using System;
using Chernobyl.Collections.Generic.Event;
using Chernobyl.Input.Controls;
using Microsoft.Xna.Framework.Input;

namespace Chernobyl.Input.Xna.Controls.Keyboard
{
    /// <summary>
    /// Represents an XNA keyboard key
    /// </summary>
    public class KeyboardKey : ButtonControl
    {
        /// <summary>
        /// Constructor.
        /// </summary>
        /// <param name="services">The services class to use when injecting this class with dependencies.</param>
        /// <param name="key">The XNA key that this keyboard key represents.</param>
        /// <param name="keyboard">The <see cref="IKeyboard"/> this 
        /// <see cref="KeyboardKey"/> is a part of.</param>
        public KeyboardKey(IEventCollection<object> services, Keys key, IKeyboard keyboard) : base(services)
        {
            Key = key;
            Name = Key.ToString();
            Keyboard = keyboard;
        }

        /// <summary>
        /// True if the button is down, false
        /// if otherwise.
        /// </summary>
        public override bool IsDown 
        {
            get { return Microsoft.Xna.Framework.Input.Keyboard.GetState().IsKeyDown(Key); }
            protected set { throw new NotImplementedException("You cannot set the state of an XNA button."); }
        }

        /// <summary>
        /// An event that is raised when this button 
        /// is pushed down or turned on.
        /// </summary>
        public override event EventHandler OnDown
        {
            add
            {
                // ensure we get updated by making ourself the keyboards child.
                if (this.ControlParent == null)
                    Control.MakeParentChild(Keyboard, this);
                base.OnDownMethod += value;
            }

            remove
            {
                base.OnDownMethod -= value;
                CheckForPotentialParentSeperation();
            }
        }

        /// <summary>
        /// An event that is raised when this button
        /// has stopped being pushed down or is off.
        /// </summary>
        public override event EventHandler OnUp
        {
            add
            {
                // ensure we get updated by making ourself the keyboards child.
                if (this.ControlParent == null)
                    Control.MakeParentChild(Keyboard, this);
                base.OnUpMethod += value;
            }

            remove
            {
                base.OnUpMethod -= value;
                CheckForPotentialParentSeperation();
            }
        }

        /// <summary>
        /// An event that is raised when this button's
        /// state has changed.
        /// </summary>
        public override event EventHandler OnChange
        {
            add
            {
                // ensure we get updated by making ourself the keyboards child.
                if (this.ControlParent == null)
                    Control.MakeParentChild(Keyboard, this);
                base.OnChangeMethod += value;
            }

            remove
            {
                base.OnChangeMethod -= value;
                CheckForPotentialParentSeperation();
            }
        }

        /// <summary>
        /// Checks the events to to see if they need updating (i.e. they have 
        /// event handlers assigned to them). If they don't, then this instance 
        /// is separated from its parent to prevent to many keyboard keys from 
        /// having to be updated.
        /// </summary>
        public void CheckForPotentialParentSeperation()
        {
            if(base.OnChangeMethod == null && base.OnUpMethod == null && 
                base.OnDownMethod == null)
                Control.SeparateParentChild(Keyboard, this);
        }

        /// <summary>
        /// The XNA keyboard key that this KeyboardKey represents.
        /// </summary>
        public Keys Key { get; protected set; }

        /// <summary>
        /// The <see cref="IKeyboard"/> this <see cref="KeyboardKey"/> is a part 
        /// of.
        /// </summary>
        IKeyboard Keyboard { get; set; }
    }
}