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

namespace hashes
{
    public class ReadonlyBytes : IEnumerable
    {
        public readonly byte[] Array;
        public int Length { get { return Array.Length; } }
        private int currentHashCode { get; set; } = 0;

        public ReadonlyBytes(params byte[] newArray)
        {
            Array = newArray ?? throw new ArgumentNullException();
        }

        public override bool Equals(object obj)
        {
            var newArray = obj as ReadonlyBytes;
            if (newArray.Length != Array.Length) return false;

            for (int i = 0; i < Array.Length; i++)
                if (Array[i] != newArray[i]) return false;

            return true;
        }

        public override int GetHashCode()
        {
            unchecked
            {
                if (currentHashCode != 0) return currentHashCode;
                currentHashCode = 1;

                foreach (var e in Array)
                    currentHashCode += (currentHashCode * 322) ^ e;

                return currentHashCode;
            }
        }

        public IEnumerator<byte> GetEnumerator()
        {
            for (int i = 0; i < Array.Length; i++)
                yield return Array[i];
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }

        public byte this[int index]
        {
            get
            {
                if (index < 0 || index >= Array.Length) throw new IndexOutOfRangeException();
                return Array[index];
            }
            set
            {
                if (index < 0 || index >= Array.Length) throw new IndexOutOfRangeException();
                Array[index] = value;
            }
        }

        public override string ToString()
        {
            return "[" + string.Join(", ", Array) + "]";
        }
    }
}