// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using System.Globalization;
using System.Runtime.Serialization; // Just for SR
 
 
namespace System.Text
{
    internal struct SurrogateChar
    {
        private char _lowChar;
        private char _highChar;
 
        public const int MinValue = 0x10000;
        public const int MaxValue = MinValue + (1 << 20) - 1;
 
        private const char surHighMin = (char)0xd800;
        private const char surHighMax = (char)0xdbff;
        private const char surLowMin = (char)0xdc00;
        private const char surLowMax = (char)0xdfff;
 
        public SurrogateChar(int ch)
        {
            if (ch < MinValue || ch > MaxValue)
                throw /*System.Runtime.Serialization.*/DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentException(string.Format(SRSerialization.XmlInvalidSurrogate, ch.ToString("X", CultureInfo.InvariantCulture)), "ch"));
 
            const int mask = ((1 << 10) - 1);
 
            _lowChar = (char)(((ch - MinValue) & mask) + surLowMin);
            _highChar = (char)((((ch - MinValue) >> 10) & mask) + surHighMin);
        }
 
        public SurrogateChar(char lowChar, char highChar)
        {
            if (lowChar < surLowMin || lowChar > surLowMax)
                throw /*System.Runtime.Serialization.*/DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentException(string.Format(SRSerialization.XmlInvalidLowSurrogate, ((int)lowChar).ToString("X", CultureInfo.InvariantCulture)), "lowChar"));
 
            if (highChar < surHighMin || highChar > surHighMax)
                throw /*System.Runtime.Serialization.*/DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentException(string.Format(SRSerialization.XmlInvalidHighSurrogate, ((int)highChar).ToString("X", CultureInfo.InvariantCulture)), "highChar"));
 
            _lowChar = lowChar;
            _highChar = highChar;
        }
 
        public char LowChar { get { return _lowChar; } }
        public char HighChar { get { return _highChar; } }
 
        public int Char
        {
            get
            {
                return (_lowChar - surLowMin) | ((_highChar - surHighMin) << 10) + MinValue;
            }
        }
    }
}