/* Copyright 2019 Google LLC. All Rights Reserved. This file and proprietary
   source code may only be used and distributed under the Widevine Master
   License Agreement. */

#include "oemcrypto_nonce_table.h"

#include "stddef.h"

#include "assert_interface.h"

void AddNonce(NonceTable* nonce_table, uint32_t nonce) {
  ASSERT(nonce_table != NULL, "nonce_table is NULL");
  int new_slot = -1;
  int oldest_slot = -1;

  /* Flush any nonce_table->nonces that have been checked but not flushed.
     After flush, nonce_table->nonces will be either valid or invalid. */
  FlushNonces(nonce_table);

  for (int i = 0; i < NONCE_TABLE_SIZE; i++) {
    /* Increase nonce_table->age of all valid nonce_table->nonces. */
    if (nonce_table->state[i] == NT_STATE_VALID) {
      nonce_table->age[i]++;
      if (oldest_slot == -1) {
        oldest_slot = i;
      } else {
        if (nonce_table->age[i] > nonce_table->age[oldest_slot]) {
          oldest_slot = i;
        }
      }
    } else {
      if (new_slot == -1) {
        nonce_table->age[i] = 0;
        nonce_table->nonces[i] = nonce;
        nonce_table->state[i] = NT_STATE_VALID;
        new_slot = i;
      }
    }
  }
  if (new_slot == -1) {
    /* reuse oldest */
    ASSERT(oldest_slot != -1, "oldest_slot is -1");
    int i = oldest_slot;
    nonce_table->age[i] = 0;
    nonce_table->nonces[i] = nonce;
    nonce_table->state[i] = NT_STATE_VALID;
  }
}

bool CheckNonce(NonceTable* nonce_table, uint32_t nonce) {
  ASSERT(nonce_table != NULL, "nonce_table is NULL");
  for (int i = 0; i < NONCE_TABLE_SIZE; i++) {
    if (nonce_table->state[i] != NT_STATE_INVALID) {
      if (nonce_table->nonces[i] == nonce) {
        nonce_table->state[i] = NT_STATE_FLUSH_PENDING;
        return true;
      }
    }
  }
  return false;
}

bool NonceCollision(NonceTable* nonce_table, uint32_t nonce) {
  ASSERT(nonce_table != NULL, "nonce_table is NULL");
  for (int i = 0; i < NONCE_TABLE_SIZE; i++) {
    if (nonce_table->nonces[i] == nonce &&
        nonce_table->state[i] != NT_STATE_INVALID) {
      return true;
    }
  }
  return false;
}

void FlushNonces(NonceTable* nonce_table) {
  ASSERT(nonce_table != NULL, "nonce_table is NULL");
  for (int i = 0; i < NONCE_TABLE_SIZE; i++) {
    if (nonce_table->state[i] == NT_STATE_FLUSH_PENDING) {
      nonce_table->state[i] = NT_STATE_INVALID;
    }
  }
}