//@version=6
indicator("Session Filter", overlay = true)

// 1. Settings: which hours you want to trade
sessionTime = input.session("0800-1600", "Trading session")
sessionZone = input.string("Europe/London", "Timezone")
fastLen     = input.int(9, "Fast average")
slowLen     = input.int(21, "Slow average")

// 2. Are we inside the session right now?
inSession = not na(time(timeframe.period, sessionTime, sessionZone))

// 3. Shade the background during the session
bgcolor(inSession ? color.new(color.blue, 92) : na)

// 4. The signal we want to filter
fast = ta.ema(close, fastLen)
slow = ta.ema(close, slowLen)
plot(fast, "Fast", color.aqua)
plot(slow, "Slow", color.orange)

// 5. The raw crossover, at any time of day
rawBuy = ta.crossover(fast, slow)

// 6. The same signal, but only inside your session
buySignal = rawBuy and inSession

// 7. Show both, so you can see what the filter removed
plotshape(rawBuy and not inSession, "Skipped", shape.xcross,
  location.belowbar, color.gray, size = size.tiny)
plotshape(buySignal, "Buy", shape.triangleup, location.belowbar,
  color.green, size = size.small)

// 8. Alert only for the filtered signal
alertcondition(buySignal, "Buy in session", "{{ticker}} buy inside session")