/*
 * $Header: /home/cvs/jakarta-commons/validator/src/share/org/apache/commons/validator/UrlValidator.java,v 1.19 2004/02/21 17:10:29 rleland Exp $
 * $Revision: 1.19 $
 * $Date: 2004/02/21 17:10:29 $
 *
 * ====================================================================
 * Copyright 2001-2004 The Apache Software Foundation
 *
 * 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.apache.commons.validator;

import java.io.Serializable;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

import org.apache.commons.validator.util.Flags;
import org.apache.oro.text.perl.Perl5Util;

/**
 * <p>Validates URLs.</p>
 * Behavour of validation is modified by passing in options:
 * <li>ALLOW_2_SLASHES - [FALSE]  Allows double '/' characters in the path
 * component.</li>
 * <li>NO_FRAGMENT- [FALSE]  By default fragments are allowed, if this option is
 * included then fragments are flagged as illegal.</li>
 * <li>ALLOW_ALL_SCHEMES - [FALSE] By default only http, https, and ftp are
 * considered valid schemes.  Enabling this option will let any scheme pass validation.</li>
 *
 * <p>Originally based in on php script by Debbie Dyer, validation.php v1.2b, Date: 03/07/02,
 * http://javascript.internet.com. However, this validation now bears little resemblance
 * to the php original.</p>
 * <pre>
 *   Example of usage:
 *   Construct a UrlValidator with valid schemes of "http", and "https".
 *
 *    String[] schemes = {"http","https"}.
 *    Urlvalidator urlValidator = new Urlvalidator(schemes);
 *    if (urlValidator.isValid("ftp")) {
 *       System.out.println("url is valid");
 *    } else {
 *       System.out.println("url is invalid");
 *    }
 *
 *    prints "url is invalid"
 *   If instead the default constructor is used.
 *
 *    Urlvalidator urlValidator = new Urlvalidator();
 *    if (urlValidator.isValid("ftp")) {
 *       System.out.println("url is valid");
 *    } else {
 *       System.out.println("url is invalid");
 *    }
 *
 *   prints out "url is valid"
 *  </pre>
 *
 * @see
 * <a href='http://www.ietf.org/rfc/rfc2396.txt' >
 *  Uniform Resource Identifiers (URI): Generic Syntax
 * </a>
 *
 * @since Validator 1.1
 */
public class UrlValidator implements Serializable {

    /**
     * Allows all validly formatted schemes to pass validation instead of supplying a
     * set of valid schemes.
     */
    public static final int ALLOW_ALL_SCHEMES = 1 << 0;

    /**
     * Allow two slashes in the path component of the URL.
     */
    public static final int ALLOW_2_SLASHES = 1 << 1;

    /**
     * Enabling this options disallows any URL fragments.
     */
    public static final int NO_FRAGMENTS = 1 << 2;

    private static final String ALPHA_CHARS = "a-zA-Z";

    private static final String ALPHA_NUMERIC_CHARS = ALPHA_CHARS + "\\d";

    private static final String SPECIAL_CHARS = ";/@&=,.?:+$";

    private static final String VALID_CHARS = "[^\\s" + SPECIAL_CHARS + "]";

    private static final String SCHEME_CHARS = ALPHA_CHARS;

    // Drop numeric, and  "+-." for now
    private static final String AUTHORITY_CHARS = ALPHA_NUMERIC_CHARS + "\\-\\.";

    private static final String ATOM = VALID_CHARS + '+';

    /**
     * This expression derived/taken from the BNF for URI (RFC2396).
     */
    private static final String URL_PATTERN =
            "/^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\\?([^#]*))?(#(.*))?/";
    //                                                                      12            3  4          5       6   7        8 9

    /**
     * Schema/Protocol (ie. http:, ftp:, file:, etc).
     */
    private static final int PARSE_URL_SCHEME = 2;

    /**
     * Includes hostname/ip and port number.
     */
    private static final int PARSE_URL_AUTHORITY = 4;

    private static final int PARSE_URL_PATH = 5;

    private static final int PARSE_URL_QUERY = 7;

    private static final int PARSE_URL_FRAGMENT = 9;

    /**
     * Protocol (ie. http:, ftp:,https:).
     */
    private static final String SCHEME_PATTERN = "/^[" + SCHEME_CHARS + "]/";

    private static final String AUTHORITY_PATTERN =
            "/^([" + AUTHORITY_CHARS + "]*)(:\\d*)?(.*)?/";
    //                                                                            1                          2  3       4

    private static final int PARSE_AUTHORITY_HOST_IP = 1;

    private static final int PARSE_AUTHORITY_PORT = 2;

