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// Copyright 2015-2024 Nstream, inc.
//
// 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 nstream.persist.api.kv;

import java.util.OptionalInt;

/**
 * The status returned from an attempt to read the state of a {@link MapIterator} into provided buffers.
 */
@SuppressWarnings("unused")
public class IterationStatus {

  private static final byte GOOD = 0x00;
  private static final byte KEY_OVERFLOW = 0x01;
  private static final byte VALUE_OVERFLOW = 0x10;
  private static final int UNKNOWN = -1;

  private byte flags;
  private int keyRequired;
  private int valueRequired;

  public IterationStatus() {
    this.flags = GOOD;
    this.keyRequired = 0;
    this.valueRequired = 0;
  }

  /**
   * Reset the status to a good state.
   */
  public void reset() {
    this.flags = GOOD;
    this.keyRequired = 0;
    this.valueRequired = 0;
  }

  /**
   * Indicate that the key buffer overflowed.
   * @param required The required number of bytes for the buffer.
   */
  public void setKeyOverflow(int required) {
    if (required <= 0) {
      throw new IllegalArgumentException("Required buffer size must be positive.");
    }
    this.flags |= KEY_OVERFLOW;
    this.keyRequired = required;
  }

  /**
   * Indicate that the key buffer overflowed without specifying the required number of bytes.
   */
  public void setKeyOverflow() {
    this.flags |= KEY_OVERFLOW;
    this.keyRequired = UNKNOWN;
  }

  /**
   * Indicate that the value buffer overflowed.
   * @param required The required number of bytes for the buffer.
   */
  public void setValueOverflow(int required) {
    if (required <= 0) {
      throw new IllegalArgumentException("Required buffer size must be positive.");
    }
    this.flags |= VALUE_OVERFLOW;
    this.valueRequired = required;
  }

  /**
   * Indicate that the value buffer overflowed without specifying the required number of bytes.
   */
  public void setValueOverflow() {
    this.flags |= VALUE_OVERFLOW;
    this.valueRequired = UNKNOWN;
  }

  /**
   * @return Get the overall result of the operation.
   */
  public IoResult getResult() {
    if (this.flags == GOOD) {
      return IoResult.Success;
    } else {
      return IoResult.BufferOverflow;
    }
  }

  /**
   * @return Following a failed read, get the number of bytes required for the key buffer, if known.
   */
  public OptionalInt getKeyRequired() {
    if (this.keyRequired <= 0) {
      return OptionalInt.empty();
    } else {
      return OptionalInt.of(this.keyRequired);
    }
  }

  /**
   * @return Following a failed read, get the number of bytes required for the value buffer, if known.
   */
  public OptionalInt getValueRequired() {
    if (this.valueRequired <= 0) {
      return OptionalInt.empty();
    } else {
      return OptionalInt.of(this.valueRequired);
    }
  }

  /**
   * @return Whether the key buffer overflowed.
   */
  public boolean keyOverflowed() {
    return (this.flags & KEY_OVERFLOW) != 0;
  }

  /**
   * @return Whether the value buffer overflowed.
   */
  public boolean valueOverflowed() {
    return (this.flags & VALUE_OVERFLOW) != 0;
  }

}