/*
	This file is part of cpp-ethereum.

	cpp-ethereum is free software: you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	cpp-ethereum is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
*/
/** @file Common.h
 * @author Alex Leverington <nessence@gmail.com>
 * @author Gav Wood <i@gavwood.com>
 * @date 2014
 *
 * Ethereum-specific data structures & algorithms.
 */

#pragma once

#include <mutex>
#include <libdevcore/Common.h>
#include <libdevcore/FixedHash.h>
#include <libdevcore/Exceptions.h>

namespace dev
{

/// A secret key: 32 bytes.
/// @NOTE This is not endian-specific; it's just a bunch of bytes.
using Secret = h256;

/// A public key: 64 bytes.
/// @NOTE This is not endian-specific; it's just a bunch of bytes.
using Public = h512;

/// A signature: 65 bytes: r: [0, 32), s: [32, 64), v: 64.
/// @NOTE This is not endian-specific; it's just a bunch of bytes.
using Signature = h520;

struct SignatureStruct
{
	SignatureStruct() = default;
	SignatureStruct(Signature const& _s) { *(h520*)this = _s; }
	SignatureStruct(h256 const& _r, h256 const& _s, byte _v): r(_r), s(_s), v(_v) {}
	operator Signature() const { return *(h520 const*)this; }

	/// @returns true if r,s,v values are valid, otherwise false
	bool isValid() const noexcept;

	/// @returns the public part of the key that signed @a _hash to give this sig.
	Public recover(h256 const& _hash) const;

	h256 r;
	h256 s;
	byte v = 0;
};

/// An Ethereum address: 20 bytes.
/// @NOTE This is not endian-specific; it's just a bunch of bytes.
using Address = h160;

/// The zero address.
extern Address ZeroAddress;

/// A vector of Ethereum addresses.
using Addresses = h160s;

/// A hash set of Ethereum addresses.
using AddressHash = std::unordered_set<h160>;

/// A vector of secrets.
using Secrets = h256s;

/// Convert a secret key into the public key equivalent.
Public toPublic(Secret const& _secret);

/// Convert a public key to address.
Address toAddress(Public const& _public);

/// Convert a secret key into address of public key equivalent.
/// @returns 0 if it's not a valid secret key.
Address toAddress(Secret const& _secret);

// Convert transaction from and nonce to address.
Address toAddress(Address const& _from, u256 const& _nonce);

/// Encrypts plain text using Public key.
void encrypt(Public const& _k, bytesConstRef _plain, bytes& o_cipher);

/// Decrypts cipher using Secret key.
bool decrypt(Secret const& _k, bytesConstRef _cipher, bytes& o_plaintext);

/// Symmetric encryption.
void encryptSym(Secret const& _k, bytesConstRef _plain, bytes& o_cipher);

/// Symmetric decryption.
bool decryptSym(Secret const& _k, bytesConstRef _cipher, bytes& o_plaintext);

/// Encrypt payload using ECIES standard with AES128-CTR.
void encryptECIES(Public const& _k, bytesConstRef _plain, bytes& o_cipher);

/// Decrypt payload using ECIES standard with AES128-CTR.
bool decryptECIES(Secret const& _k, bytesConstRef _cipher, bytes& o_plaintext);

/// Encrypts payload with random IV/ctr using AES128-CTR.
std::pair<bytes, h128> encryptSymNoAuth(h128 const& _k, bytesConstRef _plain);

/// Encrypts payload with specified IV/ctr using AES128-CTR.
bytes encryptAES128CTR(bytesConstRef _k, h128 const& _iv, bytesConstRef _plain);

/// Decrypts payload with specified IV/ctr using AES128-CTR.
bytes decryptAES128CTR(bytesConstRef _k, h128 const& _iv, bytesConstRef _cipher);

/// Encrypts payload with specified IV/ctr using AES128-CTR.
inline bytes encryptSymNoAuth(h128 const& _k, h128 const& _iv, bytesConstRef _plain) { return encryptAES128CTR(_k.ref(), _iv, _plain); }
inline bytes encryptSymNoAuth(h256 const& _k, h128 const& _iv, bytesConstRef _plain) { return encryptAES128CTR(_k.ref(), _iv, _plain); }

/// Decrypts payload with specified IV/ctr using AES128-CTR.
inline bytes decryptSymNoAuth(h128 const& _k, h128 const& _iv, bytesConstRef _cipher) { return decryptAES128CTR(_k.ref(), _iv, _cipher); }
inline bytes decryptSymNoAuth(h256 const& _k, h128 const& _iv, bytesConstRef _cipher) { return decryptAES128CTR(_k.ref(), _iv, _cipher); }

/// Recovers Public key from signed message hash.
Public recover(Signature const& _sig, h256 const& _hash);
	
/// Returns siganture of message hash.
Signature sign(Secret const& _k, h256 const& _hash);
	
/// Verify signature.
bool verify(Public const& _k, Signature const& _s, h256 const& _hash);

/// Derive key via PBKDF2.
bytes pbkdf2(std::string const& _pass, bytes const& _salt, unsigned _iterations, unsigned _dkLen = 32);

/// Derive key via Scrypt.
bytes scrypt(std::string const& _pass, bytes const& _salt, uint64_t _n, uint32_t _r, uint32_t _p, unsigned _dkLen);

/// Simple class that represents a "key pair".
/// All of the data of the class can be regenerated from the secret key (m_secret) alone.
/// Actually stores a tuplet of secret, public and address (the right 160-bits of the public).
class KeyPair
{
public:
	/// Null constructor.
	KeyPair() {}

	/// Normal constructor - populates object from the given secret key.
	KeyPair(Secret _k);

	/// Create a new, randomly generated object.
	static KeyPair create();

	/// Create from an encrypted seed.
	static KeyPair fromEncryptedSeed(bytesConstRef _seed, std::string const& _password);

	/// Retrieve the secret key.
	Secret const& secret() const { return m_secret; }
	/// Retrieve the secret key.
	Secret const& sec() const { return m_secret; }

	/// Retrieve the public key.
	Public const& pub() const { return m_public; }

	/// Retrieve the associated address of the public key.
	Address const& address() const { return m_address; }

	bool operator==(KeyPair const& _c) const { return m_secret == _c.m_secret; }
	bool operator!=(KeyPair const& _c) const { return m_secret != _c.m_secret; }

private:
	Secret m_secret;
	Public m_public;
	Address m_address;
};

namespace crypto
{
struct InvalidState: public dev::Exception {};

/// Key derivation
h256 kdf(Secret const& _priv, h256 const& _hash);

/**
 * @brief Generator for nonce material.
 */
struct Nonce
{
	/// Returns the next nonce (might be read from a file).
	static h256 get();
	/// Stores the current nonce in a file and resets Nonce to the uninitialised state.
	static void reset();
	/// Sets the location of the seed file to a non-default place. Used for testing.
	static void setSeedFilePath(std::string const& _filePath);

private:
	Nonce() {}
	~Nonce();
	/// @returns the singleton instance.
	static Nonce& singleton();
	/// Reads the last seed from the seed file.
	void initialiseIfNeeded();
	/// @returns the next nonce.
	h256 next();
	/// Stores the current seed in the seed file.
	void resetInternal();
	/// @returns the path of the seed file.
	static std::string const& seedFile();

	/// Mutex for the singleton object.
	/// @note Every access to any private function has to be guarded by this mutex.
	static std::mutex s_x;

	h256 m_value;
};
}

}