local screenSelection = 1
local screen = nil
local prevX, prevY = nil
local maxX, maxY = term.getSize()
os.loadAPI("DefAPI")
os.loadAPI("TableAPI")

function drawScreen()
	isSelectionChanged()
	isSelctionSelected()
	resetScreen()

	term.setBackgroundColor(colors.white)
	for i = 1, 3, 1 do
		term.setCursorPos(1, i)
		term.clearLine()
	end
	Print(screen["title"], getCenterX(screen["title"]), 2)
	term.setBackgroundColor(colors.gray)

	--For each option of a screen
	if type(screen["static"]) == "table" then
		local line = 0
		if type(screen["options"]) == "table" then
			line = (getCenterY() - 3 - math.floor(TableAPI.tablelength(screen["static"])) / 4)
		else
			line = (getCenterY() - 3 - math.floor(TableAPI.tablelength(screen["static"])) / 2)
		end

		if line < 1 or line > maxY then
			screenToSmall()
		else
			for k, v in ipairs(screen["static"]) do
				Print(label, 1, line + 3)
			end
		end
	end

	if type(screen["options"]) == "table" then
		local line = 0
		if type(screen["static"]) == "table" then
			line = (getCenterY() - 3 - math.floor(TableAPI.tablelength(screen["options"])) / 4) + prevY + 1
		else
			line = (getCenterY() - 3 - math.floor(TableAPI.tablelength(screen["options"])) / 2)
		end
		if line < 1 or line > maxY then
			screenToSmall()
		else
			local curSel = 1
			for k, v in ipairs(screen["options"]) do
				local label = v["option"]
				if curSel == screenSelection then
					term.setTextColor(colors.white)
					Print("[ ", getCenterX("[ " .. label .. " ]"), line)
					term.setTextColor(colors.black)
					PrintInline(label, string.len("[ "), 0, true)
					term.setTextColor(colors.white)
					PrintInline(" ]", string.len(label), 0, true)
					term.setTextColor(colors.black)
				else
					Print(label, getCenterX(label), line)
				end
				line = line + 1
				curSel = curSel + 1
			end
		end
	end
end

function setScreen(T)
	screen = T
end

function getScreen()
	return screen
end

function getCenterX(text)
	return (maxX - string.len(text)) / 2
end

function screenToSmall()
	Print("SCREEN TO SMALL FOR OPTIONS", getCenterX("SCREEN TO SMALL FOR OPTIONS"), getCenterY())
end

function getCenterY()
	return maxY / 2
end

function resetScreen()
	term.setBackgroundColor(colors.gray)
	term.setTextColor(colors.black)
	term.clear()
	term.setCursorPos(1, 1)
end

function PrintInline(text, x, y)
	term.setCursorPos(prevX + x, prevY + y)
	term.write(text)
	prevX = prevX + x
	prevY = prevY + y
end

function Print(text, x, y)
	term.setCursorPos(x, y)
	term.clearLine()
	term.write(text)
	prevX = x
	prevY = y
end

function isSelectionChanged()
	if event == "key" and type(screen["options"]) == "table" then
		if p1 == keys.up then
			if screenSelection == 1 then
				screenSelection = TableAPI.tablelength(screen["options"])
			else
				screenSelection = screenSelection - 1
			end
		elseif p1 == keys.down then
			if screenSelection == TableAPI.tablelength(screen["options"]) then
				screenSelection = 1
			else
				screenSelection = screenSelection + 1
			end
		end
	end
end

function isSelctionSelected()
	if event == "key" and type(screen["options"]) == "table" then
		if p1 == keys.enter then
			TableAPI.tableAt(screen["options"], screenSelection - 1)["func"]()
		elseif p1 == keys.backspace then
			local back = TableAPI.tableAtKey(screen["options"], "option", "Back")
			if back then
				back["func"]()
			end
		end
	end
end

function resetSelection()
	screenSelection = 1
end

function GetDefAPI()
	return DefAPI
end