-- AutoButtonColor doesn't always reset properly
function ResetButtonColor(button)
	local active = button.Active
	button.Active = not active
	button.Active = active
end

function ArrowGraphic(size,dir,scaled,template)
	local Frame = Create('Frame',{
		Name = "Arrow Graphic";
		BorderSizePixel = 0;
		Size = UDim2.new(0,size,0,size);
		Transparency = 1;
	})
	if not template then
		template = Instance.new("Frame")
		template.BorderSizePixel = 0
	end

	local transform
	if dir == nil or dir == 'Up' then
		function transform(p,s) return p,s end
	elseif dir == 'Down' then
		function transform(p,s) return UDim2.new(0,p.X.Offset,0,size-p.Y.Offset-1),s end
	elseif dir == 'Left' then
		function transform(p,s) return UDim2.new(0,p.Y.Offset,0,p.X.Offset),UDim2.new(0,s.Y.Offset,0,s.X.Offset) end
	elseif dir == 'Right' then
		function transform(p,s) return UDim2.new(0,size-p.Y.Offset-1,0,p.X.Offset),UDim2.new(0,s.Y.Offset,0,s.X.Offset) end
	end

	local scale
	if scaled then
		function scale(p,s) return UDim2.new(p.X.Offset/size,0,p.Y.Offset/size,0),UDim2.new(s.X.Offset/size,0,s.Y.Offset/size,0) end
	else
		function scale(p,s) return p,s end
	end

	local o = math.floor(size/4)
	if size%2 == 0 then
		local n = size/2-1
		for i = 0,n do
			local t = template:Clone()
			local p,s = scale(transform(
				UDim2.new(0,n-i,0,o+i),
				UDim2.new(0,(i+1)*2,0,1)
			))
			t.Position = p
			t.Size = s
			t.Parent = Frame
		end
	else
		local n = (size-1)/2
		for i = 0,n do
			local t = template:Clone()
			local p,s = scale(transform(
				UDim2.new(0,n-i,0,o+i),
				UDim2.new(0,i*2+1,0,1)
			))
			t.Position = p
			t.Size = s
			t.Parent = Frame
		end
	end
	if size%4 > 1 then
		local t = template:Clone()
		local p,s = scale(transform(
			UDim2.new(0,0,0,size-o-1),
			UDim2.new(0,size,0,1)
		))
		t.Position = p
		t.Size = s
		t.Parent = Frame
	end
	return Frame
end

function GripGraphic(size,dir,spacing,scaled,template)
	local Frame = Create('Frame',{
		Name = "Grip Graphic";
		BorderSizePixel = 0;
		Size = UDim2.new(0,size.x,0,size.y);
		Transparency = 1;
	})
	if not template then
		template = Instance.new("Frame")
		template.BorderSizePixel = 0
	end

	spacing = spacing or 2

	local scale
	if scaled then
		function scale(p) return UDim2.new(p.X.Offset/size.x,0,p.Y.Offset/size.y,0) end
	else
		function scale(p) return p end
	end

	if dir == 'Vertical' then
		for i=0,size.x-1,spacing do
			local t = template:Clone()
			t.Size = scale(UDim2.new(0,1,0,size.y))
			t.Position = scale(UDim2.new(0,i,0,0))
			t.Parent = Frame
		end
	elseif dir == nil or dir == 'Horizontal' then
		for i=0,size.y-1,spacing do
			local t = template:Clone()
			t.Size = scale(UDim2.new(0,size.x,0,1))
			t.Position = scale(UDim2.new(0,0,0,i))
			t.Parent = Frame
		end
	end

	return Frame
end

do
	local mt = {
		__index = {
			GetScrollPercent = function(self)
				return self.ScrollIndex/(self.TotalSpace-self.VisibleSpace)
			end;
			CanScrollDown = function(self)
				return self.ScrollIndex + self.VisibleSpace < self.TotalSpace
			end;
			CanScrollUp = function(self)
				return self.ScrollIndex > 0
			end;
			ScrollDown = function(self)
				self.ScrollIndex = self.ScrollIndex + self.PageIncrement
				self:Update()
			end;
			ScrollUp = function(self)
				self.ScrollIndex = self.ScrollIndex - self.PageIncrement
				self:Update()
			end;
			ScrollTo = function(self,index)
				self.ScrollIndex = index
				self:Update()
			end;
			SetScrollPercent = function(self,percent)
				self.ScrollIndex = math.floor((self.TotalSpace - self.VisibleSpace)*percent + 0.5)
				self:Update()
			end;
		};
	}
	mt.__index.CanScrollRight = mt.__index.CanScrollDown
	mt.__index.CanScrollLeft = mt.__index.CanScrollUp
	mt.__index.ScrollLeft = mt.__index.ScrollUp
	mt.__index.ScrollRight = mt.__index.ScrollDown

