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Dapr Spring Data
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/*
 * Copyright 2024 The Dapr 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.
*/

package io.dapr.spring.data;

import org.springframework.dao.InvalidDataAccessApiUsageException;
import org.springframework.data.keyvalue.core.IdentifierGenerator;
import org.springframework.data.util.TypeInformation;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;

import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Arrays;
import java.util.List;
import java.util.UUID;
import java.util.concurrent.atomic.AtomicReference;

/**
 * Default implementation of {@link IdentifierGenerator} to generate identifiers of types {@link UUID}.
 */
enum DefaultIdentifierGenerator implements IdentifierGenerator {

  INSTANCE;

  private final AtomicReference secureRandom = new AtomicReference<>(null);

  @Override
  @SuppressWarnings("unchecked")
  public  T generateIdentifierOfType(TypeInformation identifierType) {

    Class type = identifierType.getType();

    if (ClassUtils.isAssignable(UUID.class, type)) {
      return (T) UUID.randomUUID();
    } else if (ClassUtils.isAssignable(String.class, type)) {
      return (T) UUID.randomUUID().toString();
    } else if (ClassUtils.isAssignable(Integer.class, type)) {
      return (T) Integer.valueOf(getSecureRandom().nextInt());
    } else if (ClassUtils.isAssignable(Long.class, type)) {
      return (T) Long.valueOf(getSecureRandom().nextLong());
    }

    throw new InvalidDataAccessApiUsageException(
        String.format("Identifier cannot be generated for %s; Supported types are: UUID, String, Integer, and Long",
            identifierType.getType().getName()));
  }

  private SecureRandom getSecureRandom() {

    SecureRandom secureRandom = this.secureRandom.get();
    if (secureRandom != null) {
      return secureRandom;
    }

    for (String algorithm : OsTools.secureRandomAlgorithmNames()) {
      try {
        secureRandom = SecureRandom.getInstance(algorithm);
      } catch (NoSuchAlgorithmException e) {
        // ignore and try next.
      }
    }

    if (secureRandom == null) {
      throw new InvalidDataAccessApiUsageException(
          String.format("Could not create SecureRandom instance for one of the algorithms '%s'",
              StringUtils.collectionToCommaDelimitedString(OsTools.secureRandomAlgorithmNames())));
    }

    this.secureRandom.compareAndSet(null, secureRandom);

    return secureRandom;
  }

  private static class OsTools {

    private static final String OPERATING_SYSTEM_NAME = System.getProperty("os.name").toLowerCase();

    private static final List SECURE_RANDOM_ALGORITHMS_LINUX_OSX_SOLARIS = Arrays.asList("NativePRNGBlocking",
        "NativePRNGNonBlocking", "NativePRNG", "SHA1PRNG");
    private static final List SECURE_RANDOM_ALGORITHMS_WINDOWS = Arrays.asList("SHA1PRNG", "Windows-PRNG");

    static List secureRandomAlgorithmNames() {
      return OPERATING_SYSTEM_NAME.contains("win") ? SECURE_RANDOM_ALGORITHMS_WINDOWS
          : SECURE_RANDOM_ALGORITHMS_LINUX_OSX_SOLARIS;
    }
  }
}