#include "rsa.h"

void bigint_set_random_bytes(bigint_t n) {
	int fd = open("/dev/urandom", O_RDONLY);
	read(fd, n.data, n.len * sizeof(uint32_t));
	close(fd);
}

void bigint_set_msb_and_lsb_to_one(bigint_t n) {
	n.data[0] |= 1;
	n.data[n.len - 1] |= 1 << 31;
}

void bigint_bitwise_right_shift(bigint_t n) {
	size_t size = sizeof(uint32_t) * 8 - 1;
	for (size_t i = 0; i < n.len - 1; i++) {
		n.data[i] = n.data[i] >> 1 | (n.data[i + 1] & 1) << size;
	}
	n.data[n.len - 1] >>= 1;
}

void bigint_bitwise_left_shift(bigint_t n) {
	size_t size = sizeof(uint32_t) * 8 - 1;
	for (int i = n.len - 1; i > 0; i--) {
		n.data[i] = n.data[i] << 1 | ((n.data[i - 1] & (1 << size)) >> size);
	}
	n.data[0] <<= 1;
}

bigint_t assignable_bigint_bitwise_left_shift(bigint_t n) {
	bigint_t result = bigint_clone(n);
	size_t size = sizeof(uint32_t) * 8 - 1;
	for (int i = result.len - 1; i > 0; i--) {
		result.data[i] = result.data[i] << 1 | ((result.data[i - 1] & (1 << size)) >> size);
	}
	result.data[0] <<= 1;
	return result;
}

// Will underflow
void bigint_decrement(bigint_t n) {
	size_t cursor = 0;
	size_t size = sizeof(uint32_t) * 8;
	while (cursor < size * n.len) {
		n.data[cursor / size] = n.data[cursor / size] ^ (1 << (cursor % size));
		if (((n.data[cursor / size] >> (cursor % size)) & 1) == 0) {
			return;
		}
		cursor += 1;
	}
}

// TODO refactor/clean assume same length ?
int bigint_cmp(bigint_t a, bigint_t b) {
	uint32_t size = sizeof(uint32_t) * 8;
	uint32_t acursor = size * a.len - 1;
	uint32_t bcursor = size * b.len - 1;
	printf("cursors a and b %d %d\n", acursor, bcursor);
	while (acursor > bcursor) {
		if (a.data[acursor / size] & (1 << acursor % size)) {
			return 1;
		}
		acursor -= 1;
	}
	while (bcursor > acursor) {
		if (b.data[bcursor / size] & (1 << bcursor % size)) {
			return -1;
		}
		bcursor -= 1;
	}
	int cursor = acursor;
	while (cursor >= 0) {
		uint32_t abit = a.data[cursor / size] & (1 << (cursor % size));
		uint32_t bbit = b.data[cursor / size] & (1 << (cursor % size));
		//printf("cursor %d abit %ud bbit %ud\n", cursor, abit, bbit);
		if (abit > bbit) {
			return 1;
		}
		if (bbit > abit) {
			return -1;
		}
		cursor -= 1;
	}
	return 0;
}

bigint_t assignable_bigint_substraction(bigint_t a, bigint_t b) {
	if (a.len != b.len) {
		printf("error: attempting to substract numbers of different length\n");
		exit(1);
	}

	bigint_t result = bigint_clone(a);
	bigint_t borrow = bigint_clone(b);
	bigint_t y = bigint_clone(b);
	bigint_t zero = bigint_zero(a.len);
	while (bigint_cmp(borrow, zero)) {
		for (size_t i = 0; i < a.len; i++) {
			borrow.data[i] = ~result.data[i] & y.data[i];
			result.data[i] = result.data[i] ^ y.data[i];
		}
		bigint_destroy(y);
		y = assignable_bigint_bitwise_left_shift(borrow);
	}
	bigint_destroy(y);
	bigint_destroy(borrow);
	bigint_destroy(zero);
	return result;
}

void bigint_substraction(bigint_t a, bigint_t b) {
	if (a.len != b.len) {
		printf("error: attempting to substract numbers of different length\n");
		exit(1);
	}

