import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import 'package:supabase_flutter/supabase_flutter.dart';

import '../../app/router.dart';
import '../../app/theme.dart';
import '../../core/env.dart';
import '../../shared/widgets/artwork.dart';

enum _Step {
  signIn,
  signUp,
  verifySignUp, // code from the sign-up email
  codeRequest, // sign in with an emailed code instead of a password
  codeVerify,
  forgot,
  resetVerify, // code from the reset email + new password
}

/// Sign up (name, email, password, then an email code), sign in with a password,
/// sign in with a code, reset password, or preview without an account.
class LoginScreen extends ConsumerStatefulWidget {
  const LoginScreen({super.key, this.startWithSignUp = false});

  final bool startWithSignUp;

  @override
  ConsumerState<LoginScreen> createState() => _LoginScreenState();
}

class _LoginScreenState extends ConsumerState<LoginScreen> {
  final _name = TextEditingController();
  final _email = TextEditingController();
  final _password = TextEditingController();
  final _code = TextEditingController();
  late _Step _step = widget.startWithSignUp ? _Step.signUp : _Step.signIn;
  bool _busy = false;
  bool _showPassword = false;
  String? _error;
  String? _info;

  GoTrueClient get _auth => Supabase.instance.client.auth;
  String get _emailText => _email.text.trim();

  @override
  void dispose() {
    for (final c in [_name, _email, _password, _code]) {
      c.dispose();
    }
    super.dispose();
  }

  bool get _emailValid => RegExp(r'^[^@\s]+@[^@\s]+\.[^@\s]+$').hasMatch(_emailText);
  bool get _passwordValid => _password.text.length >= 8;
  bool get _codeValid => RegExp(r'^\d{6}$').hasMatch(_code.text.trim());

  void _go(_Step step) => setState(() {
        _step = step;
        _error = null;
        _info = null;
        _code.clear();
      });

  Future<void> _run(Future<void> Function() action) async {
    if (!Env.hasSupabase) {
      setState(() => _error = 'This build is not connected to the server. Tap "Preview without an account".');
      return;
    }
    setState(() {
      _busy = true;
      _error = null;
      _info = null;
    });
    try {
      await action();
    } on AuthException catch (e) {
      setState(() => _error = _friendly(e));
    } catch (_) {
      setState(() => _error = 'Something went wrong. Check your connection and try again.');
    } finally {
      if (mounted) setState(() => _busy = false);
    }
  }

  String _friendly(AuthException e) {
    final m = e.message.toLowerCase();
    if (m.contains('invalid login credentials')) {
      return 'Email or password is wrong. If you never set a password, use "Email me a code" '
          'and set one in your profile.';
    }
    if (m.contains('email not confirmed')) return 'Please confirm your email first. We can send a new code.';
    if (m.contains('expired') || m.contains('invalid') && m.contains('token')) {
      return 'That code is wrong or has expired. Check the latest email, or send a new code.';
    }
    if (m.contains('rate limit') || m.contains('security purposes')) {
      return 'Please wait a minute before asking for another code.';
    }
    return e.message;
  }

  Future<void> _signIn() => _run(() async {
        await _auth.signInWithPassword(email: _emailText, password: _password.text);
        _finish();
      });

  Future<void> _signUp() => _run(() async {
        final res = await _auth.signUp(
          email: _emailText,
          password: _password.text,
          data: {'display_name': _name.text.trim()},
        );
        // An existing, confirmed email comes back as a user with no identities.
        if (res.user != null && (res.user!.identities?.isEmpty ?? false)) {
          setState(() => _error = 'An account with this email already exists. Sign in instead.');
          return;
        }
        _go(_Step.verifySignUp);
      });

  Future<void> _verifySignUp() => _run(() async {
        await _auth.verifyOTP(type: OtpType.signup, email: _emailText, token: _code.text.trim());
        _finish();
      });

  Future<void> _resendSignUp() => _run(() async {
        await _auth.resend(type: OtpType.signup, email: _emailText);
        setState(() => _info = 'New code sent.');
      });

  Future<void> _requestCode() => _run(() async {
        await _auth.signInWithOtp(email: _emailText, shouldCreateUser: false);
        _go(_Step.codeVerify);
      });

  Future<void> _verifyCode() => _run(() async {
        await _auth.verifyOTP(type: OtpType.email, email: _emailText, token: _code.text.trim());
        _finish();
      });

  Future<void> _requestReset() => _run(() async {
        await _auth.resetPasswordForEmail(_emailText);
        _go(_Step.resetVerify);
      });

