using System.Runtime.InteropServices;
using UnityEngine.InputSystem.Controls;
using UnityEngine.InputSystem.Layouts;
using UnityEngine.InputSystem.LowLevel;
using UnityEngine.InputSystem.Utilities;

////TODO: option to allow to constrain mouse input to the screen area (i.e. no input once mouse leaves player window)

namespace UnityEngine.InputSystem.LowLevel
{
    /// <summary>
    /// Combine a single pointer with buttons and a scroll wheel.
    /// </summary>
    // IMPORTANT: State layout must match with MouseInputState in native.
    [StructLayout(LayoutKind.Explicit, Size = 30)]
    public struct MouseState : IInputStateTypeInfo
    {
        /// <summary>
        /// Memory format identifier for MouseState.
        /// </summary>
        /// <value>Returns "MOUS".</value>
        /// <seealso cref="InputStateBlock.format"/>
        public static FourCC Format => new FourCC('M', 'O', 'U', 'S');

        /// <summary>
        /// Screen-space position of the mouse in pixels.
        /// </summary>
        /// <value>Position of mouse on screen.</value>
        /// <seealso cref="Pointer.position"/>
        [InputControl(usage = "Point", dontReset = true)] // Mouse should stay put when we reset devices.
        [FieldOffset(0)]
        public Vector2 position;

        /// <summary>
        /// Screen-space motion delta of the mouse in pixels.
        /// </summary>
        /// <value>Mouse movement.</value>
        /// <seealso cref="Pointer.delta"/>
        [InputControl(usage = "Secondary2DMotion", layout = "Delta")]
        [FieldOffset(8)]
        public Vector2 delta;

        ////REVIEW: have half-axis buttons on the scroll axes? (up, down, left, right)
        /// <summary>
        /// Scroll-wheel delta of the mouse.
        /// </summary>
        /// <value>Scroll wheel delta.</value>
        /// <seealso cref="Mouse.scroll"/>
        [InputControl(displayName = "Scroll", layout = "Delta")]
        [InputControl(name = "scroll/x", aliases = new[] { "horizontal" }, usage = "ScrollHorizontal", displayName = "Left/Right")]
        [InputControl(name = "scroll/y", aliases = new[] { "vertical" }, usage = "ScrollVertical", displayName = "Up/Down", shortDisplayName = "Wheel")]
        [FieldOffset(16)]
        public Vector2 scroll;

        /// <summary>
        /// Button mask for which buttons on the mouse are currently pressed.
        /// </summary>
        /// <value>Button state mask.</value>
        /// <seealso cref="MouseButton"/>
        /// <seealso cref="Mouse.leftButton"/>
        /// <seealso cref="Mouse.middleButton"/>
        /// <seealso cref="Mouse.rightButton"/>
        /// <seealso cref="Mouse.forwardButton"/>
        /// <seealso cref="Mouse.backButton"/>
        [InputControl(name = "press", useStateFrom = "leftButton", synthetic = true, usages = new string[0])]
        [InputControl(name = "leftButton", layout = "Button", bit = (int)MouseButton.Left, usage = "PrimaryAction", displayName = "Left Button", shortDisplayName = "LMB")]
        [InputControl(name = "rightButton", layout = "Button", bit = (int)MouseButton.Right, usage = "SecondaryAction", displayName = "Right Button", shortDisplayName = "RMB")]
        [InputControl(name = "middleButton", layout = "Button", bit = (int)MouseButton.Middle, displayName = "Middle Button", shortDisplayName = "MMB")]
        [InputControl(name = "forwardButton", layout = "Button", bit = (int)MouseButton.Forward, usage = "Forward", displayName = "Forward")]
        [InputControl(name = "backButton", layout = "Button", bit = (int)MouseButton.Back, usage = "Back", displayName = "Back")]
        [FieldOffset(24)]
        // "Park" all the controls that are common to pointers but aren't use for mice such that they get
        // appended to the end of device state where they will always have default values.
        ////FIXME: InputDeviceBuilder will get fooled and set up an incorrect state layout if we don't force this to VEC2; InputControlLayout will
        ////       "infer" USHT as the format which will then end up with a layout where two 4 byte float controls are "packed" into a 16bit sized parent;
        ////       in other words, setting VEC2 here manually should *not* be necessary
        [InputControl(name = "pressure", layout = "Axis", usage = "Pressure", offset = InputStateBlock.AutomaticOffset, format = "FLT", sizeInBits = 32)]
        [InputControl(name = "radius", layout = "Vector2", usage = "Radius", offset = InputStateBlock.AutomaticOffset, format = "VEC2", sizeInBits = 64)]
        [InputControl(name = "pointerId", layout = "Digital", format = "BIT", sizeInBits = 1, offset = InputStateBlock.AutomaticOffset)] // Will stay at 0.
        public ushort buttons;

