using System;
using System.Runtime.CompilerServices;

namespace BansheeEngine
{
    /// <summary>
    /// List box GUI element which opens a drop down selection with provided elements when active.
    /// </summary>
    public sealed class GUIListBox : GUIElement
    {
        public delegate void OnSelectionChangedDelegate(int index);

        /// <summary>
        /// Triggered whenever user selects a new element in the list box. Returned index maps to the element in the elements 
        /// array that the list box was initialized with.
        /// </summary>
        public event OnSelectionChangedDelegate OnSelectionChanged;

        /// <summary>
        /// Creates a new list box with the specified elements.
        /// </summary>
        /// <param name="elements">Array of elements to display in the list box. Elements will be displayed in the same order
        /// as in the array.
        /// </param>
        /// <param name="style">Optional style to use for the element. Style controls the look of the element, as well as 
        /// default layout options. Style will be retrieved from the active GUISkin. If not specified default element style 
        /// is used.
        /// </param>
        /// <param name="options">Options that allow you to control how is the element positioned and sized. This will 
        /// override any similar options set by style.
        /// </param>
        public GUIListBox(LocString[] elements, string style, params GUIOption[] options)
        {
            Internal_CreateInstance(this, elements, style, options);
        }

        /// <summary>
        /// Creates a new list box with the specified elements.
        /// </summary>
        /// <param name="elements">Array of elements to display in the list box. Elements will be displayed in the same order
        /// as in the array.
        /// </param>
        /// <param name="options">Options that allow you to control how is the element positioned and sized. This will 
        /// override any similar options set by style.
        /// </param>
        public GUIListBox(LocString[] elements, params GUIOption[] options)
        {
            Internal_CreateInstance(this, elements, "", options);
        }

        /// <summary>
        /// Updates the list box with a new set of elements.
        /// </summary>
        /// <param name="elements">Array of elements to display in the list box. Elements will be displayed in the same order
        /// as in the array.</param>
        public void SetElements(LocString[] elements)
        {
            Internal_SetElements(mCachedPtr, elements);
        }

        /// <summary>
        /// Colors the element with a specific tint.
        /// </summary>
        /// <param name="color">Tint to apply to the element.</param>
        public void SetTint(Color color)
        {
            Internal_SetTint(mCachedPtr, color);
        }

        /// <summary>
        /// Triggered by the native interop object when a user selects an object in the list.
        /// </summary>
        private void DoOnSelectionChanged(int index)
        {
            if (OnSelectionChanged != null)
                OnSelectionChanged(index);
        }

        [MethodImpl(MethodImplOptions.InternalCall)]
        private static extern void Internal_CreateInstance(GUIListBox instance, LocString[] elements, string style, params GUIOption[] options);

        [MethodImpl(MethodImplOptions.InternalCall)]
        private static extern void Internal_SetElements(IntPtr nativeInstance, LocString[] elements);

        [MethodImpl(MethodImplOptions.InternalCall)]
        private static extern void Internal_SetTint(IntPtr nativeInstance, Color color);
    }
}