context: #region License, Terms and Conditions
  //
  // Jayrock - JSON and JSON-RPC for Microsoft .NET Framework and Mono
  // Written by Atif Aziz (www.raboof.com)
  // Copyright (c) 2005 Atif Aziz. All rights reserved.
  //
  // This library is free software; you can redistribute it and/or modify it under
  // the terms of the GNU Lesser General Public License as published by the Free
  // Software Foundation; either version 3 of the License, or (at your option)
  // any later version.
  //
  // This library is distributed in the hope that it will be useful, but WITHOUT
  // ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  // FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
  // details.
  //
  // You should have received a copy of the GNU Lesser General Public License
  // along with this library; if not, write to the Free Software Foundation, Inc.,
  // 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 
  //
  #endregion
  
  namespace Jayrock.Json
  {
      #region Imports
  
      using System;
      using System.Diagnostics;
      using System.Globalization;
      using System.Text.RegularExpressions;
      using Jayrock.Json.Conversion;
  
      #endregion
      
      /// <summary> 
      /// Represents a JSON Number.  This class models a number as a string 
      /// and only converts to a native numerical representation when needed 
      /// and therefore told.  
      /// </summary>
      /// <remarks>
      /// This class cannot be used to compare two numbers or perform
      /// mathematical operations like addition and substraction without 
      /// first converting to an actual native numerical data type.
      /// Use <see cref="LogicallyEquals"/> to test for equality.
      /// </remarks>
  
      [ Serializable ]
      public struct JsonNumber : IConvertible
      {
          private readonly string _value;
  
          public JsonNumber(string value)
          {
              if (value != null && !IsValid(value)) 
                  throw new ArgumentException("value");
  
              _value = value;
          }
  
          private string Value
          {
              get { return Mask.EmptyString(_value, "0"); }
          }
          
          public override int GetHashCode()
          {
              return Value.GetHashCode();
          }
  
          public override bool Equals(object obj)
          {
              return obj != null && (obj is JsonNumber) && Equals((JsonNumber) obj);
          }
  
          public bool Equals(JsonNumber other)
          {
              return Value.Equals(other.Value);
          }
  
          public override string ToString()
          {
              return Value;
          }
          
          public bool LogicallyEquals(object o)
          {
              if (o == null) 
                  return false;
              
              return Convert.ChangeType(this, o.GetType(), CultureInfo.InvariantCulture).Equals(o);
          }
  
          //
          // IMPORTANT! The following ToXXX methods will throw 
          // OverflowException in case the JsonNumber instance contains a value
          // that is too big or small to be represented as the request type.
          //
  
          public bool ToBoolean()
          {
              return ToInt64() != 0;
          }
  
          public char ToChar()
          {
              return (char) Convert.ToUInt16(Value, CultureInfo.InvariantCulture);
          }
  
          public byte ToByte()
          {
              return Convert.ToByte(Value, CultureInfo.InvariantCulture);
          }
  
          public short ToInt16()
          {
              return Convert.ToInt16(Value, CultureInfo.InvariantCulture);
          }
  
          public int ToInt32()
          {
              return Convert.ToInt32(Value, CultureInfo.InvariantCulture);
          }
  
          public long ToInt64()
          {
              return Convert.ToInt64(Value, CultureInfo.InvariantCulture);
          }
  
          public float ToSingle()
          {
              return Convert.ToSingle(Value, CultureInfo.InvariantCulture);
          }
  
          public double ToDouble()
          {
              return Convert.ToDouble(Value, CultureInfo.InvariantCulture);
          }
  
          public decimal ToDecimal()
          {
              return decimal.Parse(Value, NumberStyles.Float, CultureInfo.InvariantCulture);
          }
  
          #if !NET_1_0 && !NET_1_1 && !NET_2_0
  
          public System.Numerics.BigInteger ToBigInteger()
          {
              return ToBigInteger(CultureInfo.InvariantCulture);
          }
  
          private System.Numerics.BigInteger ToBigInteger(IFormatProvider provider)
          {
              return System.Numerics.BigInteger.Parse(Value, NumberStyles.Integer, provider);
          }
  
          public static explicit operator System.Numerics.BigInteger(JsonNumber number)
          {
              return number.ToBigInteger();
          }
  
          #endif // !NET_1_0 && !NET_1_1 && !NET_2_0
  
          public DateTime ToDateTime()
          {
              return UnixTime.ToDateTime(ToInt64());
          }
  
