menu

local unpack = unpack or table.unpack

local function drawMenu(menuTable, cursor, offset, colors)
	local xlim, ylim = term.getSize()
	local sT = term.isColor() and colors[1] or colors.black
	local sB = term.isColor() and colors[2] or colors.white
	local nT = term.isColor() and colors[3] or colors.white
	local nB = term.isColor() and colors[4] or colors.black
	if xlim < 3 or (ylim < 3 and #menuTable > 2) then
		return nil, "Not enought space to draw menu!"
	end
	term.setBackgroundColor(nB)
	term.setTextColor(nT)
	term.clear()
	offset = offset or 1
	for i = 1, math.min(ylim, #menuTable) do
		term.setCursorPos(1, i)
		if i == 1 and offset > 1 then
			term.write(" /\\")
		elseif i == ylim and #menuTable > offset + ylim - 1 then
			term.write(" \\/")
		else
			if i == (cursor - offset + 1) then
				term.setTextColor(sT)
				term.setBackgroundColor(sB)
			else
				term.setTextColor(nT)
				term.setBackgroundColor(nB)
			end
			local text = string.sub(menuTable[offset + i - 1], 1, xlim - 2)
			term.write(" "..text..string.rep(" ", xlim - #text - 1))
		end
	end
end


function select(menuTable, selText, selBack, normText, normBack)
	local colors = {selText or colors.white, selBack or colors.blue, normText or colors.white, normBack or colors.gray}
	local cursor, offset = 1, 1
	drawMenu(menuTable, cursor, offset, colors)
	while true do
		local e, p1, p2, p3 = os.pullEvent()
		if e == "key" then
			--up
			if p1 == 200 then
				if cursor - offset + 1 > 2 or (cursor > 1 and offset ==  1) then
					cursor = cursor - 1
					drawMenu(menuTable, cursor, offset, colors)
				elseif cursor - offset + 1 == 2 and offset > 1 then
					offset = offset - 1
					cursor = cursor - 1
					drawMenu(menuTable, cursor, offset, colors)
				end
			--down
			elseif p1 == 208 then
				_, ylim = term.getSize()
				if cursor < #menuTable and (cursor - offset + 1 < ylim - 1 or #menuTable <= ylim or (cursor == #menuTable - 1 and cursor - offset + 1 == ylim - 1)) then
					cursor = cursor + 1
					drawMenu(menuTable, cursor, offset, colors)
				elseif cursor < #menuTable and cursor - offset + 1 == ylim - 1 then
					offset = offset + 1
					cursor = cursor + 1
					drawMenu(menuTable, cursor, offset, colors)
				end
			elseif p1 == 28 then
				return cursor
			end
		elseif e == "mouse_click" and p1 == 1 then
			if p3 <= #menuTable then
				_, ylim = term.getSize()
				if offset > 1 and p3 == 1 then
					--scroll up.
					offset = offset - 1
					cursor = offset + 1
					drawMenu(menuTable, cursor, offset, colors)
				elseif offset + ylim - 1 < #menuTable and p3 == ylim then
					--scroll down.
					offset = offset + 1
					cursor = offset + ylim - 2
					drawMenu(menuTable, cursor, offset, colors)
				else
					return p3 + offset - 1
				end
			end
		elseif e == "term_resize" then
			drawMenu(menuTable, cursor, offset, colors)
		end
	end
end