// SAX Attribute List Interface.
// http://www.saxproject.org
// No warranty; no copyright -- use this as you will.

package org.xml.sax;

/**
 * Interface for an element's attribute specifications.
 *
 * <blockquote>
 * <em>This module, both source code and documentation, is in the
 * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
 * See <a href='http://www.saxproject.org'>http://www.saxproject.org</a>
 * for further information.
 * </blockquote>
 *
 * <p>This is the original SAX1 interface for reporting an element's
 * attributes.  Unlike the new {@link org.xml.sax.Attributes Attributes}
 * interface, it does not support Namespace-related information.</p>
 *
 * <p>When an attribute list is supplied as part of a
 * {@link org.xml.sax.DocumentHandler#startElement startElement}
 * event, the list will return valid results only during the
 * scope of the event; once the event handler returns control
 * to the parser, the attribute list is invalid.  To save a
 * persistent copy of the attribute list, use the SAX1 AttributeListImpl
 * helper class.</p>
 *
 * <p>An attribute list includes only attributes that have been
 * specified or defaulted: #IMPLIED attributes will not be included.</p>
 *
 * <p>There are two ways for the SAX application to obtain information
 * from the AttributeList.  First, it can iterate through the entire
 * list:</p>
 *
 * <pre>
 * public void startElement (String name, AttributeList atts) {
 *   for (int i = 0; i < atts.getLength(); i++) {
 *     String name = atts.getName(i);
 *     String type = atts.getType(i);
 *     String value = atts.getValue(i);
 *     [...]
 *   }
 * }
 * </pre>
 *
 * <p>(Note that the result of getLength() will be zero if there
 * are no attributes.)
 *
 * <p>As an alternative, the application can request the value or
 * type of specific attributes:</p>
 *
 * <pre>
 * public void startElement (String name, AttributeList atts) {
 *   String identifier = atts.getValue("id");
 *   String label = atts.getValue("label");
 *   [...]
 * }
 * </pre>
 *
 * @since SAX 1.0
 * @author David Megginson
 * @version 2.0.1 (sax2r2)
 */
public interface AttributeList {


    ////////////////////////////////////////////////////////////////////
    // Iteration methods.
    ////////////////////////////////////////////////////////////////////
    

    /**
     * Return the number of attributes in this list.
     *
     * <p>The SAX parser may provide attributes in any
     * arbitrary order, regardless of the order in which they were
     * declared or specified.  The number of attributes may be
     * zero.</p>
     *
     * @return The number of attributes in the list.  
     */
    public abstract int getLength ();
    
    
    /**
     * Return the name of an attribute in this list (by position).
     *
     * <p>The names must be unique: the SAX parser shall not include the
     * same attribute twice.  Attributes without values (those declared
     * #IMPLIED without a value specified in the start tag) will be
     * omitted from the list.</p>
     *
     * <p>If the attribute name has a namespace prefix, the prefix
     * will still be attached.</p>
     *
     * @param i The index of the attribute in the list (starting at 0).
     * @return The name of the indexed attribute, or null
     *         if the index is out of range.
     * @see #getLength 
     */
    public abstract String getName (int i);
    
    
    /**
     * Return the type of an attribute in the list (by position).
     *
     * <p>The attribute type is one of the strings "CDATA", "ID",
     * "IDREF", "IDREFS", "NMTOKEN", "NMTOKENS", "ENTITY", "ENTITIES",
     * or "NOTATION" (always in upper case).</p>
     *
     * <p>If the parser has not read a declaration for the attribute,
     * or if the parser does not report attribute types, then it must
     * return the value "CDATA" as stated in the XML 1.0 Recommentation
     * (clause 3.3.3, "Attribute-Value Normalization").</p>
     *
     * <p>For an enumerated attribute that is not a notation, the
     * parser will report the type as "NMTOKEN".</p>
     *
     * @param i The index of the attribute in the list (starting at 0).
     * @return The attribute type as a string, or
     *         null if the index is out of range.
     */
    public abstract String getType (int i);
    
    
    /**
     * Return the value of an attribute in the list (by position).
     *
     * <p>If the attribute value is a list of tokens (IDREFS,
     * ENTITIES, or NMTOKENS), the tokens will be concatenated
     * into a single string separated by whitespace.</p>
     *
     * @param i The index of the attribute in the list (starting at 0).
     * @return The attribute value as a string, or
     *         null if the index is out of range.
     * @see #getLength
     */
    public abstract String getValue (int i);


    ////////////////////////////////////////////////////////////////////
    // Lookup methods.
    ////////////////////////////////////////////////////////////////////
    
    
    /**
     * Return the type of an attribute in the list (by name).
     *
     * <p>The return value is the same as the return value for
     * getType(int).</p>
     *
     * <p>If the attribute name has a namespace prefix in the document,
     * the application must include the prefix here.</p>
     *
     * @param name The name of the attribute.
     * @return The attribute type as a string, or null if no
     *         such attribute exists.
     * @see #getType(int)
     */
    public abstract String getType (String name);
    
    
    /**
     * Return the value of an attribute in the list (by name).
     *
     * <p>The return value is the same as the return value for
     * getValue(int).</p>
     *
     * <p>If the attribute name has a namespace prefix in the document,
     * the application must include the prefix here.</p>
     *
     * @param name the name of the attribute to return
     * @return The attribute value as a string, or null if
     *         no such attribute exists.
     * @see #getValue(int)
     */
    public abstract String getValue (String name);
    
}

// end of AttributeList.java
