import 'package:auto_route/auto_route.dart';
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:google_fonts/google_fonts.dart';
import 'package:trainhub_flutter/core/constants/ui_constants.dart';
import 'package:trainhub_flutter/core/router/app_router.dart';
import 'package:trainhub_flutter/core/theme/app_colors.dart';
import 'package:trainhub_flutter/presentation/settings/ai_model_settings_controller.dart';
import 'package:trainhub_flutter/presentation/settings/ai_model_settings_state.dart';

@RoutePage()
class WelcomeScreen extends ConsumerStatefulWidget {
  const WelcomeScreen({super.key});

  @override
  ConsumerState<WelcomeScreen> createState() => _WelcomeScreenState();
}

class _WelcomeScreenState extends ConsumerState<WelcomeScreen> {
  bool _hasNavigated = false;

  @override
  void initState() {
    super.initState();
    // Validate after the first frame so the provider is ready
    WidgetsBinding.instance.addPostFrameCallback((_) {
      ref
          .read(aiModelSettingsControllerProvider.notifier)
          .validateModels()
          .then((_) {
        if (!mounted) return;
        final validated = ref
            .read(aiModelSettingsControllerProvider)
            .areModelsValidated;
        if (validated) _navigateToApp();
      });
    });
  }

  void _navigateToApp() {
    if (_hasNavigated) return;
    _hasNavigated = true;
    context.router.replace(const ShellRoute());
  }

  void _skip() => _navigateToApp();

  void _startDownload() {
    ref
        .read(aiModelSettingsControllerProvider.notifier)
        .downloadAll();
  }

  @override
  Widget build(BuildContext context) {
    final modelState = ref.watch(aiModelSettingsControllerProvider);

    // Navigate once download completes and models are validated
    ref.listen<AiModelSettingsState>(aiModelSettingsControllerProvider,
        (prev, next) {
      if (!_hasNavigated &&
          next.areModelsValidated &&
          !next.isDownloading) {
        _navigateToApp();
      }
    });

    return Scaffold(
      backgroundColor: AppColors.surface,
      body: Center(
        child: SizedBox(
          width: 560,
          child: AnimatedSwitcher(
            duration: UIConstants.animationDuration,
            child: modelState.isDownloading
                ? _DownloadProgress(modelState: modelState)
                : _InitialPrompt(
                    onDownload: _startDownload,
                    onSkip: _skip,
                  ),
          ),
        ),
      ),
    );
  }
}

// =============================================================================
// Initial prompt card — shown when models are missing
// =============================================================================
class _InitialPrompt extends StatelessWidget {
  const _InitialPrompt({
    required this.onDownload,
    required this.onSkip,
  });

  final VoidCallback onDownload;
  final VoidCallback onSkip;

  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        // Logo + wordmark
        Row(
          children: [
            Container(
              width: 48,
              height: 48,
              decoration: BoxDecoration(
                color: AppColors.accentMuted,
                borderRadius: BorderRadius.circular(12),
              ),
              child: const Icon(
                Icons.fitness_center,
                color: AppColors.accent,
                size: 24,
              ),
            ),
            const SizedBox(width: UIConstants.spacing12),
            Text(
              'TrainHub',
              style: GoogleFonts.inter(
                fontSize: 26,
                fontWeight: FontWeight.w700,
                color: AppColors.textPrimary,
                letterSpacing: -0.5,
              ),
            ),
          ],
        ),

        const SizedBox(height: UIConstants.spacing32),

        // Headline
        Text(
          'AI-powered coaching,\nright on your device.',
          style: GoogleFonts.inter(
            fontSize: 28,
            fontWeight: FontWeight.w700,
            color: AppColors.textPrimary,
            height: 1.25,
            letterSpacing: -0.5,
          ),
        ),

        const SizedBox(height: UIConstants.spacing16),

        Text(
          'TrainHub uses on-device AI models to give you intelligent '
          'training advice, exercise analysis, and personalised chat — '
          'with zero data sent to the cloud.',
          style: GoogleFonts.inter(
            fontSize: 14,
            color: AppColors.textSecondary,
            height: 1.6,
          ),
        ),

