/*
 *
 * Copyright 2018 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

#ifndef GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_COUNTER_H
#define GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_COUNTER_H

#include <grpc/support/port_platform.h>

#include <stdbool.h>
#include <stdlib.h>

#include <grpc/grpc.h>

/* Main struct for a crypter counter managed within seal/unseal operations. */
typedef struct alts_counter {
  size_t size;
  size_t overflow_size;
  unsigned char* counter;
} alts_counter;

/**
 * This method creates and initializes an alts_counter instance.
 *
 * - is_client: a flag indicating if the alts_counter instance will be used
 *   at client (is_client = true) or server (is_client = false) side.
 * - counter_size: size of buffer holding the counter value.
 * - overflow_size: overflow size in bytes. The counter instance can be used
 *   to produce at most 2^(overflow_size*8) frames.
 * - crypter_counter: an alts_counter instance to be returned from the method.
 * - error_details: a buffer containing an error message if the method does not
 *   function correctly. It is legal to pass nullptr into error_details and
 *   otherwise, the parameter should be freed with gpr_free.
 *
 * On success, the method returns GRPC_STATUS_OK. Otherwise,
 * it returns an error status code along with its details specified in
 * error_details (if error_details is not nullptr).
 */
grpc_status_code alts_counter_create(bool is_client, size_t counter_size,
                                     size_t overflow_size,
                                     alts_counter** crypter_counter,
                                     char** error_details);

/**
 * This method increments the internal counter.
 *
 * - crypter_counter: an alts_counter instance.
 * - is_overflow: after incrementing the internal counter, if an overflow
 *   occurs, is_overflow is set to true, and no further calls to
 *   alts_counter_increment() should be made. Otherwise, is_overflow is set to
 *   false.
 * - error_details: a buffer containing an error message if the method does not
 *   function correctly. It is legal to pass nullptr into error_details and
 *   otherwise, the parameter should be freed with gpr_free.
 *
 * On success, the method returns GRPC_STATUS_OK. Otherwise,
 * it returns an error status code along with its details specified in
 * error_details (if error_details is not nullptr).
 */
grpc_status_code alts_counter_increment(alts_counter* crypter_counter,
                                        bool* is_overflow,
                                        char** error_details);

/**
 * This method returns the size of counter buffer.
 *
 * - crypter_counter: an alts_counter instance.
 */
size_t alts_counter_get_size(alts_counter* crypter_counter);

/**
 * This method returns the counter buffer.
 *
 * - crypter_counter: an alts_counter instance.
 */
unsigned char* alts_counter_get_counter(alts_counter* crypter_counter);

/**
 * This method de-allocates all memory allocated to an alts_coutner instance.
 * - crypter_counter: an alts_counter instance.
 */
void alts_counter_destroy(alts_counter* crypter_counter);

#endif /* GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_COUNTER_H */