#include "curve25519.h"

#include <sodium.h>

#include <stddef.h>
#include <stdlib.h>

void init() {
	if(sodium_init() == -1) {
		exit(-1);
	}
}

void curve25519_keypair_deleter(struct KeyPair p) {
	sodium_free(p.sec);
	free(p.pub);

	p.sec = NULL;
	p.pub = NULL;
}

struct KeyPair curve25519_create_keypair() {
	init();

	unsigned char* sec = (unsigned char*) sodium_malloc(crypto_box_SECRETKEYBYTES);
	unsigned char* pub = (unsigned char*) malloc(crypto_box_PUBLICKEYBYTES);

	randombytes_buf(sec, crypto_box_SECRETKEYBYTES);
	crypto_scalarmult_base(pub, sec);

	return (struct KeyPair){
		sec,
		pub,
		crypto_box_SECRETKEYBYTES,
		crypto_box_PUBLICKEYBYTES
	};
}

void curve25519_shared_key_deleter(struct SharedKey s) {
	sodium_free(s.shared);

	s.shared = NULL;
}

struct SharedKey curve25519_derive_shared_key(struct KeyPair pair, unsigned char const* pub_key, bool swap_pub_order) {
	init();

	unsigned char* shared = (unsigned char*) sodium_malloc(crypto_generichash_BYTES);

	crypto_generichash_state h;

	unsigned char* scalarmult_q = (unsigned char*) sodium_malloc(crypto_scalarmult_BYTES);

	if (crypto_scalarmult(scalarmult_q, pair.sec, pub_key) != 0) {
		exit(-1);
	}

	crypto_generichash_init(&h, NULL, 0U, crypto_generichash_BYTES);
	crypto_generichash_update(&h, scalarmult_q, crypto_scalarmult_BYTES);
	if(swap_pub_order) {
		crypto_generichash_update(&h, pub_key, crypto_box_PUBLICKEYBYTES);
		crypto_generichash_update(&h, pair.pub, crypto_box_PUBLICKEYBYTES);
	} else {
		crypto_generichash_update(&h, pair.pub, crypto_box_PUBLICKEYBYTES);
		crypto_generichash_update(&h, pub_key, crypto_box_PUBLICKEYBYTES);
	}
	crypto_generichash_final(&h, shared, crypto_generichash_BYTES);

	sodium_free(scalarmult_q);

	return (struct SharedKey){
		shared,
		crypto_generichash_BYTES
	};
}