ДЗ Аквариум

using System;
using System.Collections.Generic;

namespace CSLight
{
    internal class Program
    {
        static void Main(string[] args)
        {
            Aquarium aquarium = new Aquarium();
            aquarium.LiveLifeCycle();
        }
    }

    class Aquarium
    {
        private int _capacity;
        private List<Fish> _fishes;

        public Aquarium()
        {
            _capacity = 10;
            InitFishes();
        }

        public void LiveLifeCycle()
        {
            const string CommandAddFish = "1";
            const string CommandRemoveFish = "2";
            const string CommandExit = "exit";

            bool isRunning = true;

            while (isRunning)
            {
                RemoveDeadFishes();
                ShowFishesInfo();
                CompleteLifeCycleIteration();

                string userInput = Console.ReadLine();

                switch (userInput)
                {
                    case CommandAddFish:
                        TryAddFish();
                        break;

                    case CommandRemoveFish:
                        RemoveRandomFish();
                        break;

                    case CommandExit:
                        isRunning = false;
                        break;

                }
            }
        }

        private void CompleteLifeCycleIteration()
        {
            foreach (Fish fish in _fishes)
            {
                fish.IncreaseAge();
            }
        }

        private void RemoveRandomFish()
        {
            int minValue = 0;
            int id = UserUtils.GenerateRandomNumber(minValue, _fishes.Count);

            _fishes.RemoveAt(id);
        }

        private void RemoveDeadFishes()
        {
            for (int i = _fishes.Count - 1; i >= 0; i--)
            {
                if (_fishes[i].HasDied)
                {
                    _fishes.Remove(_fishes[i]);
                }
            }
        }

        private void ShowFishesInfo()
        {
            foreach (Fish fish in _fishes)
            {
                Console.WriteLine($"{fish.Name} - возраст {fish.Age}/{fish.LifeTime}");
            }
        }

        private void TryAddFish()
        {
            int id = GenerateId();
            string name = "Fish " + id;

            if (_fishes.Count < _capacity)
            {
                _fishes.Add(new Fish(name, id));
            }
        }

        private int GenerateId()
        {
            List<int> ids = GetIds();
            int freeId = 0;

            bool isGenerating = true;

            while (isGenerating)
            {
                if (ids.Contains(freeId))
                {
                    freeId++;
                }
                else
                {
                    isGenerating = false;
                }
            }

            return freeId;
        }

        private List<int> GetIds()
        {
            List<int> ids = new List<int>();

            foreach (Fish fish in _fishes)
            {
                ids.Add(fish.Id);
            }

            return ids;
        }

        private void InitFishes()
        {
            _fishes = new List<Fish>();

            for (int i = 0; i < _capacity; i++)
            {
                TryAddFish();
            }
        }
    }

    class Fish
    {
        private int _maxAge;
        private int _minAge;

        public Fish(string name, int id)
        {
            Name = name;
            Age = 0;
            _minAge = 10;
            _maxAge = 20;
            LifeTime = UserUtils.GenerateRandomNumber(_minAge, _maxAge);
            Id = id;
        }

        public string Name { get; private set; }

        public int Age { get; private set; }

        public int LifeTime { get; private set; }

        public int Id { get; private set; }

        public bool HasDied
        {
            get
            {
                return Age > LifeTime;
            }
        }

        public void IncreaseAge()
        {
            Age++;
        }
    }

    class UserUtils
    {
        private static Random s_random = new Random();

        public static int GenerateRandomNumber(int minValue, int maxValue)
        {
            return s_random.Next(minValue, maxValue);
        }
    }
}