/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 * @(#)HeaderTokenizer.java   1.9 02/03/27

 */

package com.sun.xml.internal.messaging.saaj.packaging.mime.internet;

/**

 * This class tokenizes RFC822 and MIME headers into the basic

 * symbols specified by RFC822 and MIME. <p>

 *

 * This class handles folded headers (ie headers with embedded

 * CRLF SPACE sequences). The folds are removed in the returned

 * tokens.

 *

 * @version 1.9, 02/03/27

 * @author  John Mani

 */

public class HeaderTokenizer {

    /**

     * The Token class represents tokens returned by the

     * HeaderTokenizer.

     */

    public static class Token {

        private int type;

        private String value;

        /**

         * Token type indicating an ATOM.

         */

        public static final int ATOM            = -1;

        /**

         * Token type indicating a quoted string. The value

         * field contains the string without the quotes.

         */

        public static final int QUOTEDSTRING    = -2;

        /**

         * Token type indicating a comment. The value field

         * contains the comment string without the comment

         * start and end symbols.

         */

        public static final int COMMENT         = -3;

        /**

         * Token type indicating end of input.

         */

        public static final int  EOF            = -4;

        /**

         * Constructor.

         * @param       type    Token type

         * @param       value   Token value

         */

        public Token(int type, String value) {

             this.type = type;

             this.value = value;

        }

        /**

         * Return the type of the token. If the token represents a

         * delimiter or a control character, the type is that character

         * itself, converted to an integer. Otherwise, it's value is

         * one of the following:

         * <ul>

         * <li><code>ATOM</code> A sequence of ASCII characters

         * <li><code>QUOTEDSTRING</code> A sequence of ASCII characters

         * <li><code>COMMENT</code> A sequence of ASCII characters

         * </ul>

         */

        public int getType() {

            return type;

        }

        /**

         * Returns the value of the token just read. When the current

         * token is a quoted string, this field contains the body of the

         * string, without the quotes. When the current token is a comment,

         * this field contains the body of the comment.

         *

         * @return      token value

         */

        public String getValue() {

            return value;

        }

    }

    private String string; // the string to be tokenized

    private boolean skipComments; // should comments be skipped ?

    private String delimiters; // delimiter string

    private int currentPos; // current parse position

    private int maxPos; // string length

    private int nextPos; // track start of next Token for next()

    private int peekPos; // track start of next Token for peek()

    /**

     * RFC822 specials

     */

    public final static String RFC822 = "()<>@,;:\\\"\t .[]";

    /**

     * MIME specials

     */

    public final static String MIME = "()<>@,;:\\\"\t []/?=";

    // The EOF Token

    private final static Token EOFToken = new Token(Token.EOF, null);

    /**

     * Constructor that takes a rfc822 style header.

     *

     * @param   header  The rfc822 header to be tokenized

     * @param   delimiters      Set of delimiter characters

     *                          to be used to delimit ATOMS. These

     *                          are usually <code>RFC822</code> or

     *                          <code>MIME</code>

     * @param   skipComments  If true, comments are skipped and

     *                          not returned as tokens

     */

    public HeaderTokenizer(String header, String delimiters,

                           boolean skipComments) {

        string = (header == null) ? "" : header; // paranoia ?!

        this.skipComments = skipComments;

        this.delimiters = delimiters;

        currentPos = nextPos = peekPos = 0;

        maxPos = string.length();

    }

    /**

     * Constructor. Comments are ignored and not returned as tokens

     *

     * @param   header  The header that is tokenized

     * @param   delimiters  The delimiters to be used

     */

    public HeaderTokenizer(String header, String delimiters) {

        this(header, delimiters, true);

    }

    /**

     * Constructor. The RFC822 defined delimiters - RFC822 - are

     * used to delimit ATOMS. Also comments are skipped and not

     * returned as tokens

     */

    public HeaderTokenizer(String header)  {

        this(header, RFC822);

    }

    /**

     * Parses the next token from this String. <p>

     *

     * Clients sit in a loop calling next() to parse successive

     * tokens until an EOF Token is returned.

     *

     * @return          the next Token

     * @exception       ParseException if the parse fails

     */

    public Token next() throws ParseException {

        Token tk;

        currentPos = nextPos; // setup currentPos

        tk = getNext();

        nextPos = peekPos = currentPos; // update currentPos and peekPos

        return tk;

    }

    /**

     * Peek at the next token, without actually removing the token

     * from the parse stream. Invoking this method multiple times

     * will return successive tokens, until <code>next()</code> is

     * called. <p>

     *

     * @return          the next Token

     * @exception       ParseException if the parse fails

     */

    public Token peek() throws ParseException {

        Token tk;

        currentPos = peekPos; // setup currentPos

        tk = getNext();

        peekPos = currentPos; // update peekPos

        return tk;

    }

    /**

     * Return the rest of the Header.

