using System;
using System.Drawing;
using System.Windows.Forms;

namespace NullFX.Controls {
    public class MouseMessageFilter : IMessageFilter {
        // singleton implementation
        static object locker = new object();
        static MouseMessageFilter instance;
        public static MouseMessageFilter Instance { get { lock (locker) { if (instance == null) instance = new MouseMessageFilter(); } return instance; } }
        
        // win32 message notifications
        const int WM_LBUTTONDOWN = 0x0201;
        const int WM_LBUTTONUP = 0x0202;
        const int WM_LBUTTONDBLCLK = 0x0203;
        const int WM_RBUTTONDOWN = 0x0204;
        const int WM_RBUTTONUP = 0x0205;
        const int WM_RBUTTONDBLCLK = 0x0206;
        const int WM_MBUTTONDOWN = 0x0207;
        const int WM_MBUTTONUP = 0x0208;
        const int WM_MBUTTONDBLCLK = 0x0209;
        const int WM_XBUTTONDOWN = 0x020B;
        const int WM_XBUTTONUP = 0x020C;
        const int WM_XBUTTONDBLCLK = 0x020D;
        const int WM_MOUSEMOVE = 0x0200;
        const int WM_MOUSEWHEEL = 0x020A;
        const int MK_LBUTTON = 0x0001;
        const int MK_RBUTTON = 0x0002;
        const int MK_MBUTTON = 0x0010;
        const int MK_XBUTTON1 = 0x0020;
        const int MK_XBUTTON2 = 0x0040;

        // various events to produce
        public event EventHandler<MouseEventArgs> MouseMove;
        public event EventHandler<MouseEventArgs> MouseDown;
        public event EventHandler<MouseEventArgs> MouseUp;
        public event EventHandler<MouseEventArgs> Click;
        public event EventHandler<MouseEventArgs> DoubleClick;
        public event EventHandler<MouseEventArgs> MouseWheel;

        // event invokers
        protected virtual void OnMouseMove(MouseEventArgs e) { if (MouseMove != null) MouseMove(this, e); }
        protected virtual void OnMouseDown(MouseEventArgs e) { if (MouseDown != null) MouseDown(this, e); }
        protected virtual void OnMouseUp(MouseEventArgs e) { if (MouseUp != null) MouseUp(this, e); }
        protected virtual void OnClick(MouseEventArgs e) { if (Click != null) Click(this, e); }
        protected virtual void OnDoubleClick(MouseEventArgs e) { if (DoubleClick != null) DoubleClick(this, e); }
        protected virtual void OnMouseWheel(MouseEventArgs e) { if (MouseWheel != null) MouseWheel(this, e); }

        // utility to build up the mouse event args from the win32 message
        private MouseEventArgs CreateMouseEventArgs(ref Message m, int clicks) {
            Point a = MakePoint(m.WParam);
            int delta = a.Y;
            MouseButtons mb = GetMouseButton(a.X);
            Point p = MakePoint(m.LParam);
            return new MouseEventArgs(mb, clicks, p.X, p.Y, delta);
        }

        // utility to map the virtual key codes to a MouseButons value
        private MouseButtons GetMouseButton(int code) {
            MouseButtons mb = MouseButtons.None;
            if ((code & MK_LBUTTON) == MK_LBUTTON) mb |= MouseButtons.Left;
            if ((code & MK_MBUTTON) == MK_MBUTTON) mb |= MouseButtons.Middle;
            if ((code & MK_RBUTTON) == MK_RBUTTON) mb |= MouseButtons.Right;
            if ((code & MK_XBUTTON1) == MK_XBUTTON1) mb |= MouseButtons.XButton1;
            if ((code & MK_XBUTTON2) == MK_XBUTTON2) mb |= MouseButtons.XButton2;
            return mb;
        }

        // utility to get the high and low value of a message parameter
        private Point MakePoint(IntPtr param) {
            int x = param.ToInt32() & 0xffff;
            int y = (param.ToInt32() >> 16);
            return new Point(x, y);
        }

        // method gets called before the message is dispatched to the individual
        // windows of the application.  returning true will keep the message from
        // being dispatched to the application's message queue
        public bool PreFilterMessage(ref Message m) {
            switch (m.Msg) {
                case WM_LBUTTONDOWN:
                case WM_MBUTTONDOWN:
                case WM_RBUTTONDOWN: {
                    MouseEventArgs e = CreateMouseEventArgs(ref m, 0);
                    OnMouseDown(e);
                } break;
                case WM_LBUTTONUP:
                case WM_MBUTTONUP:
                case WM_RBUTTONUP: {
                    MouseEventArgs e = CreateMouseEventArgs(ref m, 1);
                    OnClick(e);
                    OnMouseUp(e);
                } break;
                case WM_LBUTTONDBLCLK:
                case WM_MBUTTONDBLCLK:
                case WM_RBUTTONDBLCLK: {
                    MouseEventArgs e = CreateMouseEventArgs(ref m, 2);
                    OnDoubleClick(e);
                } break;
                case WM_XBUTTONDOWN: {
                    MouseEventArgs e = CreateMouseEventArgs(ref m, 0);
                    OnMouseDown(e);
                } break;
                case WM_XBUTTONUP: {
                    MouseEventArgs e = CreateMouseEventArgs(ref m, 1);
                    OnClick(e);
                    OnMouseUp(e);
                } break;
                case WM_XBUTTONDBLCLK: {
                    MouseEventArgs e = CreateMouseEventArgs(ref m, 2);
                    OnDoubleClick(e);
                } break;
                case WM_MOUSEMOVE: {
                    MouseEventArgs e = CreateMouseEventArgs(ref m, 0);
                    OnMouseMove(e);
                } break;
                case WM_MOUSEWHEEL: {
                    MouseEventArgs e = CreateMouseEventArgs(ref m, 0);
                    OnMouseWheel(e);
                } break;
            }
            return false;
        }

        // private constructor to enforce singleton instanciation 
        private MouseMessageFilter() { }
    }
}