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

import java.util.List;

import org.apache.uima.jcas.JCas;
import org.apache.uima.jcas.tcas.Annotation;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.nodes.Node;
import org.jsoup.nodes.TextNode;

import com.google.common.base.Strings;

import uk.gov.dstl.baleen.contentmappers.helpers.AnnotationCollector;
import uk.gov.dstl.baleen.contentmappers.helpers.ContentMapper;
import uk.gov.dstl.baleen.contentmappers.helpers.JCasBuilder;

/**
 * Converts the HTML Document to a JCas document.
 *
 * This involves extraction of text from the HTML and then creation of annotations.
 *
 * The creation of annotations is controlled by the {@link ContentMapper}s.
 */
public class DocumentToJCasConverter {

	private final List<ContentMapper> mappers;

	/**
	 * Constructor
	 */
	public DocumentToJCasConverter(final List<ContentMapper> mappers) {
		this.mappers = mappers;
	}

	/**
	 * Convert the document into the jCas.
	 *
	 * @param document the document
	 * @param jCas the j cas
	 */
	public void apply(final Document document, final JCas jCas) {

		final JCasBuilder builder = new JCasBuilder(jCas);

		// First walk the head, but don't save the text
		walk(builder, document.head(), 1, false);
		// Then walk the body and do save the text
		walk(builder, document.body(), 1, true);

		builder.build();
	}

	/**
	 * Walk the HTML document node by node, creating annotations and text.
	 *
	 * @param builder the builder
	 * @param root the root
	 * @param depth the depth
	 */
	private void walk(final JCasBuilder builder, final Node root, final int depth,
			final boolean captureText) {
		if (root == null) {
			return;
		}

		final int begin = builder.getCurrentOffset();
		if (captureText) {
			// Generate the text and the annotations
			final String text = mapToText(root);
			if (!Strings.isNullOrEmpty(text)) {
				builder.addText(text);
			}
		}

		List<Annotation> annotations = null;
		if (root instanceof Element) {
			annotations = mapElementToAnnotations(builder.getJCas(), (Element) root);
		}

		// BUG: With multiple mappers depth here is wrong! It puts all mappers at the same depth...
		// (though in fairness they are all the same begin-end and same element too)

		// Walk the children
		for (final Node node : root.childNodes()) {
			walk(builder, node, depth + 1, captureText);
		}

		// Add annotations to the JCas
		final int end = builder.getCurrentOffset();
		if (annotations != null && !annotations.isEmpty()) {
			builder.addAnnotations(annotations, begin, end, depth);
		}
	}

	/**
	 * Map a node to text.
	 *
	 * @param node the node
	 * @return the string
	 */
	private String mapToText(final Node node) {
		if (node instanceof TextNode) {
			final TextNode t = (TextNode) node;
			return t.getWholeText();
		} else {
			return null;
		}
	}

	/**
	 * Map a HTML element to annotations.
	 *
	 * @param jCas the j cas
	 * @param element the element
	 * @return the list
	 */
	private List<Annotation> mapElementToAnnotations(final JCas jCas, final Element element) {
		final AnnotationCollector collector = new AnnotationCollector();
		for (final ContentMapper mapper : mappers) {
			mapper.map(jCas, element, collector);
		}
		return collector.getAnnotations();
	}

}