  Future<void> _verifyReset() => _run(() async {
        await _auth.verifyOTP(type: OtpType.recovery, email: _emailText, token: _code.text.trim());
        await _auth.updateUser(UserAttributes(password: _password.text));
        _finish();
      });

  void _finish() {
    ref.read(onboardingProvider.notifier).complete();
    if (mounted) context.go('/home');
  }

  void _preview() {
    ref.read(onboardingProvider.notifier).complete();
    context.go('/home');
  }

  ({String title, String subtitle, String action, VoidCallback? onAction}) get _copy => switch (_step) {
        _Step.signIn => (
            title: 'Welcome back',
            subtitle: 'Sign in to listen to full songs and keep your likes.',
            action: 'Sign in',
            onAction: _emailValid && _password.text.isNotEmpty ? _signIn : null,
          ),
        _Step.signUp => (
            title: 'Create your account',
            subtitle: 'Free to join. We will email you a code to confirm it is you.',
            action: 'Create account',
            onAction: _name.text.trim().isNotEmpty && _emailValid && _passwordValid ? _signUp : null,
          ),
        _Step.verifySignUp => (
            title: 'Check your email',
            subtitle: 'Enter the 6-digit code we sent to $_emailText to finish signing up.',
            action: 'Verify and continue',
            onAction: _codeValid ? _verifySignUp : null,
          ),
        _Step.codeRequest => (
            title: 'Sign in with a code',
            subtitle: 'We will email you a 6-digit code. No password needed.',
            action: 'Email me a code',
            onAction: _emailValid ? _requestCode : null,
          ),
        _Step.codeVerify => (
            title: 'Check your email',
            subtitle: 'Enter the 6-digit code we sent to $_emailText.',
            action: 'Verify and sign in',
            onAction: _codeValid ? _verifyCode : null,
          ),
        _Step.forgot => (
            title: 'Reset your password',
            subtitle: 'We will email you a code to set a new password.',
            action: 'Email me a reset code',
            onAction: _emailValid ? _requestReset : null,
          ),
        _Step.resetVerify => (
            title: 'Set a new password',
            subtitle: 'Enter the code we sent to $_emailText and choose a new password.',
            action: 'Save password and sign in',
            onAction: _codeValid && _passwordValid ? _verifyReset : null,
          ),
      };

  @override
  Widget build(BuildContext context) {
    final text = Theme.of(context).textTheme;
    final copy = _copy;
    final askName = _step == _Step.signUp;
    final askEmail = const [_Step.signIn, _Step.signUp, _Step.codeRequest, _Step.forgot].contains(_step);
    final askPassword = const [_Step.signIn, _Step.signUp, _Step.resetVerify].contains(_step);
    final askCode = const [_Step.verifySignUp, _Step.codeVerify, _Step.resetVerify].contains(_step);
    final newPassword = _step == _Step.signUp || _step == _Step.resetVerify;

