/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you 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.axis2.databinding.types;

import java.io.IOException;
import java.io.Serializable;

/**
 * ******************************************************************* <i>Axis Note: This class was
 * 'borrowed' from Xerces 2.0.2</i>
 * <p/>
 * A class to represent a Uniform Resource Identifier (URI). This class is designed to handle the
 * parsing of URIs and provide access to the various components (scheme, host, port, userinfo,
 * path, query string and fragment) that may constitute a URI.
 * <p/>
 * Parsing of a URI specification is done according to the URI syntax described in <a
 * href="http://www.ietf.org/rfc/rfc2396.txt?number=2396">RFC 2396</a>, and amended by <a
 * href="http://www.ietf.org/rfc/rfc2732.txt?number=2732">RFC 2732</a>.
 * <p/>
 * Every absolute URI consists of a scheme, followed by a colon (':'), followed by a
 * scheme-specific part. For URIs that follow the "generic URI" syntax, the scheme-specific part
 * begins with two slashes ("//") and may be followed by an authority segment (comprised of user
 * information, host, and port), path segment, query segment and fragment. Note that RFC 2396 no
 * longer specifies the use of the parameters segment and excludes the "user:password" syntax as
 * part of the authority segment. If "user:password" appears in a URI, the entire user/password
 * string is stored as userinfo.
 * <p/>
 * For URIs that do not follow the "generic URI" syntax (e.g. mailto), the entire scheme-specific
 * part is treated as the "path" portion of the URI.
 * <p/>
 * Note that, unlike the java.net.URL class, this class does not provide any built-in network
 * access functionality nor does it provide any scheme-specific functionality (for example, it does
 * not know a default port for a specific scheme). Rather, it only knows the grammar and basic set
 * of operations that can be applied to a URI.
 * <p/>
 * ********************************************************************
 */
public class URI implements Serializable {

    private static final long serialVersionUID = 2172306044361227627L;


    /**
     * **************************************************************** MalformedURIExceptions are
     * thrown in the process of building a URI or setting fields on a URI when an operation would
     * result in an invalid URI specification.
     * <p/>
     * ******************************************************************
     */
    public static class MalformedURIException extends IOException {

        private static final long serialVersionUID = -8488692760975768757L;

        /**
         * *************************************************************** Constructs a
         * <code>MalformedURIException</code> with no specified detail message.
         * ****************************************************************
         */
        public MalformedURIException() {
            super();
        }

        /**
         * ************************************************************** Constructs a
         * <code>MalformedURIException</code> with the specified detail message.
         *
         * @param p_msg the detail message. ****************************************************************
         */
        public MalformedURIException(String p_msg) {
            super(p_msg);
        }
    }

    private static final byte [] fgLookupTable = new byte[128];

    /**
     * Character Classes
     */

    /** reserved characters ;/?:@&=+$,[] */
    //RFC 2732 added '[' and ']' as reserved characters
    private static final int RESERVED_CHARACTERS = 0x01;

    /**
     * URI punctuation mark characters: -_.!~*'() - these, combined with alphanumerics, constitute the
     * "unreserved" characters
     */
    private static final int MARK_CHARACTERS = 0x02;

    /** scheme can be composed of alphanumerics and these characters: +-. */
    private static final int SCHEME_CHARACTERS = 0x04;

    /** userinfo can be composed of unreserved, escaped and these characters: ;:&=+$, */
    private static final int USERINFO_CHARACTERS = 0x08;

    /** ASCII letter characters */
    private static final int ASCII_ALPHA_CHARACTERS = 0x10;

    /** ASCII digit characters */
    private static final int ASCII_DIGIT_CHARACTERS = 0x20;

    /** ASCII hex characters */
    private static final int ASCII_HEX_CHARACTERS = 0x40;

    /** Path characters */
    private static final int PATH_CHARACTERS = 0x80;

    /** Mask for alpha-numeric characters */
    private static final int MASK_ALPHA_NUMERIC = ASCII_ALPHA_CHARACTERS | ASCII_DIGIT_CHARACTERS;

    /** Mask for unreserved characters */
    private static final int MASK_UNRESERVED_MASK = MASK_ALPHA_NUMERIC | MARK_CHARACTERS;

    /** Mask for URI allowable characters except for % */
    private static final int MASK_URI_CHARACTER = MASK_UNRESERVED_MASK | RESERVED_CHARACTERS;

    /** Mask for scheme characters */
    private static final int MASK_SCHEME_CHARACTER = MASK_ALPHA_NUMERIC | SCHEME_CHARACTERS;

    /** Mask for userinfo characters */
    private static final int MASK_USERINFO_CHARACTER = MASK_UNRESERVED_MASK | USERINFO_CHARACTERS;

    /** Mask for path characters */
    private static final int MASK_PATH_CHARACTER = MASK_UNRESERVED_MASK | PATH_CHARACTERS;

    static {
        // Add ASCII Digits and ASCII Hex Numbers
        for (int i = '0'; i <= '9'; ++i) {
            fgLookupTable[i] |= ASCII_DIGIT_CHARACTERS | ASCII_HEX_CHARACTERS;
        }

        // Add ASCII Letters and ASCII Hex Numbers
        for (int i = 'A'; i <= 'F'; ++i) {
            fgLookupTable[i] |= ASCII_ALPHA_CHARACTERS | ASCII_HEX_CHARACTERS;
            fgLookupTable[i + 0x00000020] |= ASCII_ALPHA_CHARACTERS | ASCII_HEX_CHARACTERS;
        }

        // Add ASCII Letters
        for (int i = 'G'; i <= 'Z'; ++i) {
            fgLookupTable[i] |= ASCII_ALPHA_CHARACTERS;
            fgLookupTable[i + 0x00000020] |= ASCII_ALPHA_CHARACTERS;
        }

        // Add Reserved Characters
        fgLookupTable[';'] |= RESERVED_CHARACTERS;
        fgLookupTable['/'] |= RESERVED_CHARACTERS;
        fgLookupTable['?'] |= RESERVED_CHARACTERS;
        fgLookupTable[':'] |= RESERVED_CHARACTERS;
        fgLookupTable['@'] |= RESERVED_CHARACTERS;
        fgLookupTable['&'] |= RESERVED_CHARACTERS;
        fgLookupTable['='] |= RESERVED_CHARACTERS;
        fgLookupTable['+'] |= RESERVED_CHARACTERS;
        fgLookupTable['$'] |= RESERVED_CHARACTERS;
        fgLookupTable[','] |= RESERVED_CHARACTERS;
        fgLookupTable['['] |= RESERVED_CHARACTERS;
        fgLookupTable[']'] |= RESERVED_CHARACTERS;

        // Add Mark Characters
        fgLookupTable['-'] |= MARK_CHARACTERS;
        fgLookupTable['_'] |= MARK_CHARACTERS;
        fgLookupTable['.'] |= MARK_CHARACTERS;
        fgLookupTable['!'] |= MARK_CHARACTERS;
        fgLookupTable['~'] |= MARK_CHARACTERS;
        fgLookupTable['*'] |= MARK_CHARACTERS;
        fgLookupTable['\''] |= MARK_CHARACTERS;
        fgLookupTable['('] |= MARK_CHARACTERS;
        fgLookupTable[')'] |= MARK_CHARACTERS;

        // Add Scheme Characters
        fgLookupTable['+'] |= SCHEME_CHARACTERS;
        fgLookupTable['-'] |= SCHEME_CHARACTERS;
        fgLookupTable['.'] |= SCHEME_CHARACTERS;

