using System;
using Chernobyl.Mathematics.Movement;

namespace Chernobyl.Interface.Input
{
    /// <summary>
    /// An interface for a type that can control the pointer based interface of 
    /// the application in some form. This interface is used for mice, touch 
    /// based interfaces, etc. (i.e., controls which can point at the screen and
    /// instruct the code to do something to the thing being pointed at). 
    /// Additionally, this interface can be used to represent more than one 
    /// control of different types. For example it can be used to represent a 
    /// mouse and two fingers (touch based control).
    /// </summary>
    public interface IPointerControl
    {
        /// <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>
        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>
        event EventHandler<PointerEventArgs> LetUp;
    }

    /// <summary>
    /// An <see cref="EventArgs"/> instance used to contain data related to
    /// pointer operations such as pressing a pointer down or letting it up.
    /// </summary>
    public class PointerEventArgs : EventArgs
    {
        /// <summary>
        /// Prevents a default instance of the <see cref="PointerEventArgs"/>
        /// class from being created.
        /// </summary>
        /// <param name="pointer">The device that is pointing to some position
        /// on the screen when the event was invoked.</param>
        public PointerEventArgs(ITransform pointer)
        {
            Pointer = pointer;
        }

        /// <summary>
        /// The device that is pointing to some position on the screen when the
        /// event was invoked.
        /// </summary>
        public ITransform Pointer { get; private set; }
    }
}