        const SizedBox(height: UIConstants.spacing24),

        // Feature list
        const _FeatureRow(
          icon: Icons.lock_outline_rounded,
          label: '100 % local — your data never leaves this machine.',
        ),
        const SizedBox(height: UIConstants.spacing12),
        const _FeatureRow(
          icon: Icons.psychology_outlined,
          label: 'Qwen 2.5 7B chat model for training advice.',
        ),
        const SizedBox(height: UIConstants.spacing12),
        const _FeatureRow(
          icon: Icons.search_rounded,
          label: 'Nomic embedding model for semantic exercise search.',
        ),

        const SizedBox(height: UIConstants.spacing32),

        // Download size notice
        Container(
          padding: const EdgeInsets.symmetric(
            horizontal: UIConstants.spacing16,
            vertical: UIConstants.spacing12,
          ),
          decoration: BoxDecoration(
            color: AppColors.accentMuted,
            borderRadius: BorderRadius.circular(UIConstants.smallBorderRadius),
            border: Border.all(
              color: AppColors.accent.withValues(alpha: 0.3),
            ),
          ),
          child: Row(
            children: [
              const Icon(
                Icons.download_outlined,
                color: AppColors.accent,
                size: 18,
              ),
              const SizedBox(width: UIConstants.spacing12),
              Expanded(
                child: Text(
                  'The download is ~5 GB and only needs to happen once. '
                  'You can skip now and download later from Settings.',
                  style: GoogleFonts.inter(
                    fontSize: 13,
                    color: AppColors.accent,
                    height: 1.5,
                  ),
                ),
              ),
            ],
          ),
        ),

        const SizedBox(height: UIConstants.spacing32),

        // Action buttons
        Row(
          children: [
            Expanded(
              child: _PrimaryButton(
                label: 'Download Now',
                icon: Icons.download_rounded,
                onPressed: onDownload,
              ),
            ),
            const SizedBox(width: UIConstants.spacing12),
            Expanded(
              child: _SecondaryButton(
                label: 'Skip for Now',
                onPressed: onSkip,
              ),
            ),
          ],
        ),
      ],
    );
  }
}

// =============================================================================
// Download progress card
// =============================================================================
class _DownloadProgress extends StatelessWidget {
  const _DownloadProgress({required this.modelState});

  final AiModelSettingsState modelState;

  @override
  Widget build(BuildContext context) {
    final pct = (modelState.progress * 100).toStringAsFixed(1);

    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        // Animated download icon
        Container(
          width: 56,
          height: 56,
          decoration: BoxDecoration(
            color: AppColors.accentMuted,
            borderRadius: BorderRadius.circular(14),
          ),
          child: const Icon(
            Icons.download_rounded,
            color: AppColors.accent,
            size: 28,
          ),
        ),

        const SizedBox(height: UIConstants.spacing24),

        Text(
          'Setting up AI models…',
          style: GoogleFonts.inter(
            fontSize: 22,
            fontWeight: FontWeight.w700,
            color: AppColors.textPrimary,
            letterSpacing: -0.3,
          ),
        ),

        const SizedBox(height: UIConstants.spacing8),

        Text(
          'Please keep the app open. This only happens once.',
          style: GoogleFonts.inter(
            fontSize: 13,
            color: AppColors.textSecondary,
          ),
        ),

        const SizedBox(height: UIConstants.spacing32),

        // Progress bar
        ClipRRect(
          borderRadius: BorderRadius.circular(4),
          child: LinearProgressIndicator(
            value: modelState.progress,
            minHeight: 6,
            backgroundColor: AppColors.zinc800,
            valueColor:
                const AlwaysStoppedAnimation<Color>(AppColors.accent),
          ),
        ),

        const SizedBox(height: UIConstants.spacing12),

        Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: [
            Expanded(
              child: Text(
                modelState.currentTask,
                style: GoogleFonts.inter(
                  fontSize: 13,
                  color: AppColors.textSecondary,
                ),
                maxLines: 1,
                overflow: TextOverflow.ellipsis,
              ),
            ),
            Text(
              '$pct %',
              style: GoogleFonts.inter(
                fontSize: 13,
                fontWeight: FontWeight.w600,
                color: AppColors.accent,
              ),
            ),
          ],
        ),

        if (modelState.errorMessage != null) ...[
          const SizedBox(height: UIConstants.spacing16),
          _ErrorBanner(message: modelState.errorMessage!),
        ],
      ],
    );
  }
}

// =============================================================================
// Small reusable widgets
// =============================================================================

class _FeatureRow extends StatelessWidget {
  const _FeatureRow({required this.icon, required this.label});

  final IconData icon;
  final String label;

