using System;
using System.Collections.Generic;
using Chernobyl.Collections.Generic.Event;
using Chernobyl.Event;

namespace Chernobyl.Interface.Input
{
    /// <summary>
    /// An <see cref="IPointerControl"/> that represents multiple <see cref="IPointerControl"/>
    /// instances (through the use of the composite design pattern).
    /// </summary>
    public class PointerControlCollection : DecoratingEventCollection<IPointerControl>, IPointerControl, IEventCollection<IPointerControl>
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="PointerControlCollection"/> class.
        /// </summary>
        public PointerControlCollection()
            : base(new List<IPointerControl>())
        {
            ItemsAdded += ControlsAdded;
            ItemsRemoved += ControlsRemoved;
        }

        /// <summary>
        /// An event that is raised each time the control mechanism is pressed
        /// down. This mechanism can only be <see cref="PressedDown"/> once per
        /// mechanism's pointer. The mechanism must raise
        /// <see cref="LetUp"/> for a pointer prior to that pointer raising
        /// <see cref="PressedDown"/> again. For example, a mouse can only raise
        /// <see cref="PressedDown"/> once and then it must raise <see cref="LetUp"/>
        /// to allow <see cref="PressedDown"/> to be raised. A touch screen on
        /// the other hand can invoke <see cref="PressedDown"/> for each finger
        /// that touches the screen but must invoke <see cref="LetUp"/> for each
        /// finger.
        /// </summary>
        public event EventHandler<PointerEventArgs> PressedDown;

        /// <summary>
        /// An event that is raised each time the control mechanism is let up.
        /// See <see cref="PressedDown"/> for more information on this topic.
        /// </summary>
        public event EventHandler<PointerEventArgs> LetUp;

        /// <summary>
        /// An event handler that is invoked when <see cref="IPointerControl"/>
        /// instances are removed from <c>this</c>.
        /// </summary>
        /// <param name="sender">The instance that generated the event.</param>
        /// <param name="e">The <see cref="ItemsEventArgs{IPointerControl}"/> 
        /// instance containing the event data.</param>
        void ControlsAdded(object sender, ItemsEventArgs<IPointerControl> e)
        {
            foreach (IPointerControl control in e.Items)
            {
                control.PressedDown += ControlPressedDown;
                control.LetUp += ControlLetUp;
            }
        }

        /// <summary>
        /// An event handler that is invoked when <see cref="IPointerControl"/> 
        /// instances are removed from <c>this</c>.
        /// </summary>
        /// <param name="sender">The instance that generated the event.</param>
        /// <param name="e">The <see cref="ItemsEventArgs{IPointerControl}"/> 
        /// instance containing the event data.</param>
        void ControlsRemoved(object sender, ItemsEventArgs<IPointerControl> e)
        {
            foreach (IPointerControl control in e.Items)
            {
                control.PressedDown -= ControlPressedDown;
                control.LetUp -= ControlLetUp;
            }
        }

        /// <summary>
        /// An event handler that is invoked when one of the 
        /// <see cref="IPointerControl"/> instances contained within this 
        /// instance raises its <see cref="IPointerControl.LetUp"/>. This method 
        /// will raise the <see cref="IPointerControl.LetUp"/> event of this 
        /// instance.
        /// </summary>
        /// <param name="sender">The instance that generated the event.</param>
        /// <param name="e">The <see cref="PointerEventArgs"/> instance 
        /// containing the event data.</param>
        void ControlLetUp(object sender, PointerEventArgs e)
        {
            if (LetUp != null)
                LetUp(this, e);
        }

        /// <summary>
        /// An event handler that is invoked when one of the 
        /// <see cref="IPointerControl"/> instances contained within this 
        /// instance raises its <see cref="IPointerControl.PressedDown"/>. This 
        /// method will raise the <see cref="IPointerControl.PressedDown"/> event 
        /// of this instance.
        /// </summary>
        /// <param name="sender">The instance that generated the event.</param>
        /// <param name="e">The <see cref="PointerEventArgs"/> instance 
        /// containing the event data.</param>
        void ControlPressedDown(object sender, PointerEventArgs e)
        {
            if (PressedDown != null)
                PressedDown(this, e);
        }
    }
}