/*
 * Copyright ConsenSys AG.
 *
 * 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.
 *
 * SPDX-License-Identifier: Apache-2.0
 */
package org.hyperledger.besu.crypto;

import com.google.common.annotations.VisibleForTesting;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/** The Signature algorithm factory. */
public class SignatureAlgorithmFactory {

  private static final Logger LOG = LoggerFactory.getLogger(SignatureAlgorithmFactory.class);

  private static SignatureAlgorithm instance = null;

  private SignatureAlgorithmFactory() {}

  /** Sets default instance. */
  public static void setDefaultInstance() {
    instance = SignatureAlgorithmType.createDefault().getInstance();
  }

  /**
   * Sets instance.
   *
   * @param signatureAlgorithmType the signature algorithm type
   * @throws IllegalStateException the illegal state exception
   */
  public static void setInstance(final SignatureAlgorithmType signatureAlgorithmType)
      throws IllegalStateException {
    if (instance != null) {
      throw new IllegalStateException(
          "Instance of SignatureAlgorithmFactory can only be set once.");
    }

    instance = signatureAlgorithmType.getInstance();

    if (!SignatureAlgorithmType.isDefault(instance)) {
      LOG.info(
          new StringBuilder("The signature algorithm uses the elliptic curve ")
              .append(instance.getCurveName())
              .append(". The usage of alternative elliptic curves is still experimental.")
              .toString());
    }
  }

  /**
   * getInstance will always return a valid SignatureAlgorithm and never null. This is necessary in
   * the unit tests be able to use the factory without having to call setInstance first.
   *
   * @return SignatureAlgorithm instance
   */
  public static SignatureAlgorithm getInstance() {
    return instance != null
        ? instance
        : SignatureAlgorithmType.DEFAULT_SIGNATURE_ALGORITHM_TYPE.get();
  }

  /**
   * Is instance set boolean.
   *
   * @return the boolean
   */
  public static boolean isInstanceSet() {
    return instance != null;
  }

  /** Reset instance. */
  @VisibleForTesting
  public static void resetInstance() {
    instance = null;
  }
}
