/*
 * 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.consensus.qbft.headervalidationrules;

import org.hyperledger.besu.consensus.common.bft.BftContext;
import org.hyperledger.besu.consensus.common.bft.BftExtraData;
import org.hyperledger.besu.consensus.common.bft.headervalidationrules.BftValidatorsValidationRule;
import org.hyperledger.besu.ethereum.ProtocolContext;
import org.hyperledger.besu.ethereum.core.BlockHeader;
import org.hyperledger.besu.ethereum.mainnet.AttachedBlockHeaderValidationRule;
import org.hyperledger.besu.ethereum.rlp.RLPException;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Ensures the Validators listed in the block header match that tracked in memory (which was in-turn
 * created by tracking votes included on the block chain).
 */
public class QbftValidatorsValidationRule implements AttachedBlockHeaderValidationRule {

  private static final Logger LOGGER = LoggerFactory.getLogger(QbftValidatorsValidationRule.class);
  private final boolean extraDataValidatorsAndVoteMustBeEmpty;
  private final BftValidatorsValidationRule bftValidatorsValidationRule =
      new BftValidatorsValidationRule();

  /**
   * Instantiates a new Qbft validators validation rule.
   *
   * @param extraDataValidatorsAndVoteMustBeEmpty the extra data validators and vote must be empty
   */
  public QbftValidatorsValidationRule(final boolean extraDataValidatorsAndVoteMustBeEmpty) {
    this.extraDataValidatorsAndVoteMustBeEmpty = extraDataValidatorsAndVoteMustBeEmpty;
  }

  @Override
  public boolean validate(
      final BlockHeader header, final BlockHeader parent, final ProtocolContext context) {
    if (!extraDataValidatorsAndVoteMustBeEmpty) {
      // delegate to common BftValidatorsValidationRule
      return bftValidatorsValidationRule.validate(header, parent, context);
    }

    // validators and votes must be empty if they are supplied by a contract.
    try {
      final BftContext bftContext = context.getConsensusContext(BftContext.class);
      final BftExtraData bftExtraData = bftContext.getBlockInterface().getExtraData(header);

      if (!bftExtraData.getValidators().isEmpty()) {
        LOGGER.info(
            "Invalid block header: Validators in extra data expected to be empty but got {}",
            bftExtraData.getValidators());
        return false;
      }

      if (bftExtraData.getVote().isPresent()) {
        LOGGER.info(
            "Invalid block header: Vote in extra data expected to be empty but got {}",
            bftExtraData.getVote().get());
        return false;
      }
    } catch (final RLPException ex) {
      LOGGER.info(
          "Invalid block header: ExtraData field was unable to be deserialized into an BFT Struct.",
          ex);
      return false;
    } catch (final IllegalArgumentException ex) {
      LOGGER.info("Invalid block header: Failed to verify extra data", ex);
      return false;
    }

    return true;
  }
}
