/*
 * Copyright 2015-2020 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
 *
 *      https://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.projection;

import lombok.extern.slf4j.Slf4j;

import java.beans.PropertyDescriptor;
import java.io.IOException;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;

import org.springframework.beans.BeanUtils;
import org.springframework.core.type.MethodMetadata;
import org.springframework.data.type.MethodsMetadata;
import org.springframework.data.type.classreading.MethodsMetadataReader;
import org.springframework.data.type.classreading.MethodsMetadataReaderFactory;
import org.springframework.data.util.StreamUtils;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;

Default implementation of ProjectionInformation. Exposes all properties of the type as required input properties. 
Author:
Oliver Gierke, Christoph Strobl, Mark Paluch
Since:
1.12/**
 * Default implementation of {@link ProjectionInformation}. Exposes all properties of the type as required input
 * properties.
 *
 * @author Oliver Gierke
 * @author Christoph Strobl
 * @author Mark Paluch
 * @since 1.12
 */
class DefaultProjectionInformation implements ProjectionInformation {

	private final Class<?> projectionType;
	private final List<PropertyDescriptor> properties;

	
Creates a new DefaultProjectionInformation for the given type. 
Params:
type – must not be null./**
	 * Creates a new {@link DefaultProjectionInformation} for the given type.
	 *
	 * @param type must not be {@literal null}.
	 */
	DefaultProjectionInformation(Class<?> type) {

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

		this.projectionType = type;
		this.properties = new PropertyDescriptorSource(type).getDescriptors();
	}

	/*
	 * (non-Javadoc)
	 * @see org.springframework.data.projection.ProjectionInformation#getType()
	 */
	@Override
	public Class<?> getType() {
		return projectionType;
	}

	/*
	 * (non-Javadoc)
	 * @see org.springframework.data.projection.ProjectionInformation#getInputProperties()
	 */
	public List<PropertyDescriptor> getInputProperties() {

		return properties.stream()//
				.filter(this::isInputProperty)//
				.distinct()//
				.collect(Collectors.toList());
	}

	/*
	 * (non-Javadoc)
	 * @see org.springframework.data.projection.ProjectionInformation#isDynamic()
	 */
	@Override
	public boolean isClosed() {
		return this.properties.equals(getInputProperties());
	}

	
Returns whether the given PropertyDescriptor describes an input property for the projection, i.e. a property that needs to be present on the source to be able to create reasonable projections for the type the descriptor was looked up on. 
Params:
descriptor – will never be null.
Returns:
/**
	 * Returns whether the given {@link PropertyDescriptor} describes an input property for the projection, i.e. a
	 * property that needs to be present on the source to be able to create reasonable projections for the type the
	 * descriptor was looked up on.
	 *
	 * @param descriptor will never be {@literal null}.
	 * @return
	 */
	protected boolean isInputProperty(PropertyDescriptor descriptor) {
		return true;
	}

	
Returns whether the given PropertyDescriptor has a getter that is a Java 8 default method. 
Params:
descriptor – must not be null.
Returns:
/**
	 * Returns whether the given {@link PropertyDescriptor} has a getter that is a Java 8 default method.
	 *
	 * @param descriptor must not be {@literal null}.
	 * @return
	 */
	private static boolean hasDefaultGetter(PropertyDescriptor descriptor) {

		Method method = descriptor.getReadMethod();

		return method != null && method.isDefault();
	}

	
Internal helper to detect PropertyDescriptor instances for a given type. 
Author:
Mark Paluch, Oliver Gierke
Since:
2.1
@soundtrack
The Meters - Cissy Strut (Here Comes The Meter Man)/**
	 * Internal helper to detect {@link PropertyDescriptor} instances for a given type.
	 *
	 * @author Mark Paluch
	 * @author Oliver Gierke
	 * @since 2.1
	 * @soundtrack The Meters - Cissy Strut (Here Comes The Meter Man)
	 */
	@Slf4j
	private static class PropertyDescriptorSource {

		private final Class<?> type;
		private final Optional<MethodsMetadata> metadata;

		
Creates a new PropertyDescriptorSource for the given type. 
Params:
type – must not be null./**
		 * Creates a new {@link PropertyDescriptorSource} for the given type.
		 *
		 * @param type must not be {@literal null}.
		 */
		PropertyDescriptorSource(Class<?> type) {

			Assert.notNull(type, "Type must not be null!");

			this.type = type;
			this.metadata = getMetadata(type);
		}

		
Returns PropertyDescriptors for all properties exposed by the given type and all its super interfaces. 
Returns:
/**
		 * Returns {@link PropertyDescriptor}s for all properties exposed by the given type and all its super interfaces.
		 *
		 * @return
		 */
		List<PropertyDescriptor> getDescriptors() {
			return collectDescriptors().distinct().collect(StreamUtils.toUnmodifiableList());
		}

		
Recursively collects PropertyDescriptors for all properties exposed by the given type and all its super interfaces. 
Returns:
/**
		 * Recursively collects {@link PropertyDescriptor}s for all properties exposed by the given type and all its super
		 * interfaces.
		 *
		 * @return
		 */
		private Stream<PropertyDescriptor> collectDescriptors() {

