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/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch licenses this file to you 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 org.elasticsearch.script.mustache;
import com.fasterxml.jackson.core.io.JsonStringEncoder;
import com.github.mustachejava.Code;
import com.github.mustachejava.DefaultMustacheFactory;
import com.github.mustachejava.DefaultMustacheVisitor;
import com.github.mustachejava.Mustache;
import com.github.mustachejava.MustacheException;
import com.github.mustachejava.MustacheVisitor;
import com.github.mustachejava.TemplateContext;
import com.github.mustachejava.codes.IterableCode;
import com.github.mustachejava.codes.WriteCode;
import com.google.common.base.Function;
import org.elasticsearch.common.xcontent.XContentBuilder;
import org.elasticsearch.common.xcontent.XContentType;
import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;
import java.util.Collections;
import java.util.Iterator;
import java.util.Map;
import java.util.Objects;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class CustomMustacheFactory extends DefaultMustacheFactory {
private final Encoder encoder;
public CustomMustacheFactory(boolean escaping) {
super();
setObjectHandler(new CustomReflectionObjectHandler());
if (escaping) {
this.encoder = new JsonEscapeEncoder();
} else {
this.encoder = new NoEscapeEncoder();
}
}
@Override
public void encode(String value, Writer writer) {
encoder.accept(value, writer);
}
@Override
public MustacheVisitor createMustacheVisitor() {
return new CustomMustacheVisitor(this);
}
class CustomMustacheVisitor extends DefaultMustacheVisitor {
public CustomMustacheVisitor(DefaultMustacheFactory df) {
super(df);
}
@Override
public void iterable(TemplateContext templateContext, String variable, Mustache mustache) {
if (ToJsonCode.match(variable)) {
list.add(new ToJsonCode(templateContext, df, mustache, variable));
} else if (JoinerCode.match(variable)) {
list.add(new JoinerCode(templateContext, df, mustache));
} else if (CustomJoinerCode.match(variable)) {
list.add(new CustomJoinerCode(templateContext, df, mustache, variable));
} else {
list.add(new IterableCode(templateContext, df, mustache, variable));
}
}
}
/**
* Base class for custom Mustache functions
*/
static abstract class CustomCode extends IterableCode {
private final String code;
public CustomCode(TemplateContext tc, DefaultMustacheFactory df, Mustache mustache, String code) {
super(tc, df, mustache, extractVariableName(code, mustache, tc));
this.code = Objects.requireNonNull(code);
}
@Override
public Writer execute(Writer writer, Object[] scopes) {
Object resolved = get(scopes);
writer = handle(writer, createFunction(resolved), scopes);
appendText(writer);
return writer;
}
@Override
protected void tag(Writer writer, String tag) throws IOException {
writer.write(tc.startChars());
writer.write(tag);
writer.write(code);
writer.write(tc.endChars());
}
protected abstract Function createFunction(Object resolved);
/**
* At compile time, this function extracts the name of the variable:
* {{#toJson}}variable_name{{/toJson}}
*/
protected static String extractVariableName(String fn, Mustache mustache, TemplateContext tc) {
Code[] codes = mustache.getCodes();
if (codes == null || codes.length != 1) {
throw new MustacheException("Mustache function [" + fn + "] must contain one and only one identifier");
}
try (StringWriter capture = new StringWriter()) {
// Variable name is in plain text and has type WriteCode
if (codes[0] instanceof WriteCode) {
codes[0].execute(capture, Collections.emptyList());
return capture.toString();
} else {
codes[0].identity(capture);
return capture.toString();
}
} catch (IOException e) {
throw new MustacheException("Exception while parsing mustache function [" + fn + "] at line " + tc.line(), e);
}
}
}
/**
* This function renders {@link Iterable} and {@link Map} as their JSON representation
*/
static class ToJsonCode extends CustomCode {
private static final String CODE = "toJson";
public ToJsonCode(TemplateContext tc, DefaultMustacheFactory df, Mustache mustache, String variable) {
super(tc, df, mustache, CODE);
if (CODE.equalsIgnoreCase(variable) == false) {
throw new MustacheException("Mismatch function code [" + CODE + "] cannot be applied to [" + variable + "]");
}
}
@Override
@SuppressWarnings("unchecked")
protected Function createFunction(final Object resolved) {
return new Function() {
@Override
public String apply(Object s) {
if (resolved == null) {
return null;
}
try (XContentBuilder builder = XContentBuilder.builder(XContentType.JSON.xContent())) {
if (resolved instanceof Iterable) {
builder.startArray();
for (Object o : (Iterable) resolved) {
builder.value(o);
}
builder.endArray();
} else if (resolved instanceof Map) {
builder.map((Map) resolved);
} else {
// Do not handle as JSON
return oh.stringify(resolved);
}
return builder.string();
} catch (IOException e) {
throw new MustacheException("Failed to convert object to JSON", e);
}
}
};
}
static boolean match(String variable) {
return CODE.equalsIgnoreCase(variable);
}
}
/**
* This function concatenates the values of an {@link Iterable} using a given delimiter
*/
static class JoinerCode extends CustomCode {
protected static final String CODE = "join";
private static final String DEFAULT_DELIMITER = ",";
private final String delimiter;
public JoinerCode(TemplateContext tc, DefaultMustacheFactory df, Mustache mustache, String delimiter) {
super(tc, df, mustache, CODE);
this.delimiter = delimiter;
}
public JoinerCode(TemplateContext tc, DefaultMustacheFactory df, Mustache mustache) {
this(tc, df, mustache, DEFAULT_DELIMITER);
}
@Override
@SuppressWarnings("unchecked")
protected Function createFunction(final Object resolved) {
return new Function() {
@Override
public Object apply(Object s) {
if (s == null) {
return null;
} else if (resolved instanceof Iterable) {
StringBuilder joiner = new StringBuilder();
Iterator it = ((Iterable) resolved).iterator();
while (it.hasNext()) {
joiner.append(oh.stringify(it.next()));
if (it.hasNext()) {
joiner.append(delimiter);
}
}
return joiner.toString();
}
return s;
}
};
}
static boolean match(String variable) {
return CODE.equalsIgnoreCase(variable);
}
}
static class CustomJoinerCode extends JoinerCode {
private static final Pattern PATTERN = Pattern.compile("^(?:" + CODE + " delimiter='(.*)')$");
public CustomJoinerCode(TemplateContext tc, DefaultMustacheFactory df, Mustache mustache, String variable) {
super(tc, df, mustache, extractDelimiter(variable));
}
private static String extractDelimiter(String variable) {
Matcher matcher = PATTERN.matcher(variable);
if (matcher.find()) {
return matcher.group(1);
}
throw new MustacheException("Failed to extract delimiter for join function");
}
static boolean match(String variable) {
return PATTERN.matcher(variable).matches();
}
}
class NoEscapeEncoder implements Encoder {
@Override
public void accept(String s, Writer writer) {
try {
writer.write(s);
} catch (IOException e) {
throw new MustacheException("Failed to encode value: " + s);
}
}
}
class JsonEscapeEncoder implements Encoder {
@Override
public void accept(String s, Writer writer) {
try {
writer.write(JsonStringEncoder.getInstance().quoteAsString(s));
} catch (IOException e) {
throw new MustacheException("Failed to escape and encode value: " + s);
}
}
}
interface Encoder {
void accept(String s, Writer writer);
}
}