sign in' : 'Email me a code'),
                        ),
                        if (_codeSent) ...[
                          const SizedBox(height: 8),
                          Row(
                            mainAxisAlignment: MainAxisAlignment.spaceBetween,
                            children: [
                              TextButton(
                                onPressed: _busy ? null : () => setState(() => _codeSent = false),
                                child: const Text('Use another email'),
                              ),
                              TextButton(onPressed: _busy ? null : _sendCode, child: const Text('Send again')),
                            ],
                          ),
                        ],
                      ],
                    ),
                  ),
                ),
              ),
            ),
          );
        },
      ),
    );
  }
}