/
PipelineFunctionDefault.java
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/
PipelineFunctionDefault.java
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/*
* Copyright (c) 2017-2018 Bosch Software Innovations GmbH.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v2.0
* which accompanies this distribution, and is available at
* https://www.eclipse.org/org/documents/epl-2.0/index.php
*
* SPDX-License-Identifier: EPL-2.0
*/
package org.eclipse.ditto.model.placeholders;
import java.util.Collections;
import java.util.List;
import java.util.Optional;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.annotation.concurrent.Immutable;
/**
* Provides the {@code fn:default('...')} function implementation.
*/
@Immutable
final class PipelineFunctionDefault implements PipelineFunction {
static final String FUNCTION_NAME = "default";
private static final String CONSTANT_PATTERN =
"\\((('(?<singleQuotedConstant>.*)')|(\"(?<doubleQuotedConstant>.*)\"))\\)";
private static final String PLACEHOLDER_PATTERN = "\\((?<placeholder>\\w+:.+)\\)";
private static final String OVERALL_PATTERN_STR = CONSTANT_PATTERN + "|" + PLACEHOLDER_PATTERN;
private static final Pattern OVERALL_PATTERN = Pattern.compile(OVERALL_PATTERN_STR);
@Override
public String getName() {
return FUNCTION_NAME;
}
@Override
public DefaultFunctionSignature getSignature() {
return DefaultFunctionSignature.INSTANCE;
}
@Override
public Optional<String> apply(final Optional<String> value, final String paramsIncludingParentheses,
final ExpressionResolver expressionResolver) {
if (value.isPresent()) {
// if previous stage was non-empty: proceed with that
return value;
} else {
// parse + resolve the specified default value:
final ResolvedFunctionParameter<String> resolvedDefaultParam =
parseAndResolve(paramsIncludingParentheses, expressionResolver);
return Optional.of(resolvedDefaultParam.getValue());
}
}
private ResolvedFunctionParameter<String> parseAndResolve(final String paramsIncludingParentheses,
final ExpressionResolver expressionResolver) {
final ParameterDefinition<String> defaultValueParam = getSignature().getParameterDefinition(0);
final Matcher matcher = OVERALL_PATTERN.matcher(paramsIncludingParentheses);
if (matcher.matches()) {
String constant = matcher.group("singleQuotedConstant");
constant = constant != null ? constant : matcher.group("doubleQuotedConstant");
if (constant != null) {
return new ResolvedDefaultValueParam(defaultValueParam, constant);
}
final String placeholder = matcher.group("placeholder");
if (placeholder != null) {
final Optional<String> resolved = expressionResolver.resolveSinglePlaceholder(placeholder);
return new ResolvedDefaultValueParam(defaultValueParam, resolved.orElse(placeholder));
}
}
throw PlaceholderFunctionSignatureInvalidException.newBuilder(paramsIncludingParentheses, this)
.build();
}
/**
* Describes the signature of the {@code default('defaultValue')} function.
*/
private static final class DefaultFunctionSignature implements PipelineFunction.Signature {
private static final DefaultFunctionSignature INSTANCE = new DefaultFunctionSignature();
private PipelineFunction.ParameterDefinition<String> defaultValueDescription;
private DefaultFunctionSignature() {
defaultValueDescription = new DefaultValueParam();
}
@Override
public List<ParameterDefinition> getParameterDefinitions() {
return Collections.singletonList(defaultValueDescription);
}
@Override
public <T> ParameterDefinition<T> getParameterDefinition(final int index) {
if (index == 0) {
return (ParameterDefinition<T>) defaultValueDescription;
}
throw new IllegalArgumentException("Signature does not define a parameter at index '" + index + "'");
}
@Override
public String toString() {
return renderSignature();
}
}
/**
* Describes the only param of the {@code default('defaultValue')} function.
*/
private static final class DefaultValueParam implements PipelineFunction.ParameterDefinition<String> {
@Override
public String getName() {
return "defaultValue";
}
@Override
public Class<String> getType() {
return String.class;
}
@Override
public String getDescription() {
return "Specifies the default/fallback value and may be a constant in single or double quotes or a placeholder";
}
}
/**
* Resolved {@link DefaultValueParam} including the 'defaultValue' value.
*/
private static final class ResolvedDefaultValueParam
implements PipelineFunction.ResolvedFunctionParameter<String> {
private final PipelineFunction.ParameterDefinition<String> definition;
private String value;
private ResolvedDefaultValueParam(
final PipelineFunction.ParameterDefinition<String> definition,
final String value) {
this.definition = definition;
this.value = value;
}
@Override
public PipelineFunction.ParameterDefinition<String> getDefinition() {
return definition;
}
@Override
public String getValue() {
return value;
}
}
}