list_extend.c -- step 3 :: ListExtendFilter_RedisCommand

list_extend.c

int ListExtendFilter_RedisCommand(RedisModuleCtx *ctx, RedisModuleString **argv,
                                  int argc) {

  // LIST_EXTEND.FILTER source_list destination_list low_value high_value
  if (argc != 5) {
    return RedisModule_WrongArity(ctx);
  }
  RedisModule_AutoMemory(ctx);

  // Open field/value list keys
  RedisModuleKey *sourceListKey =
      RedisModule_OpenKey(ctx, argv[1], REDISMODULE_READ | REDISMODULE_WRITE);
  int sourceListKeyType = RedisModule_KeyType(sourceListKey);

  if (sourceListKeyType != REDISMODULE_KEYTYPE_LIST &&
      sourceListKeyType != REDISMODULE_KEYTYPE_EMPTY) {
    RedisModule_CloseKey(sourceListKey);
    return RedisModule_ReplyWithError(ctx, REDISMODULE_ERRORMSG_WRONGTYPE);
  }

  // Open destination key
  RedisModuleKey *destinationListKey =
      RedisModule_OpenKey(ctx, argv[2], REDISMODULE_WRITE);
  RedisModule_DeleteKey(destinationListKey);

  // Get length of list
  size_t sourceListLength = RedisModule_ValueLength(sourceListKey);

  if (sourceListLength == 0) {
    RedisModule_ReplyWithLongLong(ctx, 0L);
    return REDISMODULE_OK;
  }

  char strLowerLimit[] = "-inf";
  char strUpperLimit[] = "+inf";
  RedisModuleString *expectedMinusInf, *expectedPlusInf;
  long long lowerLimit;
  long long upperLimit;
  int lowerLimitOk = 0;
  int upperLimitOk = 0;

  expectedMinusInf = RedisModule_CreateString(ctx, strLowerLimit, 4);
  expectedPlusInf = RedisModule_CreateString(ctx, strUpperLimit, 4);

  // check if argv[3] is -inf
  if (RedisModule_StringCompare(argv[3], expectedMinusInf) == 0) {
    lowerLimit = LONG_MIN;
    lowerLimitOk = 1;
  } else {
    if (RedisModule_StringToLongLong(argv[3], &lowerLimit) == REDISMODULE_OK)
      lowerLimitOk = 1;
  }

  // check if argv[4] is +inf
  if (RedisModule_StringCompare(argv[4], expectedPlusInf) == 0) {
    upperLimit = LONG_MAX;
    upperLimitOk = 1;
  } else {
    if (RedisModule_StringToLongLong(argv[4], &upperLimit) == REDISMODULE_OK)
      upperLimitOk = 1;
  }

  // the number of added elements to the destination_list
  size_t added = 0;
  // loop trough source_list
  for (size_t pos = 0; pos < sourceListLength; pos++) {
    RedisModuleString *ele =
        RedisModule_ListPop(sourceListKey, REDISMODULE_LIST_TAIL);
    RedisModule_ListPush(sourceListKey, REDISMODULE_LIST_HEAD, ele);

    long long val;

    // convert string to long long
    if ((RedisModule_StringToLongLong(ele, &val) == REDISMODULE_OK) &&
        lowerLimitOk == 1 && upperLimitOk == 1) {
      if (val >= lowerLimit && val <= upperLimit) {

        // RedisModule_Log(ctx, "notice", "element within range %d %d %d",
        // lowerLimit, val, upperLimit );
        RedisModuleString *newele =
            RedisModule_CreateStringFromLongLong(ctx, val);

        // push to destination_list
        if (RedisModule_ListPush(destinationListKey, REDISMODULE_LIST_HEAD,
                                 newele) == REDISMODULE_ERR) {
          return REDISMODULE_ERR;
        }
        added++;
      }
    }
  }

  RedisModule_ReplyWithLongLong(ctx, added);

  // propagate the command to the slaves and AOF file exactly as it was called
  RedisModule_ReplicateVerbatim(ctx);

  return REDISMODULE_OK;
}