using System.Linq;
using Chernobyl.Collections.Generic.Event;
using Chernobyl.Input.Controls;
using Chernobyl.Input.Controls.Axis;
using Chernobyl.Mathematics.Mechanics;
using Microsoft.Xna.Framework.Graphics;

namespace Chernobyl.Input.Xna.Controls.Mouse
{
    /// <summary>
    /// An XNA implementation of the Chernobyl.Input Mouse.
    /// </summary>
    public class XnaMouse : Axis3DControl, IMouse
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="XnaMouse"/> class.
        /// </summary>
        /// <param name="services">The <see cref="IEventCollection{T}"/> 
        /// instance to inject and take services from this control and it's 
        /// children.</param>
        public XnaMouse(IEventCollection<object> services)
            : base(services)
        {
            _services = services;

            LeftButton = new LeftMouseButton(_services, this);
            MiddleButton = new MiddleMouseButton(_services, this);
            RightButton = new RightMouseButton(_services, this);
            ExtraButton1 = new ExtraMouseButton1(_services, this);
            ExtraButton2 = new ExtraMouseButton2(_services, this);
        }

        /// <summary>
        /// The X axis of the 2 dimensions of this control.
        /// </summary>
        public override IAxisControl X
        {
            get
            {
                if (_x == null)
                {
                    _x = new MouseXAxis(_services);
                    Control.MakeParentChild(this, _x);
                }
                return _x;
            }
        }

        /// <summary>
        /// The Y axis of the 2 dimensions of this control.
        /// </summary>
        public override IAxisControl Y
        {
            get
            {
                if (_y == null)
                {
                    _y = new MouseYAxis(_services);
                    Control.MakeParentChild(this, _y);
                }
                return _y;
            }
        }

        /// <summary>
        /// The Z axis of the 3 dimensions of this mechanism.
        /// </summary>
        public override IAxisControl Z
        {
            get { return ScrollWheel; }
        }

        /// <summary>
        /// The left mouse button.
        /// </summary>
        public virtual IButtonControl LeftButton { get; private set; }

        /// <summary>
        /// The middle mouse button.
        /// </summary>
        public virtual IButtonControl MiddleButton { get; private set; }

        /// <summary>
        /// The right mouse button
        /// </summary>
        public virtual IButtonControl RightButton { get; private set; }

        /// <summary>
        /// An extra button available on some mouse devices.
        /// </summary>
        public virtual IButtonControl ExtraButton1 { get; private set; }

        /// <summary>
        /// An extra button available on some mouse devices.
        /// </summary>
        public virtual IButtonControl ExtraButton2 { get; private set; }

        /// <summary>
        /// Gets the position of the scroll wheel. This is a cumulative 
        /// value since the application was started. Forward on the scroll
        /// wheel is a positive direction, backward is a negative direction.
        /// </summary>
        public virtual IAxisControl ScrollWheel 
        { 
            get
            {
                // delay the creation of this IAxisControl so that it does not 
                // update when it is not needed.
                return _scrollWheel ?? (_scrollWheel = new MouseScrollWheel(_services, this));
            }
        }

        /// <summary>
        /// Represents the mouse's X axis.
        /// </summary>
        public class MouseXAxis : AxisControl
        {
            /// <summary>
            /// Constructor.
            /// </summary>
            /// <param name="services">The services that are to be injected into 
            /// this control and its children.</param>
            public MouseXAxis(IEventCollection<object> services)
                : base(services)
            {
                Name = "Mouse X Axis";
            }

            /// <summary>
            /// The amount of change, from the axis' <see cref="IAxis.PreviousValue"/>
            /// to its <see cref="IAxis.CurrentValue"/>. Implementors should return
            /// the raw change amount and not try to apply
            /// <see cref="IAxis.Sensitivity"/> to the returned value. The
            /// <see cref="AxisControl"/> class will apply the
            /// <see cref="IAxis.Sensitivity"/> value for you.
            /// </summary>
            protected override float OverridableChangeAmount
            {
                get { return Microsoft.Xna.Framework.Input.Mouse.GetState().X - PreviousValue; }
            }
        }

        /// <summary>
        /// Represents the mouse's Y axis.
        /// </summary>
        public class MouseYAxis : AxisControl
        {
            /// <summary>
            /// Constructor.
            /// </summary>
            /// <param name="services">The services that are to be injected into 
            /// this control and its children.</param>
            public MouseYAxis(IEventCollection<object> services)
                : base(services)
            {
                Name = "Mouse Y Axis";
                MaxValue = services.OfType<GraphicsDevice>().First().Viewport.Height;
            }

            /// <summary>
            /// The amount of change, from the axis' <see cref="IAxis.PreviousValue"/>
            /// to its <see cref="IAxis.CurrentValue"/>. Implementors should return
            /// the raw change amount and not try to apply
            /// <see cref="IAxis.Sensitivity"/> to the returned value. The
            /// <see cref="AxisControl"/> class will apply the
            /// <see cref="IAxis.Sensitivity"/> value for you.
            /// </summary>
            protected override float OverridableChangeAmount
            {
                get
                {
                    // we subtract from the maximum value to orient the Y axis to the bottom left corner of
                    // the screen because XNA orients to the top left.
                    return (MaxValue - Microsoft.Xna.Framework.Input.Mouse.GetState().Y) - PreviousValue;
                }
            }

            /// <summary>
            /// We use the maximum value to orient the mouse axis to the bottom
            /// left point of the screen because XNA orients to the top left.
            /// </summary>
            int MaxValue { get; set; }
        }

        /// <summary>
        /// The <see cref="IEventCollection{T}"/> instance to inject and take 
        /// services from this control and it's children.
        /// </summary>
        readonly IEventCollection<object> _services;

        /// <summary>
        /// The backing field to <see cref="ScrollWheel"/>.
        /// </summary>
        IAxisControl _scrollWheel;

        /// <summary>
        /// The backing field to <see cref="X"/>.
        /// </summary>
        IAxisControl _x;

        /// <summary>
        /// The backing field to <see cref="Y"/>.
        /// </summary>
        IAxisControl _y; 
    }
}