/*
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 */
/*
 * $Id: ExcC14NParameterSpec.java,v 1.7 2005/05/13 18:45:42 mullan Exp $
 */
package javax.xml.crypto.dsig.spec;

import javax.xml.crypto.dsig.CanonicalizationMethod;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * Parameters for the W3C Recommendation:
 * <a href="http://www.w3.org/TR/xml-exc-c14n/">
 * Exclusive XML Canonicalization (C14N) algorithm</a>. The
 * parameters include an optional inclusive namespace prefix list. The XML 
 * Schema Definition of the Exclusive XML Canonicalization parameters is
 * defined as:
 * <pre><code>
 * <schema xmlns="http://www.w3.org/2001/XMLSchema"
 *         xmlns:ec="http://www.w3.org/2001/10/xml-exc-c14n#"
 *         targetNamespace="http://www.w3.org/2001/10/xml-exc-c14n#"
 *         version="0.1" elementFormDefault="qualified">
 *
 * <element name="InclusiveNamespaces" type="ec:InclusiveNamespaces"/>
 * <complexType name="InclusiveNamespaces">
 *   <attribute name="PrefixList" type="xsd:string"/>
 * </complexType>
 * </schema>
 * </code></pre>
 *
 * @author Sean Mullan
 * @author JSR 105 Expert Group
 * @since 1.6
 * @see CanonicalizationMethod
 */
public final class ExcC14NParameterSpec implements C14NMethodParameterSpec {

    private List preList;

    /**
     * Indicates the default namespace ("#default").
     */
    public static final String DEFAULT = "#default";

    /**
     * Creates a <code>ExcC14NParameterSpec</code> with an empty prefix 
     * list.
     */
    public ExcC14NParameterSpec() {
	preList = Collections.EMPTY_LIST;
    }

    /**
     * Creates a <code>ExcC14NParameterSpec</code> with the specified list
     * of prefixes. The list is copied to protect against subsequent 
     * modification.
     *
     * @param prefixList the inclusive namespace prefix list. Each entry in
     *    the list is a <code>String</code> that represents a namespace prefix.
     * @throws NullPointerException if <code>prefixList</code> is 
     *    <code>null</code>
     * @throws ClassCastException if any of the entries in the list are not
     *    of type <code>String</code>
     */
    public ExcC14NParameterSpec(List prefixList) {
	if (prefixList == null) {
	    throw new NullPointerException("prefixList cannot be null");
	}
	this.preList = new ArrayList(prefixList);
	for (int i = 0, size = preList.size(); i < size; i++) {
	    if (!(preList.get(i) instanceof String)) {
		throw new ClassCastException("not a String");
	    }
	}
	preList = Collections.unmodifiableList(preList);
    }

    /**
     * Returns the inclusive namespace prefix list. Each entry in the list
     * is a <code>String</code> that represents a namespace prefix.
     *
     * <p>This implementation returns an {@link
     * java.util.Collections#unmodifiableList unmodifiable list}.
     *
     * @return the inclusive namespace prefix list (may be empty but never
     *    <code>null</code>)
     */
    public List getPrefixList() {
	return preList;
    }
}