// 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.

/*============================================================
**
**
**
** Purpose: The boolean class serves as a wrapper for the primitive
** type boolean.
**
** 
===========================================================*/

using System;
using System.Globalization;
using System.Diagnostics.Contracts;

namespace System
{
    // The Boolean class provides the
    // object representation of the boolean primitive type.
    [System.Runtime.InteropServices.ComVisible(true)]
    public struct Boolean : IComparable, IComparable<Boolean>, IEquatable<Boolean>, IConvertible
    {
        //
        // Member Variables
        //
        private bool _value;

        // The true value. 
        // 
        internal const int True = 1;

        // The false value.
        // 
        internal const int False = 0;


        //
        // Internal Constants are real consts for performance.
        //

        // The internal string representation of true.
        // 
        internal const String TrueLiteral = "True";

        // The internal string representation of false.
        // 
        internal const String FalseLiteral = "False";


        //
        // Public Constants
        //

        // The public string representation of true.
        // 
        public static readonly String TrueString = TrueLiteral;

        // The public string representation of false.
        // 
        public static readonly String FalseString = FalseLiteral;

        //
        // Overriden Instance Methods
        //
        /*=================================GetHashCode==================================
        **Args:  None
        **Returns: 1 or 0 depending on whether this instance represents true or false.
        **Exceptions: None
        **Overriden From: Value
        ==============================================================================*/
        // Provides a hash code for this instance.
        public override int GetHashCode()
        {
            return (_value) ? True : False;
        }

        /*===================================ToString===================================
        **Args: None
        **Returns:  "True" or "False" depending on the state of the boolean.
        **Exceptions: None.
        ==============================================================================*/
        // Converts the boolean value of this instance to a String.
        public override String ToString()
        {
            if (false == _value)
            {
                return FalseLiteral;
            }
            return TrueLiteral;
        }

        String IConvertible.ToString(IFormatProvider provider)
        {
            return ToString();
        }

        // Determines whether two Boolean objects are equal.
        public override bool Equals(Object obj)
        {
            //If it's not a boolean, we're definitely not equal
            if (!(obj is Boolean))
            {
                return false;
            }

            return (_value == ((Boolean)obj)._value);
        }

        public bool Equals(Boolean obj)
        {
            return _value == obj;
        }

        // Compares this object to another object, returning an integer that
        // indicates the relationship. For booleans, false sorts before true.
        // null is considered to be less than any instance.
        // If object is not of type boolean, this method throws an ArgumentException.
        // 
        // Returns a value less than zero if this  object
        // 
        int IComparable.CompareTo(Object obj)
        {
            if (obj == null)
            {
                return 1;
            }
            if (!(obj is Boolean))
            {
                throw new ArgumentException(SR.Arg_MustBeBoolean);
            }

            if (_value == ((Boolean)obj)._value)
            {
                return 0;
            }
            else if (_value == false)
            {
                return -1;
            }
            return 1;
        }

        public int CompareTo(Boolean value)
        {
            if (_value == value)
            {
                return 0;
            }
            else if (_value == false)
            {
                return -1;
            }
            return 1;
        }

        //
        // Static Methods
        // 

        // Determines whether a String represents true or false.
        // 
        public static Boolean Parse(String value)
        {
            if (value == null) throw new ArgumentNullException("value");
            Contract.EndContractBlock();
            Boolean result = false;
            if (!TryParse(value, out result))
            {
                throw new FormatException(SR.Format_BadBoolean);
            }
            else
            {
                return result;
            }
        }

        // Determines whether a String represents true or false.
        // 
        public static Boolean TryParse(String value, out Boolean result)
        {
            result = false;
            if (value == null)
            {
                return false;
            }
            // For perf reasons, let's first see if they're equal, then do the
            // trim to get rid of white space, and check again.
            if (TrueLiteral.Equals(value, StringComparison.OrdinalIgnoreCase))
            {
                result = true;
                return true;
            }
            if (FalseLiteral.Equals(value, StringComparison.OrdinalIgnoreCase))
            {
                result = false;
                return true;
            }

            // Special case: Trim whitespace as well as null characters.
            value = TrimWhiteSpaceAndNull(value);

            if (TrueLiteral.Equals(value, StringComparison.OrdinalIgnoreCase))
            {
                result = true;
                return true;
            }

            if (FalseLiteral.Equals(value, StringComparison.OrdinalIgnoreCase))
            {
                result = false;
                return true;
            }

            return false;
        }

        private static String TrimWhiteSpaceAndNull(String value)
        {
            int start = 0;
            int end = value.Length - 1;
            char nullChar = (char)0x0000;

            while (start < value.Length)
            {
                if (!Char.IsWhiteSpace(value[start]) && value[start] != nullChar)
                {
                    break;
                }
                start++;
            }

            while (end >= start)
            {
                if (!Char.IsWhiteSpace(value[end]) && value[end] != nullChar)
                {
                    break;
                }
                end--;
            }

            return value.Substring(start, end - start + 1);
        }

        //
        // IConvertible implementation
        // 

        TypeCode IConvertible.GetTypeCode()
        {
            return TypeCode.Boolean;
        }


        /// <internalonly/>
        bool IConvertible.ToBoolean(IFormatProvider provider)
        {
            return _value;
        }

        /// <internalonly/>
        char IConvertible.ToChar(IFormatProvider provider)
        {
            throw new InvalidCastException(String.Format(SR.InvalidCast_FromTo, "Boolean", "Char"));
        }

        /// <internalonly/>
        sbyte IConvertible.ToSByte(IFormatProvider provider)
        {
            return Convert.ToSByte(_value);
        }

        /// <internalonly/>
        byte IConvertible.ToByte(IFormatProvider provider)
        {
            return Convert.ToByte(_value);
        }

        /// <internalonly/>
        short IConvertible.ToInt16(IFormatProvider provider)
        {
            return Convert.ToInt16(_value);
        }

        /// <internalonly/>
        ushort IConvertible.ToUInt16(IFormatProvider provider)
        {
            return Convert.ToUInt16(_value);
        }

        /// <internalonly/>
        int IConvertible.ToInt32(IFormatProvider provider)
        {
            return Convert.ToInt32(_value);
        }

        /// <internalonly/>
        uint IConvertible.ToUInt32(IFormatProvider provider)
        {
            return Convert.ToUInt32(_value);
        }

        /// <internalonly/>
        long IConvertible.ToInt64(IFormatProvider provider)
        {
            return Convert.ToInt64(_value);
        }

        /// <internalonly/>
        ulong IConvertible.ToUInt64(IFormatProvider provider)
        {
            return Convert.ToUInt64(_value);
        }

        /// <internalonly/>
        float IConvertible.ToSingle(IFormatProvider provider)
        {
            return Convert.ToSingle(_value);
        }

        /// <internalonly/>
        double IConvertible.ToDouble(IFormatProvider provider)
        {
            return Convert.ToDouble(_value);
        }

        /// <internalonly/>
        Decimal IConvertible.ToDecimal(IFormatProvider provider)
        {
            return Convert.ToDecimal(_value);
        }

        /// <internalonly/>
        DateTime IConvertible.ToDateTime(IFormatProvider provider)
        {
            throw new InvalidCastException(String.Format(SR.InvalidCast_FromTo, "Boolean", "DateTime"));
        }

        /// <internalonly/>
        Object IConvertible.ToType(Type type, IFormatProvider provider)
        {
            return Convert.DefaultToType((IConvertible)this, type, provider);
        }
    }
}
