samer@0: /*
samer@0:  *	Node.java	
samer@0:  *
samer@0:  *	Copyright (c) 2000, Samer Abdallah, King's College London.
samer@0:  *	All rights reserved.
samer@0:  *
samer@0:  *	This software is provided AS iS and WITHOUT ANY WARRANTY; 
samer@0:  *	without even the implied warranty of MERCHANTABILITY or 
samer@0:  *	FITNESS FOR A PARTICULAR PURPOSE.
samer@0:  *
samer@0:  *	Change history:
samer@0:  *
samer@0:  *	Removed all references to parent nodes - each node now
samer@0:  *	stores its full name. Uses more memory but simpler in the
samer@0:  *	long run, I think.
samer@0:  */
samer@0: 
samer@0: package samer.core;
samer@0: import java.util.*;
samer@0: 
samer@0: /**
samer@0: 	<p> A Node is essentially a path in a hierarchical
samer@0: 	name space. Each node is an independent object. 
samer@0: 	A Node can be constructed either with an explicit
samer@0: 	parent Node, or with an absolute path, or as a child
samer@0: 	of the current Node maintained by the current Shell.
samer@0: 	Names are constructed in parts, concatenated with 
samer@0: 	dots, eg,
samer@0: 	<code>
samer@0: 		Node A=new Node("top",null);
samer@0: 		Node B=new Node("middle",A);
samer@0: 		Node C=new Node("bottom",B);
samer@0: 	</code>
samer@0: 	Then node A is "top", node B is "top.middle" and node
samer@0: 	C is "top.middle.bottom"
samer@0: 
samer@0: 	<p>The top level Environment (see Environment)
samer@0: 	actually uses a nameless top level node: "", so that
samer@0: 	all fully specified node paths begin with ".", eg
samer@0: 	".antelope.gibbon.firebucket"
samer@0: 	This is so that names that <I>don't</I> start with a
samer@0:  	dot are treated as relative to the current Environment's node.
samer@0:  */
samer@0: 
samer@0: public class Node implements java.io.Serializable
samer@0: {
samer@0: 	private final String	name;
samer@0: 
samer@0: 	/** Construct new Node with given name as a child of the
samer@0: 		current Environment's base node, ie
samer@0: 		<code>Shell.env().node()</code>
samer@0: 	 */
samer@0: 	public Node(String name) {
samer@0: 		if (name==null || name.equals(""))
samer@0: 			throw new Error("Node with empty name");
samer@0: 
samer@0: 		if (isAbsolute(name)) this.name=name;
samer@0: 		else this.name=Shell.env().node().fullNameFor(name);
samer@0: 	}
samer@0: 
samer@0: 
samer@0: 	private Node() { name=""; }
samer@0: 
samer@0: 	/** Construct new Node with given name and parent
samer@0: 		If parent is null, a top level node is created
samer@0: 	*/
samer@0: 	public Node(String name, Node parent) { this.name = parent.fullName()+"."+name; }
samer@0: 
samer@0: 	/** Returns parent Node, or null if no parent */
samer@0: 	public Node   getParent()	{ return new Node(name.substring(0,name.lastIndexOf('.'))); }
samer@0: 	public static String lastPart(String str) { return str.substring(1+str.lastIndexOf('.')); }
samer@0: 	public String fullName() { return name; }
samer@0: 	public String shortName() { return lastPart(name); }
samer@0: 
samer@0: 	/** Return full name of hypothetical Node with given name
samer@0: 		as a child of this Node, ie, this node's full name + "."+ nm.
samer@0: 	*/
samer@0: 	public String fullNameFor(String nm) { return name+"."+nm; }
samer@0: 
samer@0: 	/** Absolute names start with a . This is only true of the top
samer@0: 		level Node has an empty name!
samer@0: 	*/
samer@0: 	public static boolean isAbsolute(String nm) { return (nm.charAt(0)=='.'); }
samer@0: 
samer@0: 	/** Returns true if and only if the given name is a child of this one.
samer@0: 		This is trivially true if the given name is relative (ie doesn't start
samer@0: 		with a dot). If it does, then the initial substrings must match.
samer@0: 	*/
samer@0: 	public boolean isSubnode(String nm) {
samer@0: 		if (!isAbsolute(nm)) return true;
samer@0: 		return nm.startsWith(name);
samer@0: 	}
samer@0: 
samer@0: 	/** Returns the full name of this node. */
samer@0: 	public String toString() { return name; }
samer@0: 
samer@0: 	/** Returns a NEW top-level node each time it is called. */
samer@0: 	public static Node root() { return new Node(); }
samer@0: }