/**
 * MIT License
 *
 * Copyright (c) 2019-2021 EOS Sw/eden
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
#ifndef LIBEOSIO_EC_H
#define LIBEOSIO_EC_H

#include <libeosio/hash.hpp>
#include <iostream>
#include <array>

namespace libeosio {

/**
 * Elliptic curve private key size (in bytes)
 */
#define EC_PRIVKEY_SIZE 32

/**
 * Elliptic curve public key size (in bytes)
 *
 * Compressed format: z||x, where byte z specifies which (of the 2) solutions
 * of the quadratic equation y is. Each cordinate is 32 bytes.
 */
#define EC_PUBKEY_SIZE (32 + 1)

/**
 * Elliptic curve priv/pub key datastructures.
 */
typedef std::array<unsigned char, EC_PRIVKEY_SIZE> ec_privkey_t;
typedef std::array<unsigned char, EC_PUBKEY_SIZE> ec_pubkey_t;

/**
 * Elliptic curve keypair (public + private)
 */
struct ec_keypair {
	ec_privkey_t secret;
	ec_pubkey_t pub;
};


/**
 * Elliptic curve recoverable signature
 *
 * The signature consist of 2 integers r,s and v where
 * r: x cordinate of the random point
 * s: signature proof
 * v: recovery id (0, 1, 2 or 3), eg. what EC point is the public key.
 *
 * The memory layout is as follows:
 * r(32), s(32), v(1) = 65 bytes.
 */

/**
 * Elliptic curve signature key size (in bytes)
 */
#define EC_SIGNATURE_SIZE (32 + 32 + 1)

/**
 * Elliptic curve signature datastructure.
 */
typedef std::array<unsigned char, EC_SIGNATURE_SIZE> ec_signature_t;

/**
 * Initialize the ec library.
 */
int ec_init();

/**
 * Generates an new random private key using the secp256k1 curve.
 */
int ec_generate_privkey(ec_privkey_t *priv);

/**
 * Get the public key from an private key.
 */
int ec_get_publickey(const ec_privkey_t *priv, ec_pubkey_t* pub);

/**
 * Generates a keypair using the secp256k1 curve.
 * public key is in compressed format.
 */
int ec_generate_key(struct ec_keypair *pair);


/**
 * Sign
 */

/**
 * Create a ECDSA signature, returns -1 if an error occured or zero on success.
 */
int ecdsa_sign(const ec_privkey_t& key, const sha256_t* digest, ec_signature_t& sig);

/**
 * Verify an ECDSA signature,
 * returns zero if the signature is correct. -1 if the signature is incorrect or an error occured.
 */
int ecdsa_verify(const sha256_t* digest, const ec_signature_t& sig, const ec_pubkey_t& key);

/**
 * Recover the public key from the signature.
 * returns zero if the public key could be extracted. -1 if an error occured.
 */
int ecdsa_recover(const sha256_t* digest, const ec_signature_t& sig, ec_pubkey_t& key);

/**
 * Shutdown the ec library.
 */
void ec_shutdown();

} // namespace libeosio


// Stream operators

std::ostream& operator<<(std::ostream& os, const libeosio::ec_privkey_t& pk);

std::ostream& operator<<(std::ostream& os, const libeosio::ec_pubkey_t& pk);

#endif /* LIBEOSIO_EC_H */