	function ScrollBar(horizontal)
		-- create row scroll bar
		local ScrollFrame = Create('Frame',{
			Name = "ScrollFrame";
			Position = horizontal and UDim2.new(0,0,1,-ScrollBarWidth) or UDim2.new(1,-ScrollBarWidth,0,0);
			Size = horizontal and UDim2.new(1,0,0,ScrollBarWidth) or UDim2.new(0,ScrollBarWidth,1,0);
			BackgroundTransparency = 1;
			Create('ImageButton',{
				Name = "ScrollDown";
				Position = horizontal and UDim2.new(1,-ScrollBarWidth,0,0) or UDim2.new(0,0,1,-ScrollBarWidth);
				Size = UDim2.new(0, ScrollBarWidth, 0, ScrollBarWidth);
				BackgroundColor3 = ScrollStyles.Button;
				BorderColor3 = ScrollStyles.Border;
				--BorderSizePixel = 0;
			});
			Create('ImageButton',{
				Name = "ScrollUp";
				Size = UDim2.new(0, ScrollBarWidth, 0, ScrollBarWidth);
				BackgroundColor3 = ScrollStyles.Button;
				BorderColor3 = ScrollStyles.Border;
				--BorderSizePixel = 0;
			});
			Create('ImageButton',{
				Name = "ScrollBar";
				Size = horizontal and UDim2.new(1,-ScrollBarWidth*2,1,0) or UDim2.new(1,0,1,-ScrollBarWidth*2);
				Position = horizontal and UDim2.new(0,ScrollBarWidth,0,0) or UDim2.new(0,0,0,ScrollBarWidth);
				AutoButtonColor = false;
				BackgroundColor3 = Color3.new(0.94902, 0.94902, 0.94902);
				BorderColor3 = ScrollStyles.Border;
				--BorderSizePixel = 0;
				Create('ImageButton',{
					Name = "ScrollThumb";
					AutoButtonColor = false;
					Size = UDim2.new(0, ScrollBarWidth, 0, ScrollBarWidth);
					BackgroundColor3 = ScrollStyles.Button;
					BorderColor3 = ScrollStyles.Border;
					--BorderSizePixel = 0;
				});
			});
		})

		local graphicTemplate = Create('Frame',{
			Name="Graphic";
			BorderSizePixel = 0;
			BackgroundColor3 = ScrollStyles.Border;
		})
		local graphicSize = ScrollBarWidth/2

		local ScrollDownFrame = ScrollFrame.ScrollDown
			local ScrollDownGraphic = ArrowGraphic(graphicSize,horizontal and 'Right' or 'Down',true,graphicTemplate)
			ScrollDownGraphic.Position = UDim2.new(0.5,-graphicSize/2,0.5,-graphicSize/2)
			ScrollDownGraphic.Parent = ScrollDownFrame
		local ScrollUpFrame = ScrollFrame.ScrollUp
			local ScrollUpGraphic = ArrowGraphic(graphicSize,horizontal and 'Left' or 'Up',true,graphicTemplate)
			ScrollUpGraphic.Position = UDim2.new(0.5,-graphicSize/2,0.5,-graphicSize/2)
			ScrollUpGraphic.Parent = ScrollUpFrame
		local ScrollBarFrame = ScrollFrame.ScrollBar
		local ScrollThumbFrame = ScrollBarFrame.ScrollThumb
		do
			local size = ScrollBarWidth*3/8
			local Decal = GripGraphic(Vector2.new(size,size),horizontal and 'Vertical' or 'Horizontal',2,graphicTemplate)
			Decal.Position = UDim2.new(0.5,-size/2,0.5,-size/2)
			Decal.Parent = ScrollThumbFrame
		end

		local MouseDrag = Create('ImageButton',{
			Name = "MouseDrag";
			Position = UDim2.new(-0.25,0,-0.25,0);
			Size = UDim2.new(1.5,0,1.5,0);
			Transparency = 1;
			AutoButtonColor = false;
			Active = true;
			ZIndex = 10;
		})

		local Class = setmetatable({
			GUI = ScrollFrame;
			ScrollIndex = 0;
			VisibleSpace = 0;
			TotalSpace = 0;
			PageIncrement = 1;
		},mt)

