import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import '../../core/theme/app_theme.dart';
import '../../models/exam.dart';
import '../../providers/exam_provider.dart';

class ExamsScreen extends ConsumerWidget {
  const ExamsScreen({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final examsAsync = ref.watch(examProvider);

    return Scaffold(
      appBar: AppBar(
        title: const Text('Exams & Assessments'),
      ),
      body: RefreshIndicator(
        onRefresh: () async {
          ref.invalidate(examProvider);
          await ref.read(examProvider.future);
        },
        child: examsAsync.when(
          loading: () => const Center(child: CircularProgressIndicator()),
          error: (err, _) => Center(
            child: Padding(
              padding: const EdgeInsets.all(24),
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  const Icon(Icons.error_outline_rounded, size: 48, color: AppTheme.errorColor),
                  const SizedBox(height: 12),
                  const Text('Failed to load exams',
                      style: TextStyle(fontSize: 16, fontWeight: FontWeight.bold)),
                  const SizedBox(height: 8),
                  Text(err.toString(),
                      textAlign: TextAlign.center,
                      style: const TextStyle(color: AppTheme.textSecondary, fontSize: 13)),
                  const SizedBox(height: 16),
                  ElevatedButton(
                    onPressed: () => ref.refresh(examProvider),
                    child: const Text('Retry'),
                  ),
                ],
              ),
            ),
          ),
          data: (exams) {
            if (exams.isEmpty) {
              return const Center(
                child: Padding(
                  padding: EdgeInsets.all(32),
                  child: Column(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: [
                      Icon(Icons.quiz_outlined, size: 60, color: AppTheme.textMuted),
                      SizedBox(height: 12),
                      Text(
                        'No upcoming exams',
                        style: TextStyle(fontSize: 16, fontWeight: FontWeight.w600),
                      ),
                      SizedBox(height: 6),
                      Text(
                        'There are no examinations scheduled at this time.',
                        textAlign: TextAlign.center,
                        style: TextStyle(color: AppTheme.textSecondary, fontSize: 13),
                      ),
                    ],
                  ),
                ),
              );
            }

            return ListView.separated(
              padding: const EdgeInsets.all(16),
              itemCount: exams.length,
              separatorBuilder: (_, __) => const SizedBox(height: 10),
              itemBuilder: (context, index) => _buildExamCard(exams[index]),
            );
          },
        ),
      ),
    );
  }

  Widget _buildExamCard(Exam exam) {
    Color badgeBg;
    Color badgeFg;
    switch (exam.state.toLowerCase()) {
      case 'ongoing':
        badgeBg = AppTheme.warningColor.withOpacity(0.12);
        badgeFg = AppTheme.warningColor;
        break;
      case 'completed':
        badgeBg = AppTheme.successColor.withOpacity(0.12);
        badgeFg = AppTheme.successColor;
        break;
      case 'scheduled':
      default:
        badgeBg = Colors.blue.withOpacity(0.12);
        badgeFg = Colors.blue.shade700;
        break;
    }

    return Card(
      child: Padding(
        padding: const EdgeInsets.all(16),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                Expanded(
                  child: Text(
                    exam.name,
                    style: const TextStyle(
                      fontSize: 15,
                      fontWeight: FontWeight.bold,
                      color: AppTheme.textPrimary,
                    ),
                  ),
                ),
                Container(
                  padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 3),
                  decoration: BoxDecoration(
                    color: badgeBg,
                    borderRadius: BorderRadius.circular(6),
                  ),
                  child: Text(
                    exam.state.toUpperCase(),
                    style: TextStyle(
                      fontSize: 11,
                      fontWeight: FontWeight.bold,
                      color: badgeFg,
                    ),
                  ),
                ),
              ],
            ),
            const SizedBox(height: 12),
            if (exam.startDate != null)
              Row(
                children: [
                  const Icon(Icons.event_note, size: 16, color: AppTheme.textSecondary),
                  const SizedBox(width: 6),
                  Text(
                    'Start Date: ${exam.startDate!}${exam.endDate != null ? ' - ${exam.endDate!}' : ''}',
                    style: const TextStyle(fontSize: 13, color: AppTheme.textSecondary),
                  ),
                ],
              ),
            if (exam.program?.name != null) ...[
              const SizedBox(height: 6),
              Row(
                children: [
                  const Icon(Icons.school, size: 16, color: AppTheme.textSecondary),
                  const SizedBox(width: 6),
                  Text(
                    exam.program!.name,
                    style: const TextStyle(fontSize: 13, color: AppTheme.textSecondary),
                  ),
                ],
              ),
            ],
          ],
        ),
      ),
    );
  }
}