using System;
using System.Collections.Generic;
using System.Linq;

namespace Fixtures
{
    public class Person
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Email { get; set; }

        public Person(int id, string name, string email)
        {
            Id = id;
            Name = name;
            Email = email;
        }

        public override string ToString()
        {
            return $"{Name} <{Email}>";
        }
    }

    public class Repository<T>
    {
        private readonly Dictionary<int, T> _items = new();

        public void Add(int key, T item)
        {
            _items[key] = item;
        }

        public T? Find(int key)
        {
            return _items.TryGetValue(key, out var item) ? item : default;
        }

        public IEnumerable<T> GetAll()
        {
            return _items.Values.ToList();
        }
    }

    public static class Helpers
    {
        public static int Add(int a, int b) => a + b;

        public static IEnumerable<T> Filter<T>(IEnumerable<T> items, Func<T, bool> predicate)
        {
            return items.Where(predicate);
        }
    }

    public class Program
    {
        public static void Main(string[] args)
        {
            var repo = new Repository<Person>();
            repo.Add(1, new Person(1, "Alice", "alice@example.com"));
            repo.Add(2, new Person(2, "Bob", "bob@example.com"));

            var active = repo.GetAll();
            foreach (var p in active)
            {
                Console.WriteLine(p);
            }

            Console.WriteLine($"3 + 4 = {Helpers.Add(3, 4)}");
        }
    }
}