using System;
using System.Collections.Generic;
using System.Linq;
using Chernobyl.Collections.Generic.Event;
using Chernobyl.Event;
using Chernobyl.Interface.Tool;
using Chernobyl.Mathematics.Mechanics;

namespace Chernobyl.Interface.Collections
{
    /// <summary>
    /// An interface that implements and renders <see cref="IList{T}"/>s. This 
    /// class extends the <see cref="CollectionListView{T}"/> class and adds 
    /// the ability to move items in the list around.
    /// </summary>
    /// <typeparam name="T">The type that is to be held in the 
    /// <see cref="ICollection{T}"/>.</typeparam>
    public class ListView<T> : CollectionListView<T>, IList<T>
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="ListView{T}"/> class.
        /// </summary>
        /// <param name="services">The instance that gives out services for use 
        /// by this type and takes services from this type for use by other 
        /// systems.</param>
        /// <param name="list">The <see cref="ICollection{T}"/> that is to 
        /// be rendered on screen.</param>
        public ListView(IEventCollection<object> services, IList<T> list)
            : this(services, list, null)
        { }

        /// <summary>
        /// Initializes a new instance of the <see cref="ListView{T}"/> class.
        /// </summary>
        /// <param name="services">The instance that gives out services for use 
        /// by this type and takes services from this type for use by other 
        /// systems.</param>
        /// <param name="list">The <see cref="ICollection{T}"/> that is to 
        /// be rendered on screen.</param>
        /// <param name="selectionMode">The method that determines when items in
        /// the list can be selected or null if the default 
        /// <see cref="EnumerableListView{T}.SelectionModeFunc"/> should be used
        /// (The default value is given by the field
        /// <see cref="EnumerableListView{T}.SelectionModeDefault"/>). Several
        /// methods are available in the
        /// <see cref="Chernobyl.Interface.Collections.SelectionMode{T}"/> struct 
        /// or you can use your own. For performance reasons, if you don't need
        /// an item to be selected, you should use
        /// <see cref="Chernobyl.Interface.Collections.SelectionMode{T}.None"/>.</param>
        public ListView(IEventCollection<object> services, IList<T> list, SelectionModeFunc selectionMode)
            : this(services, list, selectionMode, null)
        { }

        /// <summary>
        /// Initializes a new instance of the <see cref="ListView{T}"/> class.
        /// </summary>
        /// <param name="services">The instance that gives out services for use 
        /// by this type and takes services from this type for use by other 
        /// systems.</param>
        /// <param name="list">The <see cref="IList{T}"/> that is to 
        /// be rendered on screen.</param>
        /// <param name="button">The <see cref="IButton"/> that will be used to 
        /// interact with the list or null if <see cref="ICursor.FirstButton"/> 
        /// should be used.</param>
        /// <param name="selectionMode">The method that determines when items in
        /// the list can be selected or null if the default 
        /// <see cref="EnumerableListView{T}.SelectionModeFunc"/> should be used
        /// (The default value is given by the field
        /// <see cref="EnumerableListView{T}.SelectionModeDefault"/>). Several
        /// methods are available in the
        /// <see cref="Chernobyl.Interface.Collections.SelectionMode{T}"/> struct 
        /// or you can use your own. For performance reasons, if you don't need
        /// an item to be selected, you should use
        /// <see cref="Chernobyl.Interface.Collections.SelectionMode{T}.None"/>.</param>
        public ListView(IEventCollection<object> services, IList<T> list, SelectionModeFunc selectionMode, IButton button) 
            : base(services, list, selectionMode, button)
        {
            _selectedIndices = Enumerable.Empty<uint>();
            List = list;
        }

        /// <summary>
        /// The 0 based index of the items that were selected or an empty 
        /// <see cref="IEnumerable{T}"/> if nothing is selected.
        /// </summary>
        public IEnumerable<uint> SelectedIndices
        {
            get
            {
                if (_selectedIndices == null)
                    _selectedIndices = from item in SelectedItems
                                       select (uint)List.IndexOf(item);

                return _selectedIndices;
            }
            set
            {
                // we already know that the SelectedItems are going to change so 
                // don't warn us about it.
                SelectedItemsChanged -= ListViewSelectedItemsChanged;

                _selectedIndices = value;
                SelectedItems = from index in value
                                select List[(int)index];

                SelectedItemsChanged += ListViewSelectedItemsChanged;
            }
        }        

        /// <summary>
        /// Determines the index of a specific item in the <see cref="IList{T}"/>.
        /// </summary>
        /// <param name="item">The object to locate in the <see cref="IList{T}"/>.</param>
        /// <returns>The index of <paramref name="item"/> if found in the list; 
        /// otherwise, -1.
        /// </returns>
        public int IndexOf(T item)
        {
            return List.IndexOf(item);
        }

        /// <summary>
        /// Inserts an item to the <see cref="IList{T}"/> at the specified index.
        /// </summary>
        /// <param name="index">The zero-based index at which 
        /// <paramref name="item"/> should be inserted.</param>
        /// <param name="item">The object to insert into the 
        /// <see cref="IList{T}"/>.</param>
        /// <exception cref="ArgumentOutOfRangeException"><paramref name="index"/> 
        /// is not a valid index in the <see cref="IList{T}"/>.</exception>
        /// <exception cref="NotSupportedException">The <see cref="IList{T}"/> is 
        /// read-only.</exception>
        public void Insert(int index, T item)
        {
            List.Insert(index, item);
        }

        /// <summary>
        /// Removes the <see cref="IList{T}"/> item at the specified index.
        /// </summary>
        /// <param name="index">The zero-based index of the item to remove.</param>
        /// <exception cref="ArgumentOutOfRangeException"><paramref name="index"/> 
        /// is not a valid index in the <see cref="IList{T}"/>.</exception>
        /// <exception cref="NotSupportedException">The <see cref="IList{T}"/> is 
        /// read-only.</exception>
        public void RemoveAt(int index)
        {
            List.RemoveAt(index);
        }

        /// <summary>
        /// Gets or sets the <typeparamref name="T"/> at the specified index.
        /// </summary>
        public T this[int index]
        {
            get
            {
                return List[index];
            }
            set
            {
                List[index] = value;
            }
        }


        /// <summary>
        ///An event handler that is invoked when the items in the 
        /// <see cref="EnumerableListView{T}.SelectedItems"/> property has 
        /// changed.
        /// </summary>
        /// <param name="sender">The sender of the event.</param>
        /// <param name="e">The <see cref="ValueChangedEventArgs{T}"/> 
        /// instance containing the event data.</param>
        void ListViewSelectedItemsChanged(object sender, ValueChangedEventArgs<IEnumerable<T>> e)
        {
            // clear out the selected indices so that they will get recomputed in 
            // the get of the SelectedIndices property
            _selectedIndices = null;
        }

        /// <summary>
        /// The <see cref="IList{T}"/> that is viewable in the interface list.
        /// </summary>
        IList<T> List { get; set; }

        /// <summary>
        /// The backing field to <see cref="SelectedIndices"/>.
        /// </summary>
        IEnumerable<uint> _selectedIndices;
    }
}