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StackableSail API offering full-text search on literals, based on Apache Lucene.
The newest version!
/*******************************************************************************
 * Copyright (c) 2015 Eclipse RDF4J contributors, Aduna, and others.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Distribution License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 *******************************************************************************/
package org.eclipse.rdf4j.sail.lucene;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.eclipse.rdf4j.model.BNode;
import org.eclipse.rdf4j.model.IRI;
import org.eclipse.rdf4j.model.Literal;
import org.eclipse.rdf4j.model.Resource;
import org.eclipse.rdf4j.model.Statement;
import org.eclipse.rdf4j.model.Value;
import org.eclipse.rdf4j.model.ValueFactory;
import org.eclipse.rdf4j.model.impl.SimpleValueFactory;
import org.eclipse.rdf4j.model.vocabulary.GEO;

public final class SearchFields {

	/**
	 * The name of the Document field holding the document identifier. This consists of the Resource identifier (URI or
	 * BNodeID) and the Context ID (the format is "resourceId|contextId")
	 */
	public static final String ID_FIELD_NAME = "id";

	/**
	 * The name of the Document field holding the Resource identifier. The value stored in this field is either a URI or
	 * a BNode ID.
	 */
	public static final String URI_FIELD_NAME = "uri";

	/**
	 * The name of the Document field that holds multiple text values of a Resource. The field is called "text", as it
	 * contains all text, but was called "ALL" during the discussion. For each statement-literal of the resource, the
	 * object literal is stored in a field using the predicate-literal and additionally in a TEXT_FIELD_NAME-literal
	 * field.
	 */
	public static final String TEXT_FIELD_NAME = "text";

	/**
	 * The name of the Document field holding the context identifer(s).
	 */
	public static final String CONTEXT_FIELD_NAME = "context";

	/**
	 * the null context
	 */
	public static final String CONTEXT_NULL = "null";

	/**
	 * String used to prefix BNode IDs with so that we can distinguish BNode fields from URI fields in Documents. The
	 * prefix is chosen so that it is invalid as a (part of a) URI scheme.
	 */
	public static final String BNODE_ID_PREFIX = "!";

	public static final String HIGHLIGHTER_PRE_TAG = "";

	public static final String HIGHLIGHTER_POST_TAG = "";

	public static final Pattern HIGHLIGHTER_PATTERN = Pattern
			.compile("(" + HIGHLIGHTER_PRE_TAG + ".+?" + HIGHLIGHTER_POST_TAG + ")");

	private static final ValueFactory valueFactory = SimpleValueFactory.getInstance();

	private SearchFields() {
	}

	/**
	 * Returns the String ID corresponding with the specified Resource. The id string is either the URI or a bnode
	 * prefixed with a "!".
	 */
	public static String getResourceID(Resource resource) {
		if (resource instanceof IRI) {
			return resource.toString();
		} else if (resource instanceof BNode) {
			return BNODE_ID_PREFIX + ((BNode) resource).getID();
		} else {
			throw new IllegalArgumentException("Unknown Resource type: " + resource);
		}
	}

	/**
	 * Get the ID for a context. Context can be null, then the "null" string is returned
	 *
	 * @param resource the context
	 * @return a string
	 */
	public static String getContextID(Resource resource) {
		if (resource == null) {
			return CONTEXT_NULL;
		} else {
			return getResourceID(resource);
		}
	}

	/**
	 * Parses an id-string (a serialized resource) back to a resource Inverse method of {@link #getResourceID(Resource)}
	 *
	 * @param idString
	 * @return resource
	 */
	public static Resource createResource(String idString) {
		if (idString.startsWith(BNODE_ID_PREFIX)) {
			return valueFactory.createBNode(idString.substring(BNODE_ID_PREFIX.length()));
		} else {
			return valueFactory.createIRI(idString);
		}
	}

	public static Resource createContext(String idString) {
		if (CONTEXT_NULL.equals(idString)) {
			return null;
		} else {
			return createResource(idString);
		}
	}

	public static String getLiteralPropertyValueAsString(Statement statement) {
		Value object = statement.getObject();
		if (object instanceof Literal) {
			return ((Literal) object).getLabel();
		} else {
			return null;
		}
	}

	public static String getPropertyField(IRI property) {
		return property.toString();
	}

	/**
	 * Determines whether the specified field name is a property field name.
	 */
	public static boolean isPropertyField(String fieldName) {
		return !ID_FIELD_NAME.equals(fieldName) && !URI_FIELD_NAME.equals(fieldName)
				&& !TEXT_FIELD_NAME.equals(fieldName) && !CONTEXT_FIELD_NAME.equals(fieldName)
				// geo/internal fields
				&& fieldName.charAt(0) != '_';
	}

	public static String formIdString(String resourceId, String contextId) {
		StringBuilder idBuilder = new StringBuilder(resourceId);
		idBuilder.append("|");
		idBuilder.append(contextId);
		return idBuilder.toString();
	}

	/**
	 * Returns a score value encoded as a Literal.
	 *
	 * @param score the float score to convert
	 * @return the score as a literal
	 */
	public static Literal scoreToLiteral(float score) {
		return valueFactory.createLiteral(score);
	}

	public static Literal wktToLiteral(String wkt) {
		return valueFactory.createLiteral(wkt, GEO.WKT_LITERAL);
	}

	public static Literal distanceToLiteral(double d) {
		return valueFactory.createLiteral(d);
	}

	public static String getSnippet(String highlightedValue) {
		if (highlightedValue.length() > 100) {
			StringBuilder buf = new StringBuilder();
			String separator = "";
			Matcher matcher = HIGHLIGHTER_PATTERN.matcher(highlightedValue);
			for (int i = 0; i < 2 && matcher.find(); i++) {
				buf.append(separator);
				buf.append(matcher.group());
				separator = "...";
			}
			highlightedValue = buf.toString();
		}
		return highlightedValue;
	}
}