Stochastic MACD Oscillator (STMACD)

// Licensed under the Apache License, Version 2.0
// © mihakralj
//@version=6
indicator("Stochastic MACD Oscillator (STMACD)", "STMACD", overlay = false)

//@function Stochastic MACD — normalises each EMA against the rolling high-low range,
//          converting absolute MACD into a percentage-scale momentum reading.
//          Pipeline: HH/LL(periods) → FastEMA/SlowEMA → StochNorm → Signal EMA.
//          Output unbounded (typically −100…+100), OB/OS at ±10.
//@param h High price series
//@param l Low price series
//@param c Close price series
//@param periods Rolling H-L range lookback (>= 2)
//@param fastLength Fast EMA period (>= 2)
//@param slowLength Slow EMA period (>= 2)
//@param signalLength Signal EMA period (>= 2)
//@returns [stmacd, signal] — dual output
//@reference Apirine, V. (2019). "The Stochastic MACD Oscillator."
//           Technical Analysis of Stocks & Commodities, Nov 2019.
//@optimized O(1) amortized per bar via ta.highest/ta.lowest
stmacd(series float h, series float l, series float c,
       simple int periods, simple int fastLength,
       simple int slowLength, simple int signalLength) =>
    if periods < 2 or fastLength < 2 or slowLength < 2 or signalLength < 2
        runtime.error("All periods must be at least 2")

    // --- Sliding-window extremes ---
    float hh = ta.highest(h, periods)
    float ll = ta.lowest(l, periods)

    // --- Dual EMA of Close ---
    float fastEma = ta.ema(c, fastLength)
    float slowEma = ta.ema(c, slowLength)

    // --- Stochastic normalisation ---
    float rng = hh - ll
    float fastStoch = rng > 0 ? (fastEma - ll) / rng : 0.0
    float slowStoch = rng > 0 ? (slowEma - ll) / rng : 0.0
    float stmacd_val = (fastStoch - slowStoch) * 100.0

    // --- Signal line ---
    float signal_val = ta.ema(stmacd_val, signalLength)

    [stmacd_val, signal_val]

// ── Inputs ──
int p_periods      = input.int(45, "Periods",       minval = 2)
int p_fastLength   = input.int(12, "Fast Length",    minval = 2)
int p_slowLength   = input.int(26, "Slow Length",    minval = 2)
int p_signalLength = input.int(9,  "Signal Length",  minval = 2)

// ── Calculation ──
[stmacd_out, signal_out] = stmacd(high, low, close, p_periods, p_fastLength, p_slowLength, p_signalLength)

// ── Plot ──
plot(stmacd_out, "STMACD", color.blue, 2)
plot(signal_out, "Signal", color.orange, 1)
hline(10,  "Overbought", color.new(color.gray, 50), linestyle = hline.style_dotted)
hline(-10, "Oversold",   color.new(color.gray, 50), linestyle = hline.style_dotted)
hline(0,   "Zero",       color.gray, linestyle = hline.style_dashed)