     *

     * @return String   rest of header. null is returned if we are

     *                  already at end of header

     */

    public String getRemainder() {

        return string.substring(nextPos);

    }

    /*

     * Return the next token starting from 'currentPos'. After the

     * parse, 'currentPos' is updated to point to the start of the

     * next token.

     */

    private Token getNext() throws ParseException {

        // If we're already at end of string, return EOF

        if (currentPos >= maxPos)

            return EOFToken;

        // Skip white-space, position currentPos beyond the space

        if (skipWhiteSpace() == Token.EOF)

            return EOFToken;

        char c;

        int start;

        boolean filter = false;

        c = string.charAt(currentPos);

        // Check or Skip comments and position currentPos

        // beyond the comment

        while (c == '(') {

            // Parsing comment ..

            int nesting;

            for (start = ++currentPos, nesting = 1;

                 nesting > 0 && currentPos < maxPos;

                 currentPos++) {

                c = string.charAt(currentPos);

                if (c == '\\') {  // Escape sequence

                    currentPos++; // skip the escaped character

                    filter = true;

                } else if (c == '\r')

                    filter = true;

                else if (c == '(')

                    nesting++;

                else if (c == ')')

                    nesting--;

            }

            if (nesting != 0)

                throw new ParseException("Unbalanced comments");

            if (!skipComments) {

                // Return the comment, if we are asked to.

                // Note that the comment start & end markers are ignored.

                String s;

                if (filter) // need to go thru the token again.

                    s = filterToken(string, start, currentPos-1);

                else

                    s = string.substring(start,currentPos-1);

                return new Token(Token.COMMENT, s);

            }

            // Skip any whitespace after the comment.

            if (skipWhiteSpace() == Token.EOF)

                return EOFToken;

            c = string.charAt(currentPos);

        }

        // Check for quoted-string and position currentPos

        //  beyond the terminating quote

        if (c == '"') {

            for (start = ++currentPos; currentPos < maxPos; currentPos++) {

                c = string.charAt(currentPos);

                if (c == '\\') { // Escape sequence

                    currentPos++;

                    filter = true;

                } else if (c == '\r')

                    filter = true;

                else if (c == '"') {

                    currentPos++;

                    String s;

                    if (filter)

                        s = filterToken(string, start, currentPos-1);

                    else

                        s = string.substring(start,currentPos-1);

                    return new Token(Token.QUOTEDSTRING, s);

                }

            }

            throw new ParseException("Unbalanced quoted string");

        }

        // Check for SPECIAL or CTL

        if (c < 040 || c >= 0177 || delimiters.indexOf(c) >= 0) {

            currentPos++; // re-position currentPos

            char ch[] = new char[1];

            ch[0] = c;

        }

        // Check for ATOM

        for (start = currentPos; currentPos < maxPos; currentPos++) {

            c = string.charAt(currentPos);

            // ATOM is delimited by either SPACE, CTL, "(", <">

            // or the specified SPECIALS

            if (c < 040 || c >= 0177 || c == '(' || c == ' ' ||

                c == '"' || delimiters.indexOf(c) >= 0)

                break;

        }

        return new Token(Token.ATOM, string.substring(start, currentPos));

    }

    // Skip SPACE, HT, CR and NL

    private int skipWhiteSpace() {

        char c;

        for (; currentPos < maxPos; currentPos++)

            if (((c = string.charAt(currentPos)) != ' ') &&

                (c != '\t') && (c != '\r') && (c != '\n'))

                return currentPos;

        return Token.EOF;

    }

    /* Process escape sequences and embedded LWSPs from a comment or

     * quoted string.

     */

    private static String filterToken(String s, int start, int end) {

        StringBuilder sb = new StringBuilder();

        char c;

        boolean gotEscape = false;

        boolean gotCR = false;

        for (int i = start; i < end; i++) {

            c = s.charAt(i);

            if (c == '\n' && gotCR) {

                // This LF is part of an unescaped

                // CRLF sequence (i.e, LWSP). Skip it.

                gotCR = false;

                continue;

            }

            gotCR = false;

            if (!gotEscape) {

                // Previous character was NOT '\'

                if (c == '\\') // skip this character

                    gotEscape = true;

                else if (c == '\r') // skip this character

                    gotCR = true;

                else // append this character

                    sb.append(c);

            } else {

                // Previous character was '\'. So no need to

                // bother with any special processing, just

                // append this character

                sb.append(c);

                gotEscape = false;

            }

        }

        return sb.toString();

    }

}