    return Scaffold(
      resizeToAvoidBottomInset: true,
      body: SingleChildScrollView(
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            SizedBox(
              height: 240,
              child: Stack(
                fit: StackFit.expand,
                children: [
                  Image.asset('assets/images/nilgiris_village.jpg',
                      fit: BoxFit.cover, alignment: const Alignment(-0.4, 0.2)),
                  const PhotoScrim(stops: [0.2, 1]),
                  SafeArea(
                    child: Padding(
                      padding: const EdgeInsets.all(24),
                      child: Row(
                        crossAxisAlignment: CrossAxisAlignment.start,
                        children: [
                          ClipOval(child: Image.asset('assets/images/emblem.png', width: 52, height: 52)),
                          const SizedBox(width: 12),
                          Padding(
                            padding: const EdgeInsets.only(top: 12),
                            child: Text('Nanga Kathai', style: text.titleLarge?.copyWith(fontWeight: FontWeight.w800)),
                          ),
                        ],
                      ),
                    ),
                  ),
                ],
              ),
            ),
            Padding(
              padding: const EdgeInsets.fromLTRB(24, 0, 24, 32),
              child: AutofillGroup(
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.stretch,
                  children: [
                    if (_step == _Step.signIn || _step == _Step.signUp) ...[
                      SegmentedButton<_Step>(
                        segments: const [
                          ButtonSegment(value: _Step.signUp, label: Text('Sign up')),
                          ButtonSegment(value: _Step.signIn, label: Text('Sign in')),
                        ],
                        selected: {_step},
                        showSelectedIcon: false,
                        onSelectionChanged: _busy ? null : (s) => _go(s.first),
                      ),
                      const SizedBox(height: 20),
                    ],
                    Text(copy.title, style: text.headlineMedium),
                    const SizedBox(height: 6),
                    Text(copy.subtitle, style: text.bodyLarge?.copyWith(color: NkColors.muted, height: 1.5)),
                    const SizedBox(height: 20),
                    if (askName) ...[
                      TextField(
                        controller: _name,
                        textCapitalization: TextCapitalization.words,
                        autofillHints: const [AutofillHints.name],
                        textInputAction: TextInputAction.next,
                        onChanged: (_) => setState(() {}),
                        decoration: const InputDecoration(labelText: 'Your name'),
                      ),
                      const SizedBox(height: 12),
                    ],
                    if (askEmail) ...[
                      TextField(
                        controller: _email,
                        keyboardType: TextInputType.emailAddress,
                        autofillHints: const [AutofillHints.email],
                        textInputAction: askPassword ? TextInputAction.next : TextInputAction.done,
                        onChanged: (_) => setState(() {}),
                        decoration: const InputDecoration(labelText: 'Email', hintText: 'you@example.com'),
                      ),
                      const SizedBox(height: 12),
                    ],
                    if (askCode) ...[
                      TextField(
                        controller: _code,
                        keyboardType: TextInputType.number,
                        autofillHints: const [AutofillHints.oneTimeCode],
                        maxLength: 6,
                        onChanged: (_) => setState(() {}),
                        style: const TextStyle(fontSize: 24, letterSpacing: 8, fontWeight: FontWeight.w700),
                        decoration: const InputDecoration(labelText: 'Code', counterText: ''),
                      ),
                      const SizedBox(height: 12),
                    ],
                    if (askPassword)
                      TextField(
                        controller: _password,
                        obscureText: !_showPassword,
                        autofillHints: [newPassword ? AutofillHints.newPassword : AutofillHints.password],
                        onChanged: (_) => setState(() {}),
                        onSubmitted: (_) => copy.onAction?.call(),
                        decoration: InputDecoration(
                          labelText: newPassword ? 'Choose a password' : 'Password',
                          helperText: newPassword ? 'At least 8 characters' : null,
                          suffixIcon: IconButton(
                            tooltip: _showPassword ? 'Hide password' : 'Show password',
                            icon: Icon(_showPassword ? Icons.visibility_off : Icons.visibility),
                            onPressed: () => setState(() => _showPassword = !_showPassword),
                          ),
                        ),
                      ),
                    if (_error != null) ...[
                      const SizedBox(height: 12),
                      Text(_error!, style: const TextStyle(color: Color(0xFFF2A69B))),
                    ],
                    if (_info != null) ...[
                      const SizedBox(height: 12),
                      Text(_info!, style: const TextStyle(color: NkColors.teaLeaf)),
                    ],
                    const SizedBox(height: 20),
                    FilledButton(
                      onPressed: _busy ? null : copy.onAction,
                      child: _busy
                          ? const SizedBox.square(dimension: 22, child: CircularProgressIndicator(strokeWidth: 2.5))
                          : Text(copy.action),
                    ),
                    const SizedBox(height: 8),
                    ..._links(),
                    const SizedBox(height: 16),
                    const Row(children: [
                      Expanded(child: Divider(color: NkColors.outline)),
                      Padding(
                        padding: EdgeInsets.symmetric(horizontal: 12),
                        child: Text('or', style: TextStyle(color: NkColors.muted)),
                      ),
                      Expanded(child: Divider(color: NkColors.outline)),
                    ]),
                    const SizedBox(height: 16),
                    OutlinedButton(onPressed: _busy ? null : _preview, child: const Text('Preview without an account')),
                    const SizedBox(height: 6),
                    const Text(
                      'Guests hear a 30-second preview of each song.',
                      textAlign: TextAlign.center,
                      style: TextStyle(color: NkColors.muted, fontSize: 13),
                    ),
                  ],
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }

  List<Widget> _links() {
    TextButton link(String label, VoidCallback onTap) =>
        TextButton(onPressed: _busy ? null : onTap, child: Text(label));
    return switch (_step) {
      _Step.signIn => [
          link('Forgot password?', () => _go(_Step.forgot)),
          link('Email me a code instead', () => _go(_Step.codeRequest)),
        ],
      _Step.verifySignUp => [
          link('Send a new code', _resendSignUp),
          link('Use a different email', () => _go(_Step.signUp)),
        ],
      _Step.codeVerify || _Step.resetVerify => [
          link('Use a different email', () => _go(_step == _Step.codeVerify ? _Step.codeRequest : _Step.forgot)),
        ],
      _Step.codeRequest || _Step.forgot => [link('Back to sign in', () => _go(_Step.signIn))],
      _Step.signUp => const [],
    };
  }
}