// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef GARNET_LIB_WLAN_COMMON_INCLUDE_WLAN_COMMON_MOVING_AVERAGE_H_
#define GARNET_LIB_WLAN_COMMON_INCLUDE_WLAN_COMMON_MOVING_AVERAGE_H_

#include <limits>
#include <type_traits>

#include <zircon/assert.h>
#include "energy.h"

namespace wlan {
namespace common {

template <typename ValueType, typename SumType, uint32_t N> class MovingAverage {
    static_assert(std::numeric_limits<ValueType>::max() * N < std::numeric_limits<SumType>::max(),
                  "'SumType' too small and cannot hold the maximum sum.");
    static_assert(std::is_arithmetic<ValueType>::value, "'ValueType' must be numeric.");
    static_assert(std::is_arithmetic<SumType>::value, "'SumType' must be numeric.");

   public:
    ValueType avg() const { return (n == 0 ? 0 : sum / n); }

    void add(ValueType item) {
        if (n < N) {
            n++;
        } else {
            sum -= items[i];
        }
        sum += item;
        items[i] = item;
        i = (i + 1) % N;
    }

    void reset() { i = n = sum = 0; }

   private:
    ValueType items[N];
    SumType sum = 0;
    uint32_t i = 0;
    uint32_t n = 0;
};

template <size_t N> class MovingAverageDbm {
    static_assert(N <= 256, "Adding more than 256 samples can cause overflow");

   public:
    FemtoWatt avg() const { return FemtoWatt(n == 0 ? 0 : sum.val / n); }

    void add(dBm sample) {
        if (n < N) {
            n++;
        } else {
            FemtoWatt to_subtract = to_femtoWatt_approx(samples[i]);
            ZX_DEBUG_ASSERT(sum >= to_subtract);
            sum -= to_subtract;
        }
        sum += to_femtoWatt_approx(sample);
        samples[i] = sample;
        i = (i + 1) % N;
    }

    void reset() {
        n = 0;
        sum = FemtoWatt(0);
    }

   private:
    FemtoWatt sum{};
    dBm samples[N];
    uint16_t i = 0;
    uint16_t n = 0;
};

}  // namespace common
}  // namespace wlan

#endif  // GARNET_LIB_WLAN_COMMON_INCLUDE_WLAN_COMMON_MOVING_AVERAGE_H_