/*
 * 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
 *
 *      http://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.
 */

/* $Id: DTDEntityResolver.java 1679676 2015-05-16 02:10:42Z adelmelle $ */

package org.apache.fop.afp.util;

import java.io.IOException;
import java.net.URL;

import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;

import org.apache.fop.afp.fonts.FontRuntimeException;

An entity resolver for both DOM and SAX models of the SAX document.
 The entity resolver only handles queries for the DTD. It will find any URI with a recognised public id and return an InputSource. 

This work was authored by Joe Schmetzer (joe@exubero.com).
/**
 * An entity resolver for both DOM and SAX models of the SAX document.<br>
 * The entity resolver only handles queries for the DTD. It will find any URI
 * with a recognised public id and return an {@link org.xml.sax.InputSource}.
 * <br>
 *
 * <p>This work was authored by Joe Schmetzer (joe@exubero.com).</p>
 */
public class DTDEntityResolver implements EntityResolver {

    
Public ID for the AFP fonts 1.0 DTD. /** Public ID for the AFP fonts 1.0 DTD. */
    public static final String AFP_DTD_1_0_ID
        = "-//APACHE/DTD AFP Installed Font Definition DTD 1.0//EN";

    
Resource location for the AFP fonts 1.0 DTD. /** Resource location for the AFP fonts 1.0 DTD. */
    public static final String AFP_DTD_1_0_RESOURCE
        =  "afp-fonts-1.0.dtd";

    
Public ID for the AFP fonts 1.1 DTD. /** Public ID for the AFP fonts 1.1 DTD. */
    public static final String AFP_DTD_1_1_ID
        = "-//APACHE/DTD AFP Installed Font Definition DTD 1.1//EN";

    
Resource location for the AFP fonts 1.1 DTD. /** Resource location for the AFP fonts 1.1 DTD. */
    public static final String AFP_DTD_1_1_RESOURCE
        =  "afp-fonts-1.1.dtd";

    
Public ID for the AFP fonts 1.2 DTD. /** Public ID for the AFP fonts 1.2 DTD. */
    public static final String AFP_DTD_1_2_ID
        = "-//APACHE/DTD AFP Installed Font Definition DTD 1.2//EN";

    
Resource location for the AFP fonts 1.2 DTD. /** Resource location for the AFP fonts 1.2 DTD. */
    public static final String AFP_DTD_1_2_RESOURCE
        =  "afp-fonts-1.2.dtd";

    
Resolve the combination of system and public identifiers.
If this resolver recognises the publicId, it will handle the resolution
from the classpath, otherwise it will return null and allow the default
resolution to occur.
Params:
publicId – the public identifier to use
systemId – the system identifier to resolve
Throws:
IOException – an error reading the stream
Returns:
An input source to the entity or null if not handled/**
     * Resolve the combination of system and public identifiers.
     * If this resolver recognises the publicId, it will handle the resolution
     * from the classpath, otherwise it will return null and allow the default
     * resolution to occur.
     *
     * @param publicId the public identifier to use
     * @param systemId the system identifier to resolve
     * @return An input source to the entity or null if not handled
     * @throws IOException an error reading the stream
     */
    public InputSource resolveEntity(String publicId, String systemId)
    throws IOException {

        URL resource = null;
        if (AFP_DTD_1_2_ID.equals(publicId)) {
            resource = getResource(AFP_DTD_1_2_RESOURCE);
        } else if (AFP_DTD_1_1_ID.equals(publicId)) {
            resource = getResource(AFP_DTD_1_1_RESOURCE);
        } else if (AFP_DTD_1_0_ID.equals(publicId)) {
            throw new FontRuntimeException(
                "The AFP Installed Font Definition 1.0 DTD is not longer supported");
        } else if (systemId != null && systemId.indexOf("afp-fonts.dtd") >= 0) {
            throw new FontRuntimeException(
                "The AFP Installed Font Definition DTD must be specified using the public id");
        } else {
            return null;
        }

        InputSource inputSource = new InputSource(resource.openStream());
        inputSource.setPublicId(publicId);
        inputSource.setSystemId(systemId);

        return inputSource;
    }

    
Returns the URL of a resource on the classpath
Params:
resourcePath – the path to the resource relative to the root of the
classpath.
Throws:
FontRuntimeException – if the resource could not be found.
Returns:
the URL of the required resource/**
     * Returns the URL of a resource on the classpath
     * @param resourcePath the path to the resource relative to the root of the
     * classpath.
     * @return the URL of the required resource
     * @throws FontRuntimeException if the resource could not be found.
     */
    private URL getResource(String resourcePath) {
        ClassLoader cl = Thread.currentThread().getContextClassLoader();
        if (cl == null) {
            cl = ClassLoader.getSystemClassLoader();
        }

        URL resource = cl.getResource(resourcePath);
        if (resource == null) {
            throw new FontRuntimeException("Resource " + resourcePath
                    + "could not be found on the classpath");
        }

        return resource;
    }
}