/*
 * Copyright 2012-2020 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.boot.web.servlet;

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.EnumSet;
import java.util.LinkedHashSet;
import java.util.Set;

import javax.servlet.DispatcherType;
import javax.servlet.Filter;
import javax.servlet.FilterRegistration;
import javax.servlet.FilterRegistration.Dynamic;
import javax.servlet.ServletContext;

import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;
import org.springframework.web.filter.OncePerRequestFilter;

Abstract base ServletContextInitializer to register Filters in a Servlet 3.0+ container. 
Author:
Phillip Webb, Brian Clozel
Type parameters:
<T> – the type of Filter to register
Since:
1.5.22/**
 * Abstract base {@link ServletContextInitializer} to register {@link Filter}s in a
 * Servlet 3.0+ container.
 *
 * @param <T> the type of {@link Filter} to register
 * @author Phillip Webb
 * @author Brian Clozel
 * @since 1.5.22
 */
public abstract class AbstractFilterRegistrationBean<T extends Filter> extends DynamicRegistrationBean<Dynamic> {

	private static final String[] DEFAULT_URL_MAPPINGS = { "/*" };

	private Set<ServletRegistrationBean<?>> servletRegistrationBeans = new LinkedHashSet<>();

	private Set<String> servletNames = new LinkedHashSet<>();

	private Set<String> urlPatterns = new LinkedHashSet<>();

	private EnumSet<DispatcherType> dispatcherTypes;

	private boolean matchAfter = false;

	
Create a new instance to be registered with the specified ServletRegistrationBeans. 
Params:
servletRegistrationBeans – associate ServletRegistrationBeans/**
	 * Create a new instance to be registered with the specified
	 * {@link ServletRegistrationBean}s.
	 * @param servletRegistrationBeans associate {@link ServletRegistrationBean}s
	 */
	AbstractFilterRegistrationBean(ServletRegistrationBean<?>... servletRegistrationBeans) {
		Assert.notNull(servletRegistrationBeans, "ServletRegistrationBeans must not be null");
		Collections.addAll(this.servletRegistrationBeans, servletRegistrationBeans);
	}

	
Set ServletRegistrationBeans that the filter will be registered against. 
Params:
servletRegistrationBeans – the Servlet registration beans/**
	 * Set {@link ServletRegistrationBean}s that the filter will be registered against.
	 * @param servletRegistrationBeans the Servlet registration beans
	 */
	public void setServletRegistrationBeans(Collection<? extends ServletRegistrationBean<?>> servletRegistrationBeans) {
		Assert.notNull(servletRegistrationBeans, "ServletRegistrationBeans must not be null");
		this.servletRegistrationBeans = new LinkedHashSet<>(servletRegistrationBeans);
	}

	
Return a mutable collection of the ServletRegistrationBean that the filter will be registered against. ServletRegistrationBeans. 
See Also:
setServletNames
setUrlPatterns
Returns:
the Servlet registration beans/**
	 * Return a mutable collection of the {@link ServletRegistrationBean} that the filter
	 * will be registered against. {@link ServletRegistrationBean}s.
	 * @return the Servlet registration beans
	 * @see #setServletNames
	 * @see #setUrlPatterns
	 */
	public Collection<ServletRegistrationBean<?>> getServletRegistrationBeans() {
		return this.servletRegistrationBeans;
	}

	
Add ServletRegistrationBeans for the filter. 
Params:
servletRegistrationBeans – the servlet registration beans to add
See Also:
setServletRegistrationBeans/**
	 * Add {@link ServletRegistrationBean}s for the filter.
	 * @param servletRegistrationBeans the servlet registration beans to add
	 * @see #setServletRegistrationBeans
	 */
	public void addServletRegistrationBeans(ServletRegistrationBean<?>... servletRegistrationBeans) {
		Assert.notNull(servletRegistrationBeans, "ServletRegistrationBeans must not be null");
		Collections.addAll(this.servletRegistrationBeans, servletRegistrationBeans);
	}

