using System;
using System.Drawing;

namespace OpenRA.Widgets
{
	public class SliderWidget : Widget
	{
		public event Action<float> OnChange;
		public Func<float> GetOffset;
		public float Offset = 0;
		public int Ticks = 0;
		public int TrackHeight = 5;
		
		int2 lastMouseLocation;
		bool isMoving = false;
		
		public SliderWidget () : base() 
		{
			GetOffset = () => Offset;
			OnChange = x => Offset = x;
		}

		public SliderWidget(Widget other)
			: base(other)
		{
			OnChange = (other as SliderWidget).OnChange;
			GetOffset = (other as SliderWidget).GetOffset;
			Offset = (other as SliderWidget).Offset;
			Ticks = (other as SliderWidget).Ticks;
			TrackHeight = (other as SliderWidget).TrackHeight;
			lastMouseLocation = (other as SliderWidget).lastMouseLocation;
			isMoving = (other as SliderWidget).isMoving;
		}
		
		public override bool HandleInput(MouseInput mi)
		{						
			if (mi.Event == MouseInputEvent.Down && !TakeFocus(mi))
				return false;
			
			if (!Focused)
				return false;

			switch (mi.Event)
			{
				case MouseInputEvent.Up:
				{
						if (Focused)
						{
							isMoving = false;
							base.LoseFocus(mi);
						}
				}
				break;
					
				case MouseInputEvent.Down:
				{
						if (thumbRect.Contains(mi.Location.ToPoint()))
						{
							isMoving = true;
							lastMouseLocation = mi.Location;
						}
						else if (Ticks != 0)
						{
							var pos = GetOffset();
							
							// Offset slightly the direction we want to move so we don't get stuck on a tick
							var delta = 0.001;
							var targetTick = (float)((mi.Location.X > thumbRect.Right) ? Math.Ceiling((pos+delta)*(Ticks-1))
					                         										   : Math.Floor((pos-delta)*(Ticks-1)));
							OnChange(targetTick/(Ticks-1));
							
							if (thumbRect.Contains(mi.Location.ToPoint()))
							{
								isMoving = true;
								lastMouseLocation = mi.Location;
							}
							return true;
						}
						else // No ticks; move to the mouse position
						{
							var thumb = thumbRect;
							var center = thumb.X + thumb.Width/2;
							var newOffset = OffsetBy((mi.Location.X - center)*1f/(RenderBounds.Width-thumb.Width));
							if (newOffset != GetOffset())
							{
								OnChange(newOffset);
						
								if (thumbRect.Contains(mi.Location.ToPoint()))
								{
									isMoving = true;
									lastMouseLocation = mi.Location;
								}
								return true;
							}
						}
				}
				break;
					
				case MouseInputEvent.Move:
				{
					if ((mi.Location.X != lastMouseLocation.X) && isMoving)
					{
						var newOffset = OffsetBy((mi.Location.X - lastMouseLocation.X)*1f/(RenderBounds.Width-thumbRect.Width));
						if (newOffset != Offset)
						{
							lastMouseLocation = mi.Location;
							OnChange(newOffset);
						}
					}
				}
				break;
			}
			
			return thumbRect.Contains(mi.Location.X,mi.Location.Y);
		}
		
		float OffsetBy(float amount)
		{
			var centerPos = GetOffset() + amount;
			if (centerPos < 0) centerPos = 0;
			if (centerPos > 1) centerPos = 1;
			return centerPos;
		}
		
		public override Widget Clone() { return new SliderWidget(this); }
		
		Rectangle thumbRect
		{ get { 
			var width = RenderBounds.Height;
			var height = RenderBounds.Height;
			var origin = (int)((RenderBounds.X + width/2) + GetOffset()*(RenderBounds.Width - width) - width/2f);
			return new Rectangle(origin, RenderBounds.Y, width, height);
		} }
		
		public override void DrawInner(World world) {
			if (!IsVisible())
				return;
	
			var trackWidth = RenderBounds.Width - thumbRect.Width;
			var trackOrigin = RenderBounds.X + thumbRect.Width/2;
			var trackRect = new Rectangle(trackOrigin-1, RenderBounds.Y + (RenderBounds.Height - TrackHeight)/2, trackWidth+2, TrackHeight);

			// Tickmarks (hacked until we have real art)
			for (int i = 0; i < Ticks; i++)
			{
				var tickRect = new Rectangle(trackOrigin -1 + (int)(i*trackWidth*1f/(Ticks-1)),
				          RenderBounds.Y + RenderBounds.Height/2, 2, RenderBounds.Height/2);
				WidgetUtils.DrawPanel("dialog2", tickRect);
			}
			// Track
			WidgetUtils.DrawPanel("dialog3", trackRect);

			// Thumb
			WidgetUtils.DrawPanel("dialog2", thumbRect); 	
		}
	}
}