/*
WebAssembly Example 5 - WEFAX decoder

Copyright 2019 Ahmet Inan <inan@aicodix.de>
*/

#include "quirks.hh"
#include "atan2.hh"
#include "complex.hh"
#include "const.hh"
#include "ema.hh"
#include "fmd.hh"
#include "phasor.hh"
#include "example.hh"

const int INPUT_MAX = 16384;
float input[INPUT_MAX];

typedef DSP::Complex<float> complex_type;
DSP::EMACascade<complex_type, float, 5> lowpass;
DSP::Phasor<complex_type> phasor;
DSP::FMD1<complex_type> demod;

const int FAX_WIDTH = 1024;
const int FAX_HEIGHT = 1024;
const int FAX_LENGTH = FAX_WIDTH * FAX_HEIGHT;
int pixels[FAX_LENGTH];
float line[FAX_WIDTH];

int sample_rate = 0;
int lines_per_minute = 120;
int samples_per_line = 0;
int current_position = 0;

void _start()
{
	for (int i = 0; i < FAX_LENGTH; ++i)
		pixels[i] = 0xff000000;
}

int gray(float v)
{
	v = min(max(v, 0.f), 1.f);
	v = sqrt(v);
	int V = nearbyint(255.f * v);
	return 0xff000000|(0x00010101*V);
}

void new_line()
{
	for (int j = 0; j < FAX_HEIGHT-1; ++j)
		for (int i = 0; i < FAX_WIDTH; ++i)
			pixels[FAX_WIDTH*j+i] = pixels[FAX_WIDTH*(j+1)+i];
	for (int i = 0; i < FAX_WIDTH; ++i)
		pixels[FAX_WIDTH*(FAX_HEIGHT-1)+i] =
			gray(0.5f + 0.5f * line[i]);
}

void process_input(int samples)
{
	for (int i = 0; i < samples; ++i) {
		int pos = (current_position * FAX_WIDTH) / samples_per_line;
		line[pos] = demod(lowpass(input[i] * phasor()));
		if (++current_position >= samples_per_line) {
			current_position = 0;
			new_line();
		}
	}
}

void commit_changes()
{
	lowpass.cutoff(400, sample_rate);
	phasor.omega(-1900, sample_rate);
	demod.bandwidth(800.f / sample_rate);
	float seconds_per_line = 60.f / lines_per_minute;
	samples_per_line = seconds_per_line * sample_rate;
}

void change_lpm(int lpm)
{
	lines_per_minute = lpm;
	commit_changes();
}

void change_rate(int rate)
{
	sample_rate = rate;
	commit_changes();
}

int input_length()
{
	return INPUT_MAX;
}

float *input_pointer()
{
	return input;
}

int fax_length()
{
	return FAX_LENGTH;
}

int fax_width()
{
	return FAX_WIDTH;
}

int fax_height()
{
	return FAX_HEIGHT;
}

int *fax_pointer()
{
	return pixels;
}