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/*
* Copyright (C) 2015 Google, Inc.
*
* Licensed 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 com.google.escapevelocity;
import java.util.Arrays;
import java.util.Iterator;
import java.util.Map;
/**
* A node in the parse tree that is a directive such as {@code #set ($x = $y)}
* or {@code #if ($x) y #end}.
*
* @author emcmanus@google.com (Éamonn McManus)
*/
abstract class DirectiveNode extends Node {
DirectiveNode(String resourceName, int lineNumber) {
super(resourceName, lineNumber);
}
/**
* A node in the parse tree representing a {@code #set} construct. Evaluating
* {@code #set ($x = 23)} will set {@code $x} to the value 23. It does not in itself produce
* any text in the output.
*
* <p>Velocity supports setting values within arrays or collections, with for example
* {@code $set ($x[$i] = $y)}. That is not currently supported here.
*/
static class SetNode extends DirectiveNode {
private final String var;
private final Node expression;
SetNode(String var, Node expression) {
super(expression.resourceName, expression.lineNumber);
this.var = var;
this.expression = expression;
}
@Override
Object evaluate(EvaluationContext context) {
context.setVar(var, expression.evaluate(context));
return "";
}
}
/**
* A node in the parse tree representing an {@code #if} construct. All instances of this class
* have a <i>true</i> subtree and a <i>false</i> subtree. For a plain {@code #if (cond) body
* #end}, the false subtree will be empty. For {@code #if (cond1) body1 #elseif (cond2) body2
* #else body3 #end}, the false subtree will contain a nested {@code IfNode}, as if {@code #else
* #if} had been used instead of {@code #elseif}.
*/
static class IfNode extends DirectiveNode {
private final ExpressionNode condition;
private final Node truePart;
private final Node falsePart;
IfNode(
String resourceName,
int lineNumber,
ExpressionNode condition,
Node trueNode,
Node falseNode) {
super(resourceName, lineNumber);
this.condition = condition;
this.truePart = trueNode;
this.falsePart = falseNode;
}
@Override Object evaluate(EvaluationContext context) {
Node branch = condition.isDefinedAndTrue(context) ? truePart : falsePart;
return branch.evaluate(context);
}
}
/**
* A node in the parse tree representing a {@code #foreach} construct. While evaluating
* {@code #foreach ($x in $things)}, {$code $x} will be set to each element of {@code $things} in
* turn. Once the loop completes, {@code $x} will go back to whatever value it had before, which
* might be undefined. During loop execution, the variable {@code $foreach} is also defined.
* Velocity defines a number of properties in this variable, but here we only support
* {@code $foreach.hasNext}.
*/
static class ForEachNode extends DirectiveNode {
private final String var;
private final ExpressionNode collection;
private final Node body;
ForEachNode(String resourceName, int lineNumber, String var, ExpressionNode in, Node body) {
super(resourceName, lineNumber);
this.var = var;
this.collection = in;
this.body = body;
}
@Override
Object evaluate(EvaluationContext context) {
Object collectionValue = collection.evaluate(context);
Iterable<?> iterable;
if (collectionValue instanceof Iterable<?>) {
iterable = (Iterable<?>) collectionValue;
} else if (collectionValue instanceof Object[]) {
iterable = Arrays.asList((Object[]) collectionValue);
} else if (collectionValue instanceof Map<?, ?>) {
iterable = ((Map<?, ?>) collectionValue).values();
} else {
throw evaluationException("Not iterable: " + collectionValue);
}
Runnable undo = context.setVar(var, null);
StringBuilder sb = new StringBuilder();
Iterator<?> it = iterable.iterator();
Runnable undoForEach = context.setVar("foreach", new ForEachVar(it));
while (it.hasNext()) {
context.setVar(var, it.next());
sb.append(body.evaluate(context));
}
undoForEach.run();
undo.run();
return sb.toString();
}
/**
* This class is the type of the variable {@code $foreach} that is defined within
* {@code #foreach} loops. Its {@link #getHasNext()} method means that we can write
* {@code #if ($foreach.hasNext)}.
*/
private static class ForEachVar {
private final Iterator<?> iterator;
ForEachVar(Iterator<?> iterator) {
this.iterator = iterator;
}
public boolean getHasNext() {
return iterator.hasNext();
}
}
}
/**
* A node in the parse tree representing a macro call. If the template contains a definition like
* {@code #macro (mymacro $x $y) ... #end}, then a call of that macro looks like
* {@code #mymacro (xvalue yvalue)}. The call is represented by an instance of this class. The
* definition itself does not appear in the parse tree.
*
* <p>Evaluating a macro involves temporarily setting the parameter variables ({@code $x $y} in
* the example) to thunks representing the argument expressions, evaluating the macro body, and
* restoring any previous values that the parameter variables had.
*/
static class MacroCallNode extends DirectiveNode {
private final String name;
private final ImmutableList<Node> thunks;
private Macro macro;
MacroCallNode(
String resourceName,
int lineNumber,
String name,
ImmutableList<Node> argumentNodes) {
super(resourceName, lineNumber);
this.name = name;
this.thunks = argumentNodes;
}
String name() {
return name;
}
int argumentCount() {
return thunks.size();
}
void setMacro(Macro macro) {
this.macro = macro;
}
@Override
Object evaluate(EvaluationContext context) {
assert macro != null : "Macro should have been linked: #" + name;
return macro.evaluate(context, thunks);
}
}
}
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