// Licensed under the Apache License, Version 2.0
// © mihakralj
//@version=6
indicator("Qstick Indicator", "QSTICK", overlay=false)

//@function Calculates Qstick (moving average of close-open difference)
//@param source_close Closing price series
//@param source_open Opening price series
//@param length Lookback period for moving average
//@param use_ema Use EMA (true) or SMA (false)
//@returns Qstick value
qstick(series float source_close, series float source_open, simple int length, simple bool use_ema) =>
    if length <= 0
        runtime.error("Length must be greater than 0")
    
    float diff = source_close - source_open
    
    float result = 0.0
    if use_ema
        float alpha = 2.0 / (length + 1)
        var float ema = 0.0
        ema := alpha * (diff - ema) + ema
        result := ema
    else
        var int count = 0
        var float sum = 0.0
        var int head = 0
        var array<float> buffer = array.new_float(length, na)
        
        float oldest = array.get(buffer, head)
        if not na(oldest)
            sum -= oldest
        else
            count += 1
        
        float current = nz(diff)
        sum += current
        array.set(buffer, head, current)
        head := (head + 1) % length
        
        result := sum / math.max(1, count)
    
    result

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

// Inputs
i_length = input.int(14, "Length", minval=1, tooltip="Lookback period for moving average calculation")
i_ma_type = input.string("SMA", "MA Type", options=["SMA", "EMA"], tooltip="Simple (SMA) or Exponential (EMA) moving average")
i_source_close = input.source(close, "Close Source", tooltip="Source for closing price")
i_source_open = input.source(open, "Open Source", tooltip="Source for opening price")

// Calculation
bool use_ema = i_ma_type == "EMA"
qstick_value = qstick(i_source_close, i_source_open, i_length, use_ema)

// Plot
plot(qstick_value, "Qstick", color=color.yellow, linewidth=2)
hline(0, "Zero Line", color=color.gray, linestyle=hline.style_dashed)

// Color fill for positive/negative regions
bgcolor(qstick_value > 0 ? color.new(color.green, 90) : color.new(color.red, 90), title="Background")