        // Add Userinfo Characters
        fgLookupTable[';'] |= USERINFO_CHARACTERS;
        fgLookupTable[':'] |= USERINFO_CHARACTERS;
        fgLookupTable['&'] |= USERINFO_CHARACTERS;
        fgLookupTable['='] |= USERINFO_CHARACTERS;
        fgLookupTable['+'] |= USERINFO_CHARACTERS;
        fgLookupTable['$'] |= USERINFO_CHARACTERS;
        fgLookupTable[','] |= USERINFO_CHARACTERS;

        // Add Path Characters
        fgLookupTable[';'] |= PATH_CHARACTERS;
        fgLookupTable['/'] |= PATH_CHARACTERS;
        fgLookupTable[':'] |= PATH_CHARACTERS;
        fgLookupTable['@'] |= PATH_CHARACTERS;
        fgLookupTable['&'] |= PATH_CHARACTERS;
        fgLookupTable['='] |= PATH_CHARACTERS;
        fgLookupTable['+'] |= PATH_CHARACTERS;
        fgLookupTable['$'] |= PATH_CHARACTERS;
        fgLookupTable[','] |= PATH_CHARACTERS;
    }

    /** Stores the scheme (usually the protocol) for this URI. */
    private String m_scheme = null;

    /** If specified, stores the userinfo for this URI; otherwise null */
    private String m_userinfo = null;

    /** If specified, stores the host for this URI; otherwise null */
    private String m_host = null;

    /** If specified, stores the port for this URI; otherwise -1 */
    private int m_port = -1;

    /** If specified, stores the registry based authority for this URI; otherwise -1 */
    private String m_regAuthority = null;

    /** If specified, stores the path for this URI; otherwise null */
    private String m_path = null;

    /** If specified, stores the query string for this URI; otherwise null. */
    private String m_queryString = null;

    /** If specified, stores the fragment for this URI; otherwise null */
    private String m_fragment;

    /** Construct a new and uninitialized URI. */
    public URI() {
    }

    /**
     * Construct a new URI from another URI. All fields for this URI are set equal to the fields of
     * the URI passed in.
     *
     * @param p_other the URI to copy (cannot be null)
     */
    public URI(URI p_other) {
        initialize(p_other);
    }

    /**
     * Construct a new URI from a URI specification string. If the specification follows the "generic
     * URI" syntax, (two slashes following the first colon), the specification will be parsed
     * accordingly - setting the scheme, userinfo, host,port, path, query string and fragment fields
     * as necessary. If the specification does not follow the "generic URI" syntax, the specification
     * is parsed into a scheme and scheme-specific part (stored as the path) only.
     *
     * @param p_uriSpec the URI specification string (cannot be null or empty)
     * @throws MalformedURIException if p_uriSpec violates any syntax rules
     */
    public URI(String p_uriSpec) throws MalformedURIException {
        this((URI)null, p_uriSpec);
    }

    /**
     * Construct a new URI from a base URI and a URI specification string. The URI specification
     * string may be a relative URI.
     *
     * @param p_base    the base URI (cannot be null if p_uriSpec is null or empty)
     * @param p_uriSpec the URI specification string (cannot be null or empty if p_base is null)
     * @throws MalformedURIException if p_uriSpec violates any syntax rules
     */
    public URI(URI p_base, String p_uriSpec) throws MalformedURIException {
        initialize(p_base, p_uriSpec);
    }

    /**
     * Construct a new URI that does not follow the generic URI syntax. Only the scheme and
     * scheme-specific part (stored as the path) are initialized.
     *
     * @param p_scheme             the URI scheme (cannot be null or empty)
     * @param p_schemeSpecificPart the scheme-specific part (cannot be null or empty)
     * @throws MalformedURIException if p_scheme violates any syntax rules
     */
    public URI(String p_scheme, String p_schemeSpecificPart)
            throws MalformedURIException {
        if (p_scheme == null || p_scheme.trim().length() == 0) {
            throw new MalformedURIException(
                    "Cannot construct URI with null/empty scheme!");
        }
        if (p_schemeSpecificPart == null ||
                p_schemeSpecificPart.trim().length() == 0) {
            throw new MalformedURIException(
                    "Cannot construct URI with null/empty scheme-specific part!");
        }
        setScheme(p_scheme);
        setPath(p_schemeSpecificPart);
    }

    /**
     * Construct a new URI that follows the generic URI syntax from its component parts. Each
     * component is validated for syntax and some basic semantic checks are performed as well.  See
     * the individual setter methods for specifics.
     *
     * @param p_scheme      the URI scheme (cannot be null or empty)
     * @param p_host        the hostname, IPv4 address or IPv6 reference for the URI
     * @param p_path        the URI path - if the path contains '?' or '#', then the query string
     *                      and/or fragment will be set from the path; however, if the query and
     *                      fragment are specified both in the path and as separate parameters, an
     *                      exception is thrown
     * @param p_queryString the URI query string (cannot be specified if path is null)
     * @param p_fragment    the URI fragment (cannot be specified if path is null)
     * @throws MalformedURIException if any of the parameters violates syntax rules or semantic rules
     */
    public URI(String p_scheme, String p_host, String p_path,
               String p_queryString, String p_fragment)
            throws MalformedURIException {
        this(p_scheme, null, p_host, -1, p_path, p_queryString, p_fragment);
    }

    /**
     * Construct a new URI that follows the generic URI syntax from its component parts. Each
     * component is validated for syntax and some basic semantic checks are performed as well.  See
     * the individual setter methods for specifics.
     *
     * @param p_scheme      the URI scheme (cannot be null or empty)
     * @param p_userinfo    the URI userinfo (cannot be specified if host is null)
     * @param p_host        the hostname, IPv4 address or IPv6 reference for the URI
     * @param p_port        the URI port (may be -1 for "unspecified"; cannot be specified if host is
     *                      null)
     * @param p_path        the URI path - if the path contains '?' or '#', then the query string
     *                      and/or fragment will be set from the path; however, if the query and
     *                      fragment are specified both in the path and as separate parameters, an
     *                      exception is thrown
     * @param p_queryString the URI query string (cannot be specified if path is null)
     * @param p_fragment    the URI fragment (cannot be specified if path is null)
     * @throws MalformedURIException if any of the parameters violates syntax rules or semantic rules
     */
    public URI(String p_scheme, String p_userinfo,
               String p_host, int p_port, String p_path,
               String p_queryString, String p_fragment)
            throws MalformedURIException {
        if (p_scheme == null || p_scheme.trim().length() == 0) {
            throw new MalformedURIException("Scheme is required!");
        }

        if (p_host == null) {
            if (p_userinfo != null) {
                throw new MalformedURIException(
                        "Userinfo may not be specified if host is not specified!");
            }
            if (p_port != -1) {
                throw new MalformedURIException(
                        "Port may not be specified if host is not specified!");
            }
        }

        if (p_path != null) {
            if (p_path.indexOf('?') != -1 && p_queryString != null) {
                throw new MalformedURIException(
                        "Query string cannot be specified in path and query string!");
            }

            if (p_path.indexOf('#') != -1 && p_fragment != null) {
                throw new MalformedURIException(
                        "Fragment cannot be specified in both the path and fragment!");
            }
        }

        setScheme(p_scheme);
        setHost(p_host);
        setPort(p_port);
        setUserinfo(p_userinfo);
        setPath(p_path);
        setQueryString(p_queryString);
        setFragment(p_fragment);
    }

