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/*
 * eXist-db Open Source Native XML Database
 * Copyright (C) 2001 The eXist-db Authors
 *
 * [email protected]
 * http://www.exist-db.org
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */
package org.exist.numbering;

import org.exist.storage.io.VariableByteOutputStream;

import java.io.IOException;

/**
 * Represents the internal id of a node within eXist. Basically, all
 * stored nodes in eXist need to have an id that implements this
 * interface. The id will be assigned according to used numbering
 * scheme. From a given id, we can determine the relationship
 * of the node it represents to any other node in the same document.
 */
public interface NodeId extends Comparable {

    int LENGTH_NODE_ID_UNITS = 2; //sizeof short

    /**
     * Static field representing the document node.
     */
    NodeId DOCUMENT_NODE = new DLN(0);
 
    NodeId END_OF_DOCUMENT = new DLN(0);

    NodeId ROOT_NODE = new DLN(1);

    int IS_CHILD = 1;
    int IS_DESCENDANT = 2;
    int IS_SELF = 3;

    /**
     * Returns a new NodeId representing the first child
     * node of this node. The returned id can be used
     * for creating new nodes. The actual id of the first
     * node might be different, depending on the
     * implementation.
     *
     * @return new child node id
     */
    NodeId newChild();

    /**
     * Returns a new NodeId representing the nth child node
     * of this node. The returned id can be used
     * to create new child nodes. The actual id of the
     * child might be different, depending on the
     * implementation.
     * 
     * @param child the position of the child
     * @return new node id
     */
    NodeId getChild(int child);

    /**
     * Returns a new NodeId representing the next following
     * sibling of this node. The returned id can be used
     * to create new sibling nodes. The actual id of the
     * next sibling might be different, depending on the
     * implementation.
     *
     * @return new sibling node id.
     */
    NodeId nextSibling();

    /**
     * Returns a new NodeId representing the prececing
     * sibling of this node. The returned id can be used
     * to create new sibling nodes. The actual id of the
     * next sibling might be different, depending on the
     * implementation.
     *
     * @return new sibling node id.
     */
    NodeId precedingSibling();

    NodeId insertNode(NodeId right);

    NodeId insertBefore();

    NodeId append(NodeId other);

    /**
     * Returns a new NodeId representing the parent
     * of the current node. If the parent is the document,
     * the constant {@link #DOCUMENT_NODE} will be returned.
     * For the document itself, the parent id will be null.
     *
     * @return the id of the parent node or null if the current node
     * is the document node.
     */
    NodeId getParentId();

    /**
     * Returns true if the node represented by this node id comes
     * after the argument node in document order. If isFollowing is set to true, the method
     * behaves as if called to evaluate a following::* XPath select, i.e. it
     * returns false for descendants of the current node.
     *
     * @param other the node id to compare with
     * @param isFollowing if true, return false for descendants of the current node 
     * @return true true if the current node comes after the other node in document order
     */
    boolean after(NodeId other, boolean isFollowing);

    /**
     * Returns true if the node represented by this node id comes
     * before the argument node in document order. If isPreceding is set to true, the method
     * behaves as if called to evaluate a preceding::* XPath select, i.e. it
     * returns false for ancestors of the current node.
     *
     * @param other the node id to compare with
     * @param isPreceding if true, return false for ancestors of the current node
     * @return true if the current node comes before the other node in document order.
     */
    boolean before(NodeId other, boolean isPreceding);

    /**
     * Is the current node id a descendant of the specified node?
     *
     * @param ancestor node id of the potential ancestor
     * @return true if the node id is a descendant of the given node, false otherwise
     */
    boolean isDescendantOf(NodeId ancestor);

    boolean isDescendantOrSelfOf(NodeId ancestor);

    /**
     * Is the current node a child node of the specified parent?
     *
     * @param parent the parent node
     * @return true if the current node is a child of the specified parent
     */
    boolean isChildOf(NodeId parent);

    /**
     * Computes the relationship of this node to the given potential
     * ancestor node. The method returns an int constant indicating
     * the relation. Possible relations are: {@link #IS_CHILD}, {@link #IS_DESCENDANT}
     * or {@link #IS_SELF}. If the nodes are not in a ancestor-descendant relation,
     * the method returns -1.
     *
     * @param ancestor the (potential) ancestor node to check against
     * @return an int value indicating the relation
     */
    int computeRelation(NodeId ancestor);

    boolean isSiblingOf(NodeId sibling);

    /**
     * Returns the level within the document tree at which
     * this node occurs.
     *
     * @return the tree level
     */
    int getTreeLevel();

    int compareTo(NodeId other);

    /**
     * Returns the size (in bytes) of this node id. Depends on
     * the concrete implementation.
     *
     * @return size
     */
    int size();

    int units();

    /**
     * Serializes the node id to an array of bytes. The first byte is
     * written at offset.
     *
     * @param data the byte array to be filled
     * @param offset offset into the array
     */
    void serialize(byte[] data, int offset);

    /**
     * Write the node id to a {@link org.exist.storage.io.VariableByteOutputStream}.
     *
     * @param os the output stream
     * @throws java.io.IOException if there's a problem with the underlying output stream
     */
    void write(VariableByteOutputStream os) throws IOException;

    /**
     * Write the node id to a {@link org.exist.storage.io.VariableByteOutputStream}. To save
     * storage space, only store those byte which are different from the previous node id.
     *
     * @param previous the node id previously written or null
     * @param os the output stream
     * @return this node id
     * @throws IOException if there's a problem with the underlying output stream
     */
    NodeId write(NodeId previous, VariableByteOutputStream os) throws IOException;

}