// Licensed under the Apache License, Version 2.0
// © mihakralj
//@version=6
indicator("Hanning Moving Average (HANMA)", "HANMA", overlay=true)

//@function Calculates HANMA using Hanning window weighting
//@param source Series to calculate HANMA from
//@param period Lookback period - FIR window size
//@returns HANMA value, calculates from first bar using available data
//@optimized Uses Hanning window coefficients with O(n) complexity per bar due to lookback loop
hanma(series float source, simple int period) =>
    if period <= 0
        runtime.error("Period must be greater than 0")
    int p = math.min(bar_index + 1, period)
    var array<float> weights = array.new_float(1, 1.0)
    var int last_p = 1
    if last_p != p
        weights := array.new_float(p, 0.0)
        for i = 0 to p - 1
            float w = 0.5 * (1.0 - math.cos(2.0 * math.pi * i / (p - 1)))
            array.set(weights, i, w)
        last_p := p
    float sum = 0.0
    float weight_sum = 0.0
    for i = 0 to p - 1
        float price = source[i]
        if not na(price)
            float w = array.get(weights, i)
            sum += price * w
            weight_sum += w
    nz(sum / weight_sum, source)

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

// Inputs
i_period = input.int(10, "Period", minval=1)
i_source = input.source(close, "Source")

// Calculation
hanma_value = hanma(i_source, i_period)

// Plot
plot(hanma_value, "HANMA", color=color.yellow, linewidth=2)