import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import '../models/saved_account.dart';
import '../providers/session_controller.dart';
import 'login_webview_view.dart';

class LoginView extends StatefulWidget {
  /// True when this is pushed from Settings ("Add account") on top of an
  /// already-logged-in session, rather than shown as the app's root screen
  /// with no account yet. Adds an AppBar/back affordance and auto-pops once
  /// the new account becomes active.
  final bool isAddingAccount;

  const LoginView({super.key, this.isAddingAccount = false});

  @override
  State<LoginView> createState() => _LoginViewState();
}

class _LoginViewState extends State<LoginView> {
  final _formKey = GlobalKey<FormState>();
  final _urlController = TextEditingController();
  String? _originalActiveAccountId;
  bool _popped = false;
  bool _webViewPushed = false;

  @override
  void initState() {
    super.initState();
    if (widget.isAddingAccount) {
      _originalActiveAccountId = context.read<SessionController>().activeAccountId;
    }
  }

  @override
  void dispose() {
    _urlController.dispose();
    super.dispose();
  }

  void _handleContinue() {
    if (!_formKey.currentState!.validate()) return;
    FocusScope.of(context).unfocus();
    context.read<SessionController>().startLoginFlow(
      _urlController.text.trim(),
      addAccount: widget.isAddingAccount,
    );
  }

  /// Resumes a saved account with one tap (see [SessionController.switchAccount]).
  /// That can fail silently from the account's own perspective - most often
  /// a stored app password that no longer works (revoked server-side, or
  /// left over from before a since-fixed bug that deleted it too eagerly on
  /// a plain network hiccup) - so this surfaces that as a SnackBar with a
  /// silently failing every time - a delete button on the row itself (see
  /// [_SavedAccountRow]) is the way out.
  Future<void> _continueAsAccount(SavedAccount account) async {
    final session = context.read<SessionController>();
    final success = await session.switchAccount(account.id);
    if (success || !mounted) return;
    ScaffoldMessenger.of(context)
      ..hideCurrentSnackBar()
      ..showSnackBar(
        SnackBar(
          content: Text("Couldn't sign in as ${account.username}"),
          behavior: SnackBarBehavior.floating,
        ),
      );
  }

  /// Mirrors AccountView's `_AccountsCard._confirmRemove` - same
  /// destructive-action gate, just reached from the login screen instead of
  /// Settings.
  Future<void> _confirmRemoveAccount(SavedAccount account) async {
    final host = Uri.tryParse(account.serverUrl)?.host ?? account.serverUrl;
    final confirmed = await showDialog<bool>(
      context: context,
      builder: (dialogContext) {
        return AlertDialog(
          title: const Text('Remove Account'),
          content: Text(
            'Remove ${account.username} ($host)? You can add it again later.',
          ),
          actions: [
            TextButton(
              onPressed: () => Navigator.pop(dialogContext, false),
              child: const Text('Cancel'),
            ),
            FilledButton(
              style: FilledButton.styleFrom(
                backgroundColor: Theme.of(dialogContext).colorScheme.error,
              ),
              onPressed: () => Navigator.pop(dialogContext, true),
              child: const Text('Remove'),
            ),
          ],
        );
      },
    );
    if (confirmed != true || !mounted) return;
    await context.read<SessionController>().removeAccount(account.id);
  }

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final colorScheme = theme.colorScheme;
    final session = context.watch<SessionController>();

    final isAwaitingBrowser =
        session.loginFlowStatus == LoginFlowStatus.awaitingBrowser;
    final isInitiating = session.loginFlowStatus == LoginFlowStatus.initiating;

    // A new/refreshed account has just become active - pop back to
    // Settings rather than leaving this form sitting on top of it.
    if (widget.isAddingAccount &&
        !_popped &&
        session.loginFlowStatus == LoginFlowStatus.idle &&
        session.activeAccountId != _originalActiveAccountId) {
      _popped = true;
      WidgetsBinding.instance.addPostFrameCallback((_) {
        if (mounted) Navigator.of(context).pop();
      });
    }

    // Every login (first account or an additional one) shows its login
    // page in LoginWebViewView, a real screen this app owns - see
    // SessionController.startLoginFlow's doc comment for why. Push it the
    // moment there's a URL to show; _webViewPushed resets once that route
    // pops (cancelled or done) so a retry after cancelling pushes it again.
    if (!_webViewPushed &&
        isAwaitingBrowser &&
        session.pendingLoginUrl != null) {
      _webViewPushed = true;
      final url = session.pendingLoginUrl!;
      WidgetsBinding.instance.addPostFrameCallback((_) async {
        if (!mounted) return;
        // A plain MaterialPageRoute's animated slide/fade transition can
        // leave this screen fully black after popping back off of it - a
        // known Android WebView-as-PlatformView compositing issue with the
        // Impeller renderer (the platform view's surface isn't always torn
        // down in sync with an animated route transition). An instant,
        // non-animated route sidesteps it entirely; the close (X) button
        // already reads like a immediate action, not something that needs
        // a slide, so no UX is lost.
        await Navigator.of(context).push(
          PageRouteBuilder(
            pageBuilder: (_, _, _) => LoginWebViewView(url: url),
            transitionDuration: Duration.zero,
            reverseTransitionDuration: Duration.zero,
          ),
        );
        _webViewPushed = false;
      });
    }

