/*
 *
 * (c) Copyright Ascensio System Limited 2010-2018
 *
 * This program is freeware. You can redistribute it and/or modify it under the terms of the GNU 
 * General Public License (GPL) version 3 as published by the Free Software Foundation (https://www.gnu.org/copyleft/gpl.html). 
 * In accordance with Section 7(a) of the GNU GPL its Section 15 shall be amended to the effect that 
 * Ascensio System SIA expressly excludes the warranty of non-infringement of any third-party rights.
 *
 * THIS PROGRAM IS DISTRIBUTED WITHOUT ANY WARRANTY; WITHOUT EVEN THE IMPLIED WARRANTY OF MERCHANTABILITY OR
 * FITNESS FOR A PARTICULAR PURPOSE. For more details, see GNU GPL at https://www.gnu.org/copyleft/gpl.html
 *
 * You can contact Ascensio System SIA by email at sales@onlyoffice.com
 *
 * The interactive user interfaces in modified source and object code versions of ONLYOFFICE must display 
 * Appropriate Legal Notices, as required under Section 5 of the GNU GPL version 3.
 *
 * Pursuant to Section 7 § 3(b) of the GNU GPL you must retain the original ONLYOFFICE logo which contains 
 * relevant author attributions when distributing the software. If the display of the logo in its graphic 
 * form is not reasonably feasible for technical reasons, you must include the words "Powered by ONLYOFFICE" 
 * in every copy of the program you distribute. 
 * Pursuant to Section 7 § 3(e) we decline to grant you any rights under trademark law for use of our trademarks.
 *
*/


using System;
using System.Collections.Generic;
using System.Linq;

using ASC.Common;
using ASC.Common.Security;
using ASC.Common.Security.Authentication;
using ASC.Common.Security.Authorizing;

using Constants = ASC.Core.Configuration.Constants;

namespace ASC.Core.Security.Authorizing
{
    [Scope]
    class PermissionResolver : IPermissionResolver
    {
        private readonly AzManager azManager;


        public PermissionResolver(AzManager azManager)
        {
            this.azManager = azManager ?? throw new ArgumentNullException(nameof(azManager));
        }


        public bool Check(ISubject subject, params IAction[] actions)
        {
            return Check(subject, null, null, actions);
        }

        public bool Check(ISubject subject, ISecurityObjectId objectId, ISecurityObjectProvider securityObjProvider, params IAction[] actions)
        {
            var denyActions = GetDenyActions(subject, actions, objectId, securityObjProvider);
            return denyActions.Length == 0;
        }

        public void Demand(ISubject subject, params IAction[] actions)
        {
            Demand(subject, null, null, actions);
        }

        public void Demand(ISubject subject, ISecurityObjectId objectId, ISecurityObjectProvider securityObjProvider, params IAction[] actions)
        {
            var denyActions = GetDenyActions(subject, actions, objectId, securityObjProvider);
            if (0 < denyActions.Length)
            {
                throw new AuthorizingException(
                    subject,
                    Array.ConvertAll(denyActions, r => r.TargetAction),
                    Array.ConvertAll(denyActions, r => r.DenySubject),
                    Array.ConvertAll(denyActions, r => r.DenyAction));
            }
        }


        private DenyResult[] GetDenyActions(ISubject subject, IAction[] actions, ISecurityObjectId objectId, ISecurityObjectProvider securityObjProvider)
        {
            var denyActions = new List<DenyResult>();
            if (actions == null) actions = new IAction[0];

            if (subject == null)
            {
                denyActions = actions.Select(a => new DenyResult(a, null, null)).ToList();
            }
            else if (subject is ISystemAccount && subject.ID == Constants.CoreSystem.ID)
            {
                // allow all
            }
            else
            {
                ISubject denySubject = null;
                IAction denyAction = null;
                foreach (var action in actions)
                {
                    var allow = azManager.CheckPermission(subject, action, objectId, securityObjProvider, out denySubject, out denyAction);
                    if (!allow)
                    {
                        denyActions.Add(new DenyResult(action, denySubject, denyAction));
                        break;
                    }
                }
            }

            return denyActions.ToArray();
        }

        private class DenyResult
        {
            public readonly IAction TargetAction;
            public readonly ISubject DenySubject;
            public readonly IAction DenyAction;

            public DenyResult(IAction targetAction, ISubject denySubject, IAction denyAction)
            {
                TargetAction = targetAction;
                DenySubject = denySubject;
                DenyAction = denyAction;
            }
        }
    }
}