// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Collections.Generic;
using Microsoft.AspNetCore.DataProtection.AuthenticatedEncryption;
using Microsoft.AspNetCore.DataProtection.AuthenticatedEncryption.ConfigurationModel;
using Microsoft.AspNetCore.DataProtection.Repositories;
using Microsoft.AspNetCore.DataProtection.XmlEncryption;

namespace Microsoft.AspNetCore.DataProtection.KeyManagement
{
    /// <summary>
    /// Options that control how an <see cref="IKeyManager"/> should behave.
    /// </summary>
    public class KeyManagementOptions
    {
        private static readonly TimeSpan _keyPropagationWindow = TimeSpan.FromDays(2);
        private static readonly TimeSpan _keyRingRefreshPeriod = TimeSpan.FromHours(24);
        private static readonly TimeSpan _maxServerClockSkew = TimeSpan.FromMinutes(5);
        private TimeSpan _newKeyLifetime = TimeSpan.FromDays(90);

        public KeyManagementOptions()
        {
        }

        // copy ctor
        internal KeyManagementOptions(KeyManagementOptions other)
        {
            if (other != null)
            {
                AutoGenerateKeys = other.AutoGenerateKeys;
                _newKeyLifetime = other._newKeyLifetime;
                XmlEncryptor = other.XmlEncryptor;
                XmlRepository = other.XmlRepository;
                AuthenticatedEncryptorConfiguration = other.AuthenticatedEncryptorConfiguration;

                foreach (var keyEscrowSink in other.KeyEscrowSinks)
                {
                    KeyEscrowSinks.Add(keyEscrowSink);
                }

                foreach (var encryptorFactory in other.AuthenticatedEncryptorFactories)
                {
                    AuthenticatedEncryptorFactories.Add(encryptorFactory);
                }
            }
        }

        /// <summary>
        /// Specifies whether the data protection system should auto-generate keys.
        /// </summary>
        /// <remarks>
        /// If this value is 'false', the system will not generate new keys automatically.
        /// The key ring must contain at least one active non-revoked key, otherwise calls
        /// to <see cref="IDataProtector.Protect(byte[])"/> may fail. The system may end up
        /// protecting payloads to expired keys if this property is set to 'false'.
        /// The default value is 'true'.
        /// </remarks>
        public bool AutoGenerateKeys { get; set; } = true;

        /// <summary>
        /// Specifies the period before key expiration in which a new key should be generated
        /// so that it has time to propagate fully throughout the key ring. For example, if this
        /// period is 72 hours, then a new key will be created and persisted to storage
        /// approximately 72 hours before expiration.
        /// </summary>
        /// <remarks>
        /// This value is currently fixed at 48 hours.
        /// </remarks>
        internal TimeSpan KeyPropagationWindow
        {
            get
            {
                // This value is not settable since there's a complex interaction between
                // it and the key ring refresh period.
                return _keyPropagationWindow;
            }
        }

        /// <summary>
        /// Controls the auto-refresh period where the key ring provider will
        /// flush its collection of cached keys and reread the collection from
        /// backing storage.
        /// </summary>
        /// <remarks>
        /// This value is currently fixed at 24 hours.
        /// </remarks>
        internal TimeSpan KeyRingRefreshPeriod
        {
            get
            {
                // This value is not settable since there's a complex interaction between
                // it and the key expiration safety period.
                return _keyRingRefreshPeriod;
            }
        }

        /// <summary>
        /// Specifies the maximum clock skew allowed between servers when reading
        /// keys from the key ring. The key ring may use a key which has not yet
        /// been activated or which has expired if the key's valid lifetime is within
        /// the allowed clock skew window. This value can be set to <see cref="TimeSpan.Zero"/>
        /// if key activation and expiration times should be strictly honored by this server.
        /// </summary>
        /// <remarks>
        /// This value is currently fixed at 5 minutes.
        /// </remarks>
        internal TimeSpan MaxServerClockSkew
        {
            get
            {
                return _maxServerClockSkew;
            }
        }

        /// <summary>
        /// Controls the lifetime (number of days before expiration)
        /// for newly-generated keys.
        /// </summary>
        /// <remarks>
        /// The lifetime cannot be less than one week.
        /// The default value is 90 days.
        /// </remarks>
        public TimeSpan NewKeyLifetime
        {
            get
            {
                return _newKeyLifetime;
            }
            set
            {
                if (value < TimeSpan.FromDays(7))
                {
                    throw new ArgumentOutOfRangeException(nameof(value), Resources.KeyManagementOptions_MinNewKeyLifetimeViolated);
                }
                _newKeyLifetime = value;
            }
        }

        /// <summary>
        /// The <see cref="AlgorithmConfiguration"/> instance that can be used to create
        /// the <see cref="IAuthenticatedEncryptorDescriptor"/> instance.
        /// </summary>
        public AlgorithmConfiguration AuthenticatedEncryptorConfiguration { get; set; }

        /// <summary>
        /// The list of <see cref="IKeyEscrowSink"/> to store the key material in.
        /// </summary>
        public IList<IKeyEscrowSink> KeyEscrowSinks { get; } = new List<IKeyEscrowSink>();

        /// <summary>
        /// The <see cref="IXmlRepository"/> to use for storing and retrieving XML elements.
        /// </summary>
        public IXmlRepository XmlRepository { get; set; }

        /// <summary>
        /// The <see cref="IXmlEncryptor"/> to use for encrypting XML elements.
        /// </summary>
        public IXmlEncryptor XmlEncryptor { get; set; }

        /// <summary>
        /// The list of <see cref="IAuthenticatedEncryptorFactory"/> that will be used for creating
        /// <see cref="IAuthenticatedEncryptor"/>s.
        /// </summary>
        public IList<IAuthenticatedEncryptorFactory> AuthenticatedEncryptorFactories { get; } = new List<IAuthenticatedEncryptorFactory>();
    }
}