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

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 * 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

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package com.sun.xml.internal.txw2;

import javax.xml.namespace.QName;

/**

 * Start tag.

 *

 * <p>

 * This object implements {@link NamespaceResolver} for attribute values.

 *

 * @author Kohsuke Kawaguchi

 */

class StartTag extends Content implements NamespaceResolver {

    /**

     * Tag name of the element.

     *

     * <p>

     * This field is also used as a flag to indicate

     * whether the start tag has been written.

     * This field is initially set to non-null, and

     * then reset to null when it's written.

     */

    private String uri;

    // but we keep the local name non-null so that

    // we can diagnose an error

    private final String localName;

    private Attribute firstAtt;

    private Attribute lastAtt;

    /**

     * If this {@link StartTag} has the parent {@link ContainerElement},

     * that value. Otherwise null.

     */

    private ContainerElement owner;

    /**

     * Explicitly given namespace declarations on this element.

     *

     * <p>

     * Additional namespace declarations might be necessary to

     * generate child {@link QName}s and attributes.

     */

    private NamespaceDecl firstNs;

    private NamespaceDecl lastNs;

    final Document document;

    public StartTag(ContainerElement owner, String uri, String localName) {

        this(owner.document,uri,localName);

        this.owner = owner;

    }

    public StartTag(Document document, String uri, String localName) {

        assert uri!=null;

        assert localName!=null;

        this.uri = uri;

        this.localName = localName;

        this.document = document;

        // TODO: think about a better way to maintain namespace decls.

        // this requires at least one NamespaceDecl per start tag,

        // which is rather expensive.

        addNamespaceDecl(uri,null,false);

    }

    public void addAttribute(String nsUri, String localName, Object arg) {

        checkWritable();

        // look for the existing ones

        Attribute a;

        for(a=firstAtt; a!=null; a=a.next) {

            if(a.hasName(nsUri,localName)) {

                break;

            }

        }

        // if not found, declare a new one

        if(a==null) {

            a = new Attribute(nsUri,localName);

            if(lastAtt==null) {

                assert firstAtt==null;

                firstAtt = lastAtt = a;

            } else {

                assert firstAtt!=null;

                lastAtt.next = a;

                lastAtt = a;

            }

            if(nsUri.length()>0)

                addNamespaceDecl(nsUri,null,true);

        }

        document.writeValue(arg,this,a.value);

    }

    /**

     * Declares a new namespace URI on this tag.

     *

     * @param uri

     *      namespace URI to be bound. Can be empty, but must not be null.

     * @param prefix

     *      If non-null and non-empty, this prefix is bound to the URI

     *      on this element. If empty, then the runtime will still try to

     *      use the URI as the default namespace, but it may fail to do so

     *      because of the constraints in the XML.

     *      <p>

     *      If this parameter is null, the runtime will allocate an unique prefix.

     * @param requirePrefix

     *      Used only when the prefix parameter is null. If true, this indicates

     *      that the non-empty prefix must be assigned to this URI. If false,

     *      then this URI might be used as the default namespace.

     *      <p>

     *      Normally you just need to set it to false.

     */

    public NamespaceDecl addNamespaceDecl(String uri, String prefix,boolean requirePrefix) {

        checkWritable();

        if(uri==null)

            throw new IllegalArgumentException();

        if(uri.length()==0) {

            if(requirePrefix)

                throw new IllegalArgumentException("The empty namespace cannot have a non-empty prefix");

            if(prefix!=null && prefix.length()>0)

                throw new IllegalArgumentException("The empty namespace can be only bound to the empty prefix");

            prefix = "";

        }

        // check for the duplicate

        for(NamespaceDecl n=firstNs; n!=null; n=n.next) {

            if(uri.equals(n.uri)) {

                if(prefix==null) {

                    // reuse this binding

                    n.requirePrefix |= requirePrefix;

                    return n;

                }

                if(n.prefix==null) {

                    // reuse this binding

                    n.prefix = prefix;

                    n.requirePrefix |= requirePrefix;

                    return n;

                }

                if(prefix.equals(n.prefix)) {

                    // reuse this binding

                    n.requirePrefix |= requirePrefix;

                    return n;

                }

            }

            if(prefix!=null && n.prefix!=null && n.prefix.equals(prefix))

                throw new IllegalArgumentException(

                    "Prefix '"+prefix+"' is already bound to '"+n.uri+'\'');

        }

        NamespaceDecl ns = new NamespaceDecl(document.assignNewId(),uri,prefix,requirePrefix);

        if(lastNs==null) {

            assert firstNs==null;

            firstNs = lastNs = ns;

        } else {

            assert firstNs!=null;

            lastNs.next = ns;

            lastNs = ns;

        }

        return ns;

    }

    /**

     * Throws an error if the start tag has already been committed.

     */

    private void checkWritable() {

        if(isWritten())

            throw new IllegalStateException(

                "The start tag of "+this.localName+" has already been written. " +

                "If you need out of order writing, see the TypedXmlWriter.block method");

    }

    /**

     * Returns true if this start tag has already been written.

     */

    boolean isWritten() {

        return uri==null;

    }

    /**

     * A {@link StartTag} can be only written after

     * we are sure that all the necessary namespace declarations are given.

     */

    boolean isReadyToCommit() {

        if(owner!=null && owner.isBlocked())

            return false;

        for( Content c=getNext(); c!=null; c=c.getNext() )

            if(c.concludesPendingStartTag())

                return true;

        return false;

    }

    public void written() {

        firstAtt = lastAtt = null;

        uri = null;

        if(owner!=null) {

            assert owner.startTag==this;

            owner.startTag = null;

        }

    }

    boolean concludesPendingStartTag() {

        return true;

    }

    void accept(ContentVisitor visitor) {

        visitor.onStartTag(uri,localName,firstAtt,firstNs);

    }

    public String getPrefix(String nsUri) {

        NamespaceDecl ns = addNamespaceDecl(nsUri,null,false);

        if(ns.prefix!=null)

            // if the prefix has already been declared, use it.

            return ns.prefix;

        return ns.dummyPrefix;

    }

}