    /**
     * Initialize all fields of this URI from another URI.
     *
     * @param p_other the URI to copy (cannot be null)
     */
    private void initialize(URI p_other) {
        m_scheme = p_other.getScheme();
        m_userinfo = p_other.getUserinfo();
        m_host = p_other.getHost();
        m_port = p_other.getPort();
        m_regAuthority = p_other.getRegBasedAuthority();
        m_path = p_other.getPath();
        m_queryString = p_other.getQueryString();
        m_fragment = p_other.getFragment();
    }

    /**
     * Initializes this URI from a base URI and a URI specification string. See RFC 2396 Section 4 and
     * Appendix B for specifications on parsing the URI and Section 5 for specifications on resolving
     * relative URIs and relative paths.
     *
     * @param p_base    the base URI (may be null if p_uriSpec is an absolute URI)
     * @param p_uriSpec the URI spec string which may be an absolute or relative URI (can only be
     *                  null/empty if p_base is not null)
     * @throws MalformedURIException if p_base is null and p_uriSpec is not an absolute URI or if
     *                               p_uriSpec violates syntax rules
     */
    private void initialize(URI p_base, String p_uriSpec)
            throws MalformedURIException {

        String uriSpec = p_uriSpec;
        int uriSpecLen = (uriSpec != null) ? uriSpec.length() : 0;

        if (p_base == null && uriSpecLen == 0) {
            throw new MalformedURIException(
                    "Cannot initialize URI with empty parameters.");
        }

        // just make a copy of the base if spec is empty
        if (uriSpecLen == 0) {
            initialize(p_base);
            return;
        }

        int index = 0;

        // Check for scheme, which must be before '/', '?' or '#'. Also handle
        // names with DOS drive letters ('D:'), so 1-character schemes are not
        // allowed.
        int colonIdx = uriSpec.indexOf(':');
        if (colonIdx != -1) {
            final int searchFrom = colonIdx - 1;
            // search backwards starting from character before ':'.
            int slashIdx = uriSpec.lastIndexOf('/', searchFrom);
            int queryIdx = uriSpec.lastIndexOf('?', searchFrom);
            int fragmentIdx = uriSpec.lastIndexOf('#', searchFrom);

            if (colonIdx < 2 || slashIdx != -1 ||
                    queryIdx != -1 || fragmentIdx != -1) {
                // A standalone base is a valid URI according to spec
                if (colonIdx == 0 || (p_base == null && fragmentIdx != 0)) {
                    throw new MalformedURIException("No scheme found in URI.");
                }
            } else {
                initializeScheme(uriSpec);
                index = m_scheme.length() + 1;

                // Neither 'scheme:' or 'scheme:#fragment' are valid URIs.
                if (colonIdx == uriSpecLen - 1 || uriSpec.charAt(colonIdx + 1) == '#') {
                    throw new MalformedURIException("Scheme specific part cannot be empty.");
                }
            }
        }
        // Two slashes means we may have authority, but definitely means we're either
        // matching net_path or abs_path. These two productions are ambiguous in that
        // every net_path (except those containing an IPv6Reference) is an abs_path.
        // RFC 2396 resolves this ambiguity by applying a greedy left most matching rule.
        // Try matching net_path first, and if that fails we don't have authority so
        // then attempt to match abs_path.
        //
        // net_path = "//" authority [ abs_path ]
        // abs_path = "/"  path_segments
        if (((index + 1) < uriSpecLen) &&
                (uriSpec.charAt(index) == '/' && uriSpec.charAt(index + 1) == '/')) {
            index += 2;
            int startPos = index;

            // Authority will be everything up to path, query or fragment
            char testChar = '\0';
            while (index < uriSpecLen) {
                testChar = uriSpec.charAt(index);
                if (testChar == '/' || testChar == '?' || testChar == '#') {
                    break;
                }
                index++;
            }

            // Attempt to parse authority. If the section is an empty string
            // this is a valid server based authority, so set the host to this
            // value.
            if (index > startPos) {
                // If we didn't find authority we need to back up. Attempt to
                // match against abs_path next.
                if (!initializeAuthority(uriSpec.substring(startPos, index))) {
                    index = startPos - 2;
                }
            } else {
                m_host = "";
            }
        }

        initializePath(uriSpec, index);

        // Resolve relative URI to base URI - see RFC 2396 Section 5.2
        // In some cases, it might make more sense to throw an exception
        // (when scheme is specified is the string spec and the base URI
        // is also specified, for example), but we're just following the
        // RFC specifications
        if (p_base != null) {

            // check to see if this is the current doc - RFC 2396 5.2 #2
            // note that this is slightly different from the RFC spec in that
            // we don't include the check for query string being null
            // - this handles cases where the urispec is just a query
            // string or a fragment (e.g. "?y" or "#s") -
            // see <http://www.ics.uci.edu/~fielding/url/test1.html> which
            // identified this as a bug in the RFC
            if (m_path.length() == 0 && m_scheme == null &&
                    m_host == null && m_regAuthority == null) {
                m_scheme = p_base.getScheme();
                m_userinfo = p_base.getUserinfo();
                m_host = p_base.getHost();
                m_port = p_base.getPort();
                m_regAuthority = p_base.getRegBasedAuthority();
                m_path = p_base.getPath();

                if (m_queryString == null) {
                    m_queryString = p_base.getQueryString();
                }
                return;
            }

            // check for scheme - RFC 2396 5.2 #3
            // if we found a scheme, it means absolute URI, so we're done
            if (m_scheme == null) {
                m_scheme = p_base.getScheme();
            } else {
                return;
            }

            // check for authority - RFC 2396 5.2 #4
            // if we found a host, then we've got a network path, so we're done
            if (m_host == null && m_regAuthority == null) {
                m_userinfo = p_base.getUserinfo();
                m_host = p_base.getHost();
                m_port = p_base.getPort();
                m_regAuthority = p_base.getRegBasedAuthority();
            } else {
                return;
            }

            // check for absolute path - RFC 2396 5.2 #5
            if (m_path.length() > 0 &&
                    m_path.startsWith("/")) {
                return;
            }

            // if we get to this point, we need to resolve relative path
            // RFC 2396 5.2 #6
            String path = "";
            String basePath = p_base.getPath();

            // 6a - get all but the last segment of the base URI path
            if (basePath != null && basePath.length() > 0) {
                int lastSlash = basePath.lastIndexOf('/');
                if (lastSlash != -1) {
                    path = basePath.substring(0, lastSlash + 1);
                }
            } else if (m_path.length() > 0) {
                path = "/";
            }

            // 6b - append the relative URI path
            path = path.concat(m_path);

            // 6c - remove all "./" where "." is a complete path segment
            index = -1;
            while ((index = path.indexOf("/./")) != -1) {
                path = path.substring(0, index + 1).concat(path.substring(index + 3));
            }

            // 6d - remove "." if path ends with "." as a complete path segment
            if (path.endsWith("/.")) {
                path = path.substring(0, path.length() - 1);
            }

            // 6e - remove all "<segment>/../" where "<segment>" is a complete
            // path segment not equal to ".."
            index = 1;
            int segIndex = -1;
            String tempString = null;

            while ((index = path.indexOf("/../", index)) > 0) {
                tempString = path.substring(0, path.indexOf("/../"));
                segIndex = tempString.lastIndexOf('/');
                if (segIndex != -1) {
                    if (!tempString.substring(segIndex).equals("..")) {
                        path = path.substring(0, segIndex + 1).concat(path.substring(index + 4));
                        index = segIndex;
                    } else
                        index += 4;
                } else
                    index += 4;
            }

