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/*
 * Copyright 2016-2018 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.redis.core.convert;

import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import org.springframework.context.expression.BeanFactoryResolver;
import org.springframework.data.redis.core.index.ConfigurableIndexDefinitionProvider;
import org.springframework.data.redis.core.index.IndexDefinition;
import org.springframework.data.redis.core.index.SpelIndexDefinition;
import org.springframework.data.redis.core.mapping.RedisMappingContext;
import org.springframework.data.redis.core.mapping.RedisPersistentEntity;
import org.springframework.data.util.TypeInformation;
import org.springframework.expression.BeanResolver;
import org.springframework.expression.Expression;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

/**
 * An {@link IndexResolver} that resolves {@link IndexedData} using a {@link SpelExpressionParser}.
 *
 * @author Rob Winch
 * @author Christoph Strobl
 * @since 1.7
 */
public class SpelIndexResolver implements IndexResolver {

	private final ConfigurableIndexDefinitionProvider settings;
	private final SpelExpressionParser parser;
	private final RedisMappingContext mappingContext;

	private @Nullable BeanResolver beanResolver;

	private final Map expressionCache;

	/**
	 * Creates a new instance using a default {@link SpelExpressionParser}.
	 *
	 * @param mappingContext the {@link RedisMappingContext} to use. Cannot be null.
	 */
	public SpelIndexResolver(RedisMappingContext mappingContext) {
		this(mappingContext, new SpelExpressionParser());
	}

	/**
	 * Creates a new instance
	 *
	 * @param mappingContext the {@link RedisMappingContext} to use. Cannot be null.
	 * @param parser the {@link SpelExpressionParser} to use. Cannot be null.
	 */
	public SpelIndexResolver(RedisMappingContext mappingContext, SpelExpressionParser parser) {

		Assert.notNull(mappingContext, "RedisMappingContext must not be null!");
		Assert.notNull(parser, "SpelExpressionParser must not be null!");
		this.mappingContext = mappingContext;
		this.settings = mappingContext.getMappingConfiguration().getIndexConfiguration();
		this.expressionCache = new HashMap<>();
		this.parser = parser;
	}

	/* (non-Javadoc)
	 * @see org.springframework.data.redis.core.convert.IndexResolver#resolveIndexesFor(org.springframework.data.util.TypeInformation, java.lang.Object)
	 */
	public Set resolveIndexesFor(TypeInformation typeInformation, @Nullable Object value) {

		if (value == null) {
			return Collections.emptySet();
		}

		RedisPersistentEntity entity = mappingContext.getPersistentEntity(typeInformation);

		if (entity == null) {
			return Collections.emptySet();
		}

		String keyspace = entity.getKeySpace();

		Set indexes = new HashSet<>();

		for (IndexDefinition setting : settings.getIndexDefinitionsFor(keyspace)) {

			if (setting instanceof SpelIndexDefinition) {

				Expression expression = getAndCacheIfAbsent((SpelIndexDefinition) setting);

				StandardEvaluationContext context = new StandardEvaluationContext();
				context.setRootObject(value);
				context.setVariable("this", value);

				if (beanResolver != null) {
					context.setBeanResolver(beanResolver);
				}

				Object index = expression.getValue(context);
				if (index != null) {
					indexes.add(new SimpleIndexedPropertyValue(keyspace, setting.getIndexName(), index));
				}
			}
		}

		return indexes;
	}

	/* (non-Javadoc)
	 * @see org.springframework.data.redis.core.convert.IndexResolver#resolveIndexesFor(java.lang.String, java.lang.String, org.springframework.data.util.TypeInformation, java.lang.Object)
	 */
	@Override
	public Set resolveIndexesFor(String keyspace, String path, TypeInformation typeInformation,
			Object value) {
		return Collections.emptySet();
	}

	private Expression getAndCacheIfAbsent(SpelIndexDefinition indexDefinition) {

		if (expressionCache.containsKey(indexDefinition)) {
			return expressionCache.get(indexDefinition);
		}

		Expression expression = parser.parseExpression(indexDefinition.getExpression());
		expressionCache.put(indexDefinition, expression);
		return expression;
	}

	/**
	 * Allows setting the BeanResolver
	 *
	 * @param beanResolver can be {@literal null}.
	 * @see BeanFactoryResolver
	 */
	public void setBeanResolver(BeanResolver beanResolver) {
		this.beanResolver = beanResolver;
	}
}