/runtime/Java/src/main/java/org/antlr/runtime/tree/BaseTree.java

/*
 [The "BSD license"]
 Copyright (c) 2005-2009 Terence Parr
 All rights reserved.

 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions
 are met:
 1. Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.
 2. Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in the
     documentation and/or other materials provided with the distribution.
 3. The name of the author may not be used to endorse or promote products
     derived from this software without specific prior written permission.

 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.antlr.runtime.tree;

import java.util.ArrayList;
import java.util.List;

/** A generic tree implementation with no payload.  You must subclass to
 *  actually have any user data.  ANTLR v3 uses a list of children approach
 *  instead of the child-sibling approach in v2.  A flat tree (a list) is
 *  an empty node whose children represent the list.  An empty, but
 *  non-null node is called "nil".
 */
public abstract class BaseTree implements Tree {
	protected List<Object> children;

	public BaseTree() {
	}

	/** Create a new node from an existing node does nothing for BaseTree
	 *  as there are no fields other than the children list, which cannot
	 *  be copied as the children are not considered part of this node.
	 */
	public BaseTree(Tree node) {
	}

	@Override
	public Tree getChild(int i) {
		if ( children==null || i>=children.size() ) {
			return null;
		}
		return (Tree)children.get(i);
	}

	/** Get the children internal List; note that if you directly mess with
	 *  the list, do so at your own risk.
	 */
	public List<? extends Object> getChildren() {
		return children;
	}

	public Tree getFirstChildWithType(int type) {
		for (int i = 0; children!=null && i < children.size(); i++) {
			Tree t = (Tree) children.get(i);
			if ( t.getType()==type ) {
				return t;
			}
		}
		return null;
	}

	@Override
	public int getChildCount() {
		if ( children==null ) {
			return 0;
		}
		return children.size();
	}

	/** Add t as child of this node.
	 *
	 *  Warning: if t has no children, but child does
	 *  and child isNil then this routine moves children to t via
	 *  t.children = child.children; i.e., without copying the array.
	 */
	@Override
	public void addChild(Tree t) {
		//System.out.println("add child "+t.toStringTree()+" "+this.toStringTree());
		//System.out.println("existing children: "+children);
		if ( t==null ) {
			return; // do nothing upon addChild(null)
		}
		BaseTree childTree = (BaseTree)t;
		if ( childTree.isNil() ) { // t is an empty node possibly with children
			if ( this.children!=null && this.children == childTree.children ) {
				throw new RuntimeException("attempt to add child list to itself");
			}
			// just add all of childTree's children to this
			if ( childTree.children!=null ) {
				if ( this.children!=null ) { // must copy, this has children already
					int n = childTree.children.size();
					for (int i = 0; i < n; i++) {
						Tree c = (Tree)childTree.children.get(i);
						this.children.add(c);
						// handle double-link stuff for each child of nil root
						c.setParent(this);
						c.setChildIndex(children.size()-1);
					}
				}
				else {
					// no children for this but t has children; just set pointer
					// call general freshener routine
					this.children = childTree.children;
					this.freshenParentAndChildIndexes();
				}
			}
		}
		else { // child is not nil (don't care about children)
			if ( children==null ) {
				children = createChildrenList(); // create children list on demand
			}
			children.add(t);
			childTree.setParent(this);
			childTree.setChildIndex(children.size()-1);
		}
		// System.out.println("now children are: "+children);
	}

	/** Add all elements of kids list as children of this node */
	public void addChildren(List<? extends Tree> kids) {
		for (int i = 0; i < kids.size(); i++) {
			Tree t = kids.get(i);
			addChild(t);
		}
	}

	@Override
	public void setChild(int i, Tree t) {
		if ( t==null ) {
			return;
		}
		if ( t.isNil() ) {
			throw new IllegalArgumentException("Can't set single child to a list");
		}
		if ( children==null ) {
			children = createChildrenList();
		}
		children.set(i, t);
		t.setParent(this);
		t.setChildIndex(i);
	}

	/** Insert child t at child position i (0..n-1) by shifting children
		i+1..n-1 to the right one position. Set parent / indexes properly
	 	but does NOT collapse nil-rooted t's that come in here like addChild.
	 */
	public void insertChild(int i, Object t) {
		if (i < 0 || i >= getChildCount()) {
			throw new IndexOutOfBoundsException(i+" out or range");
		}

		children.add(i, t);
		// walk others to increment their child indexes
		// set index, parent of this one too
		this.freshenParentAndChildIndexes(i);
	}

	@Override
	public Object deleteChild(int i) {
		if ( children==null ) {
			return null;
		}
		Tree killed = (Tree)children.remove(i);
		// walk rest and decrement their child indexes
		this.freshenParentAndChildIndexes(i);
		return killed;
	}