            // 6f - remove ending "<segment>/.." where "<segment>" is a
            // complete path segment
            if (path.endsWith("/..")) {
                tempString = path.substring(0, path.length() - 3);
                segIndex = tempString.lastIndexOf('/');
                if (segIndex != -1) {
                    path = path.substring(0, segIndex + 1);
                }
            }
            m_path = path;
        }
    }

    /**
     * Initialize the scheme for this URI from a URI string spec.
     *
     * @param p_uriSpec the URI specification (cannot be null)
     * @throws MalformedURIException if URI does not have a conformant scheme
     */
    private void initializeScheme(String p_uriSpec)
            throws MalformedURIException {
        int uriSpecLen = p_uriSpec.length();
        int index = 0;
        String scheme = null;
        char testChar = '\0';

        while (index < uriSpecLen) {
            testChar = p_uriSpec.charAt(index);
            if (testChar == ':' || testChar == '/' ||
                    testChar == '?' || testChar == '#') {
                break;
            }
            index++;
        }
        scheme = p_uriSpec.substring(0, index);

        if (scheme.length() == 0) {
            throw new MalformedURIException("No scheme found in URI.");
        } else {
            setScheme(scheme);
        }
    }

    /**
     * Initialize the authority (either server or registry based) for this URI from a URI string
     * spec.
     *
     * @param p_uriSpec the URI specification (cannot be null)
     * @return true if the given string matched server or registry based authority
     */
    private boolean initializeAuthority(String p_uriSpec) {

        int index = 0;
        int start = 0;
        int end = p_uriSpec.length();

        char testChar = '\0';
        String userinfo = null;

        // userinfo is everything up to @
        if (p_uriSpec.indexOf('@', start) != -1) {
            while (index < end) {
                testChar = p_uriSpec.charAt(index);
                if (testChar == '@') {
                    break;
                }
                index++;
            }
            userinfo = p_uriSpec.substring(start, index);
            index++;
        }

        // host is everything up to last ':', or up to
        // and including ']' if followed by ':'.
        String host = null;
        start = index;
        boolean hasPort = false;
        if (index < end) {
            if (p_uriSpec.charAt(start) == '[') {
                int bracketIndex = p_uriSpec.indexOf(']', start);
                index = (bracketIndex != -1) ? bracketIndex : end;
                if (index + 1 < end && p_uriSpec.charAt(index + 1) == ':') {
                    ++index;
                    hasPort = true;
                } else {
                    index = end;
                }
            } else {
                int colonIndex = p_uriSpec.lastIndexOf(':', end);
                index = (colonIndex > start) ? colonIndex : end;
                hasPort = (index != end);
            }
        }
        host = p_uriSpec.substring(start, index);
        int port = -1;
        if (host.length() > 0) {
            // port
            if (hasPort) {
                index++;
                start = index;
                while (index < end) {
                    index++;
                }
                String portStr = p_uriSpec.substring(start, index);
                if (portStr.length() > 0) {
                    // REVISIT: Remove this code.
                    /** for (int i = 0; i < portStr.length(); i++) {
                     if (!isDigit(portStr.charAt(i))) {
                     throw new MalformedURIException(
                     portStr +
                     " is invalid. Port should only contain digits!");
                     }
                     }**/
                    // REVISIT: Remove this code.
                    // Store port value as string instead of integer.
                    try {
                        port = Integer.parseInt(portStr);
                        if (port == -1) --port;
                    }
                    catch (NumberFormatException nfe) {
                        port = -2;
                    }
                }
            }
        }

        if (isValidServerBasedAuthority(host, port, userinfo)) {
            m_host = host;
            m_port = port;
            m_userinfo = userinfo;
            return true;
        }
        // Note: Registry based authority is being removed from a
        // new spec for URI which would obsolete RFC 2396. If the
        // spec is added to XML errata, processing of reg_name
        // needs to be removed. - mrglavas.
        else if (isValidRegistryBasedAuthority(p_uriSpec)) {
            m_regAuthority = p_uriSpec;
            return true;
        }
        return false;
    }

    /**
     * Determines whether the components host, port, and user info are valid as a server authority.
     *
     * @param host     the host component of authority
     * @param port     the port number component of authority
     * @param userinfo the user info component of authority
     * @return true if the given host, port, and userinfo compose a valid server authority
     */
    private boolean isValidServerBasedAuthority(String host, int port, String userinfo) {

        // Check if the host is well formed.
        if (!isWellFormedAddress(host)) {
            return false;
        }

        // Check that port is well formed if it exists.
        // REVISIT: There's no restriction on port value ranges, but
        // perform the same check as in setPort to be consistent. Pass
        // in a string to this method instead of an integer.
        if (port < -1 || port > 65535) {
            return false;
        }

        // Check that userinfo is well formed if it exists.
        if (userinfo != null) {
            // Userinfo can contain alphanumerics, mark characters, escaped
            // and ';',':','&','=','+','$',','
            int index = 0;
            int end = userinfo.length();
            char testChar = '\0';
            while (index < end) {
                testChar = userinfo.charAt(index);
                if (testChar == '%') {
                    if (index + 2 >= end ||
                            !isHex(userinfo.charAt(index + 1)) ||
                            !isHex(userinfo.charAt(index + 2))) {
                        return false;
                    }
                    index += 2;
                } else if (!isUserinfoCharacter(testChar)) {
                    return false;
                }
                ++index;
            }
        }
        return true;
    }

    /**
     * Determines whether the given string is a registry based authority.
     *
     * @param authority the authority component of a URI
     * @return true if the given string is a registry based authority
     */
    private boolean isValidRegistryBasedAuthority(String authority) {
        int index = 0;
        int end = authority.length();
        char testChar;

        while (index < end) {
            testChar = authority.charAt(index);

            // check for valid escape sequence
            if (testChar == '%') {
                if (index + 2 >= end ||
                        !isHex(authority.charAt(index + 1)) ||
                        !isHex(authority.charAt(index + 2))) {
                    return false;
                }
                index += 2;
            }
            // can check against path characters because the set
            // is the same except for '/' which we've already excluded.
            else if (!isPathCharacter(testChar)) {
                return false;
            }
            ++index;
        }
        return true;
    }

    /**
     * Initialize the path for this URI from a URI string spec.
     *
     * @param p_uriSpec     the URI specification (cannot be null)
     * @param p_nStartIndex the index to begin scanning from
     * @throws MalformedURIException if p_uriSpec violates syntax rules
     */
    private void initializePath(String p_uriSpec, int p_nStartIndex)
            throws MalformedURIException {
        if (p_uriSpec == null) {
            throw new MalformedURIException(
                    "Cannot initialize path from null string!");
        }

        int index = p_nStartIndex;
        int start = p_nStartIndex;
        int end = p_uriSpec.length();
        char testChar = '\0';

        // path - everything up to query string or fragment
        if (start < end) {
            // RFC 2732 only allows '[' and ']' to appear in the opaque part.
            if (getScheme() == null || p_uriSpec.charAt(start) == '/') {

                // Scan path.
                // abs_path = "/"  path_segments
                // rel_path = rel_segment [ abs_path ]
                while (index < end) {
                    testChar = p_uriSpec.charAt(index);

