/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 *
 *   SPDX-License-Identifier: Apache-2.0
 */

package org.apache.jena.sparql.util;

import java.util.HashMap;
import java.util.Map;

import org.apache.jena.graph.Node;

/** Map nodes to blank node representations. */
public class NodeToLabelMap {
    // Could abstract again as a node -> label cache + cache miss handler.
    int bNodeCounter = 0;
    Map<Node, String> bNodeStrings = new HashMap<>();
    boolean bNodesAsFakeURIs = false;
    String prefixString = "b";

    public NodeToLabelMap() {
        this("b");
    }

    public NodeToLabelMap(String prefix) {
        this(prefix, false);
    }

    public NodeToLabelMap(String prefix, boolean bNodesAsFakeURIs) {
        if ( prefix == null || prefix.equals("") )
            throw new IllegalArgumentException("Must provide a prefix");
        this.prefixString = "_:" + prefix;
        this.bNodesAsFakeURIs = bNodesAsFakeURIs;
    }

    // Null means not mapped
    public String asString(Node n) {
        if ( !n.isBlank() )
            return null;
        return mapNode(n);
    }

    // synchronized because this may be used from a static via FmtUtils
    protected synchronized String mapNode(Node n) {
        String s = bNodeStrings.get(n);
        if ( s != null )
            return s;

        s = genStringForNode(n);
        bNodeStrings.put(n, s);
        return s;
    }

    protected String genStringForNode(Node n) {
        if ( bNodesAsFakeURIs && n.isBlank() )
            return "<_:" + n.getBlankNodeLabel() + ">";
        return prefixString + (bNodeCounter++);
    }
}
