// 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.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.Versioning;

namespace System
{
    [Serializable]
    [CLSCompliant(false)]    [StructLayout(LayoutKind.Sequential)]
    [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
    public readonly struct SByte : IComparable, IConvertible, IFormattable, IComparable<sbyte>, IEquatable<sbyte>, ISpanFormattable
    {
        private readonly sbyte m_value; // Do not rename (binary serialization)

        // The maximum value that a Byte may represent: 127.
        public const sbyte MaxValue = (sbyte)0x7F;

        // The minimum value that a Byte may represent: -128.
        public const sbyte MinValue = unchecked((sbyte)0x80);


        // Compares this object to another object, returning an integer that
        // indicates the relationship. 
        // Returns a value less than zero if this  object
        // null is considered to be less than any instance.
        // If object is not of type SByte, this method throws an ArgumentException.
        // 
        public int CompareTo(object obj)
        {
            if (obj == null)
            {
                return 1;
            }
            if (!(obj is sbyte))
            {
                throw new ArgumentException(SR.Arg_MustBeSByte);
            }
            return m_value - ((sbyte)obj).m_value;
        }

        public int CompareTo(sbyte value)
        {
            return m_value - value;
        }

        // Determines whether two Byte objects are equal.
        public override bool Equals(object obj)
        {
            if (!(obj is sbyte))
            {
                return false;
            }
            return m_value == ((sbyte)obj).m_value;
        }

        [NonVersionable]
        public bool Equals(sbyte obj)
        {
            return m_value == obj;
        }

        // Gets a hash code for this instance.
        public override int GetHashCode()
        {
            return m_value;
        }


        // Provides a string representation of a byte.
        public override string ToString()
        {
            return Number.FormatInt32(m_value, null, null);
        }

        public string ToString(IFormatProvider provider)
        {
            return Number.FormatInt32(m_value, null, provider);
        }

        public string ToString(string format)
        {
            return ToString(format, null);
        }

        public string ToString(string format, IFormatProvider provider)
        {
            if (m_value < 0 && format != null && format.Length > 0 && (format[0] == 'X' || format[0] == 'x'))
            {
                uint temp = (uint)(m_value & 0x000000FF);
                return Number.FormatUInt32(temp, format, provider);
            }
            return Number.FormatInt32(m_value, format, provider);
        }

        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider provider = null)
        {
            if (m_value < 0 && format.Length > 0 && (format[0] == 'X' || format[0] == 'x'))
            {
                uint temp = (uint)(m_value & 0x000000FF);
                return Number.TryFormatUInt32(temp, format, provider, destination, out charsWritten);
            }
            return Number.TryFormatInt32(m_value, format, provider, destination, out charsWritten);
        }

        [CLSCompliant(false)]
        public static sbyte Parse(string s)
        {
            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
            return Parse((ReadOnlySpan<char>)s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo);
        }

        [CLSCompliant(false)]
        public static sbyte Parse(string s, NumberStyles style)
        {
            NumberFormatInfo.ValidateParseStyleInteger(style);
            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
            return Parse((ReadOnlySpan<char>)s, style, NumberFormatInfo.CurrentInfo);
        }

        [CLSCompliant(false)]
        public static sbyte Parse(string s, IFormatProvider provider)
        {
            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
            return Parse((ReadOnlySpan<char>)s, NumberStyles.Integer, NumberFormatInfo.GetInstance(provider));
        }

        // Parses a signed byte from a String in the given style.  If
        // a NumberFormatInfo isn't specified, the current culture's 
        // NumberFormatInfo is assumed.
        // 
        [CLSCompliant(false)]
        public static sbyte Parse(string s, NumberStyles style, IFormatProvider provider)
        {
            NumberFormatInfo.ValidateParseStyleInteger(style);
            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
            return Parse((ReadOnlySpan<char>)s, style, NumberFormatInfo.GetInstance(provider));
        }

        [CLSCompliant(false)]
        public static sbyte Parse(ReadOnlySpan<char> s, NumberStyles style = NumberStyles.Integer, IFormatProvider provider = null)
        {
            NumberFormatInfo.ValidateParseStyleInteger(style);
            return Parse(s, style, NumberFormatInfo.GetInstance(provider));
        }

        private static sbyte Parse(string s, NumberStyles style, NumberFormatInfo info)
        {
            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
            return Parse((ReadOnlySpan<char>)s, style, info);
        }

        private static sbyte Parse(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info)
        {
            Number.ParsingStatus status = Number.TryParseInt32(s, style, info, out int i);
            if (status != Number.ParsingStatus.OK)
            {
                Number.ThrowOverflowOrFormatException(status, TypeCode.SByte);
            }

