/*
 * Copyright 2014-2015 the original author or authors.
 *
 * Licensed 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.springframework.data.rest.webmvc.support;

import org.springframework.data.projection.ProjectionFactory;
import org.springframework.data.rest.core.mapping.ResourceMappings;
import org.springframework.data.rest.core.mapping.ResourceMetadata;
import org.springframework.data.rest.core.projection.ProjectionDefinitions;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

/**
 * {@link Projector} looking up a projection by name for the given source type.
 * 
 * @author Oliver Gierke
 */
public class PersistentEntityProjector implements Projector {

	private final ProjectionDefinitions projectionDefinitions;
	private final ProjectionFactory factory;
	private final String projection;
	private final ResourceMappings mappings;

	/**
	 * Creates a new {@link PersistentEntityProjector} using the given {@link ProjectionDefinitions},
	 * {@link ProjectionFactory} and projection name.
	 * 
	 * @param projectionDefinitions must not be {@literal null}.
	 * @param factory must not be {@literal null}.
	 * @param projection can be empty.
	 */
	public PersistentEntityProjector(ProjectionDefinitions projectionDefinitions, ProjectionFactory factory,
			String projection, ResourceMappings mappings) {

		Assert.notNull(projectionDefinitions, "ProjectionDefinitions must not be null!");
		Assert.notNull(factory, "ProjectionFactory must not be null!");

		this.projectionDefinitions = projectionDefinitions;
		this.factory = factory;
		this.projection = projection;
		this.mappings = mappings;
	}

	/*
	 * (non-Javadoc)
	 * @see org.springframework.data.rest.webmvc.support.Projector#project(java.lang.Object)
	 */
	public Object project(Object source) {

		Assert.notNull(source, "Projection source must not be null!");

		if (!StringUtils.hasText(projection)) {
			return source;
		}

		Class<?> projectionType = projectionDefinitions.getProjectionType(source.getClass(), projection);
		return projectionType == null ? source : factory.createProjection(projectionType, source);
	}

	/* 
	 * (non-Javadoc)
	 * @see org.springframework.data.rest.webmvc.support.Projector#projectExcerpt(java.lang.Object)
	 */
	@Override
	public Object projectExcerpt(Object source) {

		Assert.notNull(source, "Projection source must not be null!");

		ResourceMetadata metadata = mappings.getMetadataFor(source.getClass());
		Class<?> projection = metadata == null ? null : metadata.getExcerptProjection();

		if (projection == null) {
			return project(source);
		}

		return projection == null ? source : factory.createProjection(projection, source);
	}

	/* 
	 * (non-Javadoc)
	 * @see org.springframework.data.rest.webmvc.support.Projector#hasExcerptProjection(java.lang.Class)
	 */
	@Override
	public boolean hasExcerptProjection(Class<?> type) {

		ResourceMetadata metadata = mappings.getMetadataFor(type);
		return metadata == null ? false : metadata.getExcerptProjection() != null;
	}
}
