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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.Map;
import java.util.TreeMap;
/**
* The context of a template evaluation. This consists of the template variables and the template
* macros. The template variables start with the values supplied by the evaluation call, and can
* be changed by {@code #set} directives and during the execution of {@code #foreach} and macro
* calls. The macros are extracted from the template during parsing and never change thereafter.
*
* @author emcmanus@google.com (Éamonn McManus)
*/
interface EvaluationContext {
Object getVar(String var);
boolean varIsDefined(String var);
/**
* Sets the given variable to the given value.
*
* @return a Runnable that will restore the variable to the value it had before. If the variable
* was undefined before this method was executed, the Runnable will make it undefined again.
* This allows us to restore the state of {@code $x} after {@code #foreach ($x in ...)}.
*/
Runnable setVar(final String var, Object value);
class PlainEvaluationContext implements EvaluationContext {
private final Map<String, Object> vars;
PlainEvaluationContext(Map<String, ?> vars) {
this.vars = new TreeMap<String, Object>(vars);
}
@Override
public Object getVar(String var) {
return vars.get(var);
}
@Override
public boolean varIsDefined(String var) {
return vars.containsKey(var);
}
@Override
public Runnable setVar(final String var, Object value) {
Runnable undo;
if (vars.containsKey(var)) {
final Object oldValue = vars.get(var);
undo = new Runnable() {
@Override public void run() {
vars.put(var, oldValue);
}
};
} else {
undo = new Runnable() {
@Override public void run() {
vars.remove(var);
}
};
}
vars.put(var, value);
return undo;
}
}
}
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