/* See LICENSE file for copyright and license details. */
#include <libsimple.h>
#include <libsimple-arg.h>

USAGE("[rows columns] [checksum]");

#define BITS 2


int
main(int argc, char *argv[])
{
#if BITS == 5
	static const ssize_t x_movements[1 << BITS] = {
		-3, -2, -1, +1, +2, +3,
		-3, -2, -1, +1, +2, +3,
		-3, -2,         +2, +3,
		-3, -2,         +2, +3,
		-3, -2, -1, +1, +2, +3,
		-3, -2, -1, +1, +2, +3,
	};
	static const ssize_t y_movements[1 << BITS] = {
		-3, -3, -3, -3, -3, -3,
		-2, -2, -2, -2, -2, -2,
		-1, -1,         -1, -1,
		+1, +1,         +1, +1,
		+2, +2, +2, +2, +2, +2,
		+3, +3, +3, +3, +3, +3,
	};
#elif BITS == 4
	static const ssize_t x_movements[1 << BITS] = {
		-2, -1, 0, 0, +1, +2,
		-2, -1,       +1, +2,
		-2, -1, 0, 0, +1, +2
	};
	static const ssize_t y_movements[1 << BITS] = {
		-2, -1, -2, -1, -2, -1,
		 0,  0,          0,  0,
		+1, +2, +1, +2, +1, +2
	};
#elif BITS == 3
	static const ssize_t x_movements[1 << BITS] = {
		-1, 0, +1,
		-1,    +1,
		-1, 0, +1
	};
	static const ssize_t y_movements[1 << BITS] = {
		-1, -1, -1,
		 0,      0,
		+1, +1, +1
	};
#elif BITS == 2
# if 0
	static const ssize_t x_movements[1 << BITS] = {
		-1, +1,
		-1, +1
	};
	static const ssize_t y_movements[1 << BITS] = {
		-1, -1,
		+1, +1
	};
# else
	static const ssize_t x_movements[1 << BITS] = {
		 0, -1,
		+1,  0
	};
	static const ssize_t y_movements[1 << BITS] = {
		-1,  0,
		 0, +1
	};
# endif
#endif

	static const char *const symbols[] = {
		":", ".", "+", "=",
		"¤", "o", "*", "£",
		"X", "%", "&", "B",
		"@", "#", "/", "^"
	};
	static const char *const colours[] = {
		"", "34;1", "33;1"
	};

	const char *checksum;
	char *data = NULL, *end;
	size_t size = 0u;
	size_t len = 0u, cell;
	size_t i, n, x[2], y[2], v, bits;
	int d, colour;
	ssize_t r;
	size_t rows = 15u, cols = 32u;
	unsigned char *art;

	ARGBEGIN {
	default:
		usage();
	} ARGEND;

	if (argc > 1) {
		if ('1' > argv[0][0u] || argv[0][0u] > '9' ||
		    '1' > argv[1][0u] || argv[1][0u] > '9')
			usage();

		errno = 0;
		rows = strtouz(argv[0], &end, 10);
		if (!rows || *end || errno)
			usage();
		cols = strtouz(argv[1], &end, 10);
		if (!cols || *end || errno)
			usage();

		argc -= 2;
		argv += 2;
	}

	if (argc > 1)
		usage();

	if (argc) {
		checksum = *argv;
	} else {
		for (;;) {
			if (len == size)
				data = erealloc(data, size += 128u);
			r = read(STDIN_FILENO, &data[len], size - len);
			if (r <= 0) {
				if (!r)
					break;
				if (errno == EINVAL)
					continue;
				eprintf("read <stdin>:");
			}
			n = len + (size_t)r;
			for (i = len; i < n; i++) {
				if (('0' <= data[i] && data[i] <= '9') ||
				    ('A' <= data[i] && data[i] <= 'F') ||
				    ('a' <= data[i] && data[i] <= 'f'))
					data[len++] = data[i];
			}
		}
		data = erealloc(data, len + 1u);
		data[len] = '\0';
		checksum = data;
	}

	art = ecalloc(rows, cols);

	x[0] = x[1] = cols / 2u;
	y[0] = y[1] = rows / 2u;

	colour = 0;
	v = 0u;
	bits = 0u;
	for (i = 0u; checksum[i]; i++) {
		if (('0' > checksum[i] || checksum[i] > '9') &&
		    ('A' > checksum[i] || checksum[i] > 'F') &&
		    ('a' > checksum[i] || checksum[i] > 'f'))
			continue;
		d = ((int)checksum[i] & 15) + (checksum[i] > '9' ? 9 : 0);
		v <<= 4;
		v |= (size_t)d;
		bits += 4u;
		while (bits >= BITS) {
			x[colour] += (size_t)x_movements[v % ELEMSOF(x_movements)];
			y[colour] += (size_t)y_movements[v % ELEMSOF(y_movements)];
			x[colour] %= cols;
			y[colour] %= rows;
			cell = y[colour] * cols + x[colour];
			art[cell] = (unsigned char)(art[cell] + (colour ? 0x20u : 1u));
			art[cell] &= 0xEFu;
			v >>= BITS;
			bits -= BITS;
			if (ELEMSOF(colours) > 1u)
				colour ^= 1;
		}
	}
	if (bits) {
		x[colour] += (size_t)x_movements[v % ELEMSOF(x_movements)];
		y[colour] += (size_t)y_movements[v % ELEMSOF(y_movements)];
		x[colour] %= cols;
		y[colour] %= rows;
		cell = y[colour] * cols + x[colour];
		art[cell] = (unsigned char)(art[cell] + (colour ? 0x20u : 1u));
		art[cell] &= 0xEFu;
	}

	printf("+");
	for (i = 0u; i < cols; i++)
		printf("-");
	printf("+\n");
	for (*y = 0u; *y < rows; ++*y) {
		printf("|");
		for (*x = 0u; *x < cols; ++*x) {
			cell = *y * cols + *x;
			if (!art[cell]) {
				printf(" ");
				continue;
			}
			printf("\033[%sm%s\033[m",
			       colours[(art[cell] / 0x20u) % ELEMSOF(colours)],
			       symbols[(art[cell] & 0x0Fu) % ELEMSOF(symbols)]);
		}
		printf("|\n");
	}
	printf("+");
	for (i = 0u; i < cols; i++)
		printf("-");
	printf("+\n");

	if (ferror(stdout) || fclose(stdout))
		eprintf("printf:");
	free(art);
	free(data);
	return 0;
}