            // For hex number styles AllowHexSpecifier >> 2 == 0x80 and cancels out MinValue so the check is effectively: (uint)i > byte.MaxValue
            // For integer styles it's zero and the effective check is (uint)(i - MinValue) > byte.MaxValue
            if ((uint)(i - MinValue - ((int)(style & NumberStyles.AllowHexSpecifier) >> 2)) > byte.MaxValue)
            {
                Number.ThrowOverflowException(TypeCode.SByte);
            }
            return (sbyte)i;
        }

        [CLSCompliant(false)]
        public static bool TryParse(string s, out sbyte result)
        {
            if (s == null)
            {
                result = 0;
                return false;
            }

            return TryParse((ReadOnlySpan<char>)s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
        }

        [CLSCompliant(false)]
        public static bool TryParse(ReadOnlySpan<char> s, out sbyte result)
        {
            return TryParse(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
        }

        [CLSCompliant(false)]
        public static bool TryParse(string s, NumberStyles style, IFormatProvider provider, out sbyte result)
        {
            NumberFormatInfo.ValidateParseStyleInteger(style);

            if (s == null)
            {
                result = 0;
                return false;
            }

            return TryParse((ReadOnlySpan<char>)s, style, NumberFormatInfo.GetInstance(provider), out result);
        }

        [CLSCompliant(false)]
        public static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, IFormatProvider provider, out sbyte result)
        {
            NumberFormatInfo.ValidateParseStyleInteger(style);
            return TryParse(s, style, NumberFormatInfo.GetInstance(provider), out result);
        }

        private static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info, out sbyte result)
        {
            // For hex number styles AllowHexSpecifier >> 2 == 0x80 and cancels out MinValue so the check is effectively: (uint)i > byte.MaxValue
            // For integer styles it's zero and the effective check is (uint)(i - MinValue) > byte.MaxValue
            if (Number.TryParseInt32(s, style, info, out int i) != Number.ParsingStatus.OK
                || (uint)(i - MinValue - ((int)(style & NumberStyles.AllowHexSpecifier) >> 2)) > byte.MaxValue)
            {
                result = 0;
                return false;
            }
            result = (sbyte)i;
            return true;
        }

        //
        // IConvertible implementation
        // 

        public TypeCode GetTypeCode()
        {
            return TypeCode.SByte;
        }


        bool IConvertible.ToBoolean(IFormatProvider provider)
        {
            return Convert.ToBoolean(m_value);
        }

        char IConvertible.ToChar(IFormatProvider provider)
        {
            return Convert.ToChar(m_value);
        }

        sbyte IConvertible.ToSByte(IFormatProvider provider)
        {
            return m_value;
        }

        byte IConvertible.ToByte(IFormatProvider provider)
        {
            return Convert.ToByte(m_value);
        }

        short IConvertible.ToInt16(IFormatProvider provider)
        {
            return Convert.ToInt16(m_value);
        }

        ushort IConvertible.ToUInt16(IFormatProvider provider)
        {
            return Convert.ToUInt16(m_value);
        }

        int IConvertible.ToInt32(IFormatProvider provider)
        {
            return m_value;
        }

        uint IConvertible.ToUInt32(IFormatProvider provider)
        {
            return Convert.ToUInt32(m_value);
        }

        long IConvertible.ToInt64(IFormatProvider provider)
        {
            return Convert.ToInt64(m_value);
        }

        ulong IConvertible.ToUInt64(IFormatProvider provider)
        {
            return Convert.ToUInt64(m_value);
        }

        float IConvertible.ToSingle(IFormatProvider provider)
        {
            return Convert.ToSingle(m_value);
        }

        double IConvertible.ToDouble(IFormatProvider provider)
        {
            return Convert.ToDouble(m_value);
        }

        decimal IConvertible.ToDecimal(IFormatProvider provider)
        {
            return Convert.ToDecimal(m_value);
        }

        DateTime IConvertible.ToDateTime(IFormatProvider provider)
        {
            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "SByte", "DateTime"));
        }

        object IConvertible.ToType(Type type, IFormatProvider provider)
        {
            return Convert.DefaultToType((IConvertible)this, type, provider);
        }
    }
}