Generation.cs

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

namespace GeneticSharp
{
    /// <summary>
    /// Represents a generation of a population.
    /// </summary>
    [DebuggerDisplay("{Number} = {BestChromosome.Fitness}")]
    public sealed class Generation
    {
        #region Constructors
        /// <summary>
        /// Initializes a new instance of the <see cref="GeneticSharp.Generation"/> class.
        /// </summary>
        /// <param name="number">The generation number.</param>
        /// <param name="chromosomes">The chromosomes of the generation..</param>
        public Generation(int number, IList<IChromosome> chromosomes)
        {
            if (number < 1)
            {
                throw new ArgumentOutOfRangeException(
                    nameof(number),
                    "Generation number {0} is invalid. Generation number should be positive and start in 1.".With(number));
            }

            if (chromosomes == null || chromosomes.Count < 2)
            {
                throw new ArgumentOutOfRangeException(nameof(chromosomes), "A generation should have at least 2 chromosomes.");
            }

            Number = number;
            CreationDate = DateTime.Now;
            Chromosomes = chromosomes;
        }
        #endregion

        #region Properties
        /// <summary>
        /// Gets the number.
        /// </summary>
        /// <value>The number.</value>
        public int Number { get; private set; }

        /// <summary>
        /// Gets the creation date.
        /// </summary>
        public DateTime CreationDate { get; private set; }

        /// <summary>
        /// Gets the chromosomes.
        /// </summary>
        /// <value>The chromosomes.</value>
        public IList<IChromosome> Chromosomes { get; internal set; }

        /// <summary>
        /// Gets the best chromosome.
        /// </summary>
        /// <value>The best chromosome.</value>
        public IChromosome BestChromosome { get; internal set; }
        #endregion

        #region Methods
        /// <summary>
        /// Ends the generation.
        /// </summary>
        /// <param name="chromosomesNumber">Chromosomes number to keep on generation.</param>
        public void End(int chromosomesNumber)
        {
            Chromosomes = Chromosomes
                .Where(ValidateChromosome)
                .OrderByDescending(c => c.Fitness.Value)
                .ToList();

            if (Chromosomes.Count > chromosomesNumber)
            {
                Chromosomes = Chromosomes.Take(chromosomesNumber).ToList();
            }

            BestChromosome = Chromosomes.First();
        }

        /// <summary>
        /// Validates the chromosome.
        /// </summary>
        /// <param name="chromosome">The chromosome to validate.</param>
        /// <returns>True if a chromosome is valid.</returns>
        private static bool ValidateChromosome(IChromosome chromosome)
        {
            if (!chromosome.Fitness.HasValue)
            {
                throw new InvalidOperationException("There is unknown problem in current generation, because a chromosome has no fitness value.");
            }

            return true;
        }
        #endregion
    }
}