using System;
using System.Text;

namespace Org.BouncyCastle.Utilities
{
    /// <summary> General array utilities.</summary>
    public abstract class Arrays
    {
        public static bool AreEqual(
            bool[]  a,
            bool[]  b)
        {
            if (a == b)
                return true;

            if (a == null || b == null)
                return false;

            return HaveSameContents(a, b);
        }

        public static bool AreEqual(
            char[] a,
            char[] b)
        {
            if (a == b)
                return true;

            if (a == null || b == null)
                return false;

            return HaveSameContents(a, b);
        }

        /// <summary>
        /// Are two arrays equal.
        /// </summary>
        /// <param name="a">Left side.</param>
        /// <param name="b">Right side.</param>
        /// <returns>True if equal.</returns>
        public static bool AreEqual(
            byte[]	a,
            byte[]	b)
        {
            if (a == b)
                return true;

            if (a == null || b == null)
                return false;

            return HaveSameContents(a, b);
        }

        [Obsolete("Use 'AreEqual' method instead")]
        public static bool AreSame(
            byte[]	a,
            byte[]	b)
        {
            return AreEqual(a, b);
        }

        /// <summary>
        /// A constant time equals comparison - does not terminate early if
        /// test will fail.
        /// </summary>
        /// <param name="a">first array</param>
        /// <param name="b">second array</param>
        /// <returns>true if arrays equal, false otherwise.</returns>
        public static bool ConstantTimeAreEqual(
            byte[]	a,
            byte[]	b)
        {
            int i = a.Length;
            if (i != b.Length)
                return false;
            int cmp = 0;
            while (i != 0)
            {
                --i;
                cmp |= (a[i] ^ b[i]);
            }
            return cmp == 0;
        }

        public static bool AreEqual(
            int[]	a,
            int[]	b)
        {
            if (a == b)
                return true;

            if (a == null || b == null)
                return false;

            return HaveSameContents(a, b);
        }

        [CLSCompliantAttribute(false)]
        public static bool AreEqual(uint[] a, uint[] b)
        {
            if (a == b)
                return true;

            if (a == null || b == null)
                return false;

            return HaveSameContents(a, b);
        }

        private static bool HaveSameContents(
            bool[] a,
            bool[] b)
        {
            int i = a.Length;
            if (i != b.Length)
                return false;
            while (i != 0)
            {
                --i;
                if (a[i] != b[i])
                    return false;
            }
            return true;
        }

        private static bool HaveSameContents(
            char[] a,
            char[] b)
        {
            int i = a.Length;
            if (i != b.Length)
                return false;
            while (i != 0)
            {
                --i;
                if (a[i] != b[i])
                    return false;
            }
            return true;
        }

        private static bool HaveSameContents(
            byte[]	a,
            byte[]	b)
        {
            int i = a.Length;
            if (i != b.Length)
                return false;
            while (i != 0)
            {
                --i;
                if (a[i] != b[i])
                    return false;
            }
            return true;
        }

        private static bool HaveSameContents(
            int[]	a,
            int[]	b)
        {
            int i = a.Length;
            if (i != b.Length)
                return false;
            while (i != 0)
            {
                --i;
                if (a[i] != b[i])
                    return false;
            }
            return true;
        }

        private static bool HaveSameContents(uint[] a, uint[] b)
        {
            int i = a.Length;
            if (i != b.Length)
                return false;
            while (i != 0)
            {
                --i;
                if (a[i] != b[i])
                    return false;
            }
            return true;
        }

        public static string ToString(
            object[] a)
        {
            StringBuilder sb = new StringBuilder('[');
            if (a.Length > 0)
            {
                sb.Append(a[0]);
                for (int index = 1; index < a.Length; ++index)
                {
                    sb.Append(", ").Append(a[index]);
                }
            }
            sb.Append(']');
            return sb.ToString();
        }

        public static int GetHashCode(byte[] data)
        {
            if (data == null)
            {
                return 0;
            }

            int i = data.Length;
            int hc = i + 1;

            while (--i >= 0)
            {
                hc *= 257;
                hc ^= data[i];
            }

            return hc;
        }

        public static int GetHashCode(int[] data)
        {
            if (data == null)
                return 0;

            int i = data.Length;
            int hc = i + 1;

            while (--i >= 0)
            {
                hc *= 257;
                hc ^= data[i];
            }

            return hc;
        }

        [CLSCompliantAttribute(false)]
        public static int GetHashCode(uint[] data)
        {
            if (data == null)
                return 0;

            int i = data.Length;
            int hc = i + 1;

            while (--i >= 0)
            {
                hc *= 257;
                hc ^= (int)data[i];
            }

            return hc;
        }

        public static byte[] Clone(
            byte[] data)
        {
            return data == null ? null : (byte[])data.Clone();
        }

        public static byte[] Clone(
            byte[] data, 
            byte[] existing)
        {
            if (data == null)
            {
                return null;
            }
            if ((existing == null) || (existing.Length != data.Length))
            {
                return Clone(data);
            }
            Array.Copy(data, 0, existing, 0, existing.Length);
            return existing;
        }

        public static int[] Clone(
            int[] data)
        {
            return data == null ? null : (int[])data.Clone();
        }

        public static long[] Clone(long[] data)
        {
            return data == null ? null : (long[])data.Clone();
        }

        [CLSCompliantAttribute(false)]
        public static ulong[] Clone(
            ulong[] data)
        {
            return data == null ? null : (ulong[]) data.Clone();
        }

        [CLSCompliantAttribute(false)]
        public static ulong[] Clone(
            ulong[] data, 
            ulong[] existing)
        {
            if (data == null)
            {
                return null;
            }
            if ((existing == null) || (existing.Length != data.Length))
            {
                return Clone(data);
            }
            Array.Copy(data, 0, existing, 0, existing.Length);
            return existing;
        }

        public static void Fill(
            byte[]	buf,
            byte	b)
        {
            int i = buf.Length;
            while (i > 0)
            {
                buf[--i] = b;
            }
        }

        public static byte[] Copy(byte[] data, int off, int len)
        {
            byte[] result = new byte[len];
            Array.Copy(data, off, result, 0, len);
            return result;
        }
    }
}