/*
 * 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.mvc.condition;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;

import javax.servlet.http.HttpServletRequest;

import org.springframework.lang.Nullable;
import org.springframework.util.AntPathMatcher;
import org.springframework.util.ObjectUtils;
import org.springframework.util.PathMatcher;
import org.springframework.util.StringUtils;
import org.springframework.web.servlet.HandlerMapping;
import org.springframework.web.util.UrlPathHelper;

/**
 * A logical disjunction (' || ') request condition that matches a request
 * against a set of URL path patterns.
 *
 * @author Rossen Stoyanchev
 * @since 3.1
 */
public class PatternsRequestCondition extends AbstractRequestCondition<PatternsRequestCondition> {

        private final static Set<String> EMPTY_PATH_PATTERN = Collections.singleton("");


        private final Set<String> patterns;

        private final UrlPathHelper pathHelper;

        private final PathMatcher pathMatcher;

        private final boolean useSuffixPatternMatch;

        private final boolean useTrailingSlashMatch;

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


        /**
         * Creates a new instance with the given URL patterns. Each pattern that is
         * not empty and does not start with "/" is prepended with "/".
         * @param patterns 0 or more URL patterns; if 0 the condition will match to
         * every request.
         */
        public PatternsRequestCondition(String... patterns) {
                this(patterns, null, null, true, true, null);
        }

        /**
         * Alternative constructor with additional, optional {@link UrlPathHelper},
         * {@link PathMatcher}, and whether to automatically match trailing slashes.
         * @param patterns the URL patterns to use; if 0, the condition will match to every request.
         * @param urlPathHelper a {@link UrlPathHelper} for determining the lookup path for a request
         * @param pathMatcher a {@link PathMatcher} for pattern path matching
         * @param useTrailingSlashMatch whether to match irrespective of a trailing slash
         * @since 5.2.4
         */
        public PatternsRequestCondition(String[] patterns, @Nullable UrlPathHelper urlPathHelper,
                        @Nullable PathMatcher pathMatcher, boolean useTrailingSlashMatch) {

                this(patterns, urlPathHelper, pathMatcher, false, useTrailingSlashMatch, null);
        }

        /**
         * Alternative constructor with additional optional parameters.
         * @param patterns the URL patterns to use; if 0, the condition will match to every request.
         * @param urlPathHelper for determining the lookup path of a request
         * @param pathMatcher for path matching with patterns
         * @param useSuffixPatternMatch whether to enable matching by suffix (".*")
         * @param useTrailingSlashMatch whether to match irrespective of a trailing slash
         * @deprecated as of 5.2.4. See class-level note in
         * {@link org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping}
         * on the deprecation of path extension config options.
         */
        @Deprecated
        public PatternsRequestCondition(String[] patterns, @Nullable UrlPathHelper urlPathHelper,
                        @Nullable PathMatcher pathMatcher, boolean useSuffixPatternMatch, boolean useTrailingSlashMatch) {

                this(patterns, urlPathHelper, pathMatcher, useSuffixPatternMatch, useTrailingSlashMatch, null);
        }

        /**
         * Alternative constructor with additional optional parameters.
         * @param patterns the URL patterns to use; if 0, the condition will match to every request.
         * @param urlPathHelper a {@link UrlPathHelper} for determining the lookup path for a request
         * @param pathMatcher a {@link PathMatcher} for pattern path matching
         * @param useSuffixPatternMatch whether to enable matching by suffix (".*")
         * @param useTrailingSlashMatch whether to match irrespective of a trailing slash
         * @param fileExtensions a list of file extensions to consider for path matching
         * @deprecated as of 5.2.4. See class-level note in
         * {@link org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping}
         * on the deprecation of path extension config options.
         */
        @Deprecated
        public PatternsRequestCondition(String[] patterns, @Nullable UrlPathHelper urlPathHelper,
                        @Nullable PathMatcher pathMatcher, boolean useSuffixPatternMatch,
                        boolean useTrailingSlashMatch, @Nullable List<String> fileExtensions) {