    /**
     * Should always be empty.
     */
    private static final int PARSE_AUTHORITY_EXTRA = 3;

    private static final String PATH_PATTERN =
            "/^(/[-a-zA-Z0-9_:@&?=+,.!/~*'%$]*)$/";

    private static final String QUERY_PATTERN = "/^(.*)$/";

    private static final String LEGAL_ASCII_PATTERN = "/^[\\000-\\177]+$/";

    private static final String IP_V4_DOMAIN_PATTERN =
            "/^(\\d{1,3})[.](\\d{1,3})[.](\\d{1,3})[.](\\d{1,3})$/";

    private static final String DOMAIN_PATTERN =
            "/^" + ATOM + "(\\." + ATOM + ")*$/";

    private static final String PORT_PATTERN = "/^:(\\d{1,5})$/";

    private static final String ATOM_PATTERN = "/(" + ATOM + ")/";

    private static final String ALPHA_PATTERN = "/^[" + ALPHA_CHARS + "]/";

    /**
     * Holds the set of current validation options.
     */
    private Flags options = null;

    /**
     * The set of schemes that are allowed to be in a URL.
     */
    private Set allowedSchemes = new HashSet();

    /**
     * If no schemes are provided, default to this set.
     */
    protected String[] defaultSchemes = {"http", "https", "ftp"};

    /**
     * Create a UrlValidator with default properties.
     */
    public UrlValidator() {
        this(null);
    }

    /**
     * Behavior of validation is modified by passing in several strings options:
     * @param schemes Pass in one or more url schemes to consider valid, passing in
     *        a null will default to "http,https,ftp" being valid.
     *        If a non-null schemes is specified then all valid schemes must
     *        be specified. Setting the ALLOW_ALL_SCHEMES option will
     *        ignore the contents of schemes.
     */
    public UrlValidator(String[] schemes) {
        this(schemes, 0);
    }

    /**
     * Initialize a UrlValidator with the given validation options.
     * @param options The options should be set using the public constants declared in
     * this class.  To set multiple options you simply add them together.  For example,
     * ALLOW_2_SLASHES + NO_FRAGMENTS enables both of those options.
     */
    public UrlValidator(int options) {
        this(null, options);
    }

    /**
     * Behavour of validation is modified by passing in options:
     * @param schemes The set of valid schemes.
     * @param options The options should be set using the public constants declared in
     * this class.  To set multiple options you simply add them together.  For example,
     * ALLOW_2_SLASHES + NO_FRAGMENTS enables both of those options.
     */
    public UrlValidator(String[] schemes, int options) {
        this.options = new Flags(options);

        if (this.options.isOn(ALLOW_ALL_SCHEMES)) {
            return;
        }

        if (schemes == null) {
            schemes = this.defaultSchemes;
        }

        this.allowedSchemes.addAll(Arrays.asList(schemes));
    }

    /**
     * <p>Checks if a field has a valid url address.</p>
     *
     * @param value The value validation is being performed on.  A <code>null</code>
     * value is considered invalid.
     * @return true if the url is valid.
     */
    public boolean isValid(String value) {
        if (value == null) {
            return false;
        }

        Perl5Util matchUrlPat = new Perl5Util();
        Perl5Util matchAsciiPat = new Perl5Util();

        if (!matchAsciiPat.match(LEGAL_ASCII_PATTERN, value)) {
            return false;
        }

        // Check the whole url address structure
        if (!matchUrlPat.match(URL_PATTERN, value)) {
            return false;
        }

        if (!isValidScheme(matchUrlPat.group(PARSE_URL_SCHEME))) {
            return false;
        }

        if (!isValidAuthority(matchUrlPat.group(PARSE_URL_AUTHORITY))) {
            return false;
        }

        if (!isValidPath(matchUrlPat.group(PARSE_URL_PATH))) {
            return false;
        }

        if (!isValidQuery(matchUrlPat.group(PARSE_URL_QUERY))) {
            return false;
        }

        if (!isValidFragment(matchUrlPat.group(PARSE_URL_FRAGMENT))) {
            return false;
        }

        return true;
    }

    /**
     * Validate scheme. If schemes[] was initialized to a non null,
     * then only those scheme's are allowed.  Note this is slightly different
     * than for the constructor.
     * @param scheme The scheme to validate.  A <code>null</code> value is considered
     * invalid.
     * @return true if valid.
     */
    protected boolean isValidScheme(String scheme) {
        if (scheme == null) {
            return false;
        }

        Perl5Util schemeMatcher = new Perl5Util();
        if (!schemeMatcher.match(SCHEME_PATTERN, scheme)) {
            return false;
        }

        if (this.options.isOff(ALLOW_ALL_SCHEMES)) {

            if (!this.allowedSchemes.contains(scheme)) {
                return false;
            }
        }

        return true;
    }

    /**
     * Returns true if the authority is properly formatted.  An authority is the combination
     * of hostname and port.  A <code>null</code> authority value is considered invalid.
     */
    protected boolean isValidAuthority(String authority) {
        if (authority == null) {
            return false;
        }

