/*
    * Licensed to The Apereo Foundation under one or more contributor license
    * agreements. See the NOTICE file distributed with this work for additional
    * information regarding copyright ownership.
    *
    *
    * The Apereo Foundation licenses this file to you under the Educational
    * Community 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://opensource.org/licenses/ecl2.txt
   *
   * 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 org.opencastproject.workflow.handler.assetmanager;
  
  import org.opencastproject.assetmanager.api.AssetManager;
  import org.opencastproject.assetmanager.api.Snapshot;
  import org.opencastproject.job.api.JobContext;
  import org.opencastproject.mediapackage.MediaPackage;
  import org.opencastproject.mediapackage.MediaPackageElement;
  import org.opencastproject.mediapackage.MediaPackageElementFlavor;
  import org.opencastproject.mediapackage.selector.SimpleElementSelector;
  import org.opencastproject.workflow.api.AbstractWorkflowOperationHandler;
  import org.opencastproject.workflow.api.WorkflowInstance;
  import org.opencastproject.workflow.api.WorkflowOperationException;
  import org.opencastproject.workflow.api.WorkflowOperationHandler;
  import org.opencastproject.workflow.api.WorkflowOperationInstance;
  import org.opencastproject.workflow.api.WorkflowOperationResult;
  
  import org.apache.commons.lang3.StringUtils;
  import org.osgi.service.component.annotations.Component;
  import org.osgi.service.component.annotations.Reference;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.List;
  
  /**
   * Replaces the media package in the current workflow with a previous version from the asset manager. There are two ways
   * to choose the version: by version number or a combination of source-flavors and no-tags (choose the latest version
   * where elements with source-flavor do not have the tags specified in no-tags.
   *
   * This operation should be the first one in a workflow executed from the archive because it REPLACES the media package
   * used by the current workflow.
   */
  @Component(immediate = true, service = WorkflowOperationHandler.class, property = {
          "service.description=Selects a mp version from the archive", "workflow.operation=select-version" })
  public class SelectVersionWorkflowOperationHandler extends AbstractWorkflowOperationHandler {
  
    private static final Logger logger = LoggerFactory.getLogger(SelectVersionWorkflowOperationHandler.class);
  
    public static final String OPT_VERSION = "version";
    public static final String OPT_NO_TAGS = "no-tags";
    public static final String OPT_SOURCE_FLAVORS = "source-flavors";
  
    private AssetManager assetManager;
  
    @Override
    public WorkflowOperationResult start(final WorkflowInstance workflowInstance, JobContext context)
            throws WorkflowOperationException {
  
      final WorkflowOperationInstance currentOperation = workflowInstance.getCurrentOperation();
      if (currentOperation == null) {
        throw new WorkflowOperationException("Cannot get current workflow operation");
      }
      // Get current media package
      MediaPackage mp = workflowInstance.getMediaPackage();
      MediaPackage resultMp = null;
  
      // Make sure operation configuration is valid.
      String version = StringUtils.trimToNull(currentOperation.getConfiguration(OPT_VERSION));
      String noTagsOpt = StringUtils.trimToNull(currentOperation.getConfiguration(OPT_NO_TAGS));
      String sourceFlavorsOpt = StringUtils.trimToNull(currentOperation.getConfiguration(OPT_SOURCE_FLAVORS));
      if (version != null && (noTagsOpt != null || sourceFlavorsOpt != null)) {
        throw new WorkflowOperationException(
                String.format("Configuration error: '%s' cannot be used with '%s' and '%s'.",
                OPT_VERSION, OPT_NO_TAGS, OPT_SOURCE_FLAVORS));
      }
  
      // Specific version informed? If yes, use it.
      if (version != null) {
        try {
          // Validate the number
          Integer.parseInt(version);
          resultMp = findVersion(mp.getIdentifier().toString(), version);
          if (resultMp == null) {
            throw new WorkflowOperationException(
                    String.format("Could not find version %d of mp %s in the archive", mp.getIdentifier(), version));
         }
       } catch (NumberFormatException e) {
         throw new WorkflowOperationException("Invalid version passed: " + version);
       }
     } else {
       if (noTagsOpt == null || sourceFlavorsOpt == null) {
         throw new WorkflowOperationException(String.format("Configuration error: both '%s' and '%s' must be passed.",
                 OPT_NO_TAGS, OPT_SOURCE_FLAVORS));
       }
       Collection<String> noTags = Arrays.asList(noTagsOpt.split(","));
 
       SimpleElementSelector elementSelector = new SimpleElementSelector();
       for (MediaPackageElementFlavor flavor : parseFlavors(sourceFlavorsOpt)) {
         elementSelector.addFlavor(flavor);
       }
 
       resultMp = findVersionWithNoTags(mp.getIdentifier().toString(), elementSelector, noTags);
       if (resultMp == null) {
         throw new WorkflowOperationException(String.format(
                 "Could not find in the archive a version of mp %s that does not have the tags %s in element flavors %s",
                 mp.getIdentifier(), noTagsOpt, sourceFlavorsOpt));
       }
     }
     return createResult(resultMp, WorkflowOperationResult.Action.CONTINUE);
   }
 
   private MediaPackage findVersion(String mpId, String version) throws WorkflowOperationException {
     // Get the specific version from the asset manager
     List<Snapshot> snapshots = assetManager.getSnapshotsByIdAndVersion(mpId, assetManager.toVersion(version).get());
 
     if (snapshots.size() > 1) {
       // Version not found
       throw new WorkflowOperationException(
           String.format("Multiple media package %s, version %s found in the archive.", mpId, version));
     }
     if (snapshots.isEmpty()) {
       // Version not found
       throw new WorkflowOperationException(
               String.format("Media package %s, version %s not found in the archive.", mpId, version));
     }
 
     logger.info("Replacing current media package with version: {}", version);
     return snapshots.get(0).getMediaPackage();
   }
 
   private MediaPackage findVersionWithNoTags(String mpId, SimpleElementSelector elementSelector,
           Collection<String> tags) throws WorkflowOperationException {
     // Get all the snapshots from the asset manager
     List<Snapshot> snapshots = assetManager.getSnapshotsByIdOrderedByVersion(mpId, false);
 
     if (snapshots.isEmpty()) {
       // This is strange because it should run from the archive
       throw new WorkflowOperationException("Media package not found in the archive: " + mpId);
     }
 
     nextVersion: for (Snapshot snapshot : snapshots) {
       MediaPackage mp = snapshot.getMediaPackage();
       for (MediaPackageElement el : elementSelector.select(mp, false)) {
         for (String t : el.getTags()) {
           if (tags.contains(t)) {
             continue nextVersion;
           }
         }
       }
       logger.info("Replacing current media package with version: {}", snapshot.getVersion());
       return mp;
     }
     return null;
   }
 
   private List<MediaPackageElementFlavor> parseFlavors(String flavorStr) {
     List<MediaPackageElementFlavor> flavors = new ArrayList<MediaPackageElementFlavor>();
     if (flavorStr != null) {
       for (String flavor : asList(flavorStr)) {
         flavors.add(MediaPackageElementFlavor.parseFlavor(flavor));
       }
     }
     return flavors;
   }
 
   @Reference
   public void setAssetManager(AssetManager service) {
     this.assetManager = service;
   }
 }