	
Set servlet names that the filter will be registered against. This will replace any
previously specified servlet names.
Params:
servletNames – the servlet names
See Also:
setServletRegistrationBeans
setUrlPatterns/**
	 * Set servlet names that the filter will be registered against. This will replace any
	 * previously specified servlet names.
	 * @param servletNames the servlet names
	 * @see #setServletRegistrationBeans
	 * @see #setUrlPatterns
	 */
	public void setServletNames(Collection<String> servletNames) {
		Assert.notNull(servletNames, "ServletNames must not be null");
		this.servletNames = new LinkedHashSet<>(servletNames);
	}

	
Return a mutable collection of servlet names that the filter will be registered
against.
Returns:
the servlet names/**
	 * Return a mutable collection of servlet names that the filter will be registered
	 * against.
	 * @return the servlet names
	 */
	public Collection<String> getServletNames() {
		return this.servletNames;
	}

	
Add servlet names for the filter.
Params:
servletNames – the servlet names to add/**
	 * Add servlet names for the filter.
	 * @param servletNames the servlet names to add
	 */
	public void addServletNames(String... servletNames) {
		Assert.notNull(servletNames, "ServletNames must not be null");
		this.servletNames.addAll(Arrays.asList(servletNames));
	}

	
Set the URL patterns that the filter will be registered against. This will replace
any previously specified URL patterns.
Params:
urlPatterns – the URL patterns
See Also:
setServletRegistrationBeans
setServletNames/**
	 * Set the URL patterns that the filter will be registered against. This will replace
	 * any previously specified URL patterns.
	 * @param urlPatterns the URL patterns
	 * @see #setServletRegistrationBeans
	 * @see #setServletNames
	 */
	public void setUrlPatterns(Collection<String> urlPatterns) {
		Assert.notNull(urlPatterns, "UrlPatterns must not be null");
		this.urlPatterns = new LinkedHashSet<>(urlPatterns);
	}

	
Return a mutable collection of URL patterns, as defined in the Servlet
specification, that the filter will be registered against.
Returns:
the URL patterns/**
	 * Return a mutable collection of URL patterns, as defined in the Servlet
	 * specification, that the filter will be registered against.
	 * @return the URL patterns
	 */
	public Collection<String> getUrlPatterns() {
		return this.urlPatterns;
	}

	
Add URL patterns, as defined in the Servlet specification, that the filter will be
registered against.
Params:
urlPatterns – the URL patterns/**
	 * Add URL patterns, as defined in the Servlet specification, that the filter will be
	 * registered against.
	 * @param urlPatterns the URL patterns
	 */
	public void addUrlPatterns(String... urlPatterns) {
		Assert.notNull(urlPatterns, "UrlPatterns must not be null");
		Collections.addAll(this.urlPatterns, urlPatterns);
	}

	
Convenience method to set dispatcher types using the specified elements. 
Params:
first – the first dispatcher type
rest – additional dispatcher types/**
	 * Convenience method to {@link #setDispatcherTypes(EnumSet) set dispatcher types}
	 * using the specified elements.
	 * @param first the first dispatcher type
	 * @param rest additional dispatcher types
	 */
	public void setDispatcherTypes(DispatcherType first, DispatcherType... rest) {
		this.dispatcherTypes = EnumSet.of(first, rest);
	}

	
Sets the dispatcher types that should be used with the registration. If not specified the types will be deduced based on the value of DynamicRegistrationBean.isAsyncSupported(). 
Params:
dispatcherTypes – the dispatcher types/**
	 * Sets the dispatcher types that should be used with the registration. If not
	 * specified the types will be deduced based on the value of
	 * {@link #isAsyncSupported()}.
	 * @param dispatcherTypes the dispatcher types
	 */
	public void setDispatcherTypes(EnumSet<DispatcherType> dispatcherTypes) {
		this.dispatcherTypes = dispatcherTypes;
	}

