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package com.sun.xml.internal.bind.marshaller;

import java.io.OutputStream;

import javax.xml.bind.JAXBContext;

import javax.xml.stream.XMLEventWriter;

import javax.xml.stream.XMLStreamWriter;

import javax.xml.transform.dom.DOMResult;

import org.w3c.dom.Node;

// be careful about changing this class. this class is supposed to be

// extended by users and therefore we are not allowed to break

// those user code.

//

// this means:

// - don't add any abstract method

// - don't change any existing method signature

// - don't remove any existing method.

/**

 * Implemented by the user application to determine URI -> prefix

 * mapping.

 *

 * This is considered as an interface, though it's implemented

 * as an abstract class to make it easy to add new methods in

 * a future.

 *

 * @author

 *     Kohsuke Kawaguchi (kohsuke.kawaguchi@sun.com)

 */

public abstract class NamespacePrefixMapper {

    private static final String[] EMPTY_STRING = new String[0];

    /**

     * Returns a preferred prefix for the given namespace URI.

     *

     * This method is intended to be overrided by a derived class.

     *

     * <p>

     * As noted in the return value portion of the javadoc, there

     * are several cases where the preference cannot be honored.

     * Specifically, as of JAXB RI 2.0 and onward:

     *

     * <ol>

     * <li>

     * If the prefix returned is already in use as one of the in-scope

     * namespace bindings. This is partly necessary for correctness

     * (so that we don't unexpectedly change the meaning of QNames

     * bound to {@link String}), partly to simplify the marshaller.

     * <li>

     * If the prefix returned is "" yet the current {@link JAXBContext}

     * includes classes that use the empty namespace URI. This allows

     * the JAXB RI to reserve the "" prefix for the empty namespace URI,

     * which is the only possible prefix for the URI.

     * This restriction is also to simplify the marshaller.

     * </ol>

     *

     * @param namespaceUri

     *      The namespace URI for which the prefix needs to be found.

     *      Never be null. "" is used to denote the default namespace.

     * @param suggestion

     *      When the content tree has a suggestion for the prefix

     *      to the given namespaceUri, that suggestion is passed as a

     *      parameter. Typicall this value comes from the QName.getPrefix

     *      to show the preference of the content tree. This parameter

     *      may be null, and this parameter may represent an already

     *      occupied prefix.

     * @param requirePrefix

     *      If this method is expected to return non-empty prefix.

     *      When this flag is true, it means that the given namespace URI

     *      cannot be set as the default namespace.

     *

     * @return

     *      null if there's no prefered prefix for the namespace URI.

     *      In this case, the system will generate a prefix for you.

     *

     *      Otherwise the system will try to use the returned prefix,

     *      but generally there's no guarantee if the prefix will be

     *      actually used or not.

     *

     *      return "" to map this namespace URI to the default namespace.

     *      Again, there's no guarantee that this preference will be

     *      honored.

     *

     *      If this method returns "" when requirePrefix=true, the return

     *      value will be ignored and the system will generate one.

     *

     * @since JAXB 1.0.1

     */

    public abstract String getPreferredPrefix(String namespaceUri, String suggestion, boolean requirePrefix);

    /**

     * Returns a list of namespace URIs that should be declared

     * at the root element.

     *

     * <p>

     * By default, the JAXB RI 1.0.x produces namespace declarations only when

     * they are necessary, only at where they are used. Because of this

     * lack of look-ahead, sometimes the marshaller produces a lot of

     * namespace declarations that look redundant to human eyes. For example,

     * <pre><xmp>

     * <?xml version="1.0"?>

     * <root>

     *   <ns1:child xmlns:ns1="urn:foo"> ... </ns1:child>

     *   <ns2:child xmlns:ns2="urn:foo"> ... </ns2:child>

     *   <ns3:child xmlns:ns3="urn:foo"> ... </ns3:child>

     *   ...

     * </root>

     * </xmp></pre>

     *

     * <p>

     * The JAXB RI 2.x mostly doesn't exhibit this behavior any more,

     * as it declares all statically known namespace URIs (those URIs

     * that are used as element/attribute names in JAXB annotations),

     * but it may still declare additional namespaces in the middle of

     * a document, for example when (i) a QName as an attribute/element value

     * requires a new namespace URI, or (ii) DOM nodes as a portion of an object

     * tree requires a new namespace URI.

