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package com.sun.xml.internal.xsom;

import com.sun.xml.internal.xsom.impl.scd.Iterators;

import com.sun.xml.internal.xsom.impl.scd.ParseException;

import com.sun.xml.internal.xsom.impl.scd.SCDImpl;

import com.sun.xml.internal.xsom.impl.scd.SCDParser;

import com.sun.xml.internal.xsom.impl.scd.Step;

import com.sun.xml.internal.xsom.impl.scd.TokenMgrError;

import com.sun.xml.internal.xsom.util.DeferedCollection;

import javax.xml.namespace.NamespaceContext;

import java.util.Collection;

import java.util.Iterator;

import java.util.List;

/**

 * Schema Component Designator (SCD).

 *

 * <p>

 * SCD for schema is what XPath is for XML. SCD allows you to select a schema component(s)

 * from a schema component(s).

 *

 * <p>

 * See <a href="http://www.w3.org/TR/2005/WD-xmlschema-ref-20050329/">XML Schema: Component Designators</a>.

 * This implementation is based on 03/29/2005 working draft.

 *

 * @author Kohsuke Kawaguchi

 */

public abstract class SCD {

    /**

     * Parses the string representation of SCD.

     *

     * <p>

     * This method involves parsing the path expression and preparing the in-memory

     * structure, so this is useful when you plan to use the same SCD against

     * different context node multiple times.

     *

     * <p>

     * If you want to evaluate SCD just once, use {@link XSComponent#select} methods.

     *

     * @param path

     *      the string representation of SCD, such as "/foo/bar".

     * @param nsContext

     *      Its {@link NamespaceContext#getNamespaceURI(String)} is used

     *      to resolve prefixes in the SCD to the namespace URI.

     */

    public static SCD create(String path, NamespaceContext nsContext) throws java.text.ParseException {

        try {

            SCDParser p = new SCDParser(path,nsContext);

            List<?> list = p.RelativeSchemaComponentPath();

            return new SCDImpl(path,list.toArray(new Step[list.size()]));

        } catch (TokenMgrError e) {

            throw setCause(new java.text.ParseException(e.getMessage(), -1 ),e);

        } catch (ParseException e) {

            throw setCause(new java.text.ParseException(e.getMessage(), e.currentToken.beginColumn ),e);

        }

    }

    private static java.text.ParseException setCause(java.text.ParseException e, Throwable x) {

        e.initCause(x);

        return e;

    }

    /**

     * Evaluates the SCD against the given context node and

     * returns the matched nodes.

     *

     * @return

     *      could be empty but never be null.

     */

    public final Collection<XSComponent> select(XSComponent contextNode) {

        return new DeferedCollection<XSComponent>(select(Iterators.singleton(contextNode)));

    }

    /**

     * Evaluates the SCD against the whole schema and

     * returns the matched nodes.

     *

     * <p>

     * This method is here because {@link XSSchemaSet}

     * doesn't implement {@link XSComponent}.

     *

     * @return

     *      could be empty but never be null.

     */

    public final Collection<XSComponent> select(XSSchemaSet contextNode) {

        return select(contextNode.getSchemas());

    }

    /**

     * Evaluates the SCD against the given context node and

     * returns the matched node.

     *

     * @return

     *      null if the SCD didn't match anything. If the SCD matched more than one node,

     *      the first one will be returned.

     */

    public final XSComponent selectSingle(XSComponent contextNode) {

        Iterator<XSComponent> r = select(Iterators.singleton(contextNode));

        if(r.hasNext())     return r.next();

        return null;

    }

    /**

     * Evaluates the SCD against the whole schema set and

     * returns the matched node.

     *

     * @return

     *      null if the SCD didn't match anything. If the SCD matched more than one node,

     *      the first one will be returned.

     */

    public final XSComponent selectSingle(XSSchemaSet contextNode) {

        Iterator<XSComponent> r = select(contextNode.iterateSchema());

        if(r.hasNext())     return r.next();

        return null;

    }

    /**

     * Evaluates the SCD against the given set of context nodes and

     * returns the matched nodes.

     *

     * @param contextNodes

     *      {@link XSComponent}s that represent the context node against

     *      which {@link SCD} is evaluated.

     *

     * @return

     *      could be empty but never be null.

     */

    public abstract Iterator<XSComponent> select(Iterator<? extends XSComponent> contextNodes);

    /**

     * Evaluates the SCD against the given set of context nodes and

     * returns the matched nodes.

     *

     * @param contextNodes

     *      {@link XSComponent}s that represent the context node against

     *      which {@link SCD} is evaluated.

     *

     * @return

     *      could be empty but never be null.

     */

    public final Collection<XSComponent> select(Collection<? extends XSComponent> contextNodes) {

        return new DeferedCollection<XSComponent>(select(contextNodes.iterator()));

    }

    /**

     * Returns the textual SCD representation as given to {@link SCD#create(String, NamespaceContext)}.

     */

    public abstract String toString();

}