                this.patterns = initPatterns(patterns);
                this.pathHelper = urlPathHelper != null ? urlPathHelper : UrlPathHelper.defaultInstance;
                this.pathMatcher = pathMatcher != null ? pathMatcher : new AntPathMatcher();
                this.useSuffixPatternMatch = useSuffixPatternMatch;
                this.useTrailingSlashMatch = useTrailingSlashMatch;

                if (fileExtensions != null) {
                        for (String fileExtension : fileExtensions) {
                                if (fileExtension.charAt(0) != '.') {
                                        fileExtension = "." + fileExtension;
                                }
                                this.fileExtensions.add(fileExtension);
                        }
                }
        }

        private static Set<String> initPatterns(String[] patterns) {
                if (!hasPattern(patterns)) {
                        return EMPTY_PATH_PATTERN;
                }
                Set<String> result = new LinkedHashSet<>(patterns.length);
                for (String pattern : patterns) {
                        if (StringUtils.hasLength(pattern) && !pattern.startsWith("/")) {
                                pattern = "/" + pattern;
                        }
                        result.add(pattern);
                }
                return result;
        }

        private static boolean hasPattern(String[] patterns) {
                if (!ObjectUtils.isEmpty(patterns)) {
                        for (String pattern : patterns) {
                                if (StringUtils.hasText(pattern)) {
                                        return true;
                                }
                        }
                }
                return false;
        }

        /**
         * Private constructor for use when combining and matching.
         */
        private PatternsRequestCondition(Set<String> patterns, PatternsRequestCondition other) {
                this.patterns = patterns;
                this.pathHelper = other.pathHelper;
                this.pathMatcher = other.pathMatcher;
                this.useSuffixPatternMatch = other.useSuffixPatternMatch;
                this.useTrailingSlashMatch = other.useTrailingSlashMatch;
                this.fileExtensions.addAll(other.fileExtensions);
        }


        public Set<String> getPatterns() {
                return this.patterns;
        }

        @Override
        protected Collection<String> getContent() {
                return this.patterns;
        }

        @Override
        protected String getToStringInfix() {
                return " || ";
        }

        /**
         * Returns a new instance with URL patterns from the current instance ("this") and
         * the "other" instance as follows:
         * <ul>
         * <li>If there are patterns in both instances, combine the patterns in "this" with
         * the patterns in "other" using {@link PathMatcher#combine(String, String)}.
         * <li>If only one instance has patterns, use them.
         * <li>If neither instance has patterns, use an empty String (i.e. "").
         * </ul>
         */
        @Override
        public PatternsRequestCondition combine(PatternsRequestCondition other) {
                if (isEmptyPathPattern() && other.isEmptyPathPattern()) {
                        return this;
                }
                else if (other.isEmptyPathPattern()) {
                        return this;
                }
                else if (isEmptyPathPattern()) {
                        return other;
                }
                Set<String> result = new LinkedHashSet<>();
                if (!this.patterns.isEmpty() && !other.patterns.isEmpty()) {
                        for (String pattern1 : this.patterns) {
                                for (String pattern2 : other.patterns) {
                                        result.add(this.pathMatcher.combine(pattern1, pattern2));
                                }
                        }
                }
                return new PatternsRequestCondition(result, this);
        }

        private boolean isEmptyPathPattern() {
                return this.patterns == EMPTY_PATH_PATTERN;
        }

