local class = require('class')
local UI    = require('ui')
local Util  = require('util')

--[[-- ScrollingGrid  --]]--
UI.ScrollingGrid = class(UI.Grid)
UI.ScrollingGrid.defaults = {
	UIElement = 'ScrollingGrid',
	scrollOffset = 0,
	marginRight = 1,
}
function UI.ScrollingGrid:postInit()
	self.scrollBar = UI.ScrollBar()
end

function UI.ScrollingGrid:drawRows()
	UI.Grid.drawRows(self)
	self.scrollBar:draw()
end

function UI.ScrollingGrid:getViewArea()
	local y = 1
	if not self.disableHeader then
		y = y + self.headerHeight
	end

	return {
		static      = true,                    -- the container doesn't scroll
		y           = y,                       -- scrollbar Y
		height      = self.pageSize,           -- viewable height
		totalHeight = Util.size(self.values),  -- total height
		offsetY     = self.scrollOffset,       -- scroll offset
	}
end

function UI.ScrollingGrid:getStartRow()
	local ts = Util.size(self.values)
	if ts < self.pageSize then
		self.scrollOffset = 0
	end
	return self.scrollOffset + 1
end

function UI.ScrollingGrid:setIndex(index)
	if index < self.scrollOffset + 1 then
		self.scrollOffset = index - 1
	elseif index - self.scrollOffset > self.pageSize then
		self.scrollOffset = index - self.pageSize
	end

	if self.scrollOffset < 0 then
		self.scrollOffset = 0
	else
		local ts = Util.size(self.values)
		if self.pageSize + self.scrollOffset + 1 > ts then
			self.scrollOffset = math.max(0, ts - self.pageSize)
		end
	end
	UI.Grid.setIndex(self, index)
end