// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using System.ComponentModel;
using Microsoft.Extensions.Internal;
using Microsoft.Extensions.Options;

namespace Microsoft.Extensions.Caching.Memory
{
    /// <summary>
    /// Specifies options for <see cref="MemoryCache"/>.
    /// </summary>
    public class MemoryCacheOptions : IOptions<MemoryCacheOptions>
    {
        private long _sizeLimit = NotSet;
        private double _compactionPercentage = 0.05;

        private const int NotSet = -1;

        /// <summary>
        /// Gets or sets the clock used by the cache for expiration.
        /// </summary>
        public ISystemClock? Clock { get; set; }

        /// <summary>
        /// Gets or sets the minimum length of time between successive scans for expired items.
        /// </summary>
        public TimeSpan ExpirationScanFrequency { get; set; } = TimeSpan.FromMinutes(1);

        internal bool HasSizeLimit => _sizeLimit >= 0;

        internal long SizeLimitValue => _sizeLimit;

        /// <summary>
        /// Gets or sets the maximum size of the cache.
        /// </summary>
        /// <remarks>
        /// The units are arbitrary. Users specify the size of every entry they add to the cache.
        /// If no size is specified, the entry has no size and the size limit is ignored for that entry.
        /// For more information, see
        /// <see href="https://learn.microsoft.com/aspnet/core/performance/caching/memory#use-setsize-size-and-sizelimit-to-limit-cache-size">Use SetSize, Size, and SizeLimit to limit cache size</see>.
        /// </remarks>
        public long? SizeLimit
        {
            get => _sizeLimit < 0 ? null : _sizeLimit;
            set
            {
                if (value < 0)
                {
                    throw new ArgumentOutOfRangeException(nameof(value), value, $"{nameof(value)} must be non-negative.");
                }

                _sizeLimit = value ?? NotSet;
            }
        }

        /// <summary>
        /// Gets or sets a value that indicates whether the cache is compacted when the maximum size is exceeded.
        /// </summary>
        [EditorBrowsableAttribute(EditorBrowsableState.Never)]
        [Obsolete("This property is retained only for compatibility.  Remove use and instead call MemoryCache.Compact as needed.", error: true)]
        public bool CompactOnMemoryPressure { get; set; }

        /// <summary>
        /// Gets or sets the amount the cache is compacted by when the maximum size is exceeded.
        /// </summary>
        public double CompactionPercentage
        {
            get => _compactionPercentage;
            set
            {
                if (value is < 0 or > 1)
                {
                    throw new ArgumentOutOfRangeException(nameof(value), value, $"{nameof(value)} must be between 0 and 1 inclusive.");
                }

                _compactionPercentage = value;
            }
        }

        /// <summary>
        /// Gets or sets a value that indicates whether linked entries are tracked.
        /// </summary>
        /// <value>
        /// <see langword="true"/> if linked entries are tracked; otherwise, <see langword="false" />.
        /// The default is <see langword="false" />.
        /// </value>
        /// <remarks>Prior to .NET 7, this feature was always enabled.</remarks>
        public bool TrackLinkedCacheEntries { get; set; }

        /// <summary>
        /// Gets or sets a value that indicates whether memory cache statistics are tracked.
        /// </summary>
        /// <value>
        /// <see langword="true"/> if memory cache statistics are tracked; otherwise, <see langword="false" />.
        /// The default is <see langword="false" />.
        /// </value>
        public bool TrackStatistics { get; set; }

        /// <summary>
        /// Gets or sets the name of this cache instance.
        /// </summary>
        public string Name { get; set; } = "Default";

        MemoryCacheOptions IOptions<MemoryCacheOptions>.Value
        {
            get { return this; }
        }
    }
}