        /**
         * Checks if any of the patterns match the given request and returns an instance
         * that is guaranteed to contain matching patterns, sorted via
         * {@link PathMatcher#getPatternComparator(String)}.
         * <p>A matching pattern is obtained by making checks in the following order:
         * <ul>
         * <li>Direct match
         * <li>Pattern match with ".*" appended if the pattern doesn't already contain a "."
         * <li>Pattern match
         * <li>Pattern match with "/" appended if the pattern doesn't already end in "/"
         * </ul>
         * @param request the current request
         * @return the same instance if the condition contains no patterns;
         * or a new condition with sorted matching patterns;
         * or {@code null} if no patterns match.
         */
        @Override
        @Nullable
        public PatternsRequestCondition getMatchingCondition(HttpServletRequest request) {
                String lookupPath = this.pathHelper.getLookupPathForRequest(request, HandlerMapping.LOOKUP_PATH);
                List<String> matches = getMatchingPatterns(lookupPath);
                return !matches.isEmpty() ? new PatternsRequestCondition(new LinkedHashSet<>(matches), this) : null;
        }

        /**
         * Find the patterns matching the given lookup path. Invoking this method should
         * yield results equivalent to those of calling {@link #getMatchingCondition}.
         * This method is provided as an alternative to be used if no request is available
         * (e.g. introspection, tooling, etc).
         * @param lookupPath the lookup path to match to existing patterns
         * @return a collection of matching patterns sorted with the closest match at the top
         */
        public List<String> getMatchingPatterns(String lookupPath) {
                List<String> matches = null;
                for (String pattern : this.patterns) {
                        String match = getMatchingPattern(pattern, lookupPath);
                        if (match != null) {
                                matches = (matches != null ? matches : new ArrayList<>());
                                matches.add(match);
                        }
                }
                if (matches == null) {
                        return Collections.emptyList();
                }
                if (matches.size() > 1) {
                        matches.sort(this.pathMatcher.getPatternComparator(lookupPath));
                }
                return matches;
        }

        @Nullable
        private String getMatchingPattern(String pattern, String lookupPath) {
                if (pattern.equals(lookupPath)) {
                        return pattern;
                }
                if (this.useSuffixPatternMatch) {
                        if (!this.fileExtensions.isEmpty() && lookupPath.indexOf('.') != -1) {
                                for (String extension : this.fileExtensions) {
                                        if (this.pathMatcher.match(pattern + extension, lookupPath)) {
                                                return pattern + extension;
                                        }
                                }
                        }
                        else {
                                boolean hasSuffix = pattern.indexOf('.') != -1;
                                if (!hasSuffix && this.pathMatcher.match(pattern + ".*", lookupPath)) {
                                        return pattern + ".*";
                                }
                        }
                }
                if (this.pathMatcher.match(pattern, lookupPath)) {
                        return pattern;
                }
                if (this.useTrailingSlashMatch) {
                        if (!pattern.endsWith("/") && this.pathMatcher.match(pattern + "/", lookupPath)) {
                                return pattern + "/";
                        }
                }
                return null;
        }

        /**
         * Compare the two conditions based on the URL patterns they contain.
         * Patterns are compared one at a time, from top to bottom via
         * {@link PathMatcher#getPatternComparator(String)}. If all compared
         * patterns match equally, but one instance has more patterns, it is
         * considered a closer match.
         * <p>It is assumed that both instances have been obtained via
         * {@link #getMatchingCondition(HttpServletRequest)} to ensure they
         * contain only patterns that match the request and are sorted with
         * the best matches on top.
         */
        @Override
        public int compareTo(PatternsRequestCondition other, HttpServletRequest request) {
                String lookupPath = this.pathHelper.getLookupPathForRequest(request, HandlerMapping.LOOKUP_PATH);
                Comparator<String> patternComparator = this.pathMatcher.getPatternComparator(lookupPath);
                Iterator<String> iterator = this.patterns.iterator();
                Iterator<String> iteratorOther = other.patterns.iterator();
                while (iterator.hasNext() && iteratorOther.hasNext()) {
                        int result = patternComparator.compare(iterator.next(), iteratorOther.next());
                        if (result != 0) {
                                return result;
                        }
                }
                if (iterator.hasNext()) {
                        return -1;
                }
                else if (iteratorOther.hasNext()) {
                        return 1;
                }
                else {
                        return 0;
                }
        }

}