// Copyright (c) Charles J. Cliffe
// SPDX-License-Identifier: GPL-2.0+

#include "ModemUSB.h"

ModemUSB::ModemUSB() : ModemAnalog() {
    // half band filter used for side-band elimination
    //    demodAM_USB = ampmodem_create(0.25, -0.25, LIQUID_AMPMODEM_USB, 1);
#ifdef WIN32
	ssbFilt = firfilt_crcf_create_kaiser(23, 0.25, 90.0, 0.01f);
#else
	ssbFilt = iirfilt_crcf_create_lowpass(6, 0.25);
#endif
	ssbShift = nco_crcf_create(LIQUID_NCO);
    nco_crcf_set_frequency(ssbShift,  (2.0f * M_PI) * 0.25f);
    c2rFilt = firhilbf_create(5, 90.0);
    useSignalOutput(true);
}

ModemBase *ModemUSB::factory() {
    return new ModemUSB;
}

std::string ModemUSB::getName() {
    return "USB";
}

ModemUSB::~ModemUSB() {
#ifdef WIN32
	firfilt_crcf_destroy(ssbFilt);
#else
	iirfilt_crcf_destroy(ssbFilt);
#endif
	nco_crcf_destroy(ssbShift);
    firhilbf_destroy(c2rFilt);
    //    ampmodem_destroy(demodAM_USB);
}

int ModemUSB::checkSampleRate(long long sampleRate, int /* audioSampleRate */) {
    if (sampleRate < MIN_BANDWIDTH) {
        return MIN_BANDWIDTH;
    }
    if (sampleRate % 2 == 0) {
        return sampleRate;
    }
    return sampleRate+1;
}

int ModemUSB::getDefaultSampleRate() {
    return 5400;
}

void ModemUSB::demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut) {
    ModemKitAnalog *akit = (ModemKitAnalog *)kit;
    
    initOutputBuffers(akit,input);
    
    if (!bufSize) {
        input->decRefCount();
        return;
    }
    
    liquid_float_complex x, y;
    for (size_t i = 0; i < bufSize; i++) { // Reject lower band
        nco_crcf_step(ssbShift);
        nco_crcf_mix_down(ssbShift, input->data[i], &x);
#ifdef WIN32
		firfilt_crcf_push(ssbFilt, x);
		firfilt_crcf_execute(ssbFilt, &y);
#else
		iirfilt_crcf_execute(ssbFilt, x, &y);
#endif
		nco_crcf_mix_up(ssbShift, y, &x);
        // Liquid-DSP AMPModem SSB drifts with strong signals near baseband (like a carrier?)
        // ampmodem_demodulate(demodAM_USB, y, &demodOutputData[i]);
        firhilbf_c2r_execute(c2rFilt, x, &demodOutputData[i]);
    }
    
    buildAudioOutput(akit, audioOut, true);
}