// <copyright file="ObjectCache.cs" company="Microsoft">
//   Copyright (c) 2009 Microsoft Corporation.  All rights reserved.
// </copyright>
using System;
using System.Runtime.Caching.Resources;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics.CodeAnalysis;
using System.Security;
using System.Security.Permissions;
using System.Threading;

namespace System.Runtime.Caching {
    [SuppressMessage("Microsoft.Naming", "CA1710:IdentifiersShouldHaveCorrectSuffix", Justification= "The class represents a type of cache")]
    public abstract class ObjectCache : IEnumerable<KeyValuePair<string, object>> {
        private static IServiceProvider _host;

        public static readonly DateTimeOffset InfiniteAbsoluteExpiration = DateTimeOffset.MaxValue;
        public static readonly TimeSpan NoSlidingExpiration = TimeSpan.Zero;

        public static IServiceProvider Host {
            [PermissionSet(SecurityAction.Demand, Unrestricted = true)]
            [SecurityCritical]
            get { return _host; }

            [PermissionSet(SecurityAction.Demand, Unrestricted = true)]
            [SecurityCritical]
            set { 
                if (value == null) {
                    throw new ArgumentNullException("value");
                }
                if (Interlocked.CompareExchange(ref _host, value, null) != null) {
                    throw new InvalidOperationException(R.Property_already_set);
                }
            }
        }

        public abstract DefaultCacheCapabilities DefaultCacheCapabilities { get; }

        public abstract string Name { get; }

        //Default indexer property
        public abstract object this[string key] { get; set; }

        IEnumerator IEnumerable.GetEnumerator() {
            return ((IEnumerable<KeyValuePair<string, object>>)this).GetEnumerator();
        }

        [SuppressMessage("Microsoft.Design", "CA1026:DefaultParametersShouldNotBeUsed", Justification="This is assembly is a special case approved by the NetFx API review board")]
        public abstract CacheEntryChangeMonitor CreateCacheEntryChangeMonitor(IEnumerable<String> keys, String regionName = null);

        IEnumerator<KeyValuePair<string, object>> IEnumerable<KeyValuePair<string, object>>.GetEnumerator() {
            return GetEnumerator();
        }

        protected abstract IEnumerator<KeyValuePair<string, object>> GetEnumerator();

        //Existence check for a single item
        [SuppressMessage("Microsoft.Design", "CA1026:DefaultParametersShouldNotBeUsed", Justification="This is assembly is a special case approved by the NetFx API review board")]
        public abstract bool Contains(string key, string regionName = null);

        //The Add overloads are for adding an item without requiring the existing item to be returned.  This was requested for Velocity.
        [SuppressMessage("Microsoft.Design", "CA1026:DefaultParametersShouldNotBeUsed", Justification="This is assembly is a special case approved by the NetFx API review board")]
        public virtual bool Add(string key, object value, DateTimeOffset absoluteExpiration, string regionName = null) {
            return (AddOrGetExisting(key, value, absoluteExpiration, regionName) == null);
        }

        public virtual bool Add(CacheItem item, CacheItemPolicy policy) {
            return (AddOrGetExisting(item, policy) == null);
        }

        [SuppressMessage("Microsoft.Design", "CA1026:DefaultParametersShouldNotBeUsed", Justification="This is assembly is a special case approved by the NetFx API review board")]
        public virtual bool Add(string key, object value, CacheItemPolicy policy, string regionName = null) {
            return (AddOrGetExisting(key, value, policy, regionName) == null);
        }

        [SuppressMessage("Microsoft.Design", "CA1026:DefaultParametersShouldNotBeUsed", Justification="This is assembly is a special case approved by the NetFx API review board")]
        public abstract object AddOrGetExisting(string key, object value, DateTimeOffset absoluteExpiration, string regionName = null);
        public abstract CacheItem AddOrGetExisting(CacheItem value, CacheItemPolicy policy);

        [SuppressMessage("Microsoft.Design", "CA1026:DefaultParametersShouldNotBeUsed", Justification="This is assembly is a special case approved by the NetFx API review board")]
        public abstract object AddOrGetExisting(string key, object value, CacheItemPolicy policy, string regionName = null);

        [SuppressMessage("Microsoft.Naming", "CA1716:IdentifiersShouldNotMatchKeywords", Justification="The name best represents an operation on a cache")]
        [SuppressMessage("Microsoft.Design", "CA1026:DefaultParametersShouldNotBeUsed", Justification="This is assembly is a special case approved by the NetFx API review board")]
        public abstract object Get(string key, string regionName = null);

        [SuppressMessage("Microsoft.Design", "CA1026:DefaultParametersShouldNotBeUsed", Justification="This is assembly is a special case approved by the NetFx API review board")]
        public abstract CacheItem GetCacheItem(string key, string regionName = null);

        [SuppressMessage("Microsoft.Naming", "CA1716:IdentifiersShouldNotMatchKeywords", Justification = "The name best represents an operation on a cache")]
        [SuppressMessage("Microsoft.Design", "CA1026:DefaultParametersShouldNotBeUsed", Justification="This is assembly is a special case approved by the NetFx API review board")]
        public abstract void Set(string key, object value, DateTimeOffset absoluteExpiration, string regionName = null);

        [SuppressMessage("Microsoft.Naming", "CA1716:IdentifiersShouldNotMatchKeywords", Justification = "The name best represents an operation on a cache")]
        public abstract void Set(CacheItem item, CacheItemPolicy policy);

        [SuppressMessage("Microsoft.Naming", "CA1716:IdentifiersShouldNotMatchKeywords", Justification = "The name best represents an operation on a cache")]
        [SuppressMessage("Microsoft.Design", "CA1026:DefaultParametersShouldNotBeUsed", Justification="This is assembly is a special case approved by the NetFx API review board")]
        public abstract void Set(string key, object value, CacheItemPolicy policy, string regionName = null);

        //Get multiple items by keys
        [SuppressMessage("Microsoft.Design", "CA1026:DefaultParametersShouldNotBeUsed", Justification="This is assembly is a special case approved by the NetFx API review board")]
        public abstract IDictionary<string, object> GetValues(IEnumerable<String> keys, string regionName = null);

        public virtual IDictionary<string, object> GetValues(string regionName, params string[] keys) {
            return GetValues(keys, regionName);
        }

        [SuppressMessage("Microsoft.Design", "CA1026:DefaultParametersShouldNotBeUsed", Justification="This is assembly is a special case approved by the NetFx API review board")]
        public abstract object Remove(string key, string regionName = null);

        [SuppressMessage("Microsoft.Design", "CA1026:DefaultParametersShouldNotBeUsed", Justification="This is assembly is a special case approved by the NetFx API review board")]
        public abstract long GetCount(string regionName = null);
    }
}