using MediaBrowser.Controller.Library;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.Serialization;
using System.Threading;
using System.Threading.Tasks;

namespace MediaBrowser.Controller.Entities
{
    /// <summary>
    /// Specialized Folder class that points to a subset of the physical folders in the system.
    /// It is created from the user-specific folders within the system root
    /// </summary>
    public class CollectionFolder : Folder, ICollectionFolder
    {
        /// <summary>
        /// Gets a value indicating whether this instance is virtual folder.
        /// </summary>
        /// <value><c>true</c> if this instance is virtual folder; otherwise, <c>false</c>.</value>
        [IgnoreDataMember]
        public override bool IsVirtualFolder
        {
            get
            {
                return true;
            }
        }

        public string CollectionType { get; set; }

        /// <summary>
        /// Allow different display preferences for each collection folder
        /// </summary>
        /// <value>The display prefs id.</value>
        public override Guid DisplayPreferencesId
        {
            get
            {
                return Id;
            }
        }

        // Cache this since it will be used a lot
        /// <summary>
        /// The null task result
        /// </summary>
        private static readonly Task NullTaskResult = Task.FromResult<object>(null);

        /// <summary>
        /// Compare our current children (presumably just read from the repo) with the current state of the file system and adjust for any changes
        /// ***Currently does not contain logic to maintain items that are unavailable in the file system***
        /// </summary>
        /// <param name="progress">The progress.</param>
        /// <param name="cancellationToken">The cancellation token.</param>
        /// <param name="recursive">if set to <c>true</c> [recursive].</param>
        /// <param name="forceRefreshMetadata">if set to <c>true</c> [force refresh metadata].</param>
        /// <returns>Task.</returns>
        protected override Task ValidateChildrenInternal(IProgress<double> progress, CancellationToken cancellationToken, bool? recursive = null, bool forceRefreshMetadata = false)
        {
            //we don't directly validate our children
            //but we do need to clear out the index cache...
            IndexCache = new ConcurrentDictionary<string, List<BaseItem>>(StringComparer.OrdinalIgnoreCase);

            return NullTaskResult;
        }

        /// <summary>
        /// Our children are actually just references to the ones in the physical root...
        /// </summary>
        /// <value>The actual children.</value>
        protected override ConcurrentDictionary<Guid, BaseItem> ActualChildren
        {
            get
            {
                ItemResolveArgs resolveArgs;

                try
                {
                    resolveArgs = ResolveArgs;
                }
                catch (IOException ex)
                {
                    Logger.ErrorException("Error getting ResolveArgs for {0}", ex, Path);
                    return new ConcurrentDictionary<Guid, BaseItem>();
                }

                var ourChildren =
                    LibraryManager.RootFolder.RecursiveChildren
                    .OfType<Folder>()
                    .Where(i => i.Path != null && resolveArgs.PhysicalLocations.Contains(i.Path, StringComparer.OrdinalIgnoreCase))
                    .SelectMany(c => c.Children);

                return new ConcurrentDictionary<Guid, BaseItem>(ourChildren.ToDictionary(i => i.Id));
            }
        }
    }
}