                    // check for valid escape sequence
                    if (testChar == '%') {
                        if (index + 2 >= end ||
                                !isHex(p_uriSpec.charAt(index + 1)) ||
                                !isHex(p_uriSpec.charAt(index + 2))) {
                            throw new MalformedURIException(
                                    "Path contains invalid escape sequence!");
                        }
                        index += 2;
                    }
                    // Path segments cannot contain '[' or ']' since pchar
                    // production was not changed by RFC 2732.
                    else if (!isPathCharacter(testChar)) {
                        if (testChar == '?' || testChar == '#') {
                            break;
                        }
                        throw new MalformedURIException(
                                "Path contains invalid character: " + testChar);
                    }
                    ++index;
                }
            } else {

                // Scan opaque part.
                // opaque_part = uric_no_slash *uric
                while (index < end) {
                    testChar = p_uriSpec.charAt(index);

                    if (testChar == '?' || testChar == '#') {
                        break;
                    }

                    // check for valid escape sequence
                    if (testChar == '%') {
                        if (index + 2 >= end ||
                                !isHex(p_uriSpec.charAt(index + 1)) ||
                                !isHex(p_uriSpec.charAt(index + 2))) {
                            throw new MalformedURIException(
                                    "Opaque part contains invalid escape sequence!");
                        }
                        index += 2;
                    }
                    // If the scheme specific part is opaque, it can contain '['
                    // and ']'. uric_no_slash wasn't modified by RFC 2732, which
                    // I've interpreted as an error in the spec, since the
                    // production should be equivalent to (uric - '/'), and uric
                    // contains '[' and ']'. - mrglavas
                    else if (!isURICharacter(testChar)) {
                        throw new MalformedURIException(
                                "Opaque part contains invalid character: " + testChar);
                    }
                    ++index;
                }
            }
        }
        m_path = p_uriSpec.substring(start, index);

        // query - starts with ? and up to fragment or end
        if (testChar == '?') {
            index++;
            start = index;
            while (index < end) {
                testChar = p_uriSpec.charAt(index);
                if (testChar == '#') {
                    break;
                }
                if (testChar == '%') {
                    if (index + 2 >= end ||
                            !isHex(p_uriSpec.charAt(index + 1)) ||
                            !isHex(p_uriSpec.charAt(index + 2))) {
                        throw new MalformedURIException(
                                "Query string contains invalid escape sequence!");
                    }
                    index += 2;
                } else if (!isURICharacter(testChar)) {
                    throw new MalformedURIException(
                            "Query string contains invalid character: " + testChar);
                }
                index++;
            }
            m_queryString = p_uriSpec.substring(start, index);
        }

        // fragment - starts with #
        if (testChar == '#') {
            index++;
            start = index;
            while (index < end) {
                testChar = p_uriSpec.charAt(index);

                if (testChar == '%') {
                    if (index + 2 >= end ||
                            !isHex(p_uriSpec.charAt(index + 1)) ||
                            !isHex(p_uriSpec.charAt(index + 2))) {
                        throw new MalformedURIException(
                                "Fragment contains invalid escape sequence!");
                    }
                    index += 2;
                } else if (!isURICharacter(testChar)) {
                    throw new MalformedURIException(
                            "Fragment contains invalid character: " + testChar);
                }
                index++;
            }
            m_fragment = p_uriSpec.substring(start, index);
        }
    }

    /**
     * Get the scheme for this URI.
     *
     * @return the scheme for this URI
     */
    public String getScheme() {
        return m_scheme;
    }

    /**
     * Get the scheme-specific part for this URI (everything following the scheme and the first
     * colon). See RFC 2396 Section 5.2 for spec.
     *
     * @return the scheme-specific part for this URI
     */
    public String getSchemeSpecificPart() {
        StringBuffer schemespec = new StringBuffer();

        if (m_host != null || m_regAuthority != null) {
            schemespec.append("//");

            // Server based authority.
            if (m_host != null) {

                if (m_userinfo != null) {
                    schemespec.append(m_userinfo);
                    schemespec.append('@');
                }

                schemespec.append(m_host);

                if (m_port != -1) {
                    schemespec.append(':');
                    schemespec.append(m_port);
                }
            }
            // Registry based authority.
            else {
                schemespec.append(m_regAuthority);
            }
        }

        if (m_path != null) {
            schemespec.append((m_path));
        }

        if (m_queryString != null) {
            schemespec.append('?');
            schemespec.append(m_queryString);
        }

        if (m_fragment != null) {
            schemespec.append('#');
            schemespec.append(m_fragment);
        }

        return schemespec.toString();
    }

    /**
     * Get the userinfo for this URI.
     *
     * @return the userinfo for this URI (null if not specified).
     */
    public String getUserinfo() {
        return m_userinfo;
    }

    /**
     * Get the host for this URI.
     *
     * @return the host for this URI (null if not specified).
     */
    public String getHost() {
        return m_host;
    }

    /**
     * Get the port for this URI.
     *
     * @return the port for this URI (-1 if not specified).
     */
    public int getPort() {
        return m_port;
    }

    /**
     * Get the registry based authority for this URI.
     *
     * @return the registry based authority (null if not specified).
     */
    public String getRegBasedAuthority() {
        return m_regAuthority;
    }

    /**
     * Get the path for this URI (optionally with the query string and fragment).
     *
     * @param p_includeQueryString if true (and query string is not null), then a "?" followed by the
     *                             query string will be appended
     * @param p_includeFragment    if true (and fragment is not null), then a "#" followed by the
     *                             fragment will be appended
     * @return the path for this URI possibly including the query string and fragment
     */
    public String getPath(boolean p_includeQueryString,
                          boolean p_includeFragment) {
        StringBuffer pathString = new StringBuffer(m_path);

        if (p_includeQueryString && m_queryString != null) {
            pathString.append('?');
            pathString.append(m_queryString);
        }

        if (p_includeFragment && m_fragment != null) {
            pathString.append('#');
            pathString.append(m_fragment);
        }
        return pathString.toString();
    }

    /**
     * Get the path for this URI. Note that the value returned is the path only and does not include
     * the query string or fragment.
     *
     * @return the path for this URI.
     */
    public String getPath() {
        return m_path;
    }

    /**
     * Get the query string for this URI.
     *
     * @return the query string for this URI. Null is returned if there was no "?" in the URI spec,
     *         empty string if there was a "?" but no query string following it.
     */
    public String getQueryString() {
        return m_queryString;
    }

    /**
     * Get the fragment for this URI.
     *
     * @return the fragment for this URI. Null is returned if there was no "#" in the URI spec, empty
     *         string if there was a "#" but no fragment following it.
     */
    public String getFragment() {
        return m_fragment;
    }

    /**
     * Set the scheme for this URI. The scheme is converted to lowercase before it is set.
     *
     * @param p_scheme the scheme for this URI (cannot be null)
     * @throws MalformedURIException if p_scheme is not a conformant scheme name
     */
    public void setScheme(String p_scheme) throws MalformedURIException {
        if (p_scheme == null) {
            throw new MalformedURIException(
                    "Cannot set scheme from null string!");
        }
        if (!isConformantSchemeName(p_scheme)) {
            throw new MalformedURIException("The scheme is not conformant.");
        }

        m_scheme = p_scheme.toLowerCase();
    }

    /**
     * Set the userinfo for this URI. If a non-null value is passed in and the host value is null,
     * then an exception is thrown.
     *
     * @param p_userinfo the userinfo for this URI
     * @throws MalformedURIException if p_userinfo contains invalid characters
     */
    public void setUserinfo(String p_userinfo) throws MalformedURIException {
        if (p_userinfo == null) {
            m_userinfo = null;
            return;
        } else {
            if (m_host == null) {
                throw new MalformedURIException(
                        "Userinfo cannot be set when host is null!");
            }