			Stream<PropertyDescriptor> allButDefaultGetters = Arrays.stream(BeanUtils.getPropertyDescriptors(type)) //
					.filter(it -> !hasDefaultGetter(it));

			Stream<PropertyDescriptor> ownDescriptors = metadata.map(it -> filterAndOrder(allButDefaultGetters, it))
					.orElse(allButDefaultGetters);

			Stream<PropertyDescriptor> superTypeDescriptors = metadata.map(this::fromMetadata) //
					.orElseGet(this::fromType) //
					.flatMap(it -> new PropertyDescriptorSource(it).collectDescriptors());

			return Stream.concat(ownDescriptors, superTypeDescriptors);
		}

		
Returns a Stream of PropertyDescriptor ordered following the given MethodsMetadata only returning methods seen by the given MethodsMetadata. 
Params:
source – must not be null.
metadata – must not be null.
Returns:
/**
		 * Returns a {@link Stream} of {@link PropertyDescriptor} ordered following the given {@link MethodsMetadata} only
		 * returning methods seen by the given {@link MethodsMetadata}.
		 *
		 * @param source must not be {@literal null}.
		 * @param metadata must not be {@literal null}.
		 * @return
		 */
		private static Stream<PropertyDescriptor> filterAndOrder(Stream<PropertyDescriptor> source,
				MethodsMetadata metadata) {

			Map<String, Integer> orderedMethods = getMethodOrder(metadata);

			if (orderedMethods.isEmpty()) {
				return source;
			}

			return source.filter(descriptor -> descriptor.getReadMethod() != null)
					.filter(descriptor -> orderedMethods.containsKey(descriptor.getReadMethod().getName()))
					.sorted(Comparator.comparingInt(left -> orderedMethods.get(left.getReadMethod().getName())));
		}

		
Returns a Stream of interfaces using the given MethodsMetadata as primary source for ordering. 
Params:
metadata – must not be null.
Returns:
/**
		 * Returns a {@link Stream} of interfaces using the given {@link MethodsMetadata} as primary source for ordering.
		 *
		 * @param metadata must not be {@literal null}.
		 * @return
		 */
		private Stream<Class<?>> fromMetadata(MethodsMetadata metadata) {
			return Arrays.stream(metadata.getInterfaceNames()).map(it -> findType(it, type.getInterfaces()));
		}

		
Returns a Stream of interfaces using the given type as primary source for ordering. 
Returns:
/**
		 * Returns a {@link Stream} of interfaces using the given type as primary source for ordering.
		 *
		 * @return
		 */
		private Stream<Class<?>> fromType() {
			return Arrays.stream(type.getInterfaces());
		}

		
Attempts to obtain MethodsMetadata from Class. Returns Optional containing MethodsMetadata if metadata was read successfully, Optional.empty() otherwise. 
Params:
type – must not be null.
Returns:
the optional MethodsMetadata./**
		 * Attempts to obtain {@link MethodsMetadata} from {@link Class}. Returns {@link Optional} containing
		 * {@link MethodsMetadata} if metadata was read successfully, {@link Optional#empty()} otherwise.
		 *
		 * @param type must not be {@literal null}.
		 * @return the optional {@link MethodsMetadata}.
		 */
		private static Optional<MethodsMetadata> getMetadata(Class<?> type) {

			try {

				MethodsMetadataReaderFactory factory = new MethodsMetadataReaderFactory(type.getClassLoader());
				MethodsMetadataReader metadataReader = factory.getMetadataReader(ClassUtils.getQualifiedName(type));

				return Optional.of(metadataReader.getMethodsMetadata());

			} catch (IOException e) {

				LOG.info("Couldn't read class metadata for {}. Input property calculation might fail!", type);

				return Optional.empty();
			}
		}

		
Find the type with the given name in the given array of Class. 
Params:
name – must not be null or empty.
types – must not be null.
Returns:
/**
		 * Find the type with the given name in the given array of {@link Class}.
		 *
		 * @param name must not be {@literal null} or empty.
		 * @param types must not be {@literal null}.
		 * @return
		 */
		private static Class<?> findType(String name, Class<?>[] types) {

			return Arrays.stream(types) //
					.filter(it -> name.equals(it.getName())) //
					.findFirst()
					.orElseThrow(() -> new IllegalStateException(
							String.format("Did not find type %s in %s!", name, Arrays.toString(types))));
		}

		
Returns a Map containing method name to its positional index according to MethodsMetadata. 
Params:
metadata – 
Returns:
/**
		 * Returns a {@link Map} containing method name to its positional index according to {@link MethodsMetadata}.
		 *
		 * @param metadata
		 * @return
		 */
		private static Map<String, Integer> getMethodOrder(MethodsMetadata metadata) {

			List<String> methods = metadata.getMethods() //
					.stream() //
					.map(MethodMetadata::getMethodName) //
					.distinct() //
					.collect(Collectors.toList());

			return IntStream.range(0, methods.size()) //
					.boxed() //
					.collect(Collectors.toMap(methods::get, i -> i));
		}
	}
}