/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.uima.fit.cpe;

import static org.apache.uima.UIMAFramework.getResourceSpecifierFactory;
import static org.apache.uima.UIMAFramework.produceCollectionProcessingEngine;
import static org.apache.uima.collection.impl.metadata.cpe.CpeDescriptorFactory.produceCasProcessor;
import static org.apache.uima.collection.impl.metadata.cpe.CpeDescriptorFactory.produceCollectionReader;
import static org.apache.uima.collection.impl.metadata.cpe.CpeDescriptorFactory.produceDescriptor;

import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URL;
import java.nio.file.Files;
import java.util.Map;

import javax.xml.transform.OutputKeys;

import org.apache.uima.analysis_engine.AnalysisEngineDescription;
import org.apache.uima.analysis_engine.metadata.FixedFlow;
import org.apache.uima.collection.CollectionProcessingEngine;
import org.apache.uima.collection.CollectionReaderDescription;
import org.apache.uima.collection.StatusCallbackListener;
import org.apache.uima.collection.impl.metadata.CpeDefaultValues;
import org.apache.uima.collection.metadata.CpeCollectionReader;
import org.apache.uima.collection.metadata.CpeComponentDescriptor;
import org.apache.uima.collection.metadata.CpeDescription;
import org.apache.uima.collection.metadata.CpeDescriptorException;
import org.apache.uima.collection.metadata.CpeInclude;
import org.apache.uima.collection.metadata.CpeIntegratedCasProcessor;
import org.apache.uima.fit.internal.ResourceManagerFactory;
import org.apache.uima.resource.ResourceInitializationException;
import org.apache.uima.resource.ResourceManager;
import org.apache.uima.resource.ResourceSpecifier;
import org.apache.uima.util.InvalidXMLException;
import org.apache.uima.util.XMLSerializer;
import org.xml.sax.ContentHandler;
import org.xml.sax.SAXException;

/**
 * Build a Collection Processing Engine from a {@link CollectionReaderDescription} and a
 * {@link AnalysisEngineDescription}. If an aggregate analysis engine description is used, the
 * builder will add each child of the aggregate engine as one processor to the engine. This works
 * only for aggregate analysis engines using a {@link FixedFlow}.
 * 
 */
public class CpeBuilder {
  // private final Log log = LogFactory.getLog(getClass());

  private static final String ACTION_ON_MAX_ERROR = "terminate";

  /**
   * used for calculating the CAS pool size which needs to be adjusted to the number of parallel
   * pipelines
   */
  private int maxProcessingUnitThreadCount = 1;

  private final CpeDescription cpeDesc = produceDescriptor();

  /**
   * Set the maximum number of threads the CPE may use.
   * 
   * @param aMaxProcessingUnitThreadCount
   *          the maximum number of threads the CPE may use.
   */
  public void setMaxProcessingUnitThreadCount(int aMaxProcessingUnitThreadCount) {
    maxProcessingUnitThreadCount = aMaxProcessingUnitThreadCount;
  }

  /**
   * Set the reader used by the CPE.
   * 
   * @param aDesc
   *          the reader description.
   * @throws IOException
   *           if the descriptor cannot be written to the temporary space from where it is imported
   *           by the CPE.
   * @throws SAXException
   *           if the reader descriptor cannot be serialized to XML.
   * @throws CpeDescriptorException
   *           if there was a problem adding the reader to the CPE.
   */
  public void setReader(CollectionReaderDescription aDesc) throws IOException, SAXException,
          CpeDescriptorException {
    // Remove all collection readers
    cpeDesc.setAllCollectionCollectionReaders(new CpeCollectionReader[0]);

    URL descUrl = materializeDescriptor(aDesc).toURI().toURL();
    CpeCollectionReader reader = produceCollectionReader(descUrl.toString());
    cpeDesc.addCollectionReader(reader);
  }