        /// <summary>
        /// The index of the display that was moused.
        /// </summary>
        [InputControl(name = "displayIndex", layout = "Integer", displayName = "Display Index")]
        [FieldOffset(26)]
        public ushort displayIndex;

        /// <summary>
        /// Number of clicks performed in succession.
        /// </summary>
        /// <value>Successive click count.</value>
        /// <seealso cref="Mouse.clickCount"/>
        [InputControl(name = "clickCount", layout = "Integer", displayName = "Click Count", synthetic = true)]
        [FieldOffset(28)]
        public ushort clickCount;

        /// <summary>
        /// Set the button mask for the given button.
        /// </summary>
        /// <param name="button">Button whose state to set.</param>
        /// <param name="state">Whether to set the bit on or off.</param>
        /// <returns>The same MouseState with the change applied.</returns>
        /// <seealso cref="buttons"/>
        public MouseState WithButton(MouseButton button, bool state = true)
        {
            Debug.Assert((int)button < 16, $"Expected button < 16, so we fit into the 16 bit wide bitmask");
            var bit = 1U << (int)button;
            if (state)
                buttons |= (ushort)bit;
            else
                buttons &= (ushort)~bit;
            return this;
        }

        /// <summary>
        /// Returns <see cref="Format"/>.
        /// </summary>
        /// <seealso cref="InputStateBlock.format"/>
        public FourCC format => Format;
    }

    /// <summary>
    /// Button indices for <see cref="MouseState.buttons"/>.
    /// </summary>
    public enum MouseButton
    {
        /// <summary>
        /// Left mouse button.
        /// </summary>
        /// <seealso cref="Mouse.leftButton"/>
        Left,

        /// <summary>
        /// Right mouse button.
        /// </summary>
        /// <seealso cref="Mouse.rightButton"/>
        Right,

        /// <summary>
        /// Middle mouse button.
        /// </summary>
        /// <seealso cref="Mouse.middleButton"/>
        Middle,

        /// <summary>
        /// Second side button.
        /// </summary>
        /// <seealso cref="Mouse.forwardButton"/>
        Forward,

        /// <summary>
        /// First side button.
        /// </summary>
        /// <seealso cref="Mouse.backButton"/>
        Back
    }
}

namespace UnityEngine.InputSystem
{
    /// <summary>
    /// An input device representing a mouse.
    /// </summary>
    /// <remarks>
    /// Adds a scroll wheel and a typical 3-button setup with a left, middle, and right
    /// button.
    ///
    /// To control cursor display and behavior, use <see cref="UnityEngine.Cursor"/>.
    /// </remarks>
    [InputControlLayout(stateType = typeof(MouseState), isGenericTypeOfDevice = true)]
    public class Mouse : Pointer, IInputStateCallbackReceiver
    {
        /// <summary>
        /// The horizontal and vertical scroll wheels.
        /// </summary>
        /// <value>Control representing the mouse scroll wheels.</value>
        /// <remarks>
        /// The <c>x</c> component corresponds to the horizontal scroll wheel, the
        /// <c>y</c> component to the vertical scroll wheel. Most mice do not have
        /// horizontal scroll wheels and will thus only see activity on <c>y</c>.
        /// </remarks>
        public DeltaControl scroll { get; protected set; }

        /// <summary>
        /// The left mouse button.
        /// </summary>
        /// <value>Control representing the left mouse button.</value>
        public ButtonControl leftButton { get; protected set; }

        /// <summary>
        /// The middle mouse button.
        /// </summary>
        /// <value>Control representing the middle mouse button.</value>
        public ButtonControl middleButton { get; protected set; }