  @override
  Widget build(BuildContext context) {
    return Row(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        Container(
          width: 28,
          height: 28,
          decoration: BoxDecoration(
            color: AppColors.surfaceContainerHigh,
            borderRadius: BorderRadius.circular(6),
          ),
          child: Icon(icon, size: 14, color: AppColors.accent),
        ),
        const SizedBox(width: UIConstants.spacing12),
        Expanded(
          child: Text(
            label,
            style: GoogleFonts.inter(
              fontSize: 13,
              color: AppColors.textSecondary,
              height: 1.5,
            ),
          ),
        ),
      ],
    );
  }
}

class _PrimaryButton extends StatefulWidget {
  const _PrimaryButton({
    required this.label,
    required this.icon,
    required this.onPressed,
  });

  final String label;
  final IconData icon;
  final VoidCallback onPressed;

  @override
  State<_PrimaryButton> createState() => _PrimaryButtonState();
}

class _PrimaryButtonState extends State<_PrimaryButton> {
  bool _hovered = false;

  @override
  Widget build(BuildContext context) {
    return MouseRegion(
      onEnter: (_) => setState(() => _hovered = true),
      onExit: (_) => setState(() => _hovered = false),
      child: AnimatedContainer(
        duration: UIConstants.animationDuration,
        height: 44,
        decoration: BoxDecoration(
          color: _hovered
              ? AppColors.accent.withValues(alpha: 0.85)
              : AppColors.accent,
          borderRadius: BorderRadius.circular(UIConstants.smallBorderRadius),
        ),
        child: Material(
          color: Colors.transparent,
          child: InkWell(
            borderRadius:
                BorderRadius.circular(UIConstants.smallBorderRadius),
            onTap: widget.onPressed,
            child: Row(
              mainAxisAlignment: MainAxisAlignment.center,
              children: [
                Icon(widget.icon, color: AppColors.zinc950, size: 16),
                const SizedBox(width: UIConstants.spacing8),
                Text(
                  widget.label,
                  style: GoogleFonts.inter(
                    fontSize: 14,
                    fontWeight: FontWeight.w600,
                    color: AppColors.zinc950,
                  ),
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

class _SecondaryButton extends StatefulWidget {
  const _SecondaryButton({required this.label, required this.onPressed});

  final String label;
  final VoidCallback onPressed;

  @override
  State<_SecondaryButton> createState() => _SecondaryButtonState();
}

class _SecondaryButtonState extends State<_SecondaryButton> {
  bool _hovered = false;

  @override
  Widget build(BuildContext context) {
    return MouseRegion(
      onEnter: (_) => setState(() => _hovered = true),
      onExit: (_) => setState(() => _hovered = false),
      child: AnimatedContainer(
        duration: UIConstants.animationDuration,
        height: 44,
        decoration: BoxDecoration(
          color: _hovered ? AppColors.zinc800 : Colors.transparent,
          borderRadius: BorderRadius.circular(UIConstants.smallBorderRadius),
          border: Border.all(color: AppColors.border),
        ),
        child: Material(
          color: Colors.transparent,
          child: InkWell(
            borderRadius:
                BorderRadius.circular(UIConstants.smallBorderRadius),
            onTap: widget.onPressed,
            child: Center(
              child: Text(
                widget.label,
                style: GoogleFonts.inter(
                  fontSize: 14,
                  fontWeight: FontWeight.w500,
                  color: AppColors.textSecondary,
                ),
              ),
            ),
          ),
        ),
      ),
    );
  }
}

class _ErrorBanner extends StatelessWidget {
  const _ErrorBanner({required this.message});

  final String message;

  @override
  Widget build(BuildContext context) {
    return Container(
      padding: const EdgeInsets.all(UIConstants.spacing12),
      decoration: BoxDecoration(
        color: AppColors.destructiveMuted,
        borderRadius: BorderRadius.circular(UIConstants.smallBorderRadius),
        border: Border.all(
          color: AppColors.destructive.withValues(alpha: 0.4),
        ),
      ),
      child: Row(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          const Icon(
            Icons.error_outline_rounded,
            color: AppColors.destructive,
            size: 16,
          ),
          const SizedBox(width: UIConstants.spacing8),
          Expanded(
            child: Text(
              message,
              style: GoogleFonts.inter(
                fontSize: 12,
                color: AppColors.destructive,
                height: 1.5,
              ),
            ),
          ),
        ],
      ),
    );
  }
}