/*
 * ecgen, tool for generating Elliptic curve domain parameters
 * Copyright (C) 2017 J08nY
 */
#include "field.h"
#include "poly.h"
#include "random.h"

GEN field_primer(long bits) { return random_prime(bits); }

GEN field_binaryr(long bits) {
	if (poly_exists(bits)) {
		return poly_find_gen(bits);
	} else {
		fprintf(stderr,
		        "Unable to find a suitable binary field. Use an explicit one.");
		exit(1);
	}
}

int field_random(curve_t *curve, config_t *config, ...) {
	switch (config->field) {
		case FIELD_PRIME:
			curve->field = field_primer(config->bits);
			return 1;
		case FIELD_BINARY:
			curve->field = field_binaryr(config->bits);
			return 1;
		default:
			return 0; /* NOT REACHABLE */
	}
}

int field_input(curve_t *curve, config_t *config, ...) {
	return INT_MIN;  // NOT IMPLEMENTED
}

GEN field_params(GEN field) {
	pari_sp ltop = avma;

	if (typ(field) == t_INT) {
		GEN p3 = cgetg(2, t_VEC);
		gel(p3, 1) = gcopy(field);
		return gerepilecopy(ltop, p3);
	}

	GEN out = gtovec0(gen_0, 3);

	long j = 1;
	long l2 = glength(member_mod(field)) - 2;
	{
		pari_sp btop = avma;
		for (long i = 0; i <= l2; ++i) {
			GEN c = polcoeff0(member_mod(field), i, -1);
			if (cmpis(c, 0) != 0) {
				gel(out, j) = stoi(i);
				j++;
			}
			if (gc_needed(btop, 1)) gerepileall(btop, 3, &out, &c);
		}
	}
	return gerepilecopy(ltop, out);
}

GEN field_elementi(GEN element) {
	switch (typ(element)) {
		case t_INT:
			return element;
		case t_INTMOD:
			return lift(element);
		case t_FFELT: {
			pari_sp ltop = avma;
			GEN coeffs = FF_to_FpXQ(element);
			GEN vec = gtovec(coeffs);
			GEN n = fromdigits(vec, stoi(2));
			return gerepilecopy(ltop, n);
		}
		default:
			pari_err_TYPE("field_elementi", element);
			return NULL; /* NOT REACHABLE */
	}
}