        Perl5Util authorityMatcher = new Perl5Util();
        Perl5Util matchIPV4Pat = new Perl5Util();

        if (!authorityMatcher.match(AUTHORITY_PATTERN, authority)) {
            return false;
        }

        boolean ipV4Address = false;
        boolean hostname = false;
// check if authority is IP address or hostname
        String hostIP = authorityMatcher.group(PARSE_AUTHORITY_HOST_IP);
        ipV4Address = matchIPV4Pat.match(IP_V4_DOMAIN_PATTERN, hostIP);

        if (ipV4Address) {
            // this is an IP address so check components
            for (int i = 1; i <= 4; i++) {
                String ipSegment = matchIPV4Pat.group(i);
                if (ipSegment == null || ipSegment.length() <= 0) {
                    return false;
                }

                try {
                    if (Integer.parseInt(ipSegment) > 255) {
                        return false;
                    }
                } catch(NumberFormatException e) {
                    return false;
                }

            }
        } else {
            // Domain is hostname name
            Perl5Util domainMatcher = new Perl5Util();
            hostname = domainMatcher.match(DOMAIN_PATTERN, hostIP);
        }

//rightmost hostname will never start with a digit.
        if (hostname) {
            String[] domainSegment = new String[10];
            boolean match = true;
            int segmentCount = 0;
            int segmentLength = 0;
            Perl5Util atomMatcher = new Perl5Util();

            while (match) {
                match = atomMatcher.match(ATOM_PATTERN, hostIP);
                if (match) {
                    domainSegment[segmentCount] = atomMatcher.group(1);
                    segmentLength = domainSegment[segmentCount].length() + 1;
                    hostIP =
                            (segmentLength >= hostIP.length())
                            ? ""
                            : hostIP.substring(segmentLength);

                    segmentCount++;
                }
            }
            String topLevel = domainSegment[segmentCount - 1];
            if (topLevel.length() < 2 || topLevel.length() > 4) {
                return false;
            }

            // First letter of top level must be a alpha
            Perl5Util alphaMatcher = new Perl5Util();
            if (!alphaMatcher.match(ALPHA_PATTERN, topLevel.substring(0, 1))) {
                return false;
            }

            // Make sure there's a host name preceding the authority.
            if (segmentCount < 2) {
                return false;
            }
        }

        if (!hostname && !ipV4Address) {
            return false;
        }

        String port = authorityMatcher.group(PARSE_AUTHORITY_PORT);
        if (port != null) {
            Perl5Util portMatcher = new Perl5Util();
            if (!portMatcher.match(PORT_PATTERN, port)) {
                return false;
            }
        }

        String extra = authorityMatcher.group(PARSE_AUTHORITY_EXTRA);
        if (!GenericValidator.isBlankOrNull(extra)) {
            return false;
        }

        return true;
    }

    /**
     * Returns true if the path is valid.  A <code>null</code> value is considered invalid.
     */
    protected boolean isValidPath(String path) {
        if (path == null) {
            return false;
        }

        Perl5Util pathMatcher = new Perl5Util();

        if (!pathMatcher.match(PATH_PATTERN, path)) {
            return false;
        }

        if (path.endsWith("/")) {
            return false;
        }

        int slash2Count = countToken("//", path);
        if (this.options.isOff(ALLOW_2_SLASHES) && (slash2Count > 0)) {
            return false;
        }

        int slashCount = countToken("/", path);
        int dot2Count = countToken("..", path);
        if (dot2Count > 0) {
            if ((slashCount - slash2Count - 1) <= dot2Count) {
                return false;
            }
        }

        return true;
    }

    /**
     * Returns true if the query is null or it's a properly formatted query string.
     */
    protected boolean isValidQuery(String query) {
        if (query == null) {
            return true;
        }

        Perl5Util queryMatcher = new Perl5Util();
        return queryMatcher.match(QUERY_PATTERN, query);
    }

    /**
     * Returns true if the given fragment is null or fragments are allowed.
     */
    protected boolean isValidFragment(String fragment) {
        if (fragment == null) {
            return true;
        }

        return this.options.isOff(NO_FRAGMENTS);
    }

    /**
     * Returns the number of times the token appears in the target.
     */
    protected int countToken(String token, String target) {
        int tokenIndex = 0;
        int count = 0;
        while (tokenIndex != -1) {
            tokenIndex = target.indexOf(token, tokenIndex);
            if (tokenIndex > -1) {
                tokenIndex++;
                count++;
            }
        }
        return count;
    }
}