    final body = Scaffold(
      appBar: widget.isAddingAccount
          ? AppBar(title: const Text('Add Account'))
          : null,
      body: SafeArea(
        child: Center(
          child: SingleChildScrollView(
            physics: const BouncingScrollPhysics(),
            padding: const EdgeInsets.symmetric(horizontal: 28, vertical: 24),
            child: ConstrainedBox(
              constraints: const BoxConstraints(maxWidth: 440),
              child: Column(
                mainAxisSize: MainAxisSize.min,
                children: [
                  // A logout keeps the account saved rather than
                  // deleting it, specifically so it can be resumed
                  // from here with one tap - no need to repeat
                  // Login Flow v2.
                  if (!widget.isAddingAccount &&
                      session.accounts.isNotEmpty) ...[
                    _SavedAccountsSection(
                      accounts: session.accounts,
                      onSelect: (account) => _continueAsAccount(account),
                      onRemove: (account) => _confirmRemoveAccount(account),
                    ),
                    const SizedBox(height: 28),
                    Row(
                      children: [
                        const Expanded(child: Divider()),
                        Padding(
                          padding: const EdgeInsets.symmetric(horizontal: 12),
                          child: Text(
                            'or',
                            style: theme.textTheme.bodySmall?.copyWith(
                              color: colorScheme.onSurfaceVariant,
                            ),
                          ),
                        ),
                        const Expanded(child: Divider()),
                      ],
                    ),
                    const SizedBox(height: 28),
                  ],
                  _ServerForm(
                    formKey: _formKey,
                    urlController: _urlController,
                    isLoading:
                        isInitiating || session.isLoading || isAwaitingBrowser,
                    errorMessage:
                        session.loginFlowStatus == LoginFlowStatus.error
                        ? session.errorMessage
                        : null,
                    onContinue: _handleContinue,
                    theme: theme,
                    colorScheme: colorScheme,
                  ),
                ],
              ),
            ),
          ),
        ),
      ),
    );

    if (!widget.isAddingAccount) return body;

    // Backing out mid-flow (system back/swipe-back, not just the explicit
    // Cancel button in LoginWebViewView) should cancel the pending login
    // flow rather than leaving its poll timer running after this screen is
    // gone - this view could never be popped before "add account" existed,
    // so that case wasn't reachable until now.
    return PopScope(
      canPop: session.loginFlowStatus != LoginFlowStatus.awaitingBrowser,
      onPopInvokedWithResult: (didPop, _) {
        if (!didPop) session.cancelLoginFlow();
      },
      child: body,
    );
  }
}

class _ServerForm extends StatelessWidget {
  final GlobalKey<FormState> formKey;
  final TextEditingController urlController;
  final bool isLoading;
  final String? errorMessage;
  final VoidCallback onContinue;
  final ThemeData theme;
  final ColorScheme colorScheme;

  const _ServerForm({
    required this.formKey,
    required this.urlController,
    required this.isLoading,
    required this.errorMessage,
    required this.onContinue,
    required this.theme,
    required this.colorScheme,
  });

