/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package com.sun.xml.internal.dtdparser;

import org.xml.sax.EntityResolver;

import org.xml.sax.InputSource;

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStream;

import java.net.URL;

import java.net.URLConnection;

import java.util.Hashtable;

/**

 * This entity resolver class provides a number of utilities which can help

 * managment of external parsed entities in XML.  These are commonly used

 * to hold markup declarations that are to be used as part of a Document

 * Type Declaration (DTD), or to hold text marked up with XML.

 * <p/>

 * <P> Features include: <UL>

 * <p/>

 * <LI> Static factory methods are provided for constructing SAX InputSource

 * objects from Files, URLs, or MIME objects.  This eliminates a class of

 * error-prone coding in applications.

 * <p/>

 * <LI> Character encodings for XML documents are correctly supported: <UL>

 * <p/>

 * <LI> The encodings defined in the RFCs for MIME content types

 * (2046 for general MIME, and 2376 for XML in particular), are

 * supported, handling <em>charset=...</em> attributes and accepting

 * content types which are known to be safe for use with XML;

 * <p/>

 * <LI> The character encoding autodetection algorithm identified

 * in the XML specification is used, and leverages all of

 * the JDK 1.1 (and later) character encoding support.

 * <p/>

 * <LI> The use of MIME typing may optionally be disabled, forcing the

 * use of autodetection, to support web servers which don't correctly

 * report MIME types for XML.  For example, they may report text that

 * is encoded in EUC-JP as being US-ASCII text, leading to fatal

 * errors during parsing.

 * <p/>

 * <LI> The InputSource objects returned by this class always

 * have a <code>java.io.Reader</code> available as the "character

 * stream" property.

 * <p/>

 * </UL>

 * <p/>

 * <LI> Catalog entries can map public identifiers to Java resources or

 * to local URLs.  These are used to reduce network dependencies and loads,

 * and will often be used for external DTD components.  For example, packages

 * shipping DTD files as resources in JAR files can eliminate network traffic

 * when accessing them, and sites may provide local caches of common DTDs.

 * Note that no particular catalog syntax is supported by this class, only

 * the notion of a set of entries.

 * <p/>

 * </UL>

 * <p/>

 * <P> Subclasses can perform tasks such as supporting new URI schemes for

 * URIs which are not URLs, such as URNs (see RFC 2396) or for accessing

 * MIME entities which are part of a <em>multipart/related</em> group

 * (see RFC 2387).  They may also be used to support particular catalog

 * syntaxes, such as the <a href="http://www.oasis-open.org/html/a401.htm">

 * SGML/Open Catalog (SOCAT)</a> which supports the SGML notion of "Formal

 * Public Identifiers (FPIs).

 *

 * @author David Brownell

 * @author Janet Koenig

 * @version 1.3 00/02/24

 */

public class Resolver implements EntityResolver {

    private boolean ignoringMIME;

    // table mapping public IDs to (local) URIs

    private Hashtable id2uri;

    // tables mapping public IDs to resources and classloaders

    private Hashtable id2resource;

    private Hashtable id2loader;

    //

    // table of MIME content types (less attributes!) known

    // to be mostly "OK" to use with XML MIME entities.  the

    // idea is to rule out obvious braindamage ("image/jpg")

    // not the subtle stuff ("text/html") that might actually

    // be (or become) safe.

    //

    private static final String types [] = {

        "application/xml",

        "text/xml",

        "text/plain",

        "text/html", // commonly mis-inferred

        "application/x-netcdf", // this is often illegal XML

        "content/unknown"

    };

    /**

     * Constructs a resolver.

     */

    public Resolver() {

    }

    /**

     * Returns an input source, using the MIME type information and URL

     * scheme to statically determine the correct character encoding if

     * possible and otherwise autodetecting it.  MIME carefully specifies

     * the character encoding defaults, and how attributes of the content

     * type can change it.  XML further specifies two mandatory encodings

     * (UTF-8 and UTF-16), and includes an XML declaration which can be

     * used to internally label most documents encoded using US-ASCII

     * supersets (such as Shift_JIS, EUC-JP, ISO-2022-*, ISO-8859-*, and

     * more).

     * <p/>

     * <P> This method can be used to access XML documents which do not

     * have URIs (such as servlet input streams, or most JavaMail message

     * entities) and to support access methods such as HTTP POST or PUT.

     * (URLs normally return content using the GET method.)

     * <p/>

     * <P> <em> The caller should set the system ID in order for relative URIs

     * found in this document to be interpreted correctly.</em> In some cases,

     * a custom resolver will need to be used; for example, documents

     * may be grouped in a single MIME "multipart/related" bundle, and

     * relative URLs would refer to other documents in that bundle.

