//
// Copyright 2010-2012,2014 Ettus Research LLC
// Copyright 2018 Ettus Research, a National Instruments Company
//
// SPDX-License-Identifier: GPL-3.0-or-later
//

#include <cmath>
#include <complex>
#include <stdexcept>
#include <string>
#include <vector>

static const size_t wave_table_len = 8192;

class wave_table_class
{
public:
    wave_table_class(const std::string& wave_type, const float ampl)
        : _wave_table(wave_table_len)
    {
        // compute real wave table with 1.0 amplitude
        std::vector<float> real_wave_table(wave_table_len);
        if (wave_type == "CONST") {
            for (size_t i = 0; i < wave_table_len; i++)
                real_wave_table[i] = 1.0;
        } else if (wave_type == "SQUARE") {
            for (size_t i = 0; i < wave_table_len; i++)
                real_wave_table[i] = (i < wave_table_len / 2) ? 0.0 : 1.0;
        } else if (wave_type == "RAMP") {
            for (size_t i = 0; i < wave_table_len; i++)
                real_wave_table[i] = 2.0 * i / (wave_table_len - 1) - 1.0;
        } else if (wave_type == "SINE") {
            static const double tau = 2 * std::acos(-1.0);
            for (size_t i = 0; i < wave_table_len; i++)
                real_wave_table[i] = std::sin((tau * i) / wave_table_len);
        } else
            throw std::runtime_error("unknown waveform type: " + wave_type);

        // compute i and q pairs with 90% offset and scale to amplitude
        for (size_t i = 0; i < wave_table_len; i++) {
            const size_t q = (i + (3 * wave_table_len) / 4) % wave_table_len;
            _wave_table[i] =
                std::complex<float>(ampl * real_wave_table[i], ampl * real_wave_table[q]);
        }
    }

    inline std::complex<float> operator()(const size_t index) const
    {
        return _wave_table[index % wave_table_len];
    }

private:
    std::vector<std::complex<float>> _wave_table;
};
