/*
 * Copyright 2002-2011 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.flex.security3;

import javax.servlet.http.HttpServletRequest;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.security.web.util.RequestMatcher;
import org.springframework.util.AntPathMatcher;
import org.springframework.util.Assert;

/**
 * Matcher which compares a pre-defined ant-style pattern against the URL
 * ({@code servletPath + pathInfo}) of an {@code HttpServletRequest}.
 * The query string of the URL is ignored and matching is case-insensitive.
 * <p>
 * Using a pattern value of {@code /**} or {@code **} is treated as a universal
 * match, which will match any request. Patterns which end with {@code /**} (and have no other wildcards)
 * are optimized by using a substring match — a pattern of {@code /aaa/**} will match {@code /aaa},
 * {@code /aaa/} and any sub-directories, such as {@code /aaa/bbb/ccc}.
 * <p>
 * For all other cases, Spring's {@link AntPathMatcher} is used to perform the match. See the Spring documentation
 * for this class for comprehensive information on the syntax used.
 * <p>
 * This is essentially a direct copy of the {@code org.springframework.security.web.util.AntPathRequestMatcher} 
 * implementation in Spring Security 3.1, backported here for matching against BlazeDS Endpoint URL patterns so 
 * as to retain compatibility with Spring Security 3.0, and with the matching against HTTP method removed since 
 * that is unnecessary with Flex requests.
 *
 * @author Luke Taylor
 * @author Jeremy Grelle
 * @since 1.5
 *
 * @see org.springframework.util.AntPathMatcher
 */
public final class AntPathRequestMatcher implements RequestMatcher {
    private static final Log logger = LogFactory.getLog(AntPathRequestMatcher.class);
    private static final String MATCH_ALL = "/**";

    private final Matcher matcher;
    private final String pattern;


    /**
     * Creates a matcher with the specific pattern which will match all HTTP methods.
     *
     * @param pattern the ant pattern to use for matching
     */
    public AntPathRequestMatcher(String pattern) {
        Assert.hasText(pattern, "Pattern cannot be null or empty");

        if (pattern.equals(MATCH_ALL) || pattern.equals("**")) {
            pattern = MATCH_ALL;
            matcher = null;
        } else {
            pattern = pattern.toLowerCase();

            // If the pattern ends with {@code /**} and has no other wildcards, then optimize to a sub-path match
            if (pattern.endsWith(MATCH_ALL) && pattern.indexOf('?') == -1 &&
                    pattern.indexOf("*") == pattern.length() - 2) {
                matcher = new SubpathMatcher(pattern.substring(0, pattern.length() - 3));
            } else {
                matcher = new SpringAntMatcher(pattern);
            }
        }

        this.pattern = pattern;
    }

    /**
     * Returns true if the configured pattern (and HTTP-Method) match those of the supplied request.
     *
     * @param request the request to match against. The ant pattern will be matched against the
     *    {@code servletPath} + {@code pathInfo} of the request.
     */
    public boolean matches(HttpServletRequest request) {
        if (pattern.equals(MATCH_ALL)) {
            if (logger.isDebugEnabled()) {
                logger.debug("Request '" + getRequestPath(request) + "' matched by universal pattern '/**'");
            }

            return true;
        }

        String url = getRequestPath(request);

        if (logger.isDebugEnabled()) {
            logger.debug("Checking match of request : '" + url + "'; against '" + pattern + "'");
        }

        return matcher.matches(url);
    }

    private String getRequestPath(HttpServletRequest request) {
        String url = request.getServletPath();

        if (request.getPathInfo() != null) {
            url += request.getPathInfo();
        }

        url = url.toLowerCase();

        return url;
    }

    public String getPattern() {
        return pattern;
    }

    @Override
    public boolean equals(Object obj) {
        if (!(obj instanceof AntPathRequestMatcher)) {
            return false;
        }
        AntPathRequestMatcher other = (AntPathRequestMatcher)obj;
        return this.pattern.equals(other.pattern);
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("Ant [pattern='").append(pattern).append("'");

        sb.append("]");

        return sb.toString();
    }

    private static interface Matcher {
        boolean matches(String path);
    }

    private static class SpringAntMatcher implements Matcher {
        private static final AntPathMatcher antMatcher = new AntPathMatcher();

        private final String pattern;

        private SpringAntMatcher(String pattern) {
            this.pattern = pattern;
        }

        public boolean matches(String path) {
            return antMatcher.match(pattern, path);
        }
    }

    /**
     * Optimized matcher for trailing wildcards
     */
    private static class SubpathMatcher implements Matcher {
        private final String subpath;
        private final int length;

        private SubpathMatcher(String subpath) {
            assert !subpath.contains("*");
            this.subpath = subpath;
            this.length = subpath.length();
        }

        public boolean matches(String path) {
            return path.startsWith(subpath) && (path.length() == length || path.charAt(length) == '/');
        }
    }
}