Key Reversals with 20-Bar High/Low Lines

// This Pine Script® code is subject to the terms of the Mozilla Public License 2.0 at https://mozilla.org/MPL/2.0/
//@version=6
indicator("Key Reversals with 20-Bar High/Low Lines", overlay = true, max_lines_count = 500)

// --- Inputs ---
lookback = input.int(20, "Lookback Period", minval = 1, tooltip = "Number of bars to check for a new high or low.")
showLines = input.bool(true, "Show Horizontal Lines", tooltip = "Draw lines from the previous high/low to the reversal bar.")

// --- Colors ---
color BULL_COLOR = #5b9cf6 // Blue
color BEAR_COLOR = #f23645 // Red

// --- Core Logic ---
isBullCandle = close > open
isBearCandle = close < open

// Reference highs and lows for the lookback period (excluding current bar)
prevHighest = ta.highest(high[1], lookback)
prevLowest  = ta.lowest(low[1], lookback)

// Find the bar index of those highs/lows
// ta.highestbars returns a negative offset, so we add it to the current bar_index
prevHighestIdx = bar_index + ta.highestbars(high[1], lookback)
prevLowestIdx  = bar_index + ta.lowestbars(low[1], lookback)

// --- Key Reversal Detection ---
// Reversals must make a NEW high/low relative to the lookback period

// Bullish Reversal: New low (< prevLowest), close > prev close, bullish candle
isSingleBullish = low < prevLowest and close > close[1] and isBullCandle
isDoubleBullish = low < prevLowest and close > close[1] and close > close[2] and isBullCandle

// Bearish Reversal: New high (> prevHighest), close < prev close, bearish candle
isSingleBearish = high > prevHighest and close < close[1] and isBearCandle
isDoubleBearish = high > prevHighest and close < close[1] and close < close[2] and isBearCandle

// Prioritize double signals
isOnlySingleBullish = isSingleBullish and not isDoubleBullish
isOnlySingleBearish = isSingleBearish and not isDoubleBearish

// --- Visuals: Markers ---

// Single Reversals: One arrow
plotshape(isOnlySingleBullish, "Single Bullish", shape.arrowup,   location.belowbar, BULL_COLOR, size = size.small)
plotshape(isOnlySingleBearish, "Single Bearish", shape.arrowdown, location.abovebar, BEAR_COLOR, size = size.small)

// Double Reversals: Circles
plotshape(isDoubleBullish, "Double Bullish", shape.circle, location.belowbar, BULL_COLOR, size = size.small)
plotshape(isDoubleBearish, "Double Bearish", shape.circle, location.abovebar, BEAR_COLOR, size = size.small)

// --- Visuals: Horizontal Lines ---
if showLines
    if isSingleBullish or isDoubleBullish
        line.new(prevLowestIdx, prevLowest, bar_index, prevLowest, color = BULL_COLOR, style = line.style_dashed)
        
    if isSingleBearish or isDoubleBearish
        line.new(prevHighestIdx, prevHighest, bar_index, prevHighest, color = BEAR_COLOR, style = line.style_dashed)