//@version=5
indicator("Line", shorttitle="Line", overlay=true)
period=input(20)
exl = input.bool(false, "Extend Left")
exr = input.bool(false, "Extend Right")

exs = switch
    exl and exr => extend.both
    exl => extend.left
    exr => extend.right
    => extend.none

begin = close[period]
end = close[1]
var line line_d = na

if na(line_d) and not na(begin)
    line_d := line.new(bar_index-period, begin, bar_index-1, end, extend=exs, color=color.blue)
else
    line.set_xy1(line_d, bar_index - period, begin)
    line.set_xy2(line_d, bar_index, end)
    na