import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:tm_app/core/theme/colors.dart';
import 'package:tm_app/core/utils/size_config.dart';
import 'package:tm_app/view_models/ai_recommendations_view_model.dart';

import '../strings/tenders_strings.dart';
import 'main_tenders_slider.dart';

/// The "Recommended" tab body. Handles loading, empty/"still learning",
/// error+retry and the recommended tender list for [AiRecommendationsViewModel].
class RecommendedTendersView extends StatefulWidget {
  const RecommendedTendersView({super.key, this.isDesktop = false});

  final bool isDesktop;

  @override
  State<RecommendedTendersView> createState() => _RecommendedTendersViewState();
}

class _RecommendedTendersViewState extends State<RecommendedTendersView> {
  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (mounted) {
        context.read<AiRecommendationsViewModel>().loadIfNeeded();
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return Consumer<AiRecommendationsViewModel>(
      builder: (context, vm, child) {
        if (vm.isLoading) {
          return const _LoadingSkeleton();
        }
        if (vm.errorMessage != null) {
          return _MessageState(
            title: TendersStrings.recommendedError,
            onRetry: vm.refresh,
          );
        }
        if (vm.stillLearning) {
          return _MessageState(
            title: TendersStrings.recommendedStillLearningTitle,
            body: TendersStrings.recommendedStillLearningBody,
            onRetry: vm.refresh,
          );
        }
        if (vm.recommendedTenders.isNotEmpty) {
          if (widget.isDesktop) {
            return Padding(
              padding: EdgeInsets.symmetric(vertical: 4.0.h()),
              child: MainTendersSlider(
                tenders: vm.recommendedTenders,
                isDesktop: true,
              ),
            );
          }

          return SingleChildScrollView(
            child: Padding(
              padding: EdgeInsets.symmetric(vertical: 18.0.h()),
              child: MainTendersSlider(tenders: vm.recommendedTenders),
            ),
          );
        }
        return _MessageState(
          title: TendersStrings.recommendedEmptyTitle,
          body: TendersStrings.recommendedEmptyBody,
          onRetry: vm.refresh,
        );
      },
    );
  }
}

/// Centered title/body message with an optional retry button. Wrapped in a
/// scroll view so pull-to-refresh works even when empty.
class _MessageState extends StatelessWidget {
  const _MessageState({required this.title, this.body, this.onRetry});

  final String title;
  final String? body;
  final Future<void> Function()? onRetry;

  @override
  Widget build(BuildContext context) {
    final content = Padding(
      padding: EdgeInsets.symmetric(horizontal: 32.0.w(), vertical: 48.0.h()),
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Text(
            title,
            textAlign: TextAlign.center,
            style: TextStyle(
              fontSize: 16.0.sp(),
              fontWeight: FontWeight.w600,
              color: AppColors.grey70,
            ),
          ),
          if (body != null) ...[
            SizedBox(height: 12.0.h()),
            Text(
              body!,
              textAlign: TextAlign.center,
              style: TextStyle(
                fontSize: 14.0.sp(),
                fontWeight: FontWeight.w400,
                color: AppColors.grey60,
                height: 1.5,
              ),
            ),
          ],
          if (onRetry != null) ...[
            SizedBox(height: 24.0.h()),
            TextButton(
              onPressed: onRetry,
              child: Text(
                TendersStrings.retry,
                style: TextStyle(
                  fontSize: 14.0.sp(),
                  fontWeight: FontWeight.w600,
                  color: AppColors.mainBlue,
                ),
              ),
            ),
          ],
        ],
      ),
    );

    if (onRetry == null) {
      return Center(child: content);
    }
    return RefreshIndicator(
      color: AppColors.jellyBean,
      onRefresh: onRetry!,
      child: SingleChildScrollView(
        physics: const AlwaysScrollableScrollPhysics(),
        child: ConstrainedBox(
          constraints: BoxConstraints(minHeight: SizeConfig.screenHeight * 0.6),
          child: Center(child: content),
        ),
      ),
    );
  }
}

/// Simple placeholder list shown while recommendations load.
class _LoadingSkeleton extends StatelessWidget {
  const _LoadingSkeleton();

  @override
  Widget build(BuildContext context) {
    return ListView.separated(
      padding: EdgeInsets.all(16.0.h()),
      itemCount: 4,
      separatorBuilder: (_, __) => SizedBox(height: 12.0.h()),
      itemBuilder:
          (context, index) => Container(
            height: 120.0.h(),
            decoration: BoxDecoration(
              color: AppColors.grey0,
              borderRadius: BorderRadius.circular(12.0.w()),
              border: Border.all(color: AppColors.grey30),
            ),
          ),
    );
  }
}