		local UpdateScrollThumb
		if horizontal then
			function UpdateScrollThumb()
				ScrollThumbFrame.Size = UDim2.new(Class.VisibleSpace/Class.TotalSpace,0,0,ScrollBarWidth)
				if ScrollThumbFrame.AbsoluteSize.x < ScrollBarWidth then
					ScrollThumbFrame.Size = UDim2.new(0,ScrollBarWidth,0,ScrollBarWidth)
				end
				local barSize = ScrollBarFrame.AbsoluteSize.x
				ScrollThumbFrame.Position = UDim2.new(Class:GetScrollPercent()*(barSize - ScrollThumbFrame.AbsoluteSize.x)/barSize,0,0,0)
			end
		else
			function UpdateScrollThumb()
				ScrollThumbFrame.Size = UDim2.new(0,ScrollBarWidth,Class.VisibleSpace/Class.TotalSpace,0)
				if ScrollThumbFrame.AbsoluteSize.y < ScrollBarWidth then
					ScrollThumbFrame.Size = UDim2.new(0,ScrollBarWidth,0,ScrollBarWidth)
				end
				local barSize = ScrollBarFrame.AbsoluteSize.y
				ScrollThumbFrame.Position = UDim2.new(0,0,Class:GetScrollPercent()*(barSize - ScrollThumbFrame.AbsoluteSize.y)/barSize,0)
			end
		end

		local lastDown
		local lastUp
		local scrollStyle = {BackgroundColor3=ScrollStyles.Border,BackgroundTransparency=0}
		local scrollStyle_ds = {BackgroundColor3=ScrollStyles.Border,BackgroundTransparency=0.7}

		local function Update()
			local t = Class.TotalSpace
			local v = Class.VisibleSpace
			local s = Class.ScrollIndex
			if v <= t then
				if s > 0 then
					if s + v > t then
						Class.ScrollIndex = t - v
					end
				else
					Class.ScrollIndex = 0
				end
			else
				Class.ScrollIndex = 0
			end

			if Class.UpdateCallback then
				if Class.UpdateCallback(Class) == false then
					return
				end
			end

			local down = Class:CanScrollDown()
			local up = Class:CanScrollUp()
			if down ~= lastDown then
				lastDown = down
				ScrollDownFrame.Active = down
				ScrollDownFrame.AutoButtonColor = down
				local children = ScrollDownGraphic:GetChildren()
				local style = down and scrollStyle or scrollStyle_ds
				for i = 1,#children do
					Create(children[i],style)
				end
			end
			if up ~= lastUp then
				lastUp = up
				ScrollUpFrame.Active = up
				ScrollUpFrame.AutoButtonColor = up
				local children = ScrollUpGraphic:GetChildren()
				local style = up and scrollStyle or scrollStyle_ds
				for i = 1,#children do
					Create(children[i],style)
				end
			end
			ScrollThumbFrame.Visible = down or up
			UpdateScrollThumb()
		end
		Class.Update = Update

		SetZIndexOnChanged(ScrollFrame)

		local scrollEventID = 0
		ScrollDownFrame.MouseButton1Down:connect(function()
			scrollEventID = tick()
			local current = scrollEventID
			local up_con
			up_con = MouseDrag.MouseButton1Up:connect(function()
				scrollEventID = tick()
				MouseDrag.Parent = nil
				ResetButtonColor(ScrollDownFrame)
				up_con:disconnect(); drag = nil
			end)
			MouseDrag.Parent = GetScreen(ScrollFrame)
			Class:ScrollDown()
			wait(0.2) -- delay before auto scroll
			while scrollEventID == current do
				Class:ScrollDown()
				if not Class:CanScrollDown() then break end
				wait()
			end
		end)

		ScrollDownFrame.MouseButton1Up:connect(function()
			scrollEventID = tick()
		end)

		ScrollUpFrame.MouseButton1Down:connect(function()
			scrollEventID = tick()
			local current = scrollEventID
			local up_con
			up_con = MouseDrag.MouseButton1Up:connect(function()
				scrollEventID = tick()
				MouseDrag.Parent = nil
				ResetButtonColor(ScrollUpFrame)
				up_con:disconnect(); drag = nil
			end)
			MouseDrag.Parent = GetScreen(ScrollFrame)
			Class:ScrollUp()
			wait(0.2)
			while scrollEventID == current do
				Class:ScrollUp()
				if not Class:CanScrollUp() then break end
				wait()
			end
		end)

