/*
 * 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.evm.operation;

import org.hyperledger.besu.evm.EVM;
import org.hyperledger.besu.evm.frame.MessageFrame;
import org.hyperledger.besu.evm.gascalculator.GasCalculator;

import java.math.BigInteger;

import org.apache.tuweni.bytes.Bytes;
import org.apache.tuweni.bytes.Bytes32;

/** The Sub (Subtract) operation. */
public class SubOperation extends AbstractFixedCostOperation {

  /** The Sub operation success result. */
  static final OperationResult subSuccess = new OperationResult(3, null);

  /**
   * Instantiates a new Sub operation.
   *
   * @param gasCalculator the gas calculator
   */
  public SubOperation(final GasCalculator gasCalculator) {
    super(0x03, "SUB", 2, 1, gasCalculator, gasCalculator.getVeryLowTierGasCost());
  }

  @Override
  public Operation.OperationResult executeFixedCostOperation(
      final MessageFrame frame, final EVM evm) {
    return staticOperation(frame);
  }

  /**
   * Performs Sub operation.
   *
   * @param frame the frame
   * @return the operation result
   */
  public static OperationResult staticOperation(final MessageFrame frame) {
    final BigInteger value0 = new BigInteger(1, frame.popStackItem().toArrayUnsafe());
    final BigInteger value1 = new BigInteger(1, frame.popStackItem().toArrayUnsafe());

    final BigInteger result = value0.subtract(value1);

    byte[] resultArray = result.toByteArray();
    int length = resultArray.length;
    if (length >= 32) {
      frame.pushStackItem(Bytes.wrap(resultArray, length - 32, 32));
    } else if (result.signum() < 0) {
      frame.pushStackItem(Bytes32.leftPad(Bytes.wrap(resultArray), (byte) -1));
    } else {
      frame.pushStackItem(Bytes.wrap(resultArray));
    }

    return subSuccess;
  }
}
