/*
 * 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.web.servlet.function;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.URI;
import java.security.Principal;
import java.time.Instant;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.EnumSet;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Function;
import java.util.function.Predicate;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.core.ParameterizedTypeReference;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.server.PathContainer;
import org.springframework.lang.NonNull;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.MultiValueMap;
import org.springframework.web.cors.CorsUtils;
import org.springframework.web.util.UriBuilder;
import org.springframework.web.util.UriUtils;
import org.springframework.web.util.pattern.PathPattern;
import org.springframework.web.util.pattern.PathPatternParser;

/**
 * Implementations of {@link RequestPredicate} that implement various useful
 * request matching operations, such as matching based on path, HTTP method, etc.
 *
 * @author Arjen Poutsma
 * @since 5.2
 */
public abstract class RequestPredicates {

        private static final Log logger = LogFactory.getLog(RequestPredicates.class);

        /**
         * Return a {@code RequestPredicate} that always matches.
         * @return a predicate that always matches
         */
        public static RequestPredicate all() {
                return request -> true;
        }

        /**
         * Return a {@code RequestPredicate} that matches if the request's
         * HTTP method is equal to the given method.
         * @param httpMethod the HTTP method to match against
         * @return a predicate that tests against the given HTTP method
         */
        public static RequestPredicate method(HttpMethod httpMethod) {
                return new HttpMethodPredicate(httpMethod);
        }

        /**
         * Return a {@code RequestPredicate} that matches if the request's
         * HTTP method is equal to one the of the given methods.
         * @param httpMethods the HTTP methods to match against
         * @return a predicate that tests against the given HTTP methods
         */
        public static RequestPredicate methods(HttpMethod... httpMethods) {
                return new HttpMethodPredicate(httpMethods);
        }

        /**
         * Return a {@code RequestPredicate} that tests the request path
         * against the given path pattern.
         * @param pattern the pattern to match to
         * @return a predicate that tests against the given path pattern
         */
        public static RequestPredicate path(String pattern) {
                Assert.notNull(pattern, "'pattern' must not be null");
                if (!pattern.isEmpty() && !pattern.startsWith("/")) {
                        pattern = "/" + pattern;
                }
                return pathPredicates(PathPatternParser.defaultInstance).apply(pattern);
        }

        /**
         * Return a function that creates new path-matching {@code RequestPredicates}
         * from pattern Strings using the given {@link PathPatternParser}.
         * <p>This method can be used to specify a non-default, customized
         * {@code PathPatternParser} when resolving path patterns.
         * @param patternParser the parser used to parse patterns given to the returned function
         * @return a function that resolves a pattern String into a path-matching
         * {@code RequestPredicates} instance
         */
        public static Function<String, RequestPredicate> pathPredicates(PathPatternParser patternParser) {
                Assert.notNull(patternParser, "PathPatternParser must not be null");
                return pattern -> new PathPatternPredicate(patternParser.parse(pattern));
        }

        /**
         * Return a {@code RequestPredicate} that tests the request's headers
         * against the given headers predicate.
         * @param headersPredicate a predicate that tests against the request headers
         * @return a predicate that tests against the given header predicate
         */
        public static RequestPredicate headers(Predicate<ServerRequest.Headers> headersPredicate) {
                return new HeadersPredicate(headersPredicate);
        }

        /**
         * Return a {@code RequestPredicate} that tests if the request's
         * {@linkplain ServerRequest.Headers#contentType() content type} is
         * {@linkplain MediaType#includes(MediaType) included} by any of the given media types.
         * @param mediaTypes the media types to match the request's content type against
         * @return a predicate that tests the request's content type against the given media types
         */
        public static RequestPredicate contentType(MediaType... mediaTypes) {
                Assert.notEmpty(mediaTypes, "'mediaTypes' must not be empty");
                return new ContentTypePredicate(mediaTypes);
        }