     *

     * <p>

     * If you know in advance that you are going to use a certain set of

     * namespace URIs, you can override this method and have the marshaller

     * declare those namespace URIs at the root element.

     *

     * <p>

     * For example, by returning <code>new String[]{"urn:foo"}</code>,

     * the marshaller will produce:

     * <pre><xmp>

     * <?xml version="1.0"?>

     * <root xmlns:ns1="urn:foo">

     *   <ns1:child> ... </ns1:child>

     *   <ns1:child> ... </ns1:child>

     *   <ns1:child> ... </ns1:child>

     *   ...

     * </root>

     * </xmp></pre>

     * <p>

     * To control prefixes assigned to those namespace URIs, use the

     * {@link #getPreferredPrefix(String, String, boolean)} method.

     *

     * @return

     *      A list of namespace URIs as an array of {@link String}s.

     *      This method can return a length-zero array but not null.

     *      None of the array component can be null. To represent

     *      the empty namespace, use the empty string <code>""</code>.

     *

     * @since

     *      JAXB RI 1.0.2

     */

    public String[] getPreDeclaredNamespaceUris() {

        return EMPTY_STRING;

    }

    /**

     * Similar to {@link #getPreDeclaredNamespaceUris()} but allows the

     * (prefix,nsUri) pairs to be returned.

     *

     * <p>

     * With {@link #getPreDeclaredNamespaceUris()}, applications who wish to control

     * the prefixes as well as the namespaces needed to implement both

     * {@link #getPreDeclaredNamespaceUris()} and {@link #getPreferredPrefix(String, String, boolean)}.

     *

     * <p>

     * This version eliminates the needs by returning an array of pairs.

     *

     * @return

     *      always return a non-null (but possibly empty) array. The array stores

     *      data like (prefix1,nsUri1,prefix2,nsUri2,...) Use an empty string to represent

     *      the empty namespace URI and the default prefix. Null is not allowed as a value

     *      in the array.

     *

     * @since

     *      JAXB RI 2.0 beta

     */

    public String[] getPreDeclaredNamespaceUris2() {

        return EMPTY_STRING;

    }

    /**

     * Returns a list of (prefix,namespace URI) pairs that represents

     * namespace bindings available on ancestor elements (that need not be repeated

     * by the JAXB RI.)

     *

     * <p>

     * Sometimes JAXB is used to marshal an XML document, which will be

     * used as a subtree of a bigger document. When this happens, it's nice

     * for a JAXB marshaller to be able to use in-scope namespace bindings

     * of the larger document and avoid declaring redundant namespace URIs.

     *

     * <p>

     * This is automatically done when you are marshalling to {@link XMLStreamWriter},

     * {@link XMLEventWriter}, {@link DOMResult}, or {@link Node}, because

     * those output format allows us to inspect what's currently available

     * as in-scope namespace binding. However, with other output format,

     * such as {@link OutputStream}, the JAXB RI cannot do this automatically.

     * That's when this method comes into play.

     *

     * <p>

     * Namespace bindings returned by this method will be used by the JAXB RI,

     * but will not be re-declared. They are assumed to be available when you insert

     * this subtree into a bigger document.

     *

     * <p>

     * It is <b>NOT</b> OK to return  the same binding, or give

     * the receiver a conflicting binding information.

     * It's a responsibility of the caller to make sure that this doesn't happen

     * even if the ancestor elements look like:

     * <pre><xmp>

     *   <foo:abc xmlns:foo="abc">

     *     <foo:abc xmlns:foo="def">

     *       <foo:abc xmlns:foo="abc">

     *         ... JAXB marshalling into here.

     *       </foo:abc>

     *     </foo:abc>

     *   </foo:abc>

     * </xmp></pre>

     *

     * @return

     *      always return a non-null (but possibly empty) array. The array stores

     *      data like (prefix1,nsUri1,prefix2,nsUri2,...) Use an empty string to represent

     *      the empty namespace URI and the default prefix. Null is not allowed as a value

     *      in the array.

     *

     * @since JAXB RI 2.0 beta

     */

    public String[] getContextualNamespaceDecls() {

        return EMPTY_STRING;

    }

}