            // userinfo can contain alphanumerics, mark characters, escaped
            // and ';',':','&','=','+','$',','
            int index = 0;
            int end = p_userinfo.length();
            char testChar = '\0';
            while (index < end) {
                testChar = p_userinfo.charAt(index);
                if (testChar == '%') {
                    if (index + 2 >= end ||
                            !isHex(p_userinfo.charAt(index + 1)) ||
                            !isHex(p_userinfo.charAt(index + 2))) {
                        throw new MalformedURIException(
                                "Userinfo contains invalid escape sequence!");
                    }
                } else if (!isUserinfoCharacter(testChar)) {
                    throw new MalformedURIException(
                            "Userinfo contains invalid character:" + testChar);
                }
                index++;
            }
        }
        m_userinfo = p_userinfo;
    }

    /**
     * <p>Set the host for this URI. If null is passed in, the userinfo field is also set to null and
     * the port is set to -1.</p>
     * <p/>
     * <p>Note: This method overwrites registry based authority if it previously existed in this
     * URI.</p>
     *
     * @param p_host the host for this URI
     * @throws MalformedURIException if p_host is not a valid IP address or DNS hostname.
     */
    public void setHost(String p_host) throws MalformedURIException {
        if (p_host == null || p_host.length() == 0) {
            if (p_host != null) {
                m_regAuthority = null;
            }
            m_host = p_host;
            m_userinfo = null;
            m_port = -1;
            return;
        } else if (!isWellFormedAddress(p_host)) {
            throw new MalformedURIException("Host is not a well formed address!");
        }
        m_host = p_host;
        m_regAuthority = null;
    }

    /**
     * Set the port for this URI. -1 is used to indicate that the port is not specified, otherwise
     * valid port numbers are  between 0 and 65535. If a valid port number is passed in and the host
     * field is null, an exception is thrown.
     *
     * @param p_port the port number for this URI
     * @throws MalformedURIException if p_port is not -1 and not a valid port number
     */
    public void setPort(int p_port) throws MalformedURIException {
        if (p_port >= 0 && p_port <= 65535) {
            if (m_host == null) {
                throw new MalformedURIException(
                        "Port cannot be set when host is null!");
            }
        } else if (p_port != -1) {
            throw new MalformedURIException("Invalid port number!");
        }
        m_port = p_port;
    }

    /**
     * <p>Sets the registry based authority for this URI.</p>
     * <p/>
     * <p>Note: This method overwrites server based authority if it previously existed in this
     * URI.</p>
     *
     * @param authority the registry based authority for this URI
     * @throws MalformedURIException it authority is not a well formed registry based authority
     */
    public void setRegBasedAuthority(String authority)
            throws MalformedURIException {

        if (authority == null) {
            m_regAuthority = null;
            return;
        }
        // reg_name = 1*( unreserved | escaped | "$" | "," |
        //            ";" | ":" | "@" | "&" | "=" | "+" )
        else if (authority.length() < 1 ||
                !isValidRegistryBasedAuthority(authority) ||
                authority.indexOf('/') != -1) {
            throw new MalformedURIException("Registry based authority is not well formed.");
        }
        m_regAuthority = authority;
        m_host = null;
        m_userinfo = null;
        m_port = -1;
    }

    /**
     * Set the path for this URI. If the supplied path is null, then the query string and fragment are
     * set to null as well. If the supplied path includes a query string and/or fragment, these fields
     * will be parsed and set as well. Note that, for URIs following the "generic URI" syntax, the
     * path specified should start with a slash. For URIs that do not follow the generic URI syntax,
     * this method sets the scheme-specific part.
     *
     * @param p_path the path for this URI (may be null)
     * @throws MalformedURIException if p_path contains invalid characters
     */
    public void setPath(String p_path) throws MalformedURIException {
        if (p_path == null) {
            m_path = null;
            m_queryString = null;
            m_fragment = null;
        } else {
            initializePath(p_path, 0);
        }
    }

    /**
     * Append to the end of the path of this URI. If the current path does not end in a slash and the
     * path to be appended does not begin with a slash, a slash will be appended to the current path
     * before the new segment is added. Also, if the current path ends in a slash and the new segment
     * begins with a slash, the extra slash will be removed before the new segment is appended.
     *
     * @param p_addToPath the new segment to be added to the current path
     * @throws MalformedURIException if p_addToPath contains syntax errors
     */
    public void appendPath(String p_addToPath)
            throws MalformedURIException {
        if (p_addToPath == null || p_addToPath.trim().length() == 0) {
            return;
        }

        if (!isURIString(p_addToPath)) {
            throw new MalformedURIException(
                    "Path contains invalid character!");
        }

        if (m_path == null || m_path.trim().length() == 0) {
            if (p_addToPath.startsWith("/")) {
                m_path = p_addToPath;
            } else {
                m_path = "/" + p_addToPath;
            }
        } else if (m_path.endsWith("/")) {
            if (p_addToPath.startsWith("/")) {
                m_path = m_path.concat(p_addToPath.substring(1));
            } else {
                m_path = m_path.concat(p_addToPath);
            }
        } else {
            if (p_addToPath.startsWith("/")) {
                m_path = m_path.concat(p_addToPath);
            } else {
                m_path = m_path.concat("/" + p_addToPath);
            }
        }
    }

    /**
     * Set the query string for this URI. A non-null value is valid only if this is an URI conforming
     * to the generic URI syntax and the path value is not null.
     *
     * @param p_queryString the query string for this URI
     * @throws MalformedURIException if p_queryString is not null and this URI does not conform to the
     *                               generic URI syntax or if the path is null
     */
    public void setQueryString(String p_queryString) throws MalformedURIException {
        if (p_queryString == null) {
            m_queryString = null;
        } else if (!isGenericURI()) {
            throw new MalformedURIException(
                    "Query string can only be set for a generic URI!");
        } else if (this.m_path == null) {
            throw new MalformedURIException(
                    "Query string cannot be set when path is null!");
        } else if (!isURIString(p_queryString)) {
            throw new MalformedURIException(
                    "Query string contains invalid character!");
        } else {
            m_queryString = p_queryString;
        }
    }

    /**
     * Set the fragment for this URI. A non-null value is valid only if this is a URI conforming to
     * the generic URI syntax and the path value is not null.
     *
     * @param p_fragment the fragment for this URI
     * @throws MalformedURIException if p_fragment is not null and this URI does not conform to the
     *                               generic URI syntax or if the path is null
     */
    public void setFragment(String p_fragment) throws MalformedURIException {
        if (p_fragment == null) {
            m_fragment = null;
        } else if (!isGenericURI()) {
            throw new MalformedURIException(
                    "Fragment can only be set for a generic URI!");
        } else if (getPath() == null) {
            throw new MalformedURIException(
                    "Fragment cannot be set when path is null!");
        } else if (!isURIString(p_fragment)) {
            throw new MalformedURIException(
                    "Fragment contains invalid character!");
        } else {
            m_fragment = p_fragment;
        }
    }

