/*
 * Copyright 2003-2014 JetBrains s.r.o.
 *
 * 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 jetbrains.mps.persistence;

import jetbrains.mps.extapi.model.SModelData;
import jetbrains.mps.generator.ModelDigestUtil;
import jetbrains.mps.smodel.SModelHeader;
import jetbrains.mps.smodel.loading.ModelLoadResult;
import jetbrains.mps.smodel.loading.ModelLoadingState;
import jetbrains.mps.smodel.persistence.def.ModelReadException;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.mps.openapi.persistence.DataSource;
import org.jetbrains.mps.openapi.persistence.ModelFactory;
import org.jetbrains.mps.openapi.persistence.StreamDataSource;

import java.io.IOException;
import java.util.Map;

/**
 * Internal facility around ModelFactory which is aware of partial loading approach.
 * Initially, just an extraction of differences between LazyEditableSModelBase subclasses (DefaultSModelDescriptor, BinarySModelDescriptor and
 * FilePerRootSModel), hence awkward API.
 *
 * @author Artem Tikhomirov
 */
public abstract class LazyLoadFacility {
  private final ModelFactory myModelFactory;
  private final DataSource mySource;

  public LazyLoadFacility(@NotNull ModelFactory modelFactory, @NotNull DataSource dataSource) {
    myModelFactory = modelFactory;
    mySource = dataSource;
  }

  @NotNull
  public ModelFactory getModelFactory() {
    return myModelFactory;
  }

  @NotNull
  public DataSource getSource() {
    return mySource;
  }

  public String getModelHash() {
    // FIXME refactor DataSource to answer hash()/digest() queries itself (and move this code back to generatable model impl)
    String modelHash = ModelDigestHelper.getInstance().getModelHash((StreamDataSource) getSource());
    if (modelHash != null) {
      return modelHash;
    }

    return ModelDigestUtil.hash((StreamDataSource) getSource(), !getModelFactory().isBinary());
  }

  public abstract Map<String, String> getGenerationHashes();

  @NotNull
  public abstract SModelHeader readHeader() throws ModelReadException;

  @NotNull
  public abstract ModelLoadResult readModel(@NotNull SModelHeader header, @NotNull ModelLoadingState state) throws ModelReadException;

  /**
   * The method is quite questionable, though better than saveModel returning != null value to indicate persistence has changed during save.
   * One of alternatives is to alter header's field (persistenceVersion) on saveModel so that caller gets a chance to find out persistence had changed
   * @return true if model could not be saved with persistence version indicated in the header.
   */
  public abstract boolean doesSaveUpgradePersistence(@NotNull SModelHeader header);

  public abstract void saveModel(@NotNull SModelHeader header, SModelData modelData) throws IOException;
}