        /**
         * Return a {@code RequestPredicate} that tests if the request's
         * {@linkplain ServerRequest.Headers#accept() accept} header is
         * {@linkplain MediaType#isCompatibleWith(MediaType) compatible} with any of the given media types.
         * @param mediaTypes the media types to match the request's accept header against
         * @return a predicate that tests the request's accept header against the given media types
         */
        public static RequestPredicate accept(MediaType... mediaTypes) {
                Assert.notEmpty(mediaTypes, "'mediaTypes' must not be empty");
                return new AcceptPredicate(mediaTypes);
        }

        /**
         * Return a {@code RequestPredicate} that matches if request's HTTP method is {@code GET}
         * and the given {@code pattern} matches against the request path.
         * @param pattern the path pattern to match against
         * @return a predicate that matches if the request method is GET and if the given pattern
         * matches against the request path
         */
        public static RequestPredicate GET(String pattern) {
                return method(HttpMethod.GET).and(path(pattern));
        }

        /**
         * Return a {@code RequestPredicate} that matches if request's HTTP method is {@code HEAD}
         * and the given {@code pattern} matches against the request path.
         * @param pattern the path pattern to match against
         * @return a predicate that matches if the request method is HEAD and if the given pattern
         * matches against the request path
         */
        public static RequestPredicate HEAD(String pattern) {
                return method(HttpMethod.HEAD).and(path(pattern));
        }

        /**
         * Return a {@code RequestPredicate} that matches if request's HTTP method is {@code POST}
         * and the given {@code pattern} matches against the request path.
         * @param pattern the path pattern to match against
         * @return a predicate that matches if the request method is POST and if the given pattern
         * matches against the request path
         */
        public static RequestPredicate POST(String pattern) {
                return method(HttpMethod.POST).and(path(pattern));
        }

        /**
         * Return a {@code RequestPredicate} that matches if request's HTTP method is {@code PUT}
         * and the given {@code pattern} matches against the request path.
         * @param pattern the path pattern to match against
         * @return a predicate that matches if the request method is PUT and if the given pattern
         * matches against the request path
         */
        public static RequestPredicate PUT(String pattern) {
                return method(HttpMethod.PUT).and(path(pattern));
        }

        /**
         * Return a {@code RequestPredicate} that matches if request's HTTP method is {@code PATCH}
         * and the given {@code pattern} matches against the request path.
         * @param pattern the path pattern to match against
         * @return a predicate that matches if the request method is PATCH and if the given pattern
         * matches against the request path
         */
        public static RequestPredicate PATCH(String pattern) {
                return method(HttpMethod.PATCH).and(path(pattern));
        }

        /**
         * Return a {@code RequestPredicate} that matches if request's HTTP method is {@code DELETE}
         * and the given {@code pattern} matches against the request path.
         * @param pattern the path pattern to match against
         * @return a predicate that matches if the request method is DELETE and if the given pattern
         * matches against the request path
         */
        public static RequestPredicate DELETE(String pattern) {
                return method(HttpMethod.DELETE).and(path(pattern));
        }

        /**
         * Return a {@code RequestPredicate} that matches if request's HTTP method is {@code OPTIONS}
         * and the given {@code pattern} matches against the request path.
         * @param pattern the path pattern to match against
         * @return a predicate that matches if the request method is OPTIONS and if the given pattern
         * matches against the request path
         */
        public static RequestPredicate OPTIONS(String pattern) {
                return method(HttpMethod.OPTIONS).and(path(pattern));
        }

        /**
         * Return a {@code RequestPredicate} that matches if the request's path has the given extension.
         * @param extension the path extension to match against, ignoring case
         * @return a predicate that matches if the request's path has the given file extension
         */
        public static RequestPredicate pathExtension(String extension) {
                Assert.notNull(extension, "'extension' must not be null");
                return new PathExtensionPredicate(extension);
        }

