using System;

using Org.BouncyCastle.Utilities;

namespace Org.BouncyCastle.Asn1
{
    public class DerBoolean
        : Asn1Object
    {
        private readonly byte value;

        public static readonly DerBoolean False = new DerBoolean(false);
        public static readonly DerBoolean True  = new DerBoolean(true);

        /**
         * return a bool from the passed in object.
         *
         * @exception ArgumentException if the object cannot be converted.
         */
        public static DerBoolean GetInstance(
            object obj)
        {
            if (obj == null || obj is DerBoolean)
            {
                return (DerBoolean) obj;
            }

            throw new ArgumentException("illegal object in GetInstance: " + Platform.GetTypeName(obj));
        }

        /**
         * return a DerBoolean from the passed in bool.
         */
        public static DerBoolean GetInstance(
            bool value)
        {
            return value ? True : False;
        }

        /**
         * return a Boolean from a tagged object.
         *
         * @param obj the tagged object holding the object we want
         * @param explicitly true if the object is meant to be explicitly
         *              tagged false otherwise.
         * @exception ArgumentException if the tagged object cannot
         *               be converted.
         */
        public static DerBoolean GetInstance(
            Asn1TaggedObject	obj,
            bool				isExplicit)
        {
            Asn1Object o = obj.GetObject();

            if (isExplicit || o is DerBoolean)
            {
                return GetInstance(o);
            }

            return FromOctetString(((Asn1OctetString)o).GetOctets());
        }

        public DerBoolean(
            byte[] val)
        {
            if (val.Length != 1)
                throw new ArgumentException("byte value should have 1 byte in it", "val");

            // TODO Are there any constraints on the possible byte values?
            this.value = val[0];
        }

        private DerBoolean(
            bool value)
        {
            this.value = value ? (byte)0xff : (byte)0;
        }

        public bool IsTrue
        {
            get { return value != 0; }
        }

        internal override bool EncodeConstructed(int encoding)
        {
            return false;
        }

        internal override int EncodedLength(int encoding, bool withID)
        {
            return Asn1OutputStream.GetLengthOfEncodingDL(withID, 1);
        }

        internal override void Encode(Asn1OutputStream asn1Out, bool withID)
        {
            byte contents = value;
            if (Asn1OutputStream.EncodingDer == asn1Out.Encoding && IsTrue)
            {
                contents = 0xFF;
            }

            asn1Out.WriteEncodingDL(withID, Asn1Tags.Boolean, contents);
        }

        protected override bool Asn1Equals(
            Asn1Object asn1Object)
        {
            DerBoolean other = asn1Object as DerBoolean;

            if (other == null)
                return false;

            return IsTrue == other.IsTrue;
        }

        protected override int Asn1GetHashCode()
        {
            return IsTrue.GetHashCode();
        }

        public override string ToString()
        {
            return IsTrue ? "TRUE" : "FALSE";
        }

        internal static DerBoolean FromOctetString(byte[] value)
        {
            if (value.Length != 1)
            {
                throw new ArgumentException("BOOLEAN value should have 1 byte in it", "value");
            }

            byte b = value[0];

            return b == 0 ? False : b == 0xFF ? True : new DerBoolean(value);
        }
    }
}