/*
 * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
 * 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
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 * 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
         *      delimited by either SPACE, CTL, "(", &lt;"&gt; or the
         *      specified SPECIALS</li>
         * <li><code>QUOTEDSTRING</code> A sequence of ASCII characters
         *      within quotes</li>
         * <li><code>COMMENT</code> A sequence of ASCII characters
         *      within "(" and ")".</li>
         * <li><code>EOF</code> End of header</li>
         * </ul>
         * @return type
         */
        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
     * @param header The header that is tokenized.
     */
    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;
            return new Token(c, new String(ch));
        }

        // 