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

namespace MediaBrowser.Controller.Entities
{
    /// <summary>
    /// Specialized folder that can have items added to it's children by external entities.
    /// Used for our RootFolder so plug-ins can add items.
    /// </summary>
    public class AggregateFolder : Folder
    {
        /// <summary>
        /// The _virtual children
        /// </summary>
        private readonly ConcurrentBag<BaseItem> _virtualChildren = new ConcurrentBag<BaseItem>();

        /// <summary>
        /// Gets the virtual children.
        /// </summary>
        /// <value>The virtual children.</value>
        public ConcurrentBag<BaseItem> VirtualChildren
        {
            get { return _virtualChildren; }
        }

        /// <summary>
        /// Adds the virtual child.
        /// </summary>
        /// <param name="child">The child.</param>
        /// <exception cref="System.ArgumentNullException"></exception>
        public void AddVirtualChild(BaseItem child)
        {
            if (child == null)
            {
                throw new ArgumentNullException();
            }

            _virtualChildren.Add(child);
        }

        /// <summary>
        /// Get the children of this folder from the actual file system
        /// </summary>
        /// <returns>IEnumerable{BaseItem}.</returns>
        protected override IEnumerable<BaseItem> GetNonCachedChildren()
        {
            return base.GetNonCachedChildren().Concat(_virtualChildren);
        }

        /// <summary>
        /// Finds the virtual child.
        /// </summary>
        /// <param name="id">The id.</param>
        /// <returns>BaseItem.</returns>
        /// <exception cref="System.ArgumentNullException">id</exception>
        public BaseItem FindVirtualChild(Guid id)
        {
            if (id == Guid.Empty)
            {
                throw new ArgumentNullException("id");
            }

            return _virtualChildren.FirstOrDefault(i => i.Id == id);
        }
    }
}