/*
 * 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.Arrays;
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.util.AntPathMatcher;
import org.springframework.util.PathMatcher;
import org.springframework.util.StringUtils;
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 final class PatternsRequestCondition extends AbstractRequestCondition<PatternsRequestCondition> {

        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<String>();


        /**
         * 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(asList(patterns), null, null, true, true, null);
        }

        /**
         * Additional constructor with flags for using suffix pattern (.*) and
         * trailing slash matches.
         * @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
         */
        public PatternsRequestCondition(String[] patterns, UrlPathHelper urlPathHelper, PathMatcher pathMatcher,
                        boolean useSuffixPatternMatch, boolean useTrailingSlashMatch) {

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

        /**
         * Creates a new instance with the given URL patterns.
         * Each pattern that is not empty and does not start with "/" is pre-pended with "/".
         * @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
         */
        public PatternsRequestCondition(String[] patterns, UrlPathHelper urlPathHelper,
                        PathMatcher pathMatcher, boolean useSuffixPatternMatch, boolean useTrailingSlashMatch,
                        List<String> fileExtensions) {

                this(asList(patterns), urlPathHelper, pathMatcher, useSuffixPatternMatch, useTrailingSlashMatch, fileExtensions);
        }

        /**
         * Private constructor accepting a collection of patterns.
         */
        private PatternsRequestCondition(Collection<String> patterns, UrlPathHelper urlPathHelper,
                        PathMatcher pathMatcher, boolean useSuffixPatternMatch, boolean useTrailingSlashMatch,
                        List<String> fileExtensions) {

                this.patterns = Collections.unmodifiableSet(prependLeadingSlash(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 List<String> asList(String... patterns) {
                return (patterns != null ? Arrays.asList(patterns) : Collections.<String>emptyList());
        }

        private static Set<String> prependLeadingSlash(Collection<String> patterns) {
                if (patterns == null) {
                        return Collections.emptySet();
                }
                Set<String> result = new LinkedHashSet<String>(patterns.size());
                for (String pattern : patterns) {
                        if (StringUtils.hasLength(pattern) && !pattern.startsWith("/")) {
                                pattern = "/" + pattern;
                        }
                        result.add(pattern);
                }
                return result;
        }

        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) {
                Set<String> result = new LinkedHashSet<String>();
                if (!this.patterns.isEmpty() && !other.patterns.isEmpty()) {
                        for (String pattern1 : this.patterns) {
                                for (String pattern2 : other.patterns) {
                                        result.add(this.pathMatcher.combine(pattern1, pattern2));
                                }
                        }
                }
                else if (!this.patterns.isEmpty()) {
                        result.addAll(this.patterns);
                }
                else if (!other.patterns.isEmpty()) {
                        result.addAll(other.patterns);
                }
                else {
                        result.add("");
                }
                return new PatternsRequestCondition(result, this.pathHelper, this.pathMatcher,
                                this.useSuffixPatternMatch, this.useTrailingSlashMatch, this.fileExtensions);
        }

        /**
         * 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
        public PatternsRequestCondition getMatchingCondition(HttpServletRequest request) {
                if (this.patterns.isEmpty()) {
                        return this;
                }
                String lookupPath = this.pathHelper.getLookupPathForRequest(request);
                List<String> matches = getMatchingPatterns(lookupPath);
                return (!matches.isEmpty() ?
                                new PatternsRequestCondition(matches, this.pathHelper, this.pathMatcher,
                                                this.useSuffixPatternMatch, this.useTrailingSlashMatch, this.fileExtensions) : null);
        }

        /**
         * Find the patterns matching the given lookup path. Invoking this method should
         * yield results equivalent to those of calling
         * {@link #getMatchingCondition(javax.servlet.http.HttpServletRequest)}.
         * 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 = new ArrayList<String>();
                for (String pattern : this.patterns) {
                        String match = getMatchingPattern(pattern, lookupPath);
                        if (match != null) {
                                matches.add(match);
                        }
                }
                Collections.sort(matches, this.pathMatcher.getPatternComparator(lookupPath));
                return matches;
        }

        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);
                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;
                }
        }

}