//
//  Scroller.cs
//
//  Author:
//       Jean-Philippe Bruyère <jp_bruyere@hotmail.com>
//
//  Copyright (c) 2016 jp
//
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program.  If not, see <http://www.gnu.org/licenses/>.

using System;
using System.Xml.Serialization;
using System.ComponentModel;
using System.Diagnostics;
using Cairo;

namespace Crow
{
	public class Scroller : Container
	{
		bool _verticalScrolling;
		bool _horizontalScrolling;
		bool _scrollbarVisible;
		double _scrollX = 0.0;
		double _scrollY = 0.0;
		int scrollSpeed;

		public event EventHandler<ScrollingEventArgs> Scrolled;

		#region public properties
		[XmlAttributeAttribute][DefaultValue(false)]
		public bool VerticalScrolling {
			get { return _verticalScrolling; }
			set { _verticalScrolling = value; }
		}
        
		[XmlAttributeAttribute][DefaultValue(false)]
        public bool HorizontalScrolling {
			get { return _horizontalScrolling; }
			set { _horizontalScrolling = value; }
		}
		[XmlAttributeAttribute][DefaultValue(true)]
		public bool ScrollbarVisible {
			get { return _scrollbarVisible; }
			set { _scrollbarVisible = value; }
		}			
		[XmlAttributeAttribute][DefaultValue(0.0)]
		public double ScrollX {
			get {
				return _scrollX;
			}
			set {
				if (_scrollX == value)
					return;
				if (value < 0.0)
					_scrollX = 0.0;
				else if (value > Child.Slot.Width - ClientRectangle.Width)
					_scrollX = Math.Max(0.0, Child.Slot.Width - ClientRectangle.Width);
				else
					_scrollX = value;
				NotifyValueChanged("ScrollX", _scrollX);
				RegisterForGraphicUpdate ();
				Scrolled.Raise (this, new ScrollingEventArgs (Orientation.Horizontal));
			}
		}			
		[XmlAttributeAttribute][DefaultValue(0.0)]
		public double ScrollY {
			get {
				return _scrollY;
			}
			set {
				if (_scrollY == value)
					return;
				if (value < 0.0)
					_scrollY = 0.0;
				else if (value > Child.Slot.Height - ClientRectangle.Height)
					_scrollY = Math.Max(0.0,Child.Slot.Height - ClientRectangle.Height);
				else
					_scrollY = value;
				NotifyValueChanged("ScrollY", _scrollY);
				RegisterForGraphicUpdate ();
				Scrolled.Raise (this, new ScrollingEventArgs (Orientation.Vertical));
			}
		}

		[XmlIgnore]
		public int MaximumScroll {
			get {
				try {
					return VerticalScrolling ? 
						Math.Max(Child.Slot.Height - ClientRectangle.Height,0) :
						Math.Max(Child.Slot.Width - ClientRectangle.Width,0);					
				} catch {
					return 0;
				}
			}
		}

		[XmlAttributeAttribute][DefaultValue(30)]
		public int ScrollSpeed {
			get { return scrollSpeed; }
			set {
				scrollSpeed = value;
				NotifyValueChanged("ScrollSpeed", scrollSpeed);
			}
		}
		#endregion

        public Scroller()
            : base(){}

		#region GraphicObject Overrides
		//TODO:put this override in style
		[XmlAttributeAttribute()][DefaultValue(false)]
		public override bool CacheEnabled {
			get { return base.CacheEnabled; }
			set { base.CacheEnabled = value; }
		}
		void OnChildLayoutChanges (object sender, LayoutingEventArgs arg)
		{
			int maxScroll = MaximumScroll;
			if (_verticalScrolling) {
				if (arg.LayoutType == LayoutingType.Height) {
					if (maxScroll < ScrollY) {
						Debug.WriteLine ("scrolly={0} maxscroll={1}", ScrollY, maxScroll);
						ScrollY = 0;
					}
					NotifyValueChanged("MaximumScroll", maxScroll);
				}
			} else if (arg.LayoutType == LayoutingType.Width) {
				if (maxScroll < ScrollX)
					ScrollX = 0;
				NotifyValueChanged("MaximumScroll", maxScroll);
			}
		}
		void onChildListCleared(object sender, EventArgs e){
			ScrollY = 0;
			ScrollX = 0;
		}
		public override T SetChild<T> (T _child)
		{			
			GraphicObject c = child as GraphicObject;
			Group g = child as Group;
			if (c != null) {
				c.LayoutChanged -= OnChildLayoutChanges;
				if (g != null)
					g.ChildrenCleared -= onChildListCleared;
			}
			c = _child as GraphicObject;
			g = _child as Group;
			if (c != null) {
				c.LayoutChanged += OnChildLayoutChanges;
				if (g != null)
					g.ChildrenCleared += onChildListCleared;				
			}
			return base.SetChild (_child);
		}
		#endregion

		#region Mouse handling
		internal Point savedMousePos;
		public override bool MouseIsIn (Point m)
		{			
			return Visible ? base.ScreenCoordinates(Slot).ContainsOrIsEqual (m) : false; 
		}
		public override void checkHoverWidget (MouseMoveEventArgs e)
		{
			savedMousePos = e.Position;
			Point m = e.Position - new Point ((int)ScrollX, (int)ScrollY);
			base.checkHoverWidget (new MouseMoveEventArgs(m.X,m.Y,e.XDelta,e.YDelta));
		}
		public override void onMouseWheel (object sender, MouseWheelEventArgs e)
		{
			if (Child == null)
				return;
			
			if (VerticalScrolling )
				ScrollY -= e.Delta * ScrollSpeed;
            if (HorizontalScrolling )
				ScrollX -= e.Delta * ScrollSpeed;
        }
		public override void onMouseMove (object sender, MouseMoveEventArgs e)
		{
			savedMousePos.X += e.XDelta;
			savedMousePos.Y += e.YDelta;
			base.onMouseMove (sender, new MouseMoveEventArgs(savedMousePos.X,savedMousePos.Y,e.XDelta,e.YDelta));
		}
		public override void RegisterClip (Rectangle clip)
		{
			base.RegisterClip (clip - new Point((int)ScrollX,(int)ScrollY));
		}
		#endregion

		public override Rectangle ScreenCoordinates (Rectangle r)
		{
			return base.ScreenCoordinates (r) - new Point((int)ScrollX,(int)ScrollY);
		}
		protected override void onDraw (Context gr)
		{
			Rectangle rBack = new Rectangle (Slot.Size);

			Background.SetAsSource (gr, rBack);
			CairoHelpers.CairoRectangle(gr,rBack, CornerRadius);
			gr.Fill ();

			gr.Save ();
			//clip to scrolled client zone
			CairoHelpers.CairoRectangle (gr, ClientRectangle, CornerRadius);
			gr.Clip ();

			gr.Translate (-ScrollX, -ScrollY);
			if (child != null)
				child.Paint (ref gr);
			gr.Restore ();
		}
    }
}