// Licensed under the Apache License, Version 2.0
// © mihakralj
//@version=6
indicator("Ehlers Directional Movement with Hann (DMH)", "DMH", overlay=false)

//@function Calculates DMH (Ehlers Directional Movement with Hann Windowing)
//@param period Number of bars used in the calculation
//@returns dmh value
dmh(simple int period = 14) =>
    if period <= 0
        runtime.error("Period must be greater than 0")
    float sf = 1.0 / period

    // Stage 1: Classic DM extraction
    float upperMove = na(high[1]) ? 0.0 : high - high[1]
    float lowerMove = na(low[1]) ? 0.0 : low[1] - low
    float plusDM = 0.0
    float minusDM = 0.0
    if upperMove > lowerMove and upperMove > 0
        plusDM := upperMove
    else if lowerMove > upperMove and lowerMove > 0
        minusDM := lowerMove

    // Stage 2: EMA smoothing
    var float ema = 0.0
    ema := sf * (plusDM - minusDM) + (1.0 - sf) * ema

    // Stage 3: Hann FIR filter on EMA history
    float dmSum = 0.0
    float coef = 0.0
    for count = 1 to period
        float w = 1.0 - math.cos(2.0 * math.pi * count / (period + 1))
        dmSum += w * nz(ema[count - 1])
        coef += w
    float result = coef != 0 ? dmSum / coef : 0.0
    result

// Inputs
i_period = input.int(14, "Period", minval=1, tooltip="Number of bars used in the calculation")

// Calculate DMH
dmhVal = dmh(i_period)

// Plot
hline(0, "Zero", color=color.gray, linestyle=hline.style_dotted)
plot(dmhVal, "DMH", color=color.yellow, linewidth=2)