        /**
         * Return a {@code RequestPredicate} that matches if the request's path matches the given
         * predicate.
         * @param extensionPredicate the predicate to test against the request path extension
         * @return a predicate that matches if the given predicate matches against the request's path
         * file extension
         */
        public static RequestPredicate pathExtension(Predicate<String> extensionPredicate) {
                return new PathExtensionPredicate(extensionPredicate);
        }

        /**
         * Return a {@code RequestPredicate} that matches if the request's parameter of the given name
         * has the given value.
         * @param name the name of the parameter to test against
         * @param value the value of the parameter to test against
         * @return a predicate that matches if the parameter has the given value
         * @see ServerRequest#param(String)
         */
        public static RequestPredicate param(String name, String value) {
                return new ParamPredicate(name, value);
        }

        /**
         * Return a {@code RequestPredicate} that tests the request's parameter of the given name
         * against the given predicate.
         * @param name the name of the parameter to test against
         * @param predicate the predicate to test against the parameter value
         * @return a predicate that matches the given predicate against the parameter of the given name
         * @see ServerRequest#param(String)
         */
        public static RequestPredicate param(String name, Predicate<String> predicate) {
                return new ParamPredicate(name, predicate);
        }


        private static void traceMatch(String prefix, Object desired, @Nullable Object actual, boolean match) {
                if (logger.isTraceEnabled()) {
                        logger.trace(String.format("%s \"%s\" %s against value \"%s\"",
                                        prefix, desired, match ? "matches" : "does not match", actual));
                }
        }

        private static void restoreAttributes(ServerRequest request, Map<String, Object> attributes) {
                request.attributes().clear();
                request.attributes().putAll(attributes);
        }

        private static Map<String, String> mergePathVariables(Map<String, String> oldVariables,
                        Map<String, String> newVariables) {

                if (!newVariables.isEmpty()) {
                        Map<String, String> mergedVariables = new LinkedHashMap<>(oldVariables);
                        mergedVariables.putAll(newVariables);
                        return mergedVariables;
                }
                else {
                        return oldVariables;
                }
        }

        private static PathPattern mergePatterns(@Nullable PathPattern oldPattern, PathPattern newPattern) {
                if (oldPattern != null) {
                        return oldPattern.combine(newPattern);
                }
                else {
                        return newPattern;
                }

        }


        /**
         * Receives notifications from the logical structure of request predicates.
         */
        public interface Visitor {

                /**
                 * Receive notification of an HTTP method predicate.
                 * @param methods the HTTP methods that make up the predicate
                 * @see RequestPredicates#method(HttpMethod)
                 */
                void method(Set<HttpMethod> methods);

                /**
                 * Receive notification of an path predicate.
                 * @param pattern the path pattern that makes up the predicate
                 * @see RequestPredicates#path(String)
                 */
                void path(String pattern);

                /**
                 * Receive notification of an path extension predicate.
                 * @param extension the path extension that makes up the predicate
                 * @see RequestPredicates#pathExtension(String)
                 */
                void pathExtension(String extension);

                /**
                 * Receive notification of an HTTP header predicate.
                 * @param name the name of the HTTP header to check
                 * @param value the desired value of the HTTP header
                 * @see RequestPredicates#headers(Predicate)
                 * @see RequestPredicates#contentType(MediaType...)
                 * @see RequestPredicates#accept(MediaType...)
                 */
                void header(String name, String value);

                /**
                 * Receive notification of a parameter predicate.
                 * @param name the name of the parameter
                 * @param value the desired value of the parameter
                 * @see RequestPredicates#param(String, String)
                 */
                void param(String name, String value);

                /**
                 * Receive first notification of a logical AND predicate.
                 * The first subsequent notification will contain the left-hand side of the AND-predicate;
                 * followed by {@link #and()}, followed by the right-hand side, followed by {@link #endAnd()}.
                 * @see RequestPredicate#and(RequestPredicate)
                 */
                void startAnd();

