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

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.util.List;

import org.apache.uima.fit.descriptor.ConfigurationParameter;
import org.apache.uima.jcas.JCas;

import com.opencsv.CSVReader;

import uk.gov.dstl.baleen.contentextractors.helpers.AbstractContentExtractor;
import uk.gov.dstl.baleen.types.metadata.Metadata;

/**
 * Takes a single line of CSV data, and splits it into 'columns' based on the specified separator character.
 * The column designated as the main content is set as the JCas body, and other columns are added as Metadata annotations.
 * 
 * @baleen.javadoc
 */
public class CsvContentExtractor extends AbstractContentExtractor {

	/**
	 * Separator to split columns by.
	 * Can only be a single character, and if more than one character is provided only the first will be used.
	 * 
	 * @baleen.config ,
	 */
	public static final String PARAM_SEPARATOR = "separator";
	@ConfigurationParameter(name = PARAM_SEPARATOR, defaultValue = ",")
	String separator;
	
	/**
	 * The column number containing the content
	 * 
	 * @baleen.config 1
	 */
	public static final String PARAM_CONTENT_COLUMN = "contentColumn";
	@ConfigurationParameter(name = PARAM_CONTENT_COLUMN, defaultValue = "1")
	Integer contentColumn;
	
	/**
	 * A list of column headings (in order, skipping the content column) to use as metadata keys.
	 * If not provided, each column will be called column# where the # represents the column number.
	 * 
	 * @baleen.config
	 */
	public static final String PARAM_COLUMNS = "columns";
	@ConfigurationParameter(name = PARAM_COLUMNS, defaultValue = {})
	List<String> columns;
	
	@Override
	public void doProcessStream(InputStream stream, String source, JCas jCas) throws IOException {
		super.doProcessStream(stream, source, jCas);
		try(
			CSVReader reader = new CSVReader(new InputStreamReader(stream, StandardCharsets.UTF_8), separator.charAt(0))
		){
			String[] cols = reader.readNext();
			if(cols == null || cols.length < contentColumn){
				throw new IOException("Not enough columns");
			}
			
			for(int i = 0; i < cols.length; i++){
				if(i == (contentColumn - 1)){
					jCas.setDocumentText(cols[i]);
				}else{
					addMetadata(jCas, i, cols[i]);
				}
			}
		}
	}
	
	private void addMetadata(JCas jCas, Integer index, String value){
		Metadata md = new Metadata(jCas);
		
		Integer colNameIndex = index;
		if(index >= contentColumn)
			colNameIndex--;
		
		if(colNameIndex >= columns.size() || columns.get(colNameIndex).trim().isEmpty()){
			md.setKey("column" + (index + 1));
		}else{
			md.setKey(columns.get(colNameIndex).trim());
		}
		md.setValue(value);						
		getSupport().add(md);
	}
}