/*
   This file is part of GNUnet.
   Copyright (C) 2020--2025 GNUnet e.V.

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

   GNUnet 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
   Affero General Public License for more details.

   You should have received a copy of the GNU Affero General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.

   SPDX-License-Identifier: AGPL3.0-or-later
 */
/**
 * @author Tobias Frisch
 * @file src/messenger/messenger_api_contact.h
 * @brief messenger api: client implementation of GNUnet MESSENGER service
 */

#ifndef GNUNET_MESSENGER_API_CONTACT_H
#define GNUNET_MESSENGER_API_CONTACT_H

#include "gnunet_common.h"
#include "gnunet_util_lib.h"

struct GNUNET_MESSENGER_Contact
{
  char *name;
  size_t rc;
  size_t id;

  struct GNUNET_CRYPTO_BlindablePublicKey public_key;
  struct GNUNET_CONTAINER_MultiHashMap *encryption_keys;
};

/**
 * Creates and allocates a new contact with a given public <i>key</i>.
 *
 * @param[in] key Public key
 * @param[in] unique_id Locally unique identifier
 * @return New contact
 */
struct GNUNET_MESSENGER_Contact*
create_contact (const struct GNUNET_CRYPTO_BlindablePublicKey *key,
                size_t unique_id);

/**
 * Destroys a contact and frees its memory fully.
 *
 * @param[in,out] contact Contact
 */
void
destroy_contact (struct GNUNET_MESSENGER_Contact *contact);

/**
 * Returns the current name of a given <i>contact</i> or NULL if no valid name was assigned yet.
 *
 * @param[in] contact Contact
 * @return Name of the contact or NULL
 */
const char*
get_contact_name (const struct GNUNET_MESSENGER_Contact *contact);

/**
 * Changes the current name of a given <i>contact</i> by copying it from the parameter <i>name</i>.
 *
 * @param[in,out] contact Contact
 * @param[in] name Name
 */
void
set_contact_name (struct GNUNET_MESSENGER_Contact *contact,
                  const char *name);

/**
 * Returns the blindable public key of a given <i>contact</i>.
 *
 * @param[in] contact Contact
 * @return Public key of the contact
 */
const struct GNUNET_CRYPTO_BlindablePublicKey*
get_contact_key (const struct GNUNET_MESSENGER_Contact *contact);

/**
 * Returns the HPKE public key of a given <i>contact</i> for
 * a specific room that is identified via its own room <i>key</i>.
 *
 * @param[in] contact Contact
 * @param[in] key Room key
 * @return Public key of the contact for encrypted messages
 */
const struct GNUNET_CRYPTO_HpkePublicKey*
get_contact_encryption_key (const struct GNUNET_MESSENGER_Contact *contact,
                            const struct GNUNET_HashCode *key);

/**
 * Sets or replaces the <i>encryption_key</i> of a given <i>contact</i> for a
 * specified room that is identified via its own room <i>key</i>.
 *
 * @param[in,out] contact Contact
 * @param[in] key Room key
 * @param[in] encryption_key Public key of the contact for encrypted messages
 */
void
set_contact_encryption_key (struct GNUNET_MESSENGER_Contact *contact,
                            const struct GNUNET_HashCode *key,
                            const struct GNUNET_CRYPTO_HpkePublicKey *
                            encryption_key);

/**
 * Increases the reference counter of a given <i>contact</i> which is zero as default.
 *
 * @param[in,out] contact Contact
 */
void
increase_contact_rc (struct GNUNET_MESSENGER_Contact *contact);

/**
 * Decreases the reference counter if possible (can not underflow!) of a given <i>contact</i>
 * and returns #GNUNET_YES if the counter is equal to zero, otherwise #GNUNET_NO.
 *
 * @param[in,out] contact Contact
 * @return #GNUNET_YES or #GNUNET_NO depending on the reference counter
 */
enum GNUNET_GenericReturnValue
decrease_contact_rc (struct GNUNET_MESSENGER_Contact *contact);

/**
 * Returns the locally unique identifier of a given <i>contact</i>.
 *
 * @param[in] contact contact Contact
 * @return Locally unique identifier of contact
 */
size_t
get_contact_id (const struct GNUNET_MESSENGER_Contact *contact);

/**
 * Calculates the context <i>hash</i> of a member in a room and returns it.
 *
 * @param[in] key Key of room
 * @param[in] id Member id
 * @param[out] context Member context
 */
void
get_context_from_member (const struct GNUNET_HashCode *key,
                         const struct GNUNET_ShortHashCode *id,
                         struct GNUNET_HashCode *context);

#endif // GNUNET_MESSENGER_API_CONTACT_H