	bigint_t borrow = bigint_clone(b);
	bigint_t y = bigint_clone(b);
	bigint_t zero = bigint_zero(a.len);
	while (bigint_cmp(borrow, zero)) {
		for (size_t i = 0; i < a.len; i++) {
			borrow.data[i] = ~a.data[i] & y.data[i];
			a.data[i] = a.data[i] ^ y.data[i];
		}
		bigint_destroy(y);
		y = assignable_bigint_bitwise_left_shift(borrow);
	}
	bigint_destroy(y);
	bigint_destroy(borrow);
	bigint_destroy(zero);
}

bigint_t assignable_bigint_modulo(bigint_t a, bigint_t b) {
	bigint_t result = bigint_clone(a);
	bigint_t mod = bigint_clone(b);
	printf("a = %ud\nb = %ud\nresult = %ud\nmod = %ud\n", a.data[0], b.data[0], result.data[0], mod.data[0]);	
	if (bigint_cmp(result, b) == -1) {
		bigint_destroy(mod);
		return result;
	}
	bigint_bitwise_left_shift(mod);
	printf("after bitwise_shift\na = %ud\nb = %ud\nresult = %ud\nmod = %ud\n", a.data[0], b.data[0], result.data[0], mod.data[0]);	
	while (bigint_cmp(b, mod) == -1) {
		while (bigint_cmp(result, mod) == 1) {
			bigint_bitwise_left_shift(mod);
	printf("DOUBLE after bitwise_shift\na = %ud\nb = %ud\nresult = %ud\nmod = %ud\n", a.data[0], b.data[0], result.data[0], mod.data[0]);	
		}
		bigint_bitwise_right_shift(mod);
	printf("before sub \na = %ud\nb = %ud\nresult = %ud\nmod = %ud\n", a.data[0], b.data[0], result.data[0], mod.data[0]);	
		if (bigint_cmp(result, mod) == 1) {
		bigint_substraction(result, mod);

	printf("subbed\na = %ud\nb = %ud\nresult = %ud\nmod = %ud\n", a.data[0], b.data[0], result.data[0], mod.data[0]);	
		}
		bigint_bitwise_right_shift(mod);
	}
		while (bigint_cmp(result, b) == 1) {
		bigint_substraction(result, b);

	printf("subbed\na = %ud\nb = %ud\nresult = %ud\nmod = %ud\n", a.data[0], b.data[0], result.data[0], mod.data[0]);	
		}
	return result;
}

void bigint_print(bigint_t n) {
	for (int i = n.len - 1; i >= 0; i--) {
		printf("bigint %ud\n", n.data[i]);
	}
}

bigint_t bigint_clone(bigint_t src) {
	bigint_t dst;

	dst.len = src.len;
	dst.data = (uint32_t *)protected_malloc(src.len * sizeof(uint32_t));
	memcpy(dst.data, src.data, src.len * sizeof(uint32_t));

	return dst;
}

bigint_t bigint_prime(size_t len) {
	bigint_t n = bigint_new(len);

	printf("new\n");
	bigint_print(n);
	bigint_set_random_bytes(n);
	printf("random bytes\n");
	bigint_print(n);
	bigint_set_msb_and_lsb_to_one(n);
	printf("msb and lsb set to tone\n");
	bigint_print(n);

	bigint_t d = bigint_clone(n);
	d.data[0] -= 1;
	uint32_t s = 0;
	while (!d.data[0] & 1) {
		bigint_bitwise_right_shift(d);
		s += 1;
	}

	bigint_t two = bigint_zero(len);
	two.data[0] = 2;
	bigint_t n_minus_two = bigint_clone(d);
	bigint_decrement(n_minus_two);

	for (uint32_t k = 0; k < 128; k++) {
		bigint_t a = bigint_zero(len);
		while (bigint_cmp(a, two) == -1 || bigint_cmp(a, n_minus_two) == 1) {
			printf("this is good %d\n", k);
			bigint_set_random_bytes(a);
		}
		bigint_destroy(a);
	}
	return n;
}

bigint_t bigint_new(size_t len) {
	bigint_t bigint;

	bigint.len = len;
	bigint.data = (uint32_t *)protected_malloc(len * sizeof(uint32_t));

	return bigint;
}

bigint_t bigint_zero(size_t len) {
	bigint_t bigint;

	bigint = bigint_new(len);
	for (size_t i = 0; i < len; i++) {
		bigint.data[i] = 0;
	}

	return bigint;
}

void bigint_destroy(bigint_t n) {
	free(n.data);
	n.data = NULL;
}