Add extended trading hours (premarket and afterhours) to current pine script code - charts

Question

I have an indicator that plots percentage levels above current high/low/open/close (user selected) for the intraday levels. I would like to incorporate extended trading hours into the code. For example if the premarket high of day is higher than regular hours high of day, I'd like the indicator to calculate the percentage levels using the premarket high instead of the intraday. I'm not sure how to code this into the script but I assume it would be fairly simple (I'm just not a coder). Script below:
study(title="% Levels", overlay=true)
//Select Source to Plot Levels
calc = input(title="Calculation Source", defval="Open", options=["Open","High", "Low", "Close"])
showlast = input(title="Historical Bars to Display", defval=3, options= [1,2,3,4,5,10,15,20,30,50,100,200,300], group="Custom Line Plot Extension Settings || Base Settings for Stocks/ETF's are '1' & '0' Respectively || To Extend Lines: Ideally both values should be equal when adjusting || For Futures: 1 & 0 Recommended")
extendLines = input(title="Offset Starting Plot", defval=0, options=[0,1,3,5,10,15,20,30,50,100,200,300])
//Ticker Variables
o = security(syminfo.tickerid, "D", open)
h = security(syminfo.tickerid, "D", high)
l = security(syminfo.tickerid, "D", low)
c = security(syminfo.tickerid, "D", close)
calcm = if calc == "High"
h
else if calc == "Low"
l
else if calc == "Close"
c
else if calc == "Open"
o
//Calculations for % Levels
pct10= calcm*1.10
pctm10=calcm*0.90
pct12_5 = calcm*1.125
pctm12_5 = calcm*0.875
pct15= calcm*1.15
pctm15=calcm*0.85
//% Levels plotted based on Daily Open, High, Low, or Close
plot(pct10, title="10%", color=color.white, style=plot.style_line, show_last=showlast, offset=extendLines)
plot(pct12_5, title="12.5%", color=color.white, style=plot.style_line, show_last=showlast, offset=extendLines)
plot(pct15, title="15%", color=color.white, style=plot.style_line, show_last=showlast, offset=extendLines)
plot(pctm10, title="-10%", color=color.red, style=plot.style_line, show_last=showlast, offset=extendLines)
plot(pctm12_5, title="-12.5%", color=color.red, style=plot.style_line, show_last=showlast, offset=extendLines)
plot(pctm15, title="-15%", color=color.red, style=plot.style_line, show_last=showlast, offset=extendLines)
Not a coder so not sure what to try.

Answer 1

There are three built-in variables which you can use:
session.ismarket: Returns true if the current bar is a part of the regular trading hours (i.e. market hours), false otherwise
session.ispostmarket: Returns true if the current bar is a part of the post-market, false otherwise. On non-intraday charts always returns false.
session.ispremarket: Returns true if the current bar is a part of the pre-market, false otherwise. On non-intraday charts always returns false.