     *

     * @param contentType The MIME content type for the source for which

     *                    an InputSource is desired, such as <em>text/xml;charset=utf-8</em>.

     * @param stream      The input byte stream for the input source.

     * @param checkType   If true, this verifies that the content type is known

     *                    to support XML documents, such as <em>application/xml</em>.

     * @param scheme      Unless this is "file", unspecified MIME types

     *                    default to US-ASCII.  Files are always autodetected since most

     *                    file systems discard character encoding information.

     */

    public static InputSource createInputSource(String contentType,

                                                InputStream stream,

                                                boolean checkType,

                                                String scheme) throws IOException {

        InputSource retval;

        String charset = null;

        if (contentType != null) {

            int index;

            contentType = contentType.toLowerCase();

            index = contentType.indexOf(';');

            if (index != -1) {

                String attributes;

                attributes = contentType.substring(index + 1);

                contentType = contentType.substring(0, index);

                // use "charset=..." if it's available

                index = attributes.indexOf("charset");

                if (index != -1) {

                    attributes = attributes.substring(index + 7);

                    // strip out subsequent attributes

                    if ((index = attributes.indexOf(';')) != -1)

                        attributes = attributes.substring(0, index);

                    // find start of value

                    if ((index = attributes.indexOf('=')) != -1) {

                        attributes = attributes.substring(index + 1);

                        // strip out rfc822 comments

                        if ((index = attributes.indexOf('(')) != -1)

                            attributes = attributes.substring(0, index);

                        // double quotes are optional

                        if ((index = attributes.indexOf('"')) != -1) {

                            attributes = attributes.substring(index + 1);

                            attributes = attributes.substring(0,

                                    attributes.indexOf('"'));

                        }

                        charset = attributes.trim();

                        // XXX "\;", "\)" etc were mishandled above

                    }

                }

            }

            //

            // Check MIME type.

            //

            if (checkType) {

                boolean isOK = false;

                for (int i = 0; i < types.length; i++)

                    if (types[i].equals(contentType)) {

                        isOK = true;

                        break;

                    }

                if (!isOK)

                    throw new IOException("Not XML: " + contentType);

            }

            //

            // "text/*" MIME types have hard-wired character set

            // defaults, as specified in the RFCs.  For XML, we

            // ignore the system "file.encoding" property since

            // autodetection is more correct.

            //

            if (charset == null) {

                contentType = contentType.trim();

                if (contentType.startsWith("text/")) {

                    if (!"file".equalsIgnoreCase(scheme))

                        charset = "US-ASCII";

                }

                // "application/*" has no default

            }

        }

        retval = new InputSource(XmlReader.createReader(stream, charset));

        retval.setByteStream(stream);

        retval.setEncoding(charset);

        return retval;

    }

    /**

     * Creates an input source from a given URI.

     *

     * @param uri       the URI (system ID) for the entity

     * @param checkType if true, the MIME content type for the entity

     *                  is checked for document type and character set encoding.

     */

    static public InputSource createInputSource(URL uri, boolean checkType)

            throws IOException {

        URLConnection conn = uri.openConnection();

        InputSource retval;

        if (checkType) {

            String contentType = conn.getContentType();

            retval = createInputSource(contentType, conn.getInputStream(),

                    false, uri.getProtocol());

        } else {

            retval = new InputSource(XmlReader.createReader(conn.getInputStream()));

        }

        retval.setSystemId(conn.getURL().toString());

        return retval;

    }

    /**

     * Creates an input source from a given file, autodetecting

     * the character encoding.

     */

    static public InputSource createInputSource(File file)

            throws IOException {

        InputSource retval;

        String path;

        retval = new InputSource(XmlReader.createReader(new FileInputStream(file)));

        // On JDK 1.2 and later, simplify this:

        //    "path = file.toURL ().toString ()".

        path = file.getAbsolutePath();

        if (File.separatorChar != '/')

            path = path.replace(File.separatorChar, '/');

        if (!path.startsWith("/"))

            path = "/" + path;

        if (!path.endsWith("/") && file.isDirectory())

            path = path + "/";

        retval.setSystemId("file:" + path);

        return retval;

    }

    /**

     * <b>SAX:</b>

     * Resolve the given entity into an input source.  If the name can't

     * be mapped to a preferred form of the entity, the URI is used.  To

     * resolve the entity, first a local catalog mapping names to URIs is

     * consulted.  If no mapping is found there, a catalog mapping names

     * to java resources is consulted.  Finally, if neither mapping found

     * a copy of the entity, the specified URI is used.

     * <p/>

     * <P> When a URI is used, <a href="#createInputSource">

     * createInputSource</a> is used to correctly deduce the character

     * encoding used by this entity.  No MIME type checking is done.

