All Downloads are FREE. Search and download functionalities are using the official Maven repository.

org.eclipse.ditto.placeholders.PipelineElement Maven / Gradle / Ivy

There is a newer version: 3.6.2
Show newest version
/*
 * Copyright (c) 2021 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.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Optional;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Stream;

/**
 * An element going through some pipeline of functions.
 */
public interface PipelineElement extends Iterable {

    /**
     * Get the type of this pipeline element.
     *
     * @return the type.
     */
    Type getType();

    /**
     * Advance a resolved value to the next stage. Other elements are unchanged.
     *
     * @param stringProcessor What to do for resolved values.
     * @return the pipeline element at the next pipeline stage.
     */
    PipelineElement onResolved(Function stringProcessor);

    /**
     * Advance an unresolved value to the next stage. Other elements are unchanged.
     *
     * @param nextPipelineElement supplier of the next pipeline element.
     * @return the pipeline element at the next pipeline stage.
     */
    PipelineElement onUnresolved(Supplier nextPipelineElement);

    /**
     * Advance a deleted value to the next stage. Other elements are unchanged.
     *
     * @param nextPipelineElement supplier of the next pipeline element.
     * @return the pipeline element at the next pipeline stage.
     */
    PipelineElement onDeleted(Supplier nextPipelineElement);

    /**
     * Concatenates all resolved values of the given pipelineElement with the resolved values of this pipeline element.
     * In case this or the given pipeline element is a {@link Type#DELETED} pipeline element, the result will
     * always be a deleted pipeline element.
     *
     * @param pipelineElement the pipeline element to concatenate
     * @return the pipeline element which holds the concatenated resolved vales.
     * @since 2.4.0
     */
    PipelineElement concat(PipelineElement pipelineElement);

    /**
     * Evaluate this pipeline element by a visitor.
     *
     * @param visitor the visitor.
     * @param  the type of results.
     * @return the evaluation result.
     * @since 2.4.0
     */
     List evaluate(PipelineElementVisitor visitor);

    /**
     * Convert a resolved value into another resolved value and leave other elements untouched.
     *
     * @param mapper what to do about the resolved value.
     * @return the mapped resolved value.
     */
    default PipelineElement map(final Function mapper) {
        return onResolved(mapper.andThen(PipelineElement::resolved));
    }

    /**
     * Combine 2 pipeline elements such that unresolved elements are replaced by resolved elements, which is in turn
     * replaced by the deletion signifier.
     * 

* Consider all pipeline elements as a simple lattice with PipelineElementDeleted as top and * PipelineElementUnresolved as bottom. This function computes a maximal of 2 elements in the lattice. *

* * @param other the other element. * @return the combined element. */ default PipelineElement orElse(final PipelineElement other) { return onDeleted(() -> this) .onResolved(s -> this) .onUnresolved(() -> other); } /** * @return an optional holding the first resolved value. Empty if no values were resolved. * @since 2.4.0 */ default Optional findFirst() { return toStream().findFirst(); } /** * Converts this pipeline element into a stream of resolved strings. * If the PipelineElement did not resolve any value, the stream will be empty. * Unresolved or deleted elements will result in an empty stream. * * @return a stream of strings which this pipeline element did resolve. * @since 2.4.0 */ default Stream toStream() { return Stream.empty(); } /** * Create a builder of a visitor to evaluate pipeline elements. * * @param the type of results. * @return the visitor builder. */ static PipelineElementVisitor.Builder newVisitorBuilder() { return ImmutablePipelineElementVisitor.newBuilder(); } /** * Creat a pipeline element containing the resolved values. * * @param values the resolved values. * @return the pipeline element. */ static PipelineElement resolved(final Collection values) { return values.isEmpty() ? PipelineElement.unresolved() : PipelineElementResolved.of(values); } /** * Creat a pipeline element containing a resolved value. * * @param value the resolved value. * @return the pipeline element. */ static PipelineElement resolved(final String value) { return resolved(Collections.singletonList(value)); } /** * Get the unique pipeline element signifying deletion of the whole string containing the pipeline. * * @return the deleted element. */ static PipelineElement deleted() { return PipelineElementDeleted.INSTANCE; } /** * Get the unique pipeline element signifying failed resolution. * * @return the unresolved element. */ static PipelineElement unresolved() { return PipelineElementUnresolved.INSTANCE; } /** * Types of pipeline element. */ enum Type { /** * Type of the signifier for deletion. */ DELETED, /** * Type of resolved values. */ RESOLVED, /** * Type of the signifier for resolution failure. */ UNRESOLVED } }




© 2015 - 2024 Weber Informatics LLC | Privacy Policy