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

namespace PaintDotNet.Measurement.Tools
{
    /// <summary>
    /// 平移工具（手型）
    /// </summary>
    public class PanTool : Tool
    {
        private bool tracking = false;
        private Point lastMouseXY;
        private Cursor cursorMouseDown;
        private Cursor cursorMouseUp;
        private Cursor cursorMouseInvalid;
        private int ignoreMouseMove = 0;

        private bool CanPan()
        {
            if (DocumentWorkspace.GetVisibleDocumentRectangleF().Size == Document.Size)
            {
                return false;
            }
            else
            {
                return true;
            }
        }

        protected override void OnMouseDown(MouseEventArgs e)
        {
            base.OnMouseDown(e);

            lastMouseXY = new Point(e.X, e.Y);
            tracking = true;

            if (CanPan())
            {
                Cursor = cursorMouseDown;
            }
            else
            {
                Cursor = cursorMouseInvalid;
            }
        }

        protected override void OnMouseUp(MouseEventArgs e)
        {
            base.OnMouseUp(e);

            if (CanPan())
            {
                Cursor = cursorMouseUp;
            }
            else
            {
                Cursor = cursorMouseInvalid;
            }

            tracking = false;
        }

        protected override void OnMouseMove(MouseEventArgs e)
        {
            base.OnMouseMove(e);

            if (this.ignoreMouseMove > 0)
            {
                --this.ignoreMouseMove;
            }
            else if (tracking)
            {
                Point mouseXY = new Point(e.X, e.Y);
                Size delta = new Size(mouseXY.X - lastMouseXY.X, mouseXY.Y - lastMouseXY.Y);

                if (delta.Width != 0 || delta.Height != 0)
                {
                    PointF scrollPos = DocumentWorkspace.GetDocumentScrollPositionF();
                    PointF newScrollPos = new PointF(scrollPos.X - delta.Width, scrollPos.Y - delta.Height);
                    ++this.ignoreMouseMove; // setting DocumentScrollPosition incurs a MouseMove event
                    DocumentWorkspace.SetDocumentScrollPositionF(newScrollPos);

                    lastMouseXY = mouseXY;
                    lastMouseXY.X -= delta.Width;
                    lastMouseXY.Y -= delta.Height;
                }
            }
            else
            {
                if (CanPan())
                {
                    Cursor = cursorMouseUp;
                }
                else
                {
                    Cursor = cursorMouseInvalid;
                }
            }
        }

        protected override void OnActivate()
        {
            // cursor-action assignments
            this.cursorMouseDown = new Cursor(PdnResources.GetResourceStream("Cursors.PanToolCursorMouseDown.cur"));
            this.cursorMouseUp = new Cursor(PdnResources.GetResourceStream("Cursors.PanToolCursor.cur"));
            this.cursorMouseInvalid = new Cursor(PdnResources.GetResourceStream("Cursors.PanToolCursorInvalid.cur"));
            this.Cursor = cursorMouseUp;
            base.OnActivate();
        }

        protected override void OnDeactivate()
        {
            if (cursorMouseDown != null)
            {
                cursorMouseDown.Dispose();
                cursorMouseDown = null;
            }

            if (cursorMouseUp != null)
            {
                cursorMouseUp.Dispose();
                cursorMouseUp = null;
            }

            if (cursorMouseInvalid != null)
            {
                cursorMouseInvalid.Dispose();
                cursorMouseInvalid = null;
            }

            base.OnDeactivate();
        }

        public PanTool(IDocumentWorkspace documentWorkspace)
            : base(documentWorkspace,
                   PdnResources.GetImageResource("Icons.PanToolIcon.png"),
                   PdnResources.GetString("PanTool.Name"),
                   PdnResources.GetString("PanTool.HelpText"),
                   'h',
                   false,
                   ToolBarConfigItems.None)
        {
            autoScroll = false;
            tracking = false;
        }
    }
}