/*
    * Copyright 2002-2014 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
    *
    *      http://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 : new UrlPathHelper();
 		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() ? null :
 			new PatternsRequestCondition(matches, this.pathHelper, this.pathMatcher, this.useSuffixPatternMatch,
 					this.useTrailingSlashMatch, this.fileExtensions);
 	}
 
 	/**
 	 * 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;
 		}
 	}
 
 }