/*
 * Copyright 2002-2017 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.web.servlet.config.annotation;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.springframework.cache.Cache;
import org.springframework.http.CacheControl;
import org.springframework.util.Assert;
import org.springframework.web.servlet.resource.PathResourceResolver;
import org.springframework.web.servlet.resource.ResourceHttpRequestHandler;

/**
 * Encapsulates information required to create a resource handler.
 *
 * @author Rossen Stoyanchev
 * @author Keith Donald
 * @author Brian Clozel
 * @since 3.1
 */
public class ResourceHandlerRegistration {

        private final String[] pathPatterns;

        private final List<String> locationValues = new ArrayList<String>();

        private Integer cachePeriod;

        private CacheControl cacheControl;

        private ResourceChainRegistration resourceChainRegistration;


        /**
         * Create a {@link ResourceHandlerRegistration} instance.
         * @param pathPatterns one or more resource URL path patterns
         */
        public ResourceHandlerRegistration(String... pathPatterns) {
                Assert.notEmpty(pathPatterns, "At least one path pattern is required for resource handling.");
                this.pathPatterns = pathPatterns;
        }


        /**
         * Add one or more resource locations from which to serve static content.
         * Each location must point to a valid directory. Multiple locations may
         * be specified as a comma-separated list, and the locations will be checked
         * for a given resource in the order specified.
         * <p>For example, {{@code "/"}, {@code "classpath:/META-INF/public-web-resources/"}}
         * allows resources to be served both from the web application root and
         * from any JAR on the classpath that contains a
         * {@code /META-INF/public-web-resources/} directory, with resources in the
         * web application root taking precedence.
         * <p>For {@link org.springframework.core.io.UrlResource URL-based resources}
         * (e.g. files, HTTP URLs, etc) this method supports a special prefix to
         * indicate the charset associated with the URL so that relative paths
         * appended to it can be encoded correctly, e.g.
         * {@code [charset=Windows-31J]https://example.org/path}.
         * @return the same {@link ResourceHandlerRegistration} instance, for
         * chained method invocation
         */
        public ResourceHandlerRegistration addResourceLocations(String... resourceLocations) {
                this.locationValues.addAll(Arrays.asList(resourceLocations));
                return this;
        }

        /**
         * Specify the cache period for the resources served by the resource handler, in seconds. The default is to not
         * send any cache headers but to rely on last-modified timestamps only. Set to 0 in order to send cache headers
         * that prevent caching, or to a positive number of seconds to send cache headers with the given max-age value.
         * @param cachePeriod the time to cache resources in seconds
         * @return the same {@link ResourceHandlerRegistration} instance, for chained method invocation
         */
        public ResourceHandlerRegistration setCachePeriod(Integer cachePeriod) {
                this.cachePeriod = cachePeriod;
                return this;
        }

        /**
         * Specify the {@link org.springframework.http.CacheControl} which should be used
         * by the resource handler.
         * <p>Setting a custom value here will override the configuration set with {@link #setCachePeriod}.
         * @param cacheControl the CacheControl configuration to use
         * @return the same {@link ResourceHandlerRegistration} instance, for chained method invocation
         * @since 4.2
         */
        public ResourceHandlerRegistration setCacheControl(CacheControl cacheControl) {
                this.cacheControl = cacheControl;
                return this;
        }

        /**
         * Configure a chain of resource resolvers and transformers to use. This
         * can be useful, for example, to apply a version strategy to resource URLs.
         * <p>If this method is not invoked, by default only a simple
         * {@link PathResourceResolver} is used in order to match URL paths to
         * resources under the configured locations.
         * @param cacheResources whether to cache the result of resource resolution;
         * setting this to "true" is recommended for production (and "false" for
         * development, especially when applying a version strategy)
         * @return the same {@link ResourceHandlerRegistration} instance, for chained method invocation
         * @since 4.1
         */
        public ResourceChainRegistration resourceChain(boolean cacheResources) {
                this.resourceChainRegistration = new ResourceChainRegistration(cacheResources);
                return this.resourceChainRegistration;
        }

        /**
         * Configure a chain of resource resolvers and transformers to use. This
         * can be useful, for example, to apply a version strategy to resource URLs.
         * <p>If this method is not invoked, by default only a simple
         * {@link PathResourceResolver} is used in order to match URL paths to
         * resources under the configured locations.
         * @param cacheResources whether to cache the result of resource resolution;
         * setting this to "true" is recommended for production (and "false" for
         * development, especially when applying a version strategy
         * @param cache the cache to use for storing resolved and transformed resources;
         * by default a {@link org.springframework.cache.concurrent.ConcurrentMapCache}
         * is used. Since Resources aren't serializable and can be dependent on the
         * application host, one should not use a distributed cache but rather an
         * in-memory cache.
         * @return the same {@link ResourceHandlerRegistration} instance, for chained method invocation
         * @since 4.1
         */
        public ResourceChainRegistration resourceChain(boolean cacheResources, Cache cache) {
                this.resourceChainRegistration = new ResourceChainRegistration(cacheResources, cache);
                return this.resourceChainRegistration;
        }


        /**
         * Return the URL path patterns for the resource handler.
         */
        protected String[] getPathPatterns() {
                return this.pathPatterns;
        }

        /**
         * Return a {@link ResourceHttpRequestHandler} instance.
         */
        protected ResourceHttpRequestHandler getRequestHandler() {
                ResourceHttpRequestHandler handler = new ResourceHttpRequestHandler();
                if (this.resourceChainRegistration != null) {
                        handler.setResourceResolvers(this.resourceChainRegistration.getResourceResolvers());
                        handler.setResourceTransformers(this.resourceChainRegistration.getResourceTransformers());
                }
                handler.setLocationValues(this.locationValues);
                if (this.cacheControl != null) {
                        handler.setCacheControl(this.cacheControl);
                }
                else if (this.cachePeriod != null) {
                        handler.setCacheSeconds(this.cachePeriod);
                }
                return handler;
        }

}