                /**
                 * Receive "middle" notification of a logical AND predicate.
                 * The following notification contains the right-hand side, followed by {@link #endAnd()}.
                 * @see RequestPredicate#and(RequestPredicate)
                 */
                void and();

                /**
                 * Receive last notification of a logical AND predicate.
                 * @see RequestPredicate#and(RequestPredicate)
                 */
                void endAnd();

                /**
                 * Receive first notification of a logical OR predicate.
                 * The first subsequent notification will contain the left-hand side of the OR-predicate;
                 * the second notification contains the right-hand side, followed by {@link #endOr()}.
                 * @see RequestPredicate#or(RequestPredicate)
                 */
                void startOr();

                /**
                 * Receive "middle" notification of a logical OR predicate.
                 * The following notification contains the right-hand side, followed by {@link #endOr()}.
                 * @see RequestPredicate#or(RequestPredicate)
                 */
                void or();

                /**
                 * Receive last notification of a logical OR predicate.
                 * @see RequestPredicate#or(RequestPredicate)
                 */
                void endOr();

                /**
                 * Receive first notification of a negated predicate.
                 * The first subsequent notification will contain the negated predicated, followed
                 * by {@link #endNegate()}.
                 * @see RequestPredicate#negate()
                 */
                void startNegate();

                /**
                 * Receive last notification of a negated predicate.
                 * @see RequestPredicate#negate()
                 */
                void endNegate();

                /**
                 * Receive first notification of an unknown predicate.
                 */
                void unknown(RequestPredicate predicate);
        }

        private static class HttpMethodPredicate implements RequestPredicate {

                private final Set<HttpMethod> httpMethods;


                public HttpMethodPredicate(HttpMethod httpMethod) {
                        Assert.notNull(httpMethod, "HttpMethod must not be null");
                        this.httpMethods = EnumSet.of(httpMethod);
                }

                public HttpMethodPredicate(HttpMethod... httpMethods) {
                        Assert.notEmpty(httpMethods, "HttpMethods must not be empty");
                        this.httpMethods = EnumSet.copyOf(Arrays.asList(httpMethods));
                }

                @Override
                public boolean test(ServerRequest request) {
                        HttpMethod method = method(request);
                        boolean match = this.httpMethods.contains(method);
                        traceMatch("Method", this.httpMethods, method, match);
                        return match;
                }

                @Nullable
                private static HttpMethod method(ServerRequest request) {
                        if (CorsUtils.isPreFlightRequest(request.servletRequest())) {
                                String accessControlRequestMethod =
                                                request.headers().firstHeader(HttpHeaders.ACCESS_CONTROL_REQUEST_METHOD);
                                return HttpMethod.resolve(accessControlRequestMethod);
                        }
                        else {
                                return request.method();
                        }
                }

                @Override
                public void accept(Visitor visitor) {
                        visitor.method(Collections.unmodifiableSet(this.httpMethods));
                }

                @Override
                public String toString() {
                        if (this.httpMethods.size() == 1) {
                                return this.httpMethods.iterator().next().toString();
                        }
                        else {
                                return this.httpMethods.toString();
                        }
                }
        }


        private static class PathPatternPredicate implements RequestPredicate {

                private final PathPattern pattern;

                public PathPatternPredicate(PathPattern pattern) {
                        Assert.notNull(pattern, "'pattern' must not be null");
                        this.pattern = pattern;
                }

                @Override
                public boolean test(ServerRequest request) {
                        PathContainer pathContainer = request.pathContainer();
                        PathPattern.PathMatchInfo info = this.pattern.matchAndExtract(pathContainer);
                        traceMatch("Pattern", this.pattern.getPatternString(), request.path(), info != null);
                        if (info != null) {
                                mergeAttributes(request, info.getUriVariables(), this.pattern);
                                return true;
                        }
                        else {
                                return false;
                        }
                }

                private static void mergeAttributes(ServerRequest request, Map<String, String> variables,
                                PathPattern pattern) {
                        Map<String, String> pathVariables = mergePathVariables(request.pathVariables(), variables);
                        request.attributes().put(RouterFunctions.URI_TEMPLATE_VARIABLES_ATTRIBUTE,
                                                Collections.unmodifiableMap(pathVariables));

