//Dstl (c) Crown Copyright 2017
package uk.gov.dstl.baleen.uima;

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

import org.apache.uima.UimaContext;
import org.apache.uima.fit.descriptor.ExternalResource;
import org.apache.uima.jcas.JCas;
import org.apache.uima.jcas.tcas.Annotation;
import org.apache.uima.jcas.tcas.DocumentAnnotation;
import org.apache.uima.resource.ResourceInitializationException;

import com.google.common.base.Strings;

import uk.gov.dstl.baleen.core.history.BaleenHistory;
import uk.gov.dstl.baleen.core.pipelines.PipelineBuilder;
import uk.gov.dstl.baleen.types.metadata.Metadata;
import uk.gov.dstl.baleen.uima.utils.UimaUtils;

/** Base implementation of a ContentExtractor.
 *
 * This abstract class provides the basis for content extractors. It provides metrics and support elements
 * to help development.
 *
 * Implementors should look to override doProcessStream as per {@link IContentExtractor} processFile.
 *
 * 
 *
 */
public abstract class BaleenContentExtractor implements IContentExtractor {
	private UimaMonitor monitor;
	private UimaSupport support;

	/**
	 * Baleen History resource
	 * 
	 * @baleen.resource uk.gov.dstl.baleen.core.history.BaleenHistory
	 */
	public static final String KEY_HISTORY = PipelineBuilder.BALEEN_HISTORY;
	@ExternalResource(key = KEY_HISTORY, mandatory = false)
	BaleenHistory history;

	@Override
	public final void initialize(UimaContext context, Map<String, Object> params) throws ResourceInitializationException {

		String pipelineName = UimaUtils.getPipelineName(context);
		monitor = createMonitor(pipelineName);
		support = createSupport(pipelineName, context);
		monitor.startFunction("initialize");

		doInitialize(context, params);

		monitor.finishFunction("initialize");
	}

	protected UimaSupport createSupport(String pipelineName, UimaContext context) {
		return new UimaSupport(pipelineName, this.getClass(), history, monitor, UimaUtils.isMergeDistinctEntities(context));
	}

	protected UimaMonitor createMonitor(String pipelineName) {
		return new UimaMonitor(pipelineName, this.getClass());
	}

	/**
	 * Called when the content extractor is being initialized. Any required resources, for example, should be opened at this point.
	 *
	 * @param context
	 *            UimaContext object passed by the Collection Processing Engine
	 */
	public abstract void doInitialize(UimaContext context, Map<String, Object> params) throws ResourceInitializationException;

	@Override
	public final void processStream(InputStream stream, String source, JCas jCas) throws IOException {
		monitor.startFunction("process");

		doProcessStream(stream, source, jCas);

		monitor.finishFunction("process");
		monitor.persistCounts();
	}

	/**
	 * Called when the content extractor is being asked to process an inputstream and extract the content.
	 *
	 * @param stream InputStream to process
	 * @param jCas JCas to add content to
	 */
	protected abstract void doProcessStream(InputStream stream, String source, JCas jCas) throws IOException;

	@Override
	public final void destroy() {
		monitor.startFunction("destroy");

		doDestroy();

		monitor.finishFunction("destroy");
	}

	/**
	 * Called when the content extractor has finished and is closing down. Any open resources, for example, should be closed at this point.
	 */
	protected abstract void doDestroy();

	/**
	 * Gets the UimaMonitor object associated with this ContentExtractor, for instance to log errors.
	 *
	 * @return UimaMonitor object
	 */
	protected UimaMonitor getMonitor() {
		return monitor;
	}

	/**
	 * Gets the UimaSupport object associated with this ContentExtractor, for instance to log errors.
	 *
	 * @return UimaSupport object
	 */
	protected UimaSupport getSupport() {
		return support;
	}

	// Common Support functions for quick access

	/**
	 * Return the document annotation.
	 *
	 * @param jCas
	 * @return the document annotation
	 */
	protected DocumentAnnotation getDocumentAnnotation(JCas jCas){
		return getSupport().getDocumentAnnotation(jCas);
	}


	/**
	 * Add an annotation to the JCas index, notifying UimaMonitor of the fact we
	 * have done so
	 *
	 * @param annot
	 *            Annotation(s) to add
	 */
	protected void addToJCasIndex(Annotation... annotations) {
		getSupport().add(annotations);
	}

	/**
	 * Add an annotation to the JCas index, notifying UimaMonitor of the fact we
	 * have done so
	 *
	 * @param annot
	 *            Annotation(s) to add
	 */
	protected void addToJCasIndex(Collection<? extends Annotation> annotations) {
		getSupport().add(annotations);
	}
	
	/**
	 * Adds a metadata annotation to the JCas
	 * 
	 * @param jCas The JCas object to add the annotation to
	 * @param name The metadata key
	 * @param value The metadata value
	 */
	protected Metadata addMetadata(JCas jCas, String name, String value){
		if (!Strings.isNullOrEmpty(name) && !Strings.isNullOrEmpty(value)) {
			Metadata md = new Metadata(jCas);

			md.setKey(name);
			md.setValue(value);

			addToJCasIndex(md);
			
			return md;
		}
		
		return null;
	}
}