        /// <summary>
        /// The right mouse button.
        /// </summary>
        /// <value>Control representing the right mouse button.</value>
        public ButtonControl rightButton { get; protected set; }

        /// <summary>
        /// The first side button, often labeled/used as "back".
        /// </summary>
        /// <value>Control representing the back button on the mouse.</value>
        /// <remarks>
        /// On Windows, this corresponds to <c>RI_MOUSE_BUTTON_4</c>.
        /// </remarks>
        public ButtonControl backButton { get; protected set; }

        /// <summary>
        /// The second side button, often labeled/used as "forward".
        /// </summary>
        /// <value>Control representing the forward button on the mouse.</value>
        /// <remarks>
        /// On Windows, this corresponds to <c>RI_MOUSE_BUTTON_5</c>.
        /// </remarks>
        public ButtonControl forwardButton { get; protected set; }

        /// <summary>
        /// Number of times any of the mouse buttons has been clicked in succession within
        /// the system-defined click time threshold.
        /// </summary>
        /// <value>Control representing the mouse click count.</value>
        public IntegerControl clickCount { get; protected set;  }

        /// <summary>
        /// The mouse that was added or updated last or null if there is no mouse
        /// connected to the system.
        /// </summary>
        /// <seealso cref="InputDevice.MakeCurrent"/>
        public new static Mouse current { get; private set; }

        /// <summary>
        /// Called when the mouse becomes the current mouse.
        /// </summary>
        public override void MakeCurrent()
        {
            base.MakeCurrent();
            current = this;
        }

        /// <summary>
        /// Called when the mouse is added to the system.
        /// </summary>
        protected override void OnAdded()
        {
            base.OnAdded();

            if (native && s_PlatformMouseDevice == null)
                s_PlatformMouseDevice = this;
        }

        /// <summary>
        /// Called when the device is removed from the system.
        /// </summary>
        protected override void OnRemoved()
        {
            base.OnRemoved();
            if (current == this)
                current = null;
        }

        internal static Mouse s_PlatformMouseDevice;

        ////REVIEW: how should we handle this being called from EditorWindow's? (where the editor window space processor will turn coordinates automatically into editor window space)
        /// <summary>
        /// Move the operating system's mouse cursor.
        /// </summary>
        /// <param name="position">New position in player window space.</param>
        /// <remarks>
        /// The <see cref="Pointer.position"/> property will not update immediately but rather will update in the
        /// next input update.
        /// </remarks>
        public void WarpCursorPosition(Vector2 position)
        {
            var command = WarpMousePositionCommand.Create(position);
            ExecuteCommand(ref command);
        }

        /// <inheritdoc />
        protected override void FinishSetup()
        {
            scroll = GetChildControl<DeltaControl>("scroll");
            leftButton = GetChildControl<ButtonControl>("leftButton");
            middleButton = GetChildControl<ButtonControl>("middleButton");
            rightButton = GetChildControl<ButtonControl>("rightButton");
            forwardButton = GetChildControl<ButtonControl>("forwardButton");
            backButton = GetChildControl<ButtonControl>("backButton");
            displayIndex = GetChildControl<IntegerControl>("displayIndex");
            clickCount = GetChildControl<IntegerControl>("clickCount");
            base.FinishSetup();
        }

        /// <summary>
        /// Implements <see cref="IInputStateCallbackReceiver.OnNextUpdate"/> for the mouse.
        /// </summary>
        protected new void OnNextUpdate()
        {
            base.OnNextUpdate();
            InputState.Change(scroll, Vector2.zero);
        }

        /// <summary>
        /// Implements <see cref="IInputStateCallbackReceiver.OnStateEvent"/> for the mouse.
        /// </summary>
        /// <param name="eventPtr"></param>
        protected new unsafe void OnStateEvent(InputEventPtr eventPtr)
        {
            scroll.AccumulateValueInEvent(currentStatePtr, eventPtr);
            base.OnStateEvent(eventPtr);
        }

        void IInputStateCallbackReceiver.OnNextUpdate()
        {
            OnNextUpdate();
        }

        void IInputStateCallbackReceiver.OnStateEvent(InputEventPtr eventPtr)
        {
            OnStateEvent(eventPtr);
        }
    }
}