                        pattern = mergePatterns(
                                        (PathPattern) request.attributes().get(RouterFunctions.MATCHING_PATTERN_ATTRIBUTE),
                                        pattern);
                        request.attributes().put(RouterFunctions.MATCHING_PATTERN_ATTRIBUTE, pattern);
                }
                @Override
                public Optional<ServerRequest> nest(ServerRequest request) {
                        return Optional.ofNullable(this.pattern.matchStartOfPath(request.pathContainer()))
                                        .map(info -> new SubPathServerRequestWrapper(request, info, this.pattern));
                }

                @Override
                public void accept(Visitor visitor) {
                        visitor.path(this.pattern.getPatternString());
                }

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


        private static class HeadersPredicate implements RequestPredicate {

                private final Predicate<ServerRequest.Headers> headersPredicate;

                public HeadersPredicate(Predicate<ServerRequest.Headers> headersPredicate) {
                        Assert.notNull(headersPredicate, "Predicate must not be null");
                        this.headersPredicate = headersPredicate;
                }

                @Override
                public boolean test(ServerRequest request) {
                        if (CorsUtils.isPreFlightRequest(request.servletRequest())) {
                                return true;
                        }
                        else {
                                return this.headersPredicate.test(request.headers());
                        }
                }

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

        private static class ContentTypePredicate extends HeadersPredicate {

                private final Set<MediaType> mediaTypes;

                public ContentTypePredicate(MediaType... mediaTypes) {
                        this(new HashSet<>(Arrays.asList(mediaTypes)));
                }

                private ContentTypePredicate(Set<MediaType> mediaTypes) {
                        super(headers -> {
                                MediaType contentType =
                                                headers.contentType().orElse(MediaType.APPLICATION_OCTET_STREAM);
                                boolean match = mediaTypes.stream()
                                                .anyMatch(mediaType -> mediaType.includes(contentType));
                                traceMatch("Content-Type", mediaTypes, contentType, match);
                                return match;
                        });
                        this.mediaTypes = mediaTypes;
                }

                @Override
                public void accept(Visitor visitor) {
                        visitor.header(HttpHeaders.CONTENT_TYPE,
                                        (this.mediaTypes.size() == 1) ?
                                                        this.mediaTypes.iterator().next().toString() :
                                                        this.mediaTypes.toString());
                }

                @Override
                public String toString() {
                        return String.format("Content-Type: %s",
                                        (this.mediaTypes.size() == 1) ?
                                                        this.mediaTypes.iterator().next().toString() :
                                                        this.mediaTypes.toString());
                }
        }

        private static class AcceptPredicate extends HeadersPredicate {

                private final Set<MediaType> mediaTypes;

                public AcceptPredicate(MediaType... mediaTypes) {
                        this(new HashSet<>(Arrays.asList(mediaTypes)));
                }

                private AcceptPredicate(Set<MediaType> mediaTypes) {
                        super(headers -> {
                                List<MediaType> acceptedMediaTypes = acceptedMediaTypes(headers);
                                boolean match = acceptedMediaTypes.stream()
                                                .anyMatch(acceptedMediaType -> mediaTypes.stream()
                                                                .anyMatch(acceptedMediaType::isCompatibleWith));
                                traceMatch("Accept", mediaTypes, acceptedMediaTypes, match);
                                return match;
                        });
                        this.mediaTypes = mediaTypes;
                }

                @NonNull
                private static List<MediaType> acceptedMediaTypes(ServerRequest.Headers headers) {
                        List<MediaType> acceptedMediaTypes = headers.accept();
                        if (acceptedMediaTypes.isEmpty()) {
                                acceptedMediaTypes = Collections.singletonList(MediaType.ALL);
                        }
                        else {
                                MediaType.sortBySpecificityAndQuality(acceptedMediaTypes);
                        }
                        return acceptedMediaTypes;
                }

