#include "erl_nif.h"

#include <sodium.h>

/* Errors */
static
ERL_NIF_TERM nacl_error_tuple(ErlNifEnv *env, char *error_atom) {
	return enif_make_tuple2(env, enif_make_atom(env, "error"), enif_make_atom(env, error_atom));
}

/* Helper functions (Hashing, String Equality, ...) */

static
ERL_NIF_TERM enif_crypto_hash(ErlNifEnv *env, int argc, ERL_NIF_TERM const argv[]) {
	ErlNifBinary input;
	ErlNifBinary result;
	
	if ((argc != 1) || (!enif_inspect_iolist_as_binary(env, argv[0], &input))) {
		return enif_make_badarg(env);
	}
	
	if (!enif_alloc_binary(crypto_hash_BYTES, &result)) {
		return nacl_error_tuple(env, "alloc_failed");
	}
	
	crypto_hash(result.data, input.data, input.size);
	
	return enif_make_binary(env, &result);
}

/* Public-key cryptography */
static
ERL_NIF_TERM enif_crypto_box_NONCEBYTES(ErlNifEnv *env, int argc, ERL_NIF_TERM const argv[]) {
	return enif_make_int64(env, crypto_box_NONCEBYTES);
}

static
ERL_NIF_TERM enif_crypto_box_ZEROBYTES(ErlNifEnv *env, int argc, ERL_NIF_TERM const argv[]) {
	return enif_make_int64(env, crypto_box_ZEROBYTES);
}

static
ERL_NIF_TERM enif_crypto_box_BOXZEROBYTES(ErlNifEnv *env, int argc, ERL_NIF_TERM const argv[]) {
	return enif_make_int64(env, crypto_box_BOXZEROBYTES);
}

static
ERL_NIF_TERM enif_crypto_box_keypair(ErlNifEnv *env, int argc, ERL_NIF_TERM const argv[]) {
	ErlNifBinary pk, sk;
	
	if (argc != 0) {
		return enif_make_badarg(env);
	}
	
	if (!enif_alloc_binary(crypto_box_PUBLICKEYBYTES, &pk)) {
		return nacl_error_tuple(env, "alloc_failed");
	}
	
	if (!enif_alloc_binary(crypto_box_SECRETKEYBYTES, &sk)) {
		return nacl_error_tuple(env, "alloc_failed");
	}
	
	crypto_box_keypair(pk.data, sk.data);
	
	return enif_make_tuple3(env, enif_make_atom(env, "ok"), enif_make_binary(env, &pk), enif_make_binary(env, &sk));
}

static
ERL_NIF_TERM enif_crypto_box(ErlNifEnv *env, int argc, ERL_NIF_TERM const argv[]) {
	ErlNifBinary padded_msg, nonce, pk, sk, result;
	
	if (
	  (argc != 4) ||
	  (!enif_inspect_iolist_as_binary(env, argv[0], &padded_msg)) ||
	  (!enif_inspect_iolist_as_binary(env, argv[1], &nonce)) ||
	  (!enif_inspect_iolist_as_binary(env, argv[2], &pk)) ||
	  (!enif_inspect_iolist_as_binary(env, argv[3], &sk))) {
	  	return enif_make_badarg(env);
	}
	
	if (
	    (nonce.size != crypto_box_NONCEBYTES) ||
	    (pk.size != crypto_box_PUBLICKEYBYTES) ||
	    (sk.size != crypto_box_SECRETKEYBYTES) ||
	    (padded_msg.size < crypto_box_ZEROBYTES)) {
		return enif_make_badarg(env);
	}
	
	if (!enif_alloc_binary(padded_msg.size, &result)) {
		return nacl_error_tuple(env, "alloc_failed");
	}
	
	crypto_box(result.data, padded_msg.data, padded_msg.size, nonce.data, pk.data, sk.data);
	
	return enif_make_sub_binary(
		env,
		enif_make_binary(env, &result),
		crypto_box_BOXZEROBYTES,
		padded_msg.size - crypto_box_BOXZEROBYTES);
}

static
ERL_NIF_TERM enif_crypto_box_open(ErlNifEnv *env, int argc, ERL_NIF_TERM const argv[]) {
	ErlNifBinary padded_ciphertext, nonce, pk, sk, result;
	
	if (
	  (argc != 4) ||
	  (!enif_inspect_iolist_as_binary(env, argv[0], &padded_ciphertext)) ||
	  (!enif_inspect_iolist_as_binary(env, argv[1], &nonce)) ||
	  (!enif_inspect_iolist_as_binary(env, argv[2], &pk)) ||
	  (!enif_inspect_iolist_as_binary(env, argv[3], &sk))) {
		return enif_make_badarg(env);
	}
	
	if (
	  (nonce.size != crypto_box_NONCEBYTES) ||
	  (pk.size != crypto_box_PUBLICKEYBYTES) ||
	  (sk.size != crypto_box_SECRETKEYBYTES) ||
	  (padded_ciphertext.size < crypto_box_BOXZEROBYTES)) {
		return enif_make_badarg(env);
	}
	
	if (!enif_alloc_binary(padded_ciphertext.size, &result)) {
		return nacl_error_tuple(env, "alloc_failed");
	}
	
	if (crypto_box_open(result.data, padded_ciphertext.data, padded_ciphertext.size, nonce.data, pk.data, sk.data)) {
		return nacl_error_tuple(env, "failed_verification");
	}
	
	return enif_make_sub_binary(
		env,
		enif_make_binary(env, &result),
		crypto_box_ZEROBYTES,
		padded_ciphertext.size - crypto_box_ZEROBYTES);
}

/* Tie the knot to the Erlang world */
static ErlNifFunc nif_funcs[] = {
	{"crypto_box_NONCEBYTES", 0, enif_crypto_box_NONCEBYTES},
	{"crypto_box_ZEROBYTES", 0, enif_crypto_box_ZEROBYTES},
	{"crypto_box_BOXZEROBYTES", 0, enif_crypto_box_BOXZEROBYTES},
	{"crypto_box_keypair", 0, enif_crypto_box_keypair},
	{"crypto_box", 4, enif_crypto_box, ERL_NIF_DIRTY_JOB_CPU_BOUND},
	{"crypto_box_open", 4, enif_crypto_box_open, ERL_NIF_DIRTY_JOB_CPU_BOUND},
	{"crypto_hash", 1, enif_crypto_hash, ERL_NIF_DIRTY_JOB_CPU_BOUND}
};

ERL_NIF_INIT(enacl_nif, nif_funcs, NULL, NULL, NULL, NULL);