/*
 * Copyright 2002-2020 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.core.env;

import java.util.Iterator;
import java.util.List;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.stream.Stream;

import org.springframework.lang.Nullable;

The default implementation of the PropertySources interface. Allows manipulation of contained property sources and provides a constructor for copying an existing PropertySources instance. 
Where precedence is mentioned in methods such as addFirst and addLast, this is with regard to the order in which property sources will be searched when resolving a given property with a PropertyResolver. 
Author:
Chris Beams, Juergen Hoeller
See Also:
PropertySourcesPropertyResolver
Since:
3.1/**
 * The default implementation of the {@link PropertySources} interface.
 * Allows manipulation of contained property sources and provides a constructor
 * for copying an existing {@code PropertySources} instance.
 *
 * <p>Where <em>precedence</em> is mentioned in methods such as {@link #addFirst}
 * and {@link #addLast}, this is with regard to the order in which property sources
 * will be searched when resolving a given property with a {@link PropertyResolver}.
 *
 * @author Chris Beams
 * @author Juergen Hoeller
 * @since 3.1
 * @see PropertySourcesPropertyResolver
 */
public class MutablePropertySources implements PropertySources {

	private final List<PropertySource<?>> propertySourceList = new CopyOnWriteArrayList<>();


	
Create a new MutablePropertySources object. /**
	 * Create a new {@link MutablePropertySources} object.
	 */
	public MutablePropertySources() {
	}

	
Create a new MutablePropertySources from the given propertySources object, preserving the original order of contained PropertySource objects. /**
	 * Create a new {@code MutablePropertySources} from the given propertySources
	 * object, preserving the original order of contained {@code PropertySource} objects.
	 */
	public MutablePropertySources(PropertySources propertySources) {
		this();
		for (PropertySource<?> propertySource : propertySources) {
			addLast(propertySource);
		}
	}


	@Override
	public Iterator<PropertySource<?>> iterator() {
		return this.propertySourceList.iterator();
	}

	@Override
	public Spliterator<PropertySource<?>> spliterator() {
		return Spliterators.spliterator(this.propertySourceList, 0);
	}

	@Override
	public Stream<PropertySource<?>> stream() {
		return this.propertySourceList.stream();
	}

	@Override
	public boolean contains(String name) {
		for (PropertySource<?> propertySource : this.propertySourceList) {
			if (propertySource.getName().equals(name)) {
				return true;
			}
		}
		return false;
	}

	@Override
	@Nullable
	public PropertySource<?> get(String name) {
		for (PropertySource<?> propertySource : this.propertySourceList) {
			if (propertySource.getName().equals(name)) {
				return propertySource;
			}
		}
		return null;
	}


	
Add the given property source object with highest precedence.
/**
	 * Add the given property source object with highest precedence.
	 */
	public void addFirst(PropertySource<?> propertySource) {
		synchronized (this.propertySourceList) {
			removeIfPresent(propertySource);
			this.propertySourceList.add(0, propertySource);
		}
	}

	
Add the given property source object with lowest precedence.
/**
	 * Add the given property source object with lowest precedence.
	 */
	public void addLast(PropertySource<?> propertySource) {
		synchronized (this.propertySourceList) {
			removeIfPresent(propertySource);
			this.propertySourceList.add(propertySource);
		}
	}

	
Add the given property source object with precedence immediately higher
than the named relative property source.
/**
	 * Add the given property source object with precedence immediately higher
	 * than the named relative property source.
	 */
	public void addBefore(String relativePropertySourceName, PropertySource<?> propertySource) {
		assertLegalRelativeAddition(relativePropertySourceName, propertySource);
		synchronized (this.propertySourceList) {
			removeIfPresent(propertySource);
			int index = assertPresentAndGetIndex(relativePropertySourceName);
			addAtIndex(index, propertySource);
		}
	}

	
Add the given property source object with precedence immediately lower
than the named relative property source.
/**
	 * Add the given property source object with precedence immediately lower
	 * than the named relative property source.
	 */
	public void addAfter(String relativePropertySourceName, PropertySource<?> propertySource) {
		assertLegalRelativeAddition(relativePropertySourceName, propertySource);
		synchronized (this.propertySourceList) {
			removeIfPresent(propertySource);
			int index = assertPresentAndGetIndex(relativePropertySourceName);
			addAtIndex(index + 1, propertySource);
		}
	}

	
Return the precedence of the given property source, -1 if not found. /**
	 * Return the precedence of the given property source, {@code -1} if not found.
	 */
	public int precedenceOf(PropertySource<?> propertySource) {
		return this.propertySourceList.indexOf(propertySource);
	}

	
Remove and return the property source with the given name, null if not found. 
Params:
name – the name of the property source to find and remove/**
	 * Remove and return the property source with the given name, {@code null} if not found.
	 * @param name the name of the property source to find and remove
	 */
	@Nullable
	public PropertySource<?> remove(String name) {
		synchronized (this.propertySourceList) {
			int index = this.propertySourceList.indexOf(PropertySource.named(name));
			return (index != -1 ? this.propertySourceList.remove(index) : null);
		}
	}

	
Replace the property source with the given name with the given property source object.
Params:
name – the name of the property source to find and replace
propertySource – the replacement property source
Throws:
IllegalArgumentException – if no property source with the given name is present
See Also:
contains/**
	 * Replace the property source with the given name with the given property source object.
	 * @param name the name of the property source to find and replace
	 * @param propertySource the replacement property source
	 * @throws IllegalArgumentException if no property source with the given name is present
	 * @see #contains
	 */
	public void replace(String name, PropertySource<?> propertySource) {
		synchronized (this.propertySourceList) {
			int index = assertPresentAndGetIndex(name);
			this.propertySourceList.set(index, propertySource);
		}
	}

	
Return the number of PropertySource objects contained. /**
	 * Return the number of {@link PropertySource} objects contained.
	 */
	public int size() {
		return this.propertySourceList.size();
	}

	@Override
	public String toString() {
		return this.propertySourceList.toString();
	}


	
Ensure that the given property source is not being added relative to itself.
/**
	 * Ensure that the given property source is not being added relative to itself.
	 */
	protected void assertLegalRelativeAddition(String relativePropertySourceName, PropertySource<?> propertySource) {
		String newPropertySourceName = propertySource.getName();
		if (relativePropertySourceName.equals(newPropertySourceName)) {
			throw new IllegalArgumentException(
					"PropertySource named '" + newPropertySourceName + "' cannot be added relative to itself");
		}
	}

	
Remove the given property source if it is present.
/**
	 * Remove the given property source if it is present.
	 */
	protected void removeIfPresent(PropertySource<?> propertySource) {
		this.propertySourceList.remove(propertySource);
	}

	
Add the given property source at a particular index in the list.
/**
	 * Add the given property source at a particular index in the list.
	 */
	private void addAtIndex(int index, PropertySource<?> propertySource) {
		removeIfPresent(propertySource);
		this.propertySourceList.add(index, propertySource);
	}

	
Assert that the named property source is present and return its index.
Params:
name – name of the property source to find
Throws:
IllegalArgumentException – if the named property source is not present/**
	 * Assert that the named property source is present and return its index.
	 * @param name {@linkplain PropertySource#getName() name of the property source} to find
	 * @throws IllegalArgumentException if the named property source is not present
	 */
	private int assertPresentAndGetIndex(String name) {
		int index = this.propertySourceList.indexOf(PropertySource.named(name));
		if (index == -1) {
			throw new IllegalArgumentException("PropertySource named '" + name + "' does not exist");
		}
		return index;
	}

}