// 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.ServiceModel.Security;
using System.IdentityModel.Claims;
using System.IdentityModel.Policy;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Security.Principal;
 
namespace System.ServiceModel
{
    public class ServiceSecurityContext
    {
        private static ServiceSecurityContext s_anonymous;
        private AuthorizationContext _authorizationContext;
        private IIdentity _primaryIdentity;
        private Claim _identityClaim;
 
        // Perf: delay created authorizationContext using forward chain.
        public ServiceSecurityContext(ReadOnlyCollection<IAuthorizationPolicy> authorizationPolicies)
        {
            _authorizationContext = null;
            AuthorizationPolicies = authorizationPolicies ?? throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull(nameof(authorizationPolicies));
        }
 
        public ServiceSecurityContext(AuthorizationContext authorizationContext)
            : this(authorizationContext, EmptyReadOnlyCollection<IAuthorizationPolicy>.Instance)
        {
        }
 
        public ServiceSecurityContext(AuthorizationContext authorizationContext, ReadOnlyCollection<IAuthorizationPolicy> authorizationPolicies)
        {
            _authorizationContext = authorizationContext ?? throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull(nameof(authorizationContext));
            AuthorizationPolicies = authorizationPolicies ?? throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull(nameof(authorizationPolicies));
        }
 
        public static ServiceSecurityContext Anonymous
        {
            get
            {
                if (s_anonymous == null)
                {
                    s_anonymous = new ServiceSecurityContext(EmptyReadOnlyCollection<IAuthorizationPolicy>.Instance);
                }
                return s_anonymous;
            }
        }
 
 
        public bool IsAnonymous
        {
            get
            {
                return this == Anonymous || IdentityClaim == null;
            }
        }
 
        internal Claim IdentityClaim
        {
            get
            {
                if (_identityClaim == null)
                {
                    _identityClaim = SecurityUtils.GetPrimaryIdentityClaim(AuthorizationContext);
                }
                return _identityClaim;
            }
        }
 
        public IIdentity PrimaryIdentity
        {
            get
            {
                if (_primaryIdentity == null)
                {
                    IIdentity primaryIdentity = null;
                    IList<IIdentity> identities = GetIdentities();
                    // Multiple Identities is treated as anonymous
                    if (identities != null && identities.Count == 1)
                    {
                        primaryIdentity = identities[0];
                    }
 
                    _primaryIdentity = primaryIdentity ?? SecurityUtils.AnonymousIdentity;
                }
                return _primaryIdentity;
            }
        }
 
        public ReadOnlyCollection<IAuthorizationPolicy> AuthorizationPolicies { get; set; }
 
        public AuthorizationContext AuthorizationContext
        {
            get
            {
                if (_authorizationContext == null)
                {
                    _authorizationContext = AuthorizationContext.CreateDefaultAuthorizationContext(AuthorizationPolicies);
                }
                return _authorizationContext;
            }
        }
 
        private IList<IIdentity> GetIdentities()
        {
            object identities;
            AuthorizationContext authContext = AuthorizationContext;
            if (authContext != null && authContext.Properties.TryGetValue(SecurityUtils.Identities, out identities))
            {
                return identities as IList<IIdentity>;
            }
            return null;
        }
    }
}