                @Override
                public void accept(Visitor visitor) {
                        visitor.header(HttpHeaders.ACCEPT,
                                        (this.mediaTypes.size() == 1) ?
                                                        this.mediaTypes.iterator().next().toString() :
                                                        this.mediaTypes.toString());
                }

                @Override
                public String toString() {
                        return String.format("Accept: %s",
                                        (this.mediaTypes.size() == 1) ?
                                                        this.mediaTypes.iterator().next().toString() :
                                                        this.mediaTypes.toString());
                }
        }

        private static class PathExtensionPredicate implements RequestPredicate {

                private final Predicate<String> extensionPredicate;

                @Nullable
                private final String extension;
                public PathExtensionPredicate(Predicate<String> extensionPredicate) {
                        Assert.notNull(extensionPredicate, "Predicate must not be null");
                        this.extensionPredicate = extensionPredicate;
                        this.extension = null;
                }

                public PathExtensionPredicate(String extension) {
                        Assert.notNull(extension, "Extension must not be null");

                        this.extensionPredicate = s -> {
                                boolean match = extension.equalsIgnoreCase(s);
                                traceMatch("Extension", extension, s, match);
                                return match;
                        };
                        this.extension = extension;
                }

                @Override
                public boolean test(ServerRequest request) {
                        String pathExtension = UriUtils.extractFileExtension(request.path());
                        return this.extensionPredicate.test(pathExtension);
                }

                @Override
                public void accept(Visitor visitor) {
                        visitor.pathExtension(
                                        (this.extension != null) ?
                                                        this.extension :
                                                        this.extensionPredicate.toString());
                }

                @Override
                public String toString() {
                        return String.format("*.%s",
                                        (this.extension != null) ?
                                                        this.extension :
                                                        this.extensionPredicate);
                }

        }


        private static class ParamPredicate implements RequestPredicate {

                private final String name;

                private final Predicate<String> valuePredicate;

                @Nullable
                private final String value;

                public ParamPredicate(String name, Predicate<String> valuePredicate) {
                        Assert.notNull(name, "Name must not be null");
                        Assert.notNull(valuePredicate, "Predicate must not be null");
                        this.name = name;
                        this.valuePredicate = valuePredicate;
                        this.value = null;
                }

                public ParamPredicate(String name, String value) {
                        Assert.notNull(name, "Name must not be null");
                        Assert.notNull(value, "Value must not be null");
                        this.name = name;
                        this.valuePredicate = value::equals;
                        this.value = value;
                }

                @Override
                public boolean test(ServerRequest request) {
                        Optional<String> s = request.param(this.name);
                        return s.filter(this.valuePredicate).isPresent();
                }

                @Override
                public void accept(Visitor visitor) {
                        visitor.param(this.name,
                                        (this.value != null) ?
                                                        this.value :
                                                        this.valuePredicate.toString());
                }

                @Override
                public String toString() {
                        return String.format("?%s %s", this.name,
                                        (this.value != null) ?
                                                        this.value :
                                                        this.valuePredicate);
                }
        }


        /**
         * {@link RequestPredicate} for where both {@code left} and {@code right} predicates
         * must match.
         */
        static class AndRequestPredicate implements RequestPredicate {

                private final RequestPredicate left;

                private final RequestPredicate right;

                public AndRequestPredicate(RequestPredicate left, RequestPredicate right) {
                        Assert.notNull(left, "Left RequestPredicate must not be null");
                        Assert.notNull(right, "Right RequestPredicate must not be null");
                        this.left = left;
                        this.right = right;
                }

                @Override
                public boolean test(ServerRequest request) {
                        Map<String, Object> oldAttributes = new HashMap<>(request.attributes());

