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

namespace Algorithms.Sequences
{
    /// <summary>
    ///     <para>
    ///         Sequence of prime numbers.
    ///     </para>
    ///     <para>
    ///         Wikipedia: https://wikipedia.org/wiki/Prime_number.
    ///     </para>
    ///     <para>
    ///         OEIS: https://oeis.org/A000040.
    ///     </para>
    /// </summary>
    public class PrimesSequence : ISequence
    {
        /// <summary>
        ///     Gets sequence of prime numbers.
        /// </summary>
        public IEnumerable<BigInteger> Sequence
        {
            get
            {
                yield return 2;
                var primes = new List<BigInteger>
                {
                    2,
                };
                var n = new BigInteger(3);

                while (true)
                {
                    if (primes.All(p => n % p != 0))
                    {
                        yield return n;
                        primes.Add(n);
                    }

                    n += 2;
                }
            }
        }
    }
}