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PipelineFunctionJoin.java
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PipelineFunctionJoin.java
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/*
* Copyright (c) 2023 Contributors to the Eclipse Foundation
*
* See the NOTICE file(s) distributed with this work for additional
* information regarding copyright ownership.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0
*
* SPDX-License-Identifier: EPL-2.0
*/
package org.eclipse.ditto.placeholders;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;
import javax.annotation.concurrent.Immutable;
/**
* Provides the {@code fn:join('delimiter')} function implementation.
*/
@Immutable
final class PipelineFunctionJoin implements PipelineFunction {
private static final String FUNCTION_NAME = "join";
private final PipelineFunctionParameterResolverFactory.SingleParameterResolver parameterResolver =
PipelineFunctionParameterResolverFactory.forStringParameter();
@Override
public String getName() {
return FUNCTION_NAME;
}
@Override
public Signature getSignature() {
return JoinFunctionSignature.INSTANCE;
}
@Override
public PipelineElement apply(final PipelineElement value, final String paramsIncludingParentheses,
final ExpressionResolver expressionResolver) {
final String joinDelimiter = parseAndResolve(paramsIncludingParentheses, expressionResolver);
if (value.toStream().count() == 0) {
return PipelineElement.unresolved();
} else {
return PipelineElement.resolved(
value.toStream().collect(Collectors.joining(joinDelimiter))
);
}
}
private String parseAndResolve(final String paramsIncludingParentheses,
final ExpressionResolver expressionResolver) {
return parameterResolver.apply(paramsIncludingParentheses, expressionResolver, this)
.findFirst()
.orElseThrow(
() -> PlaceholderFunctionSignatureInvalidException.newBuilder(paramsIncludingParentheses, this)
.build());
}
/**
* Describes the signature of the {@code join('delimiter')} function.
*/
private static final class JoinFunctionSignature implements Signature {
private static final JoinFunctionSignature INSTANCE = new JoinFunctionSignature();
private final ParameterDefinition<String> givenStringDescription;
private JoinFunctionSignature() {
givenStringDescription = new GivenStringParam();
}
@Override
public List<ParameterDefinition<?>> getParameterDefinitions() {
return Collections.singletonList(givenStringDescription);
}
@Override
public String toString() {
return renderSignature();
}
}
/**
* Describes the only param of the {@code join('delimiter')} function.
*/
private static final class GivenStringParam implements ParameterDefinition<String> {
private GivenStringParam() {
}
@Override
public String getName() {
return "delimiter";
}
@Override
public Class<String> getType() {
return String.class;
}
@Override
public String getDescription() {
return "Specifies the string to use as delimiter when joining elements of an array to a string";
}
}
}