                        if (this.left.test(request) && this.right.test(request)) {
                                return true;
                        }
                        restoreAttributes(request, oldAttributes);
                        return false;
                }

                @Override
                public Optional<ServerRequest> nest(ServerRequest request) {
                        return this.left.nest(request).flatMap(this.right::nest);
                }

                @Override
                public void accept(Visitor visitor) {
                        visitor.startAnd();
                        this.left.accept(visitor);
                        visitor.and();
                        this.right.accept(visitor);
                        visitor.endAnd();
                }

                @Override
                public String toString() {
                        return String.format("(%s && %s)", this.left, this.right);
                }
        }

        /**
         * {@link RequestPredicate} that negates a delegate predicate.
         */
        static class NegateRequestPredicate implements RequestPredicate {
                private final RequestPredicate delegate;

                public NegateRequestPredicate(RequestPredicate delegate) {
                        Assert.notNull(delegate, "Delegate must not be null");
                        this.delegate = delegate;
                }

                @Override
                public boolean test(ServerRequest request) {
                        Map<String, Object> oldAttributes = new HashMap<>(request.attributes());
                        boolean result = !this.delegate.test(request);
                        if (!result) {
                                restoreAttributes(request, oldAttributes);
                        }
                        return result;
                }

                @Override
                public void accept(Visitor visitor) {
                        visitor.startNegate();
                        this.delegate.accept(visitor);
                        visitor.endNegate();
                }

                @Override
                public String toString() {
                        return "!" + this.delegate.toString();
                }
        }

        /**
         * {@link RequestPredicate} where either {@code left} or {@code right} predicates
         * may match.
         */
        static class OrRequestPredicate implements RequestPredicate {

                private final RequestPredicate left;

                private final RequestPredicate right;

                public OrRequestPredicate(RequestPredicate left, RequestPredicate right) {
                        Assert.notNull(left, "Left RequestPredicate must not be null");
                        Assert.notNull(right, "Right RequestPredicate must not be null");
                        this.left = left;
                        this.right = right;
                }

                @Override
                public boolean test(ServerRequest request) {
                        Map<String, Object> oldAttributes = new HashMap<>(request.attributes());

                        if (this.left.test(request)) {
                                return true;
                        }
                        else {
                                restoreAttributes(request, oldAttributes);
                                if (this.right.test(request)) {
                                        return true;
                                }
                        }
                        restoreAttributes(request, oldAttributes);
                        return false;
                }

                @Override
                public Optional<ServerRequest> nest(ServerRequest request) {
                        Optional<ServerRequest> leftResult = this.left.nest(request);
                        if (leftResult.isPresent()) {
                                return leftResult;
                        }
                        else {
                                return this.right.nest(request);
                        }
                }

                @Override
                public void accept(Visitor visitor) {
                        visitor.startOr();
                        this.left.accept(visitor);
                        visitor.or();
                        this.right.accept(visitor);
                        visitor.endOr();
                }

                @Override
                public String toString() {
                        return String.format("(%s || %s)", this.left, this.right);
                }
        }


        private static class SubPathServerRequestWrapper implements ServerRequest {

                private final ServerRequest request;

                private final PathContainer pathContainer;

                private final Map<String, Object> attributes;

                public SubPathServerRequestWrapper(ServerRequest request,
                                PathPattern.PathRemainingMatchInfo info, PathPattern pattern) {
                        this.request = request;
                        this.pathContainer = new SubPathContainer(info.getPathRemaining());
                        this.attributes = mergeAttributes(request, info.getUriVariables(), pattern);
                }

                private static Map<String, Object> mergeAttributes(ServerRequest request,
                Map<String, String> pathVariables, PathPattern pattern) {
                        Map<String, Object> result = new ConcurrentHashMap<>(request.attributes());

                        result.put(RouterFunctions.URI_TEMPLATE_VARIABLES_ATTRIBUTE,
                                        mergePathVariables(request.pathVariables(), pathVariables));

