/// <summary>
/// Defines the set of constants for the Simple Web Token.
/// </summary>
public static class SimpleWebTokenConstants
{
    public const string Audience = "Audience";
    public const string ExpiresOn = "ExpiresOn";
    public const string Id = "Id";
    public const string Issuer = "Issuer";
    public const string Signature = "HMACSHA256";
    public const string ValidFrom = "ValidFrom";
    public const string ValueTypeUri = "http://schemas.xmlsoap.org/ws/2009/11/swt-token-profile-1.0";     
}

//引入命名空间
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.IdentityModel.Tokens;

namespace SimpleWebToken
{
    /// <summary>
    /// This class represents the token format for the SimpleWebToken.
    /// </summary>
    public class SimpleWebToken : SecurityToken
    {
        public static DateTime SwtBaseTime = new DateTime( 1970, 1, 1, 0, 0, 0, 0 ); // per SWT psec

        NameValueCollection _properties;
        string _serializedToken;

        /// <summary>
        /// Initializes a new instance of the <see cref="SimpleWebToken"/> class.
        /// This is an internal constructor that is only called from the <see cref="SimpleWebTokenHandler"/> when reading a token received from the wire.
        /// </summary>
        /// <param name="properties">The collection representing all the key value pairs in the token.</param>
        /// <param name="serializedToken">The serialized form of the token.</param>
        internal SimpleWebToken( NameValueCollection properties, string serializedToken )
            : this(properties)
        {
            _serializedToken = serializedToken;
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="SimpleWebToken"/> class.
        /// </summary>
        /// <param name="properties">The collection representing all the key value pairs in the token.</param>
        public SimpleWebToken( NameValueCollection properties )
        {
            if ( properties == null )
            {
                throw new ArgumentNullException( "properties" );
            }

            _properties = properties;
        }

        /// <summary>
        /// Gets the Id of the token.
        /// </summary>
        /// <value>The Id of the token.</value>
        public override string Id
        {
            get 
            {
                return _properties[SimpleWebTokenConstants.Id];
            }
        }

        /// <summary>
        /// Gets the keys associated with this token.
        /// </summary>
        /// <value>The keys associated with this token.</value>
        public override ReadOnlyCollection<SecurityKey> SecurityKeys
        {
            get 
            { 
                return new ReadOnlyCollection<SecurityKey>( new List<SecurityKey>() ); 
            }
        }

        /// <summary>
        /// Gets the time from when the token is valid.
        /// </summary>
        /// <value>The time from when the token is valid.</value>
        public override DateTime ValidFrom
        {
            get 
            {
                string validFrom = _properties[SimpleWebTokenConstants.ValidFrom];
                return GetTimeAsDateTime( String.IsNullOrEmpty( validFrom ) ? "0" : validFrom );
            }
        }

        /// <summary>
        /// Gets the time when the token expires.
        /// </summary>
        /// <value>The time up to which the token is valid.</value>
        public override DateTime ValidTo
        {
            get
            {
                string expiryTime = _properties[SimpleWebTokenConstants.ExpiresOn];
                return GetTimeAsDateTime( String.IsNullOrEmpty( expiryTime ) ? "0" : expiryTime );
            }
        }

        /// <summary>
        /// Gets the Audience for the token.
        /// </summary>
        /// <value>The audience of the token.</value>
        public string Audience
        {
            get 
            {
                return _properties[SimpleWebTokenConstants.Audience];
            }
        }

        /// <summary>
        /// Gets the Issuer for the token.
        /// </summary>
        /// <value>The issuer for the token.</value>
        public string Issuer
        {
            get 
            { 
                return _properties[SimpleWebTokenConstants.Issuer]; 
            }
        }

        /// <summary>
        /// Gets the signature for the token.
        /// </summary>
        /// <value>The signature for the token.</value>
        public string Signature
        {
            get 
            { 
                return _properties[SimpleWebTokenConstants.Signature]; 
            }
        }

        /// <summary>
        /// Gets the serialized form of the token if the token was created from its serialized form by the token handler.
        /// </summary>
        /// <value>The serialized form of the token.</value>
        public string SerializedToken
        {
            get
            {
                return _serializedToken;
            }
        }

        /// <summary>
        /// Creates a copy of all key value pairs of the token.
        /// </summary>
        /// <returns>A copy of all the key value pairs in the token.</returns>
        public NameValueCollection GetAllProperties()
        {
            return new NameValueCollection( _properties );
        }

        /// <summary>
        /// Converts the time in seconds to a <see cref="DateTime"/> object based on the base time 
        /// defined by the Simple Web Token.
        /// </summary>
        /// <param name="expiryTime">The time in seconds.</param>
        /// <returns>The time as a <see cref="DateTime"/> object.</returns>
        protected virtual DateTime GetTimeAsDateTime( string expiryTime )
        {
            long totalSeconds = 0;
            if ( !long.TryParse( expiryTime, out totalSeconds ) )
            {
                throw new SecurityTokenException("Invalid expiry time. Expected the time to be in seconds passed from 1 January 1970.");
            }

            long maxSeconds = (long)( DateTime.MaxValue - SwtBaseTime ).TotalSeconds - 1;
            if ( totalSeconds > maxSeconds )
            {
                totalSeconds = maxSeconds;
            }

            return SwtBaseTime.AddSeconds( totalSeconds );
        } 
    }    
}