     *

     * @param name Used to find alternate copies of the entity, when

     *             this value is non-null; this is the XML "public ID".

     * @param uri  Used when no alternate copy of the entity is found;

     *             this is the XML "system ID", normally a URI.

     */

    public InputSource resolveEntity(String name, String uri)

            throws IOException {

        InputSource retval;

        String mappedURI = name2uri(name);

        InputStream stream;

        // prefer explicit URI mappings, then bundled resources...

        if (mappedURI == null && (stream = mapResource(name)) != null) {

            uri = "java:resource:" + (String) id2resource.get(name);

            retval = new InputSource(XmlReader.createReader(stream));

            // ...and treat all URIs the same (as URLs for now).

        } else {

            URL url;

            URLConnection conn;

            if (mappedURI != null)

                uri = mappedURI;

            else if (uri == null)

                return null;

            url = new URL(uri);

            conn = url.openConnection();

            uri = conn.getURL().toString();

            // System.out.println ("++ URI: " + url);

            if (ignoringMIME)

                retval = new InputSource(XmlReader.createReader(conn.getInputStream()));

            else {

                String contentType = conn.getContentType();

                retval = createInputSource(contentType,

                        conn.getInputStream(),

                        false, url.getProtocol());

            }

        }

        retval.setSystemId(uri);

        retval.setPublicId(name);

        return retval;

    }

    /**

     * Returns true if this resolver is ignoring MIME types in the documents

     * it returns, to work around bugs in how servers have reported the

     * documents' MIME types.

     */

    public boolean isIgnoringMIME() {

        return ignoringMIME;

    }

    /**

     * Tells the resolver whether to ignore MIME types in the documents it

     * retrieves.  Many web servers incorrectly assign text documents a

     * default character encoding, even when that is incorrect.  For example,

     * all HTTP text documents default to use ISO-8859-1 (used for Western

     * European languages), and other MIME sources default text documents

     * to use US-ASCII (a seven bit encoding).  For XML documents which

     * include text encoding declarations (as most should do), these server

     * bugs can be worked around by ignoring the MIME type entirely.

     */

    public void setIgnoringMIME(boolean value) {

        ignoringMIME = value;

    }

    // maps the public ID to an alternate URI, if one is registered

    private String name2uri(String publicId) {

        if (publicId == null || id2uri == null)

            return null;

        return (String) id2uri.get(publicId);

    }

    /**

     * Registers the given public ID as corresponding to a particular

     * URI, typically a local copy.  This URI will be used in preference

     * to ones provided as system IDs in XML entity declarations.  This

     * mechanism would most typically be used for Document Type Definitions

     * (DTDs), where the public IDs are formally managed and versioned.

     *

     * @param publicId The managed public ID being mapped

     * @param uri      The URI of the preferred copy of that entity

     */

    public void registerCatalogEntry(String publicId,

                                     String uri) {

        if (id2uri == null)

            id2uri = new Hashtable(17);

        id2uri.put(publicId, uri);

    }

    // return the resource as a stream

    private InputStream mapResource(String publicId) {

        // System.out.println ("++ PUBLIC: " + publicId);

        if (publicId == null || id2resource == null)

            return null;

        String resourceName = (String) id2resource.get(publicId);

        ClassLoader loader = null;

        if (resourceName == null)

            return null;

        // System.out.println ("++ Resource: " + resourceName);

        if (id2loader != null)

            loader = (ClassLoader) id2loader.get(publicId);

        // System.out.println ("++ Loader: " + loader);

        if (loader == null)

            return ClassLoader.getSystemResourceAsStream(resourceName);

        return loader.getResourceAsStream(resourceName);

    }

    /**

     * Registers a given public ID as corresponding to a particular Java

     * resource in a given class loader, typically distributed with a

     * software package.  This resource will be preferred over system IDs

     * included in XML documents.  This mechanism should most typically be

     * used for Document Type Definitions (DTDs), where the public IDs are

     * formally managed and versioned.

     * <p/>

     * <P> If a mapping to a URI has been provided, that mapping takes

     * precedence over this one.

     *

     * @param publicId     The managed public ID being mapped

     * @param resourceName The name of the Java resource

     * @param loader       The class loader holding the resource, or null if

     *                     it is a system resource.

     */

    public void registerCatalogEntry(String publicId,

                                     String resourceName,

                                     ClassLoader loader) {

        if (id2resource == null)

            id2resource = new Hashtable(17);

        id2resource.put(publicId, resourceName);

        if (loader != null) {

            if (id2loader == null)

                id2loader = new Hashtable(17);

            id2loader.put(publicId, loader);

        }

    }

}