/*
 * Copyright (c) 2011, University of Konstanz, Distributed Systems Group All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted
 * provided that the following conditions are met: * Redistributions of source code must retain the
 * above copyright notice, this list of conditions and the following disclaimer. * Redistributions
 * in binary form must reproduce the above copyright notice, this list of conditions and the
 * following disclaimer in the documentation and/or other materials provided with the distribution.
 * * Neither the name of the University of Konstanz nor the names of its contributors may be used to
 * endorse or promote products derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package io.sirix.io;

import com.github.benmanes.caffeine.cache.AsyncCache;
import io.sirix.exception.SirixIOException;
import io.sirix.io.bytepipe.ByteHandler;
import io.sirix.page.PageReference;
import io.sirix.page.UberPage;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

/**
 * Interface to generate access to the storage. The storage is flexible as long as {@link Reader}
 * and {@link Writer}-implementations are provided. Utility methods for common interaction with the
 * storage are provided via the {@code Storage}.
 *
 * @author Sebastian Graf, University of Konstanz
 */
public interface IOStorage {

  /**
   * Data file name.
   */
  String FILENAME = "sirix.data";

  /**
   * Revisions file name.
   */
  String REVISIONS_FILENAME = "sirix.revisions";

  /**
   * Beacon of first references.
   */
  int FIRST_BEACON = Writer.UBER_PAGE_BYTE_ALIGN << 1;

  /**
   * Beacon of the other references.
   */
  int OTHER_BEACON = Integer.BYTES;

  /**
   * Getting a writer.
   *
   * @return an {@link Writer} instance
   * @throws SirixIOException if the initialization fails
   */
  Writer createWriter();

  /**
   * Getting a reader.
   *
   * @return an {@link Reader} instance
   * @throws SirixIOException if the initialization fails
   */
  Reader createReader();

  /**
   * Closing this storage.
   *
   * @throws SirixIOException if an I/O error occurs
   */
  void close();

  /**
   * Check if storage exists.
   *
   * @return true if storage holds data, false otherwise
   * @throws SirixIOException if storage is not accessible
   */
  boolean exists();

  /**
   * Load the revision file data into an in-memory cache.
   *
   * @param cache the cache to
   */
  default void loadRevisionFileDataIntoMemory(AsyncCache<Integer, RevisionFileData> cache) {
    if (!cache.asMap().isEmpty()) {
      return;
    }

    final UberPage uberPage;
    if (exists()) {
      final Reader reader = createReader();
      final PageReference firstRef = reader.readUberPageReference();
      uberPage = (UberPage) firstRef.getPage();

      final var revisionNumber = uberPage.getRevisionNumber();
      final var revisionNumbers = new ArrayList<Integer>(revisionNumber);

      for (int i = 1; i <= revisionNumber; i++) {
        revisionNumbers.add(i);
      }

      cache.getAll(revisionNumbers, keys -> {
        final Map<Integer, RevisionFileData> result = new HashMap<>();
        keys.forEach(key -> result.put(key, reader.getRevisionFileData(key)));
        reader.close();
        return result;
      });
    }
  }

  /**
   * Get the byte handler pipeline.
   *
   * @return byte handler pipeline
   */
  ByteHandler getByteHandler();
}