  /**
   * Set the analysis engine used by the CPE. If this is an aggregate analysis engine, it will be
   * disassembled and each delegate becomes one CPE CAS processor.
   * 
   * @param aDesc
   *          the analysis engine description.
   * @throws IOException
   *           if the descriptor cannot be written to the temporary space from where it is imported
   *           by the CPE.
   * @throws SAXException
   *           if the analysis engine descriptor cannot be serialized to XML.
   * @throws CpeDescriptorException
   *           if there was a problem adding the analysis engine to the CPE.
   * @throws InvalidXMLException
   *           if import resolution failed
   */
  public void setAnalysisEngine(AnalysisEngineDescription aDesc) throws IOException, SAXException,
          CpeDescriptorException, InvalidXMLException {
    // Remove all CAS processors
    cpeDesc.setCpeCasProcessors(null);

    if (aDesc.isPrimitive()) {
      // For a primitive AE we just add it.
      CpeIntegratedCasProcessor proc = createProcessor("delegate", aDesc);
      cpeDesc.addCasProcessor(proc);
    } else {
      // For an aggregate AE we dive into the first aggregation level and add each of the
      // contained AEs separately, thus allowing us to control their properties separately

      Map<String, ResourceSpecifier> delegates = aDesc.getDelegateAnalysisEngineSpecifiers();
      FixedFlow flow = (FixedFlow) aDesc.getAnalysisEngineMetaData().getFlowConstraints();
      for (String key : flow.getFixedFlow()) {
        AnalysisEngineDescription aeDesc = (AnalysisEngineDescription) delegates.get(key);
        // boolean multi = aeDesc.getAnalysisEngineMetaData().getOperationalProperties()
        // .isMultipleDeploymentAllowed();
        // log.info("["+key+"] runs "+ (multi ? "multi-threaded" : "single-threaded"));
        CpeIntegratedCasProcessor proc = createProcessor(key, aeDesc);
        cpeDesc.addCasProcessor(proc);
      }
    }
  }

  public CpeDescription getCpeDescription() {
    return cpeDesc;
  }

  public CollectionProcessingEngine createCpe(StatusCallbackListener aListener)
          throws ResourceInitializationException, CpeDescriptorException {
    ResourceManager resMgr = ResourceManagerFactory.newResourceManager();
    if (maxProcessingUnitThreadCount == 0) {
      cpeDesc.getCpeCasProcessors().setPoolSize(3);
    } else {
      cpeDesc.getCpeCasProcessors().setPoolSize(maxProcessingUnitThreadCount + 2);
      cpeDesc.setProcessingUnitThreadCount(maxProcessingUnitThreadCount);
    }
    CollectionProcessingEngine cpe = produceCollectionProcessingEngine(cpeDesc, resMgr, null);
    if (aListener != null) {
      cpe.addStatusCallbackListener(aListener);
    }
    return cpe;
  }

  /**
   * Writes a temporary file containing a XML descriptor of the given resource. Returns the file.
   * 
   * @param resource
   *          A resource specifier that should we materialized.
   * @return The file containing the XML representation of the given resource.
   */
  private static File materializeDescriptor(ResourceSpecifier resource) throws IOException,
          SAXException {
    File tempDesc = File.createTempFile("desc", ".xml");
    tempDesc.deleteOnExit();

    // Write the descriptor using XML 1.1 to allow a wider range of characters for parameter values
    try (OutputStream os = Files.newOutputStream(tempDesc.toPath())) {
      XMLSerializer sax2xml = new XMLSerializer(os, true);
      sax2xml.setOutputProperty(OutputKeys.VERSION, "1.1");
      ContentHandler contentHandler = sax2xml.getContentHandler();
      contentHandler.startDocument();
      resource.toXML(sax2xml.getContentHandler(), true);
      contentHandler.endDocument();
    }

    return tempDesc;
  }

  private static CpeIntegratedCasProcessor createProcessor(String key,
          AnalysisEngineDescription aDesc) throws IOException, SAXException, CpeDescriptorException {
    URL descUrl = materializeDescriptor(aDesc).toURI().toURL();

    CpeInclude cpeInclude = getResourceSpecifierFactory().createInclude();
    cpeInclude.set(descUrl.toString());

    CpeComponentDescriptor ccd = getResourceSpecifierFactory().createDescriptor();
    ccd.setInclude(cpeInclude);

    CpeIntegratedCasProcessor proc = produceCasProcessor(key);
    proc.setCpeComponentDescriptor(ccd);
    proc.setAttributeValue(CpeDefaultValues.PROCESSING_UNIT_THREAD_COUNT, 1);
    proc.setActionOnMaxError(ACTION_ON_MAX_ERROR);
    proc.setMaxErrorCount(0);

    return proc;
  }
}