/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.jxpath.ri;

import java.io.Serializable;
import java.util.HashMap;

import org.apache.commons.jxpath.Pointer;
import org.apache.commons.jxpath.ri.model.NodeIterator;
import org.apache.commons.jxpath.ri.model.NodePointer;

/**
 * Namespace resolver for {@link JXPathContextReferenceImpl}.
 */
public class NamespaceResolver implements Cloneable, Serializable {

    private static final long serialVersionUID = 1085590057838651311L;

    /**
     * Find the namespace prefix for the specified namespace URI and NodePointer.
     *
     * @param pointer      location
     * @param namespaceURI to check
     * @return prefix if found
     * @since JXPath 1.3
     */
    protected static String getPrefix(final NodePointer pointer, final String namespaceURI) {
        NodePointer currentPointer = pointer;
        while (currentPointer != null) {
            final NodeIterator ni = currentPointer.namespaceIterator();
            for (int position = 1; ni != null && ni.setPosition(position); position++) {
                final NodePointer nsPointer = ni.getNodePointer();
                final String uri = nsPointer.getNamespaceURI();
                if (uri.equals(namespaceURI)) {
                    final String prefix = nsPointer.getName().getName();
                    if (!"".equals(prefix)) {
                        return prefix;
                    }
                }
            }
            currentPointer = currentPointer.getParent();
        }
        return null;
    }

    /** Parent NamespaceResolver. */
    protected final NamespaceResolver parent;

    /** Namespace map. */
    protected HashMap<String, String> namespaceMap = new HashMap<>();

    /** Reverse lookup map */
    protected HashMap<String, String> reverseMap = new HashMap<>();

    /** Node pointer. */
    protected NodePointer pointer;

    /**
     * Whether this instance is sealed.
     */
    private boolean sealed;

    /**
     * Constructs a new NamespaceResolver.
     */
    public NamespaceResolver() {
        this(null);
    }

    /**
     * Constructs a new NamespaceResolver.
     *
     * @param parent NamespaceResolver
     */
    public NamespaceResolver(final NamespaceResolver parent) {
        this.parent = parent;
    }

    @Override
    public Object clone() {
        try {
            final NamespaceResolver result = (NamespaceResolver) super.clone();
            result.sealed = false;
            return result;
        } catch (final CloneNotSupportedException e) {
            // Of course, it's supported.
            e.printStackTrace();
            return null;
        }
    }

    /**
     * Given a prefix, returns an externally registered namespace URI.
     *
     * @param prefix The namespace prefix to look up
     * @return namespace URI or null if the prefix is undefined.
     * @since JXPath 1.3
     */
    protected synchronized String getExternallyRegisteredNamespaceURI(final String prefix) {
        final String uri = namespaceMap.get(prefix);
        return uri == null && parent != null ? parent.getExternallyRegisteredNamespaceURI(prefix) : uri;
    }

    /**
     * Gets the nearest prefix found that matches an externally-registered namespace.
     *
     * @param namespaceURI the ns URI to check.
     * @return String prefix if found.
     * @since JXPath 1.3
     */
    protected synchronized String getExternallyRegisteredPrefix(final String namespaceURI) {
        final String prefix = reverseMap.get(namespaceURI);
        return prefix == null && parent != null ? parent.getExternallyRegisteredPrefix(namespaceURI) : prefix;
    }

    /**
     * Gets the namespace context pointer.
     *
     * @return Pointer
     */
    public Pointer getNamespaceContextPointer() {
        if (pointer == null && parent != null) {
            return parent.getNamespaceContextPointer();
        }
        return pointer;
    }

    /**
     * Given a prefix, returns a registered namespace URI. If the requested prefix was not defined explicitly using the registerNamespace method, JXPathContext
     * will then check the context node to see if the prefix is defined there. See {@link #setNamespaceContextPointer(NodePointer) setNamespaceContextPointer}.
     *
     * @param prefix The namespace prefix to look up
     * @return namespace URI or null if the prefix is undefined.
     */
    public synchronized String getNamespaceURI(final String prefix) {
        final String uri = getExternallyRegisteredNamespaceURI(prefix);
        return uri == null && pointer != null ? pointer.getNamespaceURI(prefix) : uri;
    }

    /**
     * Gets the prefix associated with the specifed namespace URI.
     *
     * @param namespaceURI the ns URI to check.
     * @return String prefix
     */
    public synchronized String getPrefix(final String namespaceURI) {
        final String prefix = getExternallyRegisteredPrefix(namespaceURI);
        return prefix == null && pointer != null ? getPrefix(pointer, namespaceURI) : prefix;
    }

    /**
     * Tests whether this NamespaceResolver has been sealed.
     *
     * @return boolean
     */
    public boolean isSealed() {
        return sealed;
    }

    /**
     * Registers a namespace prefix.
     *
     * @param prefix       A namespace prefix
     * @param namespaceURI A URI for that prefix
     */
    public synchronized void registerNamespace(final String prefix, final String namespaceURI) {
        if (isSealed()) {
            throw new IllegalStateException("Cannot register namespaces on a sealed NamespaceResolver");
        }
        namespaceMap.put(prefix, namespaceURI);
        reverseMap.put(namespaceURI, prefix);
    }

    /**
     * Seal this {@link NamespaceResolver}.
     */
    public void seal() {
        sealed = true;
        if (parent != null) {
            parent.seal();
        }
    }

    /**
     * Register a namespace for the expression context.
     *
     * @param pointer the Pointer to set.
     */
    public void setNamespaceContextPointer(final NodePointer pointer) {
        this.pointer = pointer;
    }
}