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

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;

import org.apache.commons.io.IOUtils;
import org.apache.uima.UimaContext;
import org.apache.uima.collection.CollectionException;
import org.apache.uima.fit.descriptor.ConfigurationParameter;
import org.apache.uima.jcas.JCas;
import org.apache.uima.resource.ResourceInitializationException;

import uk.gov.dstl.baleen.core.utils.BaleenDefaults;
import uk.gov.dstl.baleen.exceptions.InvalidParameterException;
import uk.gov.dstl.baleen.types.metadata.Metadata;
import uk.gov.dstl.baleen.uima.BaleenCollectionReader;
import uk.gov.dstl.baleen.uima.IContentExtractor;

/**
 * Reads a file, and treats each line as a separate document.
 * Once completed, the pipeline will stay active (because pipelines are persistent in Baleen),
 * but the file will not be monitored for changes and no further documents will be processed.
 * 
 * This could be useful for processing a CSV, where you want each line of the CSV to be processed separately.
 * 
 * @baleen.javadoc
 */
public class LineReader extends BaleenCollectionReader {
	/**
	 * The file to process
	 * 
	 * @baleen.config
	 */
	public static final String PARAM_FILE = "file";
	@ConfigurationParameter(name = PARAM_FILE, defaultValue = "")
	private File file;
	
	/**
	 * The content extractor to use to extract content from files
	 * 
	 * @baleen.config Value of BaleenDefaults.DEFAULT_CONTENT_EXTRACTOR
	 */
	public static final String PARAM_CONTENT_EXTRACTOR = "contentExtractor";
	@ConfigurationParameter(name = PARAM_CONTENT_EXTRACTOR, defaultValue=BaleenDefaults.DEFAULT_CONTENT_EXTRACTOR)
	private String contentExtractor;
	
	private BufferedReader br;
	private String line;
	private Integer lineNumber = 0;
	
	private IContentExtractor extractor;

	
	@Override
	protected void doInitialize(UimaContext context) throws ResourceInitializationException {
		if(file == null || !file.canRead() || !file.isFile()){
			throw new ResourceInitializationException(
				new InvalidParameterException("Specified parameter '"+PARAM_FILE+"' was not valid")
			);
		}
		
		try{
			br = new BufferedReader(new InputStreamReader(new FileInputStream(file), StandardCharsets.UTF_8));
		}catch(IOException ioe){
			throw new ResourceInitializationException(ioe);
		}
		
		try{
			extractor = getContentExtractor(contentExtractor);
		}catch(InvalidParameterException ipe){
			throw new ResourceInitializationException(ipe);
		}
		extractor.initialize(context, getConfigParameters(context));
	}

	@Override
	public boolean doHasNext() throws IOException, CollectionException {
		if(br == null)
			return false;
		
		while((line = br.readLine()) != null){
			lineNumber++;
			
			line = line.trim();
			if(!line.isEmpty()){
				return true;
			}
		}
		
		try{
			br.close();
		}catch(IOException ioe){
			getMonitor().debug("An error occurred when closing the BufferedReader", ioe);
		}
		br = null;
		
		return false;
	}
	
	@Override
	protected void doGetNext(JCas jCas) throws IOException, CollectionException {
		InputStream is = IOUtils.toInputStream(line, Charset.defaultCharset());
		extractor.processStream(is, file.getPath() + "#" + lineNumber, jCas);
		
		Metadata md = new Metadata(jCas);
		md.setKey("lineNumber");
		md.setValue(lineNumber.toString());
		getSupport().add(md);
	}

	@Override
	protected void doClose() throws IOException {
		if(br != null){
			try{
				br.close();
			}catch(IOException ioe){
				getMonitor().debug("An error occurred when closing the BufferedReader", ioe);
			}
			br = null;
		}
		
		if(extractor != null) {
			extractor.destroy();
			extractor = null;
		}
	}

}