Swing High/Low Detection

// Licensed under the Apache License, Version 2.0
// © mihakralj
//@version=6
indicator("Swing High/Low Detection", "SWINGS", overlay=true)

//@function Detects swing highs and swing lows using lookback period
//@param lookback Number of bars on each side to confirm swing point
//@param source_high Price series for swing high detection (typically high)
//@param source_low Price series for swing low detection (typically low)
//@returns Tuple [swing_high, swing_low] with swing point values (na if no swing)
swings(simple int lookback, series float source_high, series float source_low) =>
    if lookback <= 0
        runtime.error("Lookback must be greater than 0")
    if lookback > 100
        runtime.error("Lookback exceeds maximum of 100")
    bool is_swing_high = true
    bool is_swing_low = true
    if bar_index < lookback * 2
        is_swing_high := false
        is_swing_low := false
    else
        float center_high = source_high[lookback]
        float center_low = source_low[lookback]
        for i = 1 to lookback
            if source_high[lookback - i] > center_high or source_high[lookback + i] > center_high
                is_swing_high := false
            if source_low[lookback - i] < center_low or source_low[lookback + i] < center_low
                is_swing_low := false
    float swing_high_value = is_swing_high ? source_high[lookback] : na
    float swing_low_value = is_swing_low ? source_low[lookback] : na
    [swing_high_value, swing_low_value]

// ---------- Main loop ----------

// Inputs
i_lookback = input.int(5, "Lookback Period", minval=1, maxval=100, tooltip="Number of bars on each side to confirm swing point")
i_source_high = input.source(high, "Source High", tooltip="Price series for swing high detection")
i_source_low = input.source(low, "Source Low", tooltip="Price series for swing low detection")
i_show_high = input.bool(true, "Show Swing High Lines")
i_show_low = input.bool(true, "Show Swing Low Lines")
i_color_high = input.color(color.red, "Swing High Color")
i_color_low = input.color(color.green, "Swing Low Color")

// Calculation
[swing_high, swing_low] = swings(i_lookback, i_source_high, i_source_low)

// Track last confirmed swing points
var float last_swing_high = na
var float last_swing_low = na

// Update swing levels
if not na(swing_high)
    last_swing_high := swing_high

if not na(swing_low)
    last_swing_low := swing_low

// Plot swing levels as continuous lines
plot(i_show_high ? last_swing_high : na, "Swing High", color=i_color_high, linewidth=2, style=plot.style_line)
plot(i_show_low ? last_swing_low : na, "Swing Low", color=i_color_low, linewidth=2, style=plot.style_line)