    /**
     * Determines if the passed-in Object is equivalent to this URI.
     *
     * @param p_test the Object to test for equality.
     * @return true if p_test is a URI with all values equal to this URI, false otherwise
     */
    public boolean equals(Object p_test) {
        if (p_test instanceof URI) {
            URI testURI = (URI)p_test;
            if (((m_scheme == null && testURI.m_scheme == null) ||
                    (m_scheme != null && testURI.m_scheme != null &&
                            m_scheme.equals(testURI.m_scheme))) &&
                    ((m_userinfo == null && testURI.m_userinfo == null) ||
                            (m_userinfo != null && testURI.m_userinfo != null &&
                                    m_userinfo.equals(testURI.m_userinfo))) &&
                    ((m_host == null && testURI.m_host == null) ||
                            (m_host != null && testURI.m_host != null &&
                                    m_host.equals(testURI.m_host))) &&
                    m_port == testURI.m_port &&
                    ((m_path == null && testURI.m_path == null) ||
                            (m_path != null && testURI.m_path != null &&
                                    m_path.equals(testURI.m_path))) &&
                    ((m_queryString == null && testURI.m_queryString == null) ||
                            (m_queryString != null && testURI.m_queryString != null &&
                                    m_queryString.equals(testURI.m_queryString))) &&
                    ((m_fragment == null && testURI.m_fragment == null) ||
                            (m_fragment != null && testURI.m_fragment != null &&
                                    m_fragment.equals(testURI.m_fragment)))) {
                return true;
            }
        }
        return false;
    }

    /**
     * Returns a hash-code value for this URI.  The hash code is based upon all of the URI's
     * components, and satisfies the general contract of the {@link Object#hashCode()
     * Object.hashCode} method. </p>
     *
     * @return A hash-code value for this URI
     */
    public int hashCode() {
        return toString().hashCode();
    }

    /**
     * Get the URI as a string specification. See RFC 2396 Section 5.2.
     *
     * @return the URI string specification
     */
    public String toString() {
        StringBuffer uriSpecString = new StringBuffer();

        if (m_scheme != null) {
            uriSpecString.append(m_scheme);
            uriSpecString.append(':');
        }
        uriSpecString.append(getSchemeSpecificPart());
        return uriSpecString.toString();
    }

    /**
     * Get the indicator as to whether this URI uses the "generic URI" syntax.
     *
     * @return true if this URI uses the "generic URI" syntax, false otherwise
     */
    public boolean isGenericURI() {
        // presence of the host (whether valid or empty) means
        // double-slashes which means generic uri
        return (m_host != null);
    }

    /**
     * Determine whether a scheme conforms to the rules for a scheme name. A scheme is conformant if
     * it starts with an alphanumeric, and contains only alphanumerics, '+','-' and '.'.
     *
     * @return true if the scheme is conformant, false otherwise
     */
    public static boolean isConformantSchemeName(String p_scheme) {
        if (p_scheme == null || p_scheme.trim().length() == 0) {
            return false;
        }

        if (!isAlpha(p_scheme.charAt(0))) {
            return false;
        }

        char testChar;
        int schemeLength = p_scheme.length();
        for (int i = 1; i < schemeLength; ++i) {
            testChar = p_scheme.charAt(i);
            if (!isSchemeCharacter(testChar)) {
                return false;
            }
        }

        return true;
    }

    /**
     * Determine whether a string is syntactically capable of representing a valid IPv4 address, IPv6
     * reference or the domain name of a network host. A valid IPv4 address consists of four decimal
     * digit groups separated by a '.'. Each group must consist of one to three digits. See RFC 2732
     * Section 3, and RFC 2373 Section 2.2, for the definition of IPv6 references. A hostname consists
     * of domain labels (each of which must begin and end with an alphanumeric but may contain '-')
     * separated & by a '.'. See RFC 2396 Section 3.2.2.
     *
     * @return true if the string is a syntactically valid IPv4 address, IPv6 reference or hostname
     */
    public static boolean isWellFormedAddress(String address) {
        if (address == null) {
            return false;
        }

        int addrLength = address.length();
        if (addrLength == 0) {
            return false;
        }

        // Check if the host is a valid IPv6reference.
        if (address.startsWith("[")) {
            return isWellFormedIPv6Reference(address);
        }

        // Cannot start with a '.', '-', or end with a '-'.
        if (address.startsWith(".") ||
                address.startsWith("-") ||
                address.endsWith("-")) {
            return false;
        }

        // rightmost domain label starting with digit indicates IP address
        // since top level domain label can only start with an alpha
        // see RFC 2396 Section 3.2.2
        int index = address.lastIndexOf('.');
        if (address.endsWith(".")) {
            index = address.substring(0, index).lastIndexOf('.');
        }

        if (index + 1 < addrLength && isDigit(address.charAt(index + 1))) {
            return isWellFormedIPv4Address(address);
        } else {
            // hostname      = *( domainlabel "." ) toplabel [ "." ]
            // domainlabel   = alphanum | alphanum *( alphanum | "-" ) alphanum
            // toplabel      = alpha | alpha *( alphanum | "-" ) alphanum

            // RFC 2396 states that hostnames take the form described in
            // RFC 1034 (Section 3) and RFC 1123 (Section 2.1). According
            // to RFC 1034, hostnames are limited to 255 characters.
            if (addrLength > 255) {
                return false;
            }

            // domain labels can contain alphanumerics and '-"
            // but must start and end with an alphanumeric
            char testChar;
            int labelCharCount = 0;

            for (int i = 0; i < addrLength; i++) {
                testChar = address.charAt(i);
                if (testChar == '.') {
                    if (!isAlphanum(address.charAt(i - 1))) {
                        return false;
                    }
                    if (i + 1 < addrLength && !isAlphanum(address.charAt(i + 1))) {
                        return false;
                    }
                    labelCharCount = 0;
                } else if (!isAlphanum(testChar) && testChar != '-') {
                    return false;
                }
                // RFC 1034: Labels must be 63 characters or less.
                else if (++labelCharCount > 63) {
                    return false;
                }
            }
        }
        return true;
    }

    /**
     * <p>Determines whether a string is an IPv4 address as defined by RFC 2373, and under the further
     * constraint that it must be a 32-bit address. Though not expressed in the grammar, in order to
     * satisfy the 32-bit address constraint, each segment of the address cannot be greater than 255
     * (8 bits of information).</p>
     * <p/>
     * <p><code>IPv4address = 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT</code></p>
     *
     * @return true if the string is a syntactically valid IPv4 address
     */
    public static boolean isWellFormedIPv4Address(String address) {

        int addrLength = address.length();
        char testChar;
        int numDots = 0;
        int numDigits = 0;

        // make sure that 1) we see only digits and dot separators, 2) that
        // any dot separator is preceded and followed by a digit and
        // 3) that we find 3 dots
        //
        // RFC 2732 amended RFC 2396 by replacing the definition
        // of IPv4address with the one defined by RFC 2373. - mrglavas
        //
        // IPv4address = 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT
        //
        // One to three digits must be in each segment.
        for (int i = 0; i < addrLength; i++) {
            testChar = address.charAt(i);
            if (testChar == '.') {
                if ((i > 0 && !isDigit(address.charAt(i - 1))) ||
                        (i + 1 < addrLength && !isDigit(address.charAt(i + 1)))) {
                    return false;
                }
                numDigits = 0;
                if (++numDots > 3) {
                    return false;
                }
            } else if (!isDigit(testChar)) {
                return false;
            }
            // Check that that there are no more than three digits
            // in this segment.
            else if (++numDigits > 3) {
                return false;
            }
            // Check that this segment is not greater than 255.
            else if (numDigits == 3) {
                char first = address.charAt(i - 2);
                char second = address.charAt(i - 1);
                if (!(first < '2' ||
                        (first == '2' &&
                                (second < '5' ||
                                        (second == '5' && testChar <= '5'))))) {
                    return false;
                }
            }
        }
        return (numDots == 3);
    }