	/** Delete children from start to stop and replace with t even if t is
	 *  a list (nil-root tree).  num of children can increase or decrease.
	 *  For huge child lists, inserting children can force walking rest of
	 *  children to set their childindex; could be slow.
	 */
	@Override
	public void replaceChildren(int startChildIndex, int stopChildIndex, Object t) {
		/*
		System.out.println("replaceChildren "+startChildIndex+", "+stopChildIndex+
						   " with "+((BaseTree)t).toStringTree());
		System.out.println("in="+toStringTree());
		*/
		if ( children==null ) {
			throw new IllegalArgumentException("indexes invalid; no children in list");
		}
		int replacingHowMany = stopChildIndex - startChildIndex + 1;
		int replacingWithHowMany;
		BaseTree newTree = (BaseTree)t;
		List<Object> newChildren;
		// normalize to a list of children to add: newChildren
		if ( newTree.isNil() ) {
			newChildren = newTree.children;
		}
		else {
			newChildren = new ArrayList<Object>(1);
			newChildren.add(newTree);
		}
		replacingWithHowMany = newChildren.size();
		int numNewChildren = newChildren.size();
		int delta = replacingHowMany - replacingWithHowMany;
		// if same number of nodes, do direct replace
		if ( delta == 0 ) {
			int j = 0; // index into new children
			for (int i=startChildIndex; i<=stopChildIndex; i++) {
				BaseTree child = (BaseTree)newChildren.get(j);
				children.set(i, child);
				child.setParent(this);
				child.setChildIndex(i);
                j++;
            }
		}
		else if ( delta > 0 ) { // fewer new nodes than there were
			// set children and then delete extra
			for (int j=0; j<numNewChildren; j++) {
				children.set(startChildIndex+j, newChildren.get(j));
			}
			int indexToDelete = startChildIndex+numNewChildren;
			for (int c=indexToDelete; c<=stopChildIndex; c++) {
				// delete same index, shifting everybody down each time
				children.remove(indexToDelete);
			}
			freshenParentAndChildIndexes(startChildIndex);
		}
		else { // more new nodes than were there before
			// fill in as many children as we can (replacingHowMany) w/o moving data
			for (int j=0; j<replacingHowMany; j++) {
				children.set(startChildIndex+j, newChildren.get(j));
			}
			int numToInsert = replacingWithHowMany-replacingHowMany;
			for (int j=replacingHowMany; j<replacingWithHowMany; j++) {
				children.add(startChildIndex+j, newChildren.get(j));
			}
			freshenParentAndChildIndexes(startChildIndex);
		}
		//System.out.println("out="+toStringTree());
	}

	/** Override in a subclass to change the impl of children list */
	protected List<Object> createChildrenList() {
		return new ArrayList<Object>();
	}

	@Override
	public boolean isNil() {
		return false;
	}

	/** Set the parent and child index values for all child of t */
	@Override
	public void freshenParentAndChildIndexes() {
		freshenParentAndChildIndexes(0);
	}

	public void freshenParentAndChildIndexes(int offset) {
		int n = getChildCount();
		for (int c = offset; c < n; c++) {
			Tree child = getChild(c);
			child.setChildIndex(c);
			child.setParent(this);
		}
	}

	public void freshenParentAndChildIndexesDeeply() {
		freshenParentAndChildIndexesDeeply(0);
	}

	public void freshenParentAndChildIndexesDeeply(int offset) {
		int n = getChildCount();
		for (int c = offset; c < n; c++) {
			BaseTree child = (BaseTree)getChild(c);
			child.setChildIndex(c);
			child.setParent(this);
			child.freshenParentAndChildIndexesDeeply();
		}
	}

	public void sanityCheckParentAndChildIndexes() {
		sanityCheckParentAndChildIndexes(null, -1);
	}

	public void sanityCheckParentAndChildIndexes(Tree parent, int i) {
		if ( parent!=this.getParent() ) {
			throw new IllegalStateException("parents don't match; expected "+parent+" found "+this.getParent());
		}
		if ( i!=this.getChildIndex() ) {
			throw new IllegalStateException("child indexes don't match; expected "+i+" found "+this.getChildIndex());
		}
		int n = this.getChildCount();
		for (int c = 0; c < n; c++) {
			CommonTree child = (CommonTree)this.getChild(c);
			child.sanityCheckParentAndChildIndexes(this, c);
		}
	}

	/** BaseTree doesn't track child indexes. */
	@Override
	public int getChildIndex() {
		return 0;
	}
	@Override
	public void setChildIndex(int index) {
	}

	/** BaseTree doesn't track parent pointers. */
	@Override
	public Tree getParent() {
		return null;
	}

	@Override
    public void setParent(Tree t) {
	}

    /** Walk upwards looking for ancestor with this token type. */
	@Override
    public boolean hasAncestor(int ttype) { return getAncestor(ttype)!=null; }

    /** Walk upwards and get first ancestor with this token type. */
	@Override
    public Tree getAncestor(int ttype) {
        Tree t = this;
        t = t.getParent();
        while ( t!=null ) {
            if ( t.getType()==ttype ) return t;
            t = t.getParent();
        }
        return null;
    }

    /** Return a list of all ancestors of this node.  The first node of
     *  list is the root and the last is the parent of this node.
     */
	@Override
    public List<? extends Tree> getAncestors() {
        if ( getParent()==null ) return null;
        List<Tree> ancestors = new ArrayList<Tree>();
        Tree t = this;
        t = t.getParent();
        while ( t!=null ) {
            ancestors.add(0, t); // insert at start
            t = t.getParent();
        }
        return ancestors;
    }

    /** Print out a whole tree not just a node */
	@Override
    public String toStringTree() {
		if ( children==null || children.isEmpty() ) {
			return this.toString();
		}
		StringBuilder buf = new StringBuilder();
		if ( !isNil() ) {
			buf.append("(");
			buf.append(this.toString());
			buf.append(' ');
		}
		for (int i = 0; children!=null && i < children.size(); i++) {
			Tree t = (Tree)children.get(i);
			if ( i>0 ) {
				buf.append(' ');
			}
			buf.append(t.toStringTree());
		}
		if ( !isNil() ) {
			buf.append(")");
		}
		return buf.toString();
	}

	@Override
    public int getLine() {
		return 0;
	}

	@Override
	public int getCharPositionInLine() {
		return 0;
	}

	/** Override to say how a node (not a tree) should look as text */
	@Override
	public abstract String toString();
}