          #region IConvertible implementation
  
          TypeCode IConvertible.GetTypeCode()
          {
              return TypeCode.Object;
          }
  
          bool IConvertible.ToBoolean(IFormatProvider provider)
          {
              return ToBoolean();
          }
  
          char IConvertible.ToChar(IFormatProvider provider)
          {
              return ToChar();
          }
  
          sbyte IConvertible.ToSByte(IFormatProvider provider)
          {
              return Convert.ToSByte(ToInt32());
          }
  
          byte IConvertible.ToByte(IFormatProvider provider)
          {
              return ToByte();
          }
  
          short IConvertible.ToInt16(IFormatProvider provider)
          {
              return ToInt16();
          }
  
          ushort IConvertible.ToUInt16(IFormatProvider provider)
          {
              return Convert.ToUInt16(Value, provider);
          }
  
          int IConvertible.ToInt32(IFormatProvider provider)
          {
              return ToInt32();
          }
  
          uint IConvertible.ToUInt32(IFormatProvider provider)
          {
              return Convert.ToUInt32(Value, provider);
          }
  
          long IConvertible.ToInt64(IFormatProvider provider)
          {
              return ToInt64();
          }
  
          ulong IConvertible.ToUInt64(IFormatProvider provider)
          {
              return Convert.ToUInt64(Value, provider);
          }
  
          float IConvertible.ToSingle(IFormatProvider provider)
          {
              return ToSingle();
          }
  
          double IConvertible.ToDouble(IFormatProvider provider)
          {
              return ToDouble();
          }
  
          decimal IConvertible.ToDecimal(IFormatProvider provider)
          {
              return ToDecimal();
          }
  
          DateTime IConvertible.ToDateTime(IFormatProvider provider)
          {
              return ToDateTime();
          }
  
          string IConvertible.ToString(IFormatProvider provider)
          {
              return ToString();
          }
  
          object IConvertible.ToType(Type conversionType, IFormatProvider provider)
          {
              #if !NET_1_0 && !NET_1_1 && !NET_2_0
              
              if (conversionType == typeof(System.Numerics.BigInteger))
                  return ToBigInteger(provider);
              
              #endif // !NET_1_0 && !NET_1_1 && !NET_2_0
  
              return Convert.ChangeType(this, conversionType, provider);
          }
  
          #endregion
  
          //
          // Explicit conversion operators.
          //
          
          public static explicit operator byte(JsonNumber number)
          {
              return number.ToByte();
          }
  
          public static explicit operator short(JsonNumber number)
          {
              return number.ToInt16();
          }
  
          public static explicit operator int(JsonNumber number)
          {
              return number.ToInt32();
          }
          
          public static explicit operator long(JsonNumber number)
          {
              return number.ToInt64();
          }
          
          public static explicit operator float(JsonNumber number)
          {
              return number.ToSingle();
          }
          
          public static explicit operator double(JsonNumber number)
          {
              return number.ToDouble();
          }
          
          public static explicit operator decimal(JsonNumber number)
          {
              return number.ToDecimal();
          }
          
          public static explicit operator DateTime(JsonNumber number)
          {
              return number.ToDateTime();
          }
  
          /// <summary>
          /// Determines if given text is a valid number per JSON grammar
          /// described in RFC 4627.
          /// </summary>
  
          public static bool IsValid(string text)
          {
              return IsValid(text, NumberStyles.None);
          }
  
          /// <summary>
          /// Determines if given text is a valid number per JSON grammar
          /// described in RFC 4627. An additional parameter can be used
          /// to specify whether leading and/or trailing white space should
          /// be allowed or not.
          /// </summary>
          /// <remarks>
          /// If whitespace is allowed then any whitespace as per Unicode
          /// is permitted, which is a wider set than what, for example,
          /// <see cref="NumberStyles.AllowTrailingWhite"/> and
          /// <see cref="NumberStyles.AllowLeadingWhite"/> list in their
          /// documentation.
          /// </remarks>
  
          public static bool IsValid(string text, NumberStyles styles)
          {
              if (text == null) throw new ArgumentNullException("text");
  
              if (styles >= 0 && (int) styles < _grammars.Length)
                  return _grammars[(int) styles].IsMatch(text);
  
              throw new ArgumentException(null, "styles");
          }
  
          // WARNING! There be dragons!
          // We assume that MS will never change the values assigned to 
          // the members of NumberStyles, at least not the following ones.
  
          private static readonly Regex[] _grammars = new Regex[]
          {
              Regex(false, false), // 0 = None
              Regex(true,  false), // 1 = AllowLeadingWhite
              Regex(false, true),  // 2 = AllowTrailingWhite
              Regex(true,  true),  // 3 = AllowLeadingWhite | AllowTrailingWhite
          };
  
          private static Regex Regex(bool lws, bool rws)
          {
              return new Regex(
                  "^" 
                  + (lws ? @"\s*" : null)
                  /*
                          number = [ minus ] int [ frac ] [ exp ]
                          decimal-point = %x2E       ; .
                          digit1-9 = %x31-39         ; 1-9
                          e = %x65 / %x45            ; e E
                          exp = e [ minus / plus ] 1*DIGIT
  
gt:                         frac = decimal-point 1*DIGIT