                        pattern = mergePatterns(
                                        (PathPattern) request.attributes().get(RouterFunctions.MATCHING_PATTERN_ATTRIBUTE),
                                        pattern);
                        result.put(RouterFunctions.MATCHING_PATTERN_ATTRIBUTE, pattern);
                        return result;
                }

                @Override
                public HttpMethod method() {
                        return this.request.method();
                }

                @Override
                public String methodName() {
                        return this.request.methodName();
                }

                @Override
                public URI uri() {
                        return this.request.uri();
                }

                @Override
                public UriBuilder uriBuilder() {
                        return this.request.uriBuilder();
                }

                @Override
                public String path() {
                        return this.pathContainer.value();
                }

                @Override
                public PathContainer pathContainer() {
                        return this.pathContainer;
                }

                @Override
                public Headers headers() {
                        return this.request.headers();
                }

                @Override
                public MultiValueMap<String, Cookie> cookies() {
                        return this.request.cookies();
                }

                @Override
                public Optional<InetSocketAddress> remoteAddress() {
                        return this.request.remoteAddress();
                }

                @Override
                public List<HttpMessageConverter<?>> messageConverters() {
                        return this.request.messageConverters();
                }

                @Override
                public <T> T body(Class<T> bodyType) throws ServletException, IOException {
                        return this.request.body(bodyType);
                }

                @Override
                public <T> T body(ParameterizedTypeReference<T> bodyType)
                                throws ServletException, IOException {
                        return this.request.body(bodyType);
                }

                @Override
                public Optional<Object> attribute(String name) {
                        return this.request.attribute(name);
                }

                @Override
                public Map<String, Object> attributes() {
                        return this.attributes;
                }

                @Override
                public Optional<String> param(String name) {
                        return this.request.param(name);
                }

                @Override
                public MultiValueMap<String, String> params() {
                        return this.request.params();
                }

                @Override
                @SuppressWarnings("unchecked")
                public Map<String, String> pathVariables() {
                        return (Map<String, String>) this.attributes.getOrDefault(
                                        RouterFunctions.URI_TEMPLATE_VARIABLES_ATTRIBUTE, Collections.emptyMap());
                }

                @Override
                public HttpSession session() {
                        return this.request.session();
                }



                @Override
                public Optional<Principal> principal() {
                        return this.request.principal();
                }

                @Override
                public HttpServletRequest servletRequest() {
                        return this.request.servletRequest();
                }

                @Override
                public Optional<ServerResponse> checkNotModified(Instant lastModified) {
                        return this.request.checkNotModified(lastModified);
                }

                @Override
                public Optional<ServerResponse> checkNotModified(String etag) {
                        return this.request.checkNotModified(etag);
                }

                @Override
                public Optional<ServerResponse> checkNotModified(Instant lastModified, String etag) {
                        return this.request.checkNotModified(lastModified, etag);
                }

                @Override
                public String toString() {
                        return method() + " " +  path();
                }

                private static class SubPathContainer implements PathContainer {

                        private static final PathContainer.Separator SEPARATOR = () -> "/";


                        private final String value;

                        private final List<Element> elements;

                        public SubPathContainer(PathContainer original) {
                                this.value = prefixWithSlash(original.value());
                                this.elements = prependWithSeparator(original.elements());
                        }

                        private static String prefixWithSlash(String path) {
                                if (!path.startsWith("/")) {
                                        path = "/" + path;
                                }
                                return path;
                        }

                        private static List<Element> prependWithSeparator(List<Element> elements) {
                                List<Element> result = new ArrayList<>(elements);
                                if (result.isEmpty() || !(result.get(0) instanceof Separator)) {
                                        result.add(0, SEPARATOR);
                                }
                                return Collections.unmodifiableList(result);
                        }


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

                        @Override
                        public List<Element> elements() {
                                return this.elements;
                        }
                }
        }

}