Session Highs and Lows Indicator (SMC Sessions, DST-safe)

// TradingView Pine Script V5 Indicator to mark the latest important levels
// This Pine Script™ code is subject to the terms of the Mozilla Public License 2.0 at https://mozilla.org/MPL/2.0/
// © tc3oliver

//@version=6
indicator("Session Highs and Lows Indicator (SMC Sessions, DST-safe)", overlay=true)

// Session windows are meaningless once one candle spans the whole day —
// without this guard the script silently draws wrong levels on 1D and above.
if not timeframe.isintraday and barstate.islast
    runtime.error("This indicator requires an intraday timeframe (< 1D).")

// ======== Visibility toggles ========
// Names must match the killzone names used on the chart labels below.
showLondon      = input.bool(true, "Show London Open Killzone")
showNewYork     = input.bool(true, "Show New York AM Killzone")
showAsia        = input.bool(true, "Show Asian Range")
showLondonClose = input.bool(true, "Show London Close Killzone")

// ======== Line styling ========
londonColor      = input.color(color.new(#47abfd, 70), "London Open Line Color")
londonWidth      = input.int(1, "London Open Line Width", minval=1, maxval=5)

newYorkColor     = input.color(color.new(#ff6565, 70), "New York AM Line Color")
newYorkWidth     = input.int(1, "New York AM Line Width", minval=1, maxval=5)

londonCloseColor = input.color(color.new(#ff9f43, 70), "London Close Line Color")
londonCloseWidth = input.int(1, "London Close Line Width", minval=1, maxval=5)

asiaColor        = input.color(color.new(#75ff79, 70), "Asian Range Line Color")
asiaWidth        = input.int(1, "Asian Range Line Width", minval=1, maxval=5)

// --- SMC/ICT Sessions in New York time (DST-safe via America/New_York) ---
asianRangeSession  = input.session("2000-0000", "Asian Range [NY time]")
londonSession      = input.session("0300-0500", "London Open [NY time]")
newYorkSession     = input.session("0830-1100", "New York AM [NY time]")
londonCloseSession = input.session("1000-1200", "London Close [NY time]")

TZ = "America/New_York"

// ======== High/low tracking for a single session ========
// A function-local `var` holds independent state per call site, so all four
// sessions share this one implementation. Deliberately not an array or UDT:
// container rollback on realtime bars is a known source of repainting.
// Must be called unconditionally on every bar or the var state desyncs.
trackSession(sess, show, col, wid, name) =>
    // v6: a `bool` can never be `na`, so `inSess[1]` is already false on the
    // first bar. The v5 code wrapped it in nz(), which v6 rejects for bools.
    inSess  = not na(time("", sess, TZ))
    isStart = inSess and not inSess[1]
    isEnd   = not inSess and inSess[1]

    var float hi       = na
    var float lo       = na
    var int   hiBar    = na
    var int   loBar    = na
    var int   startBar = na
    var label hiLbl    = na
    var label loLbl    = na
    var line  hiLn     = na
    var line  loLn     = na
    var label warnLbl  = na

    if isStart
        hi := high
        lo := low
        hiBar := bar_index
        loBar := bar_index
        startBar := bar_index
    else if inSess
        if high > hi
            hi := high
            hiBar := bar_index
        if low < lo
            lo := low
            loBar := bar_index
    else if isEnd and show
        label.delete(hiLbl)
        label.delete(loLbl)
        line.delete(hiLn)
        line.delete(loLn)
        hiLbl := label.new(hiBar, hi, name + " High", yloc=yloc.abovebar, color=col, textcolor=color.white, style=label.style_label_down, size=size.small)
        loLbl := label.new(loBar, lo, name + " Low",  yloc=yloc.belowbar, color=col, textcolor=color.white, style=label.style_label_up,   size=size.small)
        hiLn := line.new(startBar, hi, bar_index, hi, xloc.bar_index, extend=extend.right, color=col, width=wid, style=line.style_dashed)
        loLn := line.new(startBar, lo, bar_index, lo, xloc.bar_index, extend=extend.right, color=col, width=wid, style=line.style_dashed)

    // A session window only registers if some bar OPENS inside it. On coarse
    // timeframes (3h/4h) a 2-hour window can contain zero bar opens, and the
    // session silently never fires — which reads as "the toggle does nothing".
    // Which sessions are affected shifts with DST, so say so explicitly.
    // `barstate.islast` is true on every bar while it is forming, and the label
    // is committed when that bar closes — so it must be deleted before redrawing
    // or one warning label accumulates per bar.
    if barstate.islast and show and na(hi)
        label.delete(warnLbl)
        warnLbl := label.new(bar_index, close, "⚠ " + name + ": no bar opens inside this session on the " + timeframe.period + " timeframe. Use 30m or lower.", yloc=yloc.price, color=color.orange, textcolor=color.white, style=label.style_label_left, size=size.small)

    [hi, lo, hiBar, loBar]

// ======== The four sessions ========
[londonHigh, londonLow, londonHighBar, londonLowBar] =
  trackSession(londonSession, showLondon, londonColor, londonWidth, "London Open Killzone")

[newYorkHigh, newYorkLow, newYorkHighBar, newYorkLowBar] =
  trackSession(newYorkSession, showNewYork, newYorkColor, newYorkWidth, "New York AM Killzone")

[asiaHigh, asiaLow, asiaHighBar, asiaLowBar] =
  trackSession(asianRangeSession, showAsia, asiaColor, asiaWidth, "Asian Range")

[londonCloseHigh, londonCloseLow, londonCloseHighBar, londonCloseLowBar] =
  trackSession(londonCloseSession, showLondonClose, londonCloseColor, londonCloseWidth, "London Close Killzone")

// ======== Test hooks — hidden from the chart and the Data Window ========
// Read by tests.mjs to reconcile against independently computed ground truth.
plot(londonHigh,         "london_hi",         display=display.none)
plot(londonLow,          "london_lo",         display=display.none)
plot(londonHighBar,      "london_hiBar",      display=display.none)
plot(londonLowBar,       "london_loBar",      display=display.none)
plot(newYorkHigh,        "newYork_hi",        display=display.none)
plot(newYorkLow,         "newYork_lo",        display=display.none)
plot(newYorkHighBar,     "newYork_hiBar",     display=display.none)
plot(newYorkLowBar,      "newYork_loBar",     display=display.none)
plot(asiaHigh,           "asia_hi",           display=display.none)
plot(asiaLow,            "asia_lo",           display=display.none)
plot(asiaHighBar,        "asia_hiBar",        display=display.none)
plot(asiaLowBar,         "asia_loBar",        display=display.none)
plot(londonCloseHigh,    "londonClose_hi",    display=display.none)
plot(londonCloseLow,     "londonClose_lo",    display=display.none)
plot(londonCloseHighBar, "londonClose_hiBar", display=display.none)
plot(londonCloseLowBar,  "londonClose_loBar", display=display.none)