// Sample C# file for testing — SampleFiles.online
// C# source file with common language features for parser testing.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace SampleApp.Models
{
    /// <summary>Represents an order in the system.</summary>
    public record Order(int Id, string Customer, decimal Total, DateTime CreatedAt)
    {
        public string Summary => $"#{Id}: {Customer} — {Total:C}";
    }

    public interface IRepository<T> where T : class
    {
        Task<T?> FindAsync(int id);
        Task<IReadOnlyList<T>> ListAsync();
    }

    public sealed class OrderService
    {
        private readonly IRepository<Order> _repo;
        private readonly ILogger _logger;

        public OrderService(IRepository<Order> repo, ILogger logger)
        {
            _repo = repo ?? throw new ArgumentNullException(nameof(repo));
            _logger = logger;
        }

        public async Task<decimal> GetTotalRevenueAsync()
        {
            var orders = await _repo.ListAsync();
            return orders.Sum(o => o.Total);
        }

        public static IEnumerable<int> Fibonacci(int count)
        {
            int a = 0, b = 1;
            for (int i = 0; i < count; i++)
            {
                yield return a;
                (a, b) = (b, a + b);
            }
        }
    }
}