		ScrollUpFrame.MouseButton1Up:connect(function()
			scrollEventID = tick()
		end)

		if horizontal then
			ScrollBarFrame.MouseButton1Down:connect(function(x,y)
				scrollEventID = tick()
				local current = scrollEventID
				local up_con
				up_con = MouseDrag.MouseButton1Up:connect(function()
					scrollEventID = tick()
					MouseDrag.Parent = nil
					ResetButtonColor(ScrollUpFrame)
					up_con:disconnect(); drag = nil
				end)
				MouseDrag.Parent = GetScreen(ScrollFrame)
				if x > ScrollThumbFrame.AbsolutePosition.x then
					Class:ScrollTo(Class.ScrollIndex + Class.VisibleSpace)
					wait(0.2)
					while scrollEventID == current do
						if x < ScrollThumbFrame.AbsolutePosition.x + ScrollThumbFrame.AbsoluteSize.x then break end
						Class:ScrollTo(Class.ScrollIndex + Class.VisibleSpace)
						wait()
					end
				else
					Class:ScrollTo(Class.ScrollIndex - Class.VisibleSpace)
					wait(0.2)
					while scrollEventID == current do
						if x > ScrollThumbFrame.AbsolutePosition.x then break end
						Class:ScrollTo(Class.ScrollIndex - Class.VisibleSpace)
						wait()
					end
				end
			end)
		else
			ScrollBarFrame.MouseButton1Down:connect(function(x,y)
				scrollEventID = tick()
				local current = scrollEventID
				local up_con
				up_con = MouseDrag.MouseButton1Up:connect(function()
					scrollEventID = tick()
					MouseDrag.Parent = nil
					ResetButtonColor(ScrollUpFrame)
					up_con:disconnect(); drag = nil
				end)
				MouseDrag.Parent = GetScreen(ScrollFrame)
				if y > ScrollThumbFrame.AbsolutePosition.y then
					Class:ScrollTo(Class.ScrollIndex + Class.VisibleSpace)
					wait(0.2)
					while scrollEventID == current do
						if y < ScrollThumbFrame.AbsolutePosition.y + ScrollThumbFrame.AbsoluteSize.y then break end
						Class:ScrollTo(Class.ScrollIndex + Class.VisibleSpace)
						wait()
					end
				else
					Class:ScrollTo(Class.ScrollIndex - Class.VisibleSpace)
					wait(0.2)
					while scrollEventID == current do
						if y > ScrollThumbFrame.AbsolutePosition.y then break end
						Class:ScrollTo(Class.ScrollIndex - Class.VisibleSpace)
						wait()
					end
				end
			end)
		end

		if horizontal then
			ScrollThumbFrame.MouseButton1Down:connect(function(x,y)
				scrollEventID = tick()
				local mouse_offset = x - ScrollThumbFrame.AbsolutePosition.x
				local drag_con
				local up_con
				drag_con = MouseDrag.MouseMoved:connect(function(x,y)
					local bar_abs_pos = ScrollBarFrame.AbsolutePosition.x
					local bar_drag = ScrollBarFrame.AbsoluteSize.x - ScrollThumbFrame.AbsoluteSize.x
					local bar_abs_one = bar_abs_pos + bar_drag
					x = x - mouse_offset
					x = x < bar_abs_pos and bar_abs_pos or x > bar_abs_one and bar_abs_one or x
					x = x - bar_abs_pos
					Class:SetScrollPercent(x/(bar_drag))
				end)
				up_con = MouseDrag.MouseButton1Up:connect(function()
					scrollEventID = tick()
					MouseDrag.Parent = nil
					ResetButtonColor(ScrollThumbFrame)
					drag_con:disconnect(); drag_con = nil
					up_con:disconnect(); drag = nil
				end)
				MouseDrag.Parent = GetScreen(ScrollFrame)
			end)
		else
			ScrollThumbFrame.MouseButton1Down:connect(function(x,y)
				scrollEventID = tick()
				local mouse_offset = y - ScrollThumbFrame.AbsolutePosition.y
				local drag_con
				local up_con
				drag_con = MouseDrag.MouseMoved:connect(function(x,y)
					local bar_abs_pos = ScrollBarFrame.AbsolutePosition.y
					local bar_drag = ScrollBarFrame.AbsoluteSize.y - ScrollThumbFrame.AbsoluteSize.y
					local bar_abs_one = bar_abs_pos + bar_drag
					y = y - mouse_offset
					y = y < bar_abs_pos and bar_abs_pos or y > bar_abs_one and bar_abs_one or y
					y = y - bar_abs_pos
					Class:SetScrollPercent(y/(bar_drag))
				end)
				up_con = MouseDrag.MouseButton1Up:connect(function()
					scrollEventID = tick()
					MouseDrag.Parent = nil
					ResetButtonColor(ScrollThumbFrame)
					drag_con:disconnect(); drag_con = nil
					up_con:disconnect(); drag = nil
				end)
				MouseDrag.Parent = GetScreen(ScrollFrame)
			end)
		end

		function Class:Destroy()
			ScrollFrame:Destroy()
			MouseDrag:Destroy()
			for k in pairs(Class) do
				Class[k] = nil
			end
			setmetatable(Class,nil)
		end

		Update()

		return Class
	end
end