#include <math.h>
#include "libleds.h"
#include "img_mono.xbm"

static char const PORT = 0;
static char const PINS = 1<<7;

char const is_active(unsigned int const n)
{
	/*
	 * The first led is in the top left corner.
	 * After that it goes down the column, then up the next and so on.
	 *
	 * This means all columns with an even index count down.
	 * Those with an odd index count up.
	 *
	 *
	 * With a height of 8 the led numbers would look like this:
	 *
	 * 00  0F  10  1F  20  ...
	 * 01  0E  11  1E  21  ...
	 * 02  0D  12  1D  ...
	 * 03  0C  13  1C  ...
	 * 04  0B  14  1B  ...
	 * 05  0A  15  1A  ...
	 * 06  09  16  19  ...
	 * 07  08  17  18  ...
	 */

	unsigned int const bytes_per_row = ceil(img_width / 8.0);
	unsigned int col = n / img_height;
	unsigned int row = n % img_height;
	if (col % 2)
		row = img_height - 1 - row;
	
	// calculate byte to access
	unsigned int byte = row * bytes_per_row;
	byte += col / 8;

	unsigned char data = img_bits[byte];
	unsigned char mask = 1<<(col % 8);
	return data & mask;
}

void led_main()
{
	const int length = img_width * img_height;

	struct led_color pixel[length];

	for (unsigned int i = 0; i < length; i++) {
		unsigned char out = is_active(i) ? 0xFF : 0x00;
		pixel[i] = (struct led_color){out, out, out};
	}

	for (unsigned int i = 0; i < length; i++)
		led_write_rgb(PORT, PINS, pixel[i]);
}