  @override
  Widget build(BuildContext context) {
    return Form(
      key: formKey,
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          Center(
            // Same monochrome-tinted treatment as the splash/lock screens
            // (see main.dart's _SplashView) - the asset is a plain white
            // silhouette on transparent, meant to be recolored rather than
            // shown as-is. Used everywhere the app shows its own icon
            // in-app, rather than the full-color launcher icon.
            child: ColorFiltered(
              colorFilter: ColorFilter.mode(
                Theme.of(context).colorScheme.onSurface,
                BlendMode.srcIn,
              ),
              child: Image.asset(
                'assets/icon/app_icon_monochrome.png',
                width: 80,
                height: 80,
              ),
            ),
          ),
          const SizedBox(height: 24),
          Text(
            'Noo',
            textAlign: TextAlign.center,
            style: theme.textTheme.headlineMedium?.copyWith(
              fontWeight: FontWeight.w800,
              letterSpacing: -0.5,
            ),
          ),
          const SizedBox(height: 6),
          Text(
            'Connect to your self-hosted server',
            textAlign: TextAlign.center,
            style: theme.textTheme.bodyMedium?.copyWith(
              color: colorScheme.onSurfaceVariant,
            ),
          ),
          const SizedBox(height: 36),
          if (errorMessage != null)
            Container(
              margin: const EdgeInsets.only(bottom: 20),
              padding: const EdgeInsets.all(14),
              decoration: BoxDecoration(
                color: colorScheme.errorContainer,
                borderRadius: BorderRadius.circular(16),
              ),
              child: Row(
                children: [
                  Icon(
                    Icons.error_outline_rounded,
                    color: colorScheme.onErrorContainer,
                    size: 20,
                  ),
                  const SizedBox(width: 12),
                  Expanded(
                    child: Text(
                      errorMessage!,
                      style: theme.textTheme.bodySmall?.copyWith(
                        color: colorScheme.onErrorContainer,
                        fontWeight: FontWeight.w500,
                      ),
                    ),
                  ),
                ],
              ),
            ),
          TextFormField(
            controller: urlController,
            keyboardType: TextInputType.url,
            autofillHints: const [AutofillHints.url],
            decoration: InputDecoration(
              labelText: 'Server Address',
              hintText: 'cloud.example.com',
              prefixIcon: const Icon(Icons.dns_outlined),
              border: OutlineInputBorder(
                borderRadius: BorderRadius.circular(16),
              ),
              filled: true,
              fillColor: colorScheme.surfaceContainerLow,
            ),
            validator: (val) {
              if (val == null || val.trim().isEmpty) {
                return 'Please enter your Nextcloud server address';
              }
              return null;
            },
            onFieldSubmitted: (_) => onContinue(),
          ),
          const SizedBox(height: 28),
          SizedBox(
            height: 54,
            child: FilledButton(
              onPressed: isLoading ? null : onContinue,
              style: FilledButton.styleFrom(
                shape: RoundedRectangleBorder(
                  borderRadius: BorderRadius.circular(27),
                ),
              ),
              child: isLoading
                  ? SizedBox(
                      width: 24,
                      height: 24,
                      child: CircularProgressIndicator(
                        strokeWidth: 2.5,
                        color: colorScheme.onPrimary,
                      ),
                    )
                  : const Text(
                      'Continue',
                      style: TextStyle(
                        fontSize: 16,
                        fontWeight: FontWeight.bold,
                      ),
                    ),
            ),
          ),
          const SizedBox(height: 24),
          Text(
            "You'll finish signing in on the page that opens. This app never sees your password.",
            textAlign: TextAlign.center,
            style: theme.textTheme.bodySmall?.copyWith(
              color: colorScheme.onSurfaceVariant,
              fontSize: 11,
            ),
          ),
        ],
      ),
    );
  }
}

/// Saved accounts a logout left recoverable - tapping one resumes it via
/// [SessionController.switchAccount] instead of repeating Login Flow v2.
class _SavedAccountsSection extends StatelessWidget {
  final List<SavedAccount> accounts;
  final ValueChanged<SavedAccount> onSelect;
  final ValueChanged<SavedAccount> onRemove;

  const _SavedAccountsSection({
    required this.accounts,
    required this.onSelect,
    required this.onRemove,
  });

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final colorScheme = theme.colorScheme;

    return Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: [
        Padding(
          padding: const EdgeInsets.only(left: 4, bottom: 8),
          child: Text(
            'Continue as',
            style: theme.textTheme.labelLarge?.copyWith(
              color: colorScheme.onSurfaceVariant,
              fontWeight: FontWeight.w600,
            ),
          ),
        ),
        Card(
          margin: EdgeInsets.zero,
          child: Column(
            children: [
              for (final account in accounts) ...[
                _SavedAccountRow(
                  account: account,
                  onTap: () => onSelect(account),
                  onRemove: () => onRemove(account),
                ),
                if (account != accounts.last)
                  const Divider(height: 1, indent: 16, endIndent: 16),
              ],
            ],
          ),
        ),
      ],
    );
  }
}

class _SavedAccountRow extends StatelessWidget {
  final SavedAccount account;
  final VoidCallback onTap;
  final VoidCallback onRemove;

  const _SavedAccountRow({
    required this.account,
    required this.onTap,
    required this.onRemove,
  });

  @override
  Widget build(BuildContext context) {
    final colorScheme = Theme.of(context).colorScheme;
    final host = Uri.tryParse(account.serverUrl)?.host ?? account.serverUrl;
    final initial = account.username.isNotEmpty
        ? account.username[0].toUpperCase()
        : '?';

    return ListTile(
      leading: CircleAvatar(
        backgroundColor: colorScheme.primary,
        child: Text(
          initial,
          style: TextStyle(
            color: colorScheme.onPrimary,
            fontWeight: FontWeight.bold,
          ),
        ),
      ),
      title: Text(account.username),
      subtitle: Text(host),
      trailing: IconButton(
        icon: const Icon(Icons.close_rounded),
        tooltip: 'Remove account',
        visualDensity: VisualDensity.compact,
        onPressed: onRemove,
      ),
      onTap: onTap,
    );
  }
}