	
Set if the filter mappings should be matched after any declared filter mappings of the ServletContext. Defaults to false indicating the filters are supposed to be matched before any declared filter mappings of the ServletContext. 
Params:
matchAfter – if filter mappings are matched after/**
	 * Set if the filter mappings should be matched after any declared filter mappings of
	 * the ServletContext. Defaults to {@code false} indicating the filters are supposed
	 * to be matched before any declared filter mappings of the ServletContext.
	 * @param matchAfter if filter mappings are matched after
	 */
	public void setMatchAfter(boolean matchAfter) {
		this.matchAfter = matchAfter;
	}

	
Return if filter mappings should be matched after any declared Filter mappings of
the ServletContext.
Returns:
if filter mappings are matched after/**
	 * Return if filter mappings should be matched after any declared Filter mappings of
	 * the ServletContext.
	 * @return if filter mappings are matched after
	 */
	public boolean isMatchAfter() {
		return this.matchAfter;
	}

	@Override
	protected String getDescription() {
		Filter filter = getFilter();
		Assert.notNull(filter, "Filter must not be null");
		return "filter " + getOrDeduceName(filter);
	}

	@Override
	protected Dynamic addRegistration(String description, ServletContext servletContext) {
		Filter filter = getFilter();
		return servletContext.addFilter(getOrDeduceName(filter), filter);
	}

	
Configure registration settings. Subclasses can override this method to perform
additional configuration if required.
Params:
registration – the registration/**
	 * Configure registration settings. Subclasses can override this method to perform
	 * additional configuration if required.
	 * @param registration the registration
	 */
	@Override
	protected void configure(FilterRegistration.Dynamic registration) {
		super.configure(registration);
		EnumSet<DispatcherType> dispatcherTypes = this.dispatcherTypes;
		if (dispatcherTypes == null) {
			T filter = getFilter();
			if (ClassUtils.isPresent("org.springframework.web.filter.OncePerRequestFilter",
					filter.getClass().getClassLoader()) && filter instanceof OncePerRequestFilter) {
				dispatcherTypes = EnumSet.allOf(DispatcherType.class);
			}
			else {
				dispatcherTypes = EnumSet.of(DispatcherType.REQUEST);
			}
		}
		Set<String> servletNames = new LinkedHashSet<>();
		for (ServletRegistrationBean<?> servletRegistrationBean : this.servletRegistrationBeans) {
			servletNames.add(servletRegistrationBean.getServletName());
		}
		servletNames.addAll(this.servletNames);
		if (servletNames.isEmpty() && this.urlPatterns.isEmpty()) {
			registration.addMappingForUrlPatterns(dispatcherTypes, this.matchAfter, DEFAULT_URL_MAPPINGS);
		}
		else {
			if (!servletNames.isEmpty()) {
				registration.addMappingForServletNames(dispatcherTypes, this.matchAfter,
						StringUtils.toStringArray(servletNames));
			}
			if (!this.urlPatterns.isEmpty()) {
				registration.addMappingForUrlPatterns(dispatcherTypes, this.matchAfter,
						StringUtils.toStringArray(this.urlPatterns));
			}
		}
	}

	
Return the Filter to be registered. 
Returns:
the filter/**
	 * Return the {@link Filter} to be registered.
	 * @return the filter
	 */
	public abstract T getFilter();

	@Override
	public String toString() {
		StringBuilder builder = new StringBuilder(getOrDeduceName(this));
		if (this.servletNames.isEmpty() && this.urlPatterns.isEmpty()) {
			builder.append(" urls=").append(Arrays.toString(DEFAULT_URL_MAPPINGS));
		}
		else {
			if (!this.servletNames.isEmpty()) {
				builder.append(" servlets=").append(this.servletNames);
			}
			if (!this.urlPatterns.isEmpty()) {
				builder.append(" urls=").append(this.urlPatterns);
			}
		}
		builder.append(" order=").append(getOrder());
		return builder.toString();
	}

}