plugins/org.eclipse.sirius.services.graphql.core/src/org/eclipse/sirius/services/graphql/core/internal/schema/RepresentationDescriptionIdentifierField.java

/*******************************************************************************
 * Copyright (c) 2019 Obeo.
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *    Obeo - initial API and implementation
 *******************************************************************************/
package org.eclipse.sirius.services.graphql.core.internal.schema;

import java.util.Optional;

import org.eclipse.sirius.viewpoint.description.RepresentationDescription;

import graphql.Scalars;
import graphql.schema.DataFetcher;
import graphql.schema.GraphQLFieldDefinition;
import graphql.schema.GraphQLNonNull;

/**
 * Used to create the identifier field of the representation description.
 *
 * @author sbegaudeau
 */
public final class RepresentationDescriptionIdentifierField {
    /**
     * The name of the identifier field.
     */
    private static final String IDENTIFIER_FIELD = "identifier"; //$NON-NLS-1$

    /**
     * The constructor.
     */
    private RepresentationDescriptionIdentifierField() {
        // Prevent instantiation
    }

    /**
     * Returns the identifier field.
     *
     * @return The identifier field
     */
    public static GraphQLFieldDefinition build() {
        // @formatter:off
        return GraphQLFieldDefinition.newFieldDefinition()
                .name(IDENTIFIER_FIELD)
                .type(new GraphQLNonNull(Scalars.GraphQLString))
                .dataFetcher(RepresentationDescriptionIdentifierField.getIdentifierDataFetcher())
                .build();
        // @formatter:on
    }

    /**
     * Returns the identifier of the viewpoint.
     *
     * @return The identifier of the viewpoint
     */
    private static DataFetcher<String> getIdentifierDataFetcher() {
        // @formatter:off
        return environment -> Optional.of(environment.getSource())
                .filter(RepresentationDescription.class::isInstance)
                .map(RepresentationDescription.class::cast)
                .map(RepresentationDescription::getName)
                .orElse(null);
        // @formatter:on
    }
}