    /**
     * <p>Determines whether a string is an IPv6 reference as defined by RFC 2732, where IPv6address
     * is defined in RFC 2373. The IPv6 address is parsed according to Section 2.2 of RFC 2373, with
     * the additional constraint that the address be composed of 128 bits of information.</p>
     * <p/>
     * <p><code>IPv6reference = "[" IPv6address "]"</code></p>
     * <p/>
     * <p>Note: The BNF expressed in RFC 2373 Appendix B does not accurately describe section 2.2, and
     * was in fact removed from RFC 3513, the successor of RFC 2373.</p>
     *
     * @return true if the string is a syntactically valid IPv6 reference
     */
    public static boolean isWellFormedIPv6Reference(String address) {

        int addrLength = address.length();
        int index = 1;
        int end = addrLength - 1;

        // Check if string is a potential match for IPv6reference.
        if (!(addrLength > 2 && address.charAt(0) == '['
                && address.charAt(end) == ']')) {
            return false;
        }

        // Counter for the number of 16-bit sections read in the address.
        int [] counter = new int[1];

        // Scan hex sequence before possible '::' or IPv4 address.
        index = scanHexSequence(address, index, end, counter);
        if (index == -1) {
            return false;
        }
        // Address must contain 128-bits of information.
        else if (index == end) {
            return (counter[0] == 8);
        }

        if (index + 1 < end && address.charAt(index) == ':') {
            if (address.charAt(index + 1) == ':') {
                // '::' represents at least one 16-bit group of zeros.
                if (++counter[0] > 8) {
                    return false;
                }
                index += 2;
                // Trailing zeros will fill out the rest of the address.
                if (index == end) {
                    return true;
                }
            }
            // If the second character wasn't ':', in order to be valid,
            // the remainder of the string must match IPv4Address,
            // and we must have read exactly 6 16-bit groups.
            else {
                return (counter[0] == 6) &&
                        isWellFormedIPv4Address(address.substring(index + 1, end));
            }
        } else {
            return false;
        }

        // 3. Scan hex sequence after '::'.
        int prevCount = counter[0];
        index = scanHexSequence(address, index, end, counter);

        // We've either reached the end of the string, the address ends in
        // an IPv4 address, or it is invalid. scanHexSequence has already
        // made sure that we have the right number of bits.
        return (index == end) ||
                (index != -1 && isWellFormedIPv4Address(
                        address.substring((counter[0] > prevCount) ? index + 1 : index, end)));
    }

    /**
     * Helper method for isWellFormedIPv6Reference which scans the hex sequences of an IPv6 address.
     * It returns the index of the next character to scan in the address, or -1 if the string cannot
     * match a valid IPv6 address.
     *
     * @param address the string to be scanned
     * @param index   the beginning index (inclusive)
     * @param end     the ending index (exclusive)
     * @param counter a counter for the number of 16-bit sections read in the address
     * @return the index of the next character to scan, or -1 if the string cannot match a valid IPv6
     *         address
     */
    private static int scanHexSequence(String address, int index, int end, int [] counter) {

        char testChar;
        int numDigits = 0;
        int start = index;

        // Trying to match the following productions:
        // hexseq = hex4 *( ":" hex4)
        // hex4   = 1*4HEXDIG
        for (; index < end; ++index) {
            testChar = address.charAt(index);
            if (testChar == ':') {
                // IPv6 addresses are 128-bit, so there can be at most eight sections.
                if (numDigits > 0 && ++counter[0] > 8) {
                    return -1;
                }
                // This could be '::'.
                if (numDigits == 0 || ((index + 1 < end) && address.charAt(index + 1) == ':')) {
                    return index;
                }
                numDigits = 0;
            }
            // This might be invalid or an IPv4address. If it's potentially an IPv4address,
            // backup to just after the last valid character that matches hexseq.
            else if (!isHex(testChar)) {
                if (testChar == '.' && numDigits < 4 && numDigits > 0 && counter[0] <= 6) {
                    int back = index - numDigits - 1;
                    return (back >= start) ? back : (back + 1);
                }
                return -1;
            }
            // There can be at most 4 hex digits per group.
            else if (++numDigits > 4) {
                return -1;
            }
        }
        return (numDigits > 0 && ++counter[0] <= 8) ? end : -1;
    }


    /**
     * Determine whether a char is a digit.
     *
     * @return true if the char is betweeen '0' and '9', false otherwise
     */
    private static boolean isDigit(char p_char) {
        return p_char >= '0' && p_char <= '9';
    }

    /**
     * Determine whether a character is a hexadecimal character.
     *
     * @return true if the char is betweeen '0' and '9', 'a' and 'f' or 'A' and 'F', false otherwise
     */
    private static boolean isHex(char p_char) {
        return (p_char <= 'f' && (fgLookupTable[p_char] & ASCII_HEX_CHARACTERS) != 0);
    }

    /**
     * Determine whether a char is an alphabetic character: a-z or A-Z
     *
     * @return true if the char is alphabetic, false otherwise
     */
    private static boolean isAlpha(char p_char) {
        return ((p_char >= 'a' && p_char <= 'z') || (p_char >= 'A' && p_char <= 'Z'));
    }

    /**
     * Determine whether a char is an alphanumeric: 0-9, a-z or A-Z
     *
     * @return true if the char is alphanumeric, false otherwise
     */
    private static boolean isAlphanum(char p_char) {
        return (p_char <= 'z' && (fgLookupTable[p_char] & MASK_ALPHA_NUMERIC) != 0);
    }

    /**
     * Determine whether a char is a URI character (reserved or unreserved, not including '%' for
     * escaped octets).
     *
     * @return true if the char is a URI character, false otherwise
     */
    private static boolean isURICharacter(char p_char) {
        return (p_char <= '~' && (fgLookupTable[p_char] & MASK_URI_CHARACTER) != 0);
    }

    /**
     * Determine whether a char is a scheme character.
     *
     * @return true if the char is a scheme character, false otherwise
     */
    private static boolean isSchemeCharacter(char p_char) {
        return (p_char <= 'z' && (fgLookupTable[p_char] & MASK_SCHEME_CHARACTER) != 0);
    }

    /**
     * Determine whether a char is a userinfo character.
     *
     * @return true if the char is a userinfo character, false otherwise
     */
    private static boolean isUserinfoCharacter(char p_char) {
        return (p_char <= 'z' && (fgLookupTable[p_char] & MASK_USERINFO_CHARACTER) != 0);
    }

    /**
     * Determine whether a char is a path character.
     *
     * @return true if the char is a path character, false otherwise
     */
    private static boolean isPathCharacter(char p_char) {
        return (p_char <= '~' && (fgLookupTable[p_char] & MASK_PATH_CHARACTER) != 0);
    }


    /**
     * Determine whether a given string contains only URI characters (also
     * called "uric" in RFC 2396). uric consist of all reserved
     * characters, unreserved characters and escaped characters.
     *
     * @return true if the string is comprised of uric, false otherwise
     */
    private static boolean isURIString(String p_uric) {
        if (p_uric == null) {
            return false;
        }
        int end = p_uric.length();
        char testChar = '\0';
        for (int i = 0; i < end; i++) {
            testChar = p_uric.charAt(i);
            if (testChar == '%') {
                if (i + 2 >= end ||
                        !isHex(p_uric.charAt(i + 1)) ||
                        !isHex(p_uric.charAt(i + 2))) {
                    return false;
                } else {
                    i += 2;
                    continue;
        }
      }
        if (!isURICharacter(testChar)) {
          return false;
        }
    }
    return true;
  }
}