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

import java.io.IOException;
import java.util.Collections;
import java.util.List;

import org.apache.uima.UimaContext;
import org.apache.uima.analysis_engine.AnalysisEngineProcessException;
import org.apache.uima.jcas.JCas;
import org.apache.uima.jcas.tcas.DocumentAnnotation;
import org.apache.uima.resource.ResourceInitializationException;

import com.google.common.base.Optional;
import com.google.common.collect.ImmutableSet;
import com.optimaize.langdetect.LanguageDetector;
import com.optimaize.langdetect.LanguageDetectorBuilder;
import com.optimaize.langdetect.i18n.LdLocale;
import com.optimaize.langdetect.ngram.NgramExtractors;
import com.optimaize.langdetect.profiles.LanguageProfile;
import com.optimaize.langdetect.profiles.LanguageProfileReader;
import com.optimaize.langdetect.text.CommonTextObjectFactories;
import com.optimaize.langdetect.text.TextObject;
import com.optimaize.langdetect.text.TextObjectFactory;

import uk.gov.dstl.baleen.core.pipelines.orderers.AnalysisEngineAction;
import uk.gov.dstl.baleen.uima.BaleenAnnotator;

/**
 * Sets the document language using Language Detector library.
 * 
 * <p>Uses the Language Detector library to identify the language of the document from a random sample of N-grams.
 * If the language can't be detected, then <i>x-unspecified</i> is returned.</p>
 *
 * 
 */
public class DocumentLanguage extends BaleenAnnotator {
	private LanguageDetector languageDetector;
	private TextObjectFactory textObjectFactory;
	
	@Override
	public void doInitialize(UimaContext aContext) throws ResourceInitializationException {
		try{
			List<LanguageProfile> languageProfiles = new LanguageProfileReader().readAllBuiltIn();
			languageDetector = LanguageDetectorBuilder.create(NgramExtractors.standard())
					.withProfiles(languageProfiles)
					.build();
			
			textObjectFactory = CommonTextObjectFactories.forDetectingOnLargeText();
		}catch(IOException ioe){
			throw new ResourceInitializationException(ioe);
		}
	}

	@Override
	public void doProcess(JCas aJCas) throws AnalysisEngineProcessException {
		TextObject textObject = textObjectFactory.forText(aJCas.getDocumentText());
		Optional<LdLocale> lang = languageDetector.detect(textObject);
		
		if(lang.isPresent()){
			aJCas.setDocumentLanguage(lang.get().getLanguage());
		}
	}

	@Override
	public void doDestroy(){
		textObjectFactory = null;
		languageDetector = null;
	}
	
	@Override
	public AnalysisEngineAction getAction() {
		return new AnalysisEngineAction(Collections.emptySet(), ImmutableSet.of(DocumentAnnotation.class));
	}
}