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package bjc.utils.parserutils;
import java.util.Map;
import java.util.function.BinaryOperator;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.UnaryOperator;
import bjc.utils.funcdata.ITreePart.TreeLinearizationMethod;
/**
* A simple binary tree meant for use as an AST
*
* @author ben
*
* @param <T>
* The type of token in this AST
*/
public class AST<T> {
private T token;
private AST<T> left;
private AST<T> right;
/**
* Create a new leaf AST node
*
* @param tokn
* The token in this node
*/
public AST(T tokn) {
token = tokn;
left = null;
right = null;
}
/**
* Create a new AST node with the specified data and children
*
* @param tokn
* The token in this node
* @param left
* The left child of this AST
* @param right
* The right child of this AST
*/
public AST(T tokn, AST<T> lft, AST<T> rght) {
token = tokn;
left = lft;
right = rght;
}
public void traverse(TreeLinearizationMethod tlm, Consumer<T> con) {
switch (tlm) {
case INORDER:
left.traverse(tlm, con);
con.accept(token);
right.traverse(tlm, con);
break;
case POSTORDER:
left.traverse(tlm, con);
right.traverse(tlm, con);
con.accept(token);
break;
case PREORDER:
con.accept(token);
left.traverse(tlm, con);
right.traverse(tlm, con);
break;
default:
throw new IllegalArgumentException(
"Got a invalid tree linearizer " + tlm + ". WAT");
}
}
/**
* Collapse this tree into a single node
*
* @param tokenTransform
* The function to transform nodes into data
* @param nodeTransform
* A map of functions for operator collapsing
* @param resultTransform
* The function for transforming the result
* @return The collapsed value of the tree
*/
public <E, T2> E collapse(Function<T, T2> tokenTransform,
Map<T, BinaryOperator<T2>> nodeTransform,
Function<T2, E> resultTransform) {
return resultTransform
.apply(internalCollapse(tokenTransform, nodeTransform));
}
/*
* Internal recursive collapser
*/
private <T2> T2 internalCollapse(Function<T, T2> tokenTransform,
Map<T, BinaryOperator<T2>> nodeTransform) {
if (left == null && right == null) {
return tokenTransform.apply(token);
} else {
T2 leftCollapsed = left.internalCollapse(tokenTransform,
nodeTransform);
T2 rightCollapsed = right.internalCollapse(tokenTransform,
nodeTransform);
return nodeTransform.get(token).apply(leftCollapsed,
rightCollapsed);
}
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
internalToString(sb, -1);
return sb.toString();
}
/**
* Internal version of toString for proper rendering
*
* @param sb
* The string rendering being built
* @param indentLevel
* The current level to indent the tree
*/
private void internalToString(StringBuilder sb, int indentLevel) {
indentNLevels(sb, indentLevel);
if (left == null && right == null) {
sb.append("Node: ");
sb.append(token.toString());
sb.append("\n");
} else {
sb.append("Node: ");
sb.append(token.toString());
sb.append("\n");
left.internalToString(sb, indentLevel + 2);
right.internalToString(sb, indentLevel + 2);
}
}
/**
* Indent a string n levels
*
* @param sb
* The string to indent
* @param n
* The number of levels to indent
*/
private void indentNLevels(StringBuilder sb, int n) {
for (int i = 0; i <= n; i++) {
sb.append("\t");
}
}
/**
* Execute a transform on selective nodes of the tree
*
* @param transformPred
* The predicate to pick nodes to transform
* @param transformer
* The thing to use to transform the nodes
*/
public void selectiveTransform(Predicate<T> transformPred,
UnaryOperator<T> transformer) {
if (transformPred.test(token)) {
token = transformer.apply(token);
}
if (left != null) {
left.selectiveTransform(transformPred, transformer);
}
if (right != null) {
right.selectiveTransform(transformPred, transformer);
}
}
/**
* Transmute the tokens in an AST into a different sort of token
*
* @param tokenTransformer
* The transform to run on the tokens
* @return The AST with transformed tokens
*/
public <E> AST<E> transmuteAST(Function<T, E> tokenTransformer) {
AST<E> l = null;
AST<E> r = null;
if (left != null) {
l = left.transmuteAST(tokenTransformer);
}
if (right != null) {
r = right.transmuteAST(tokenTransformer);
}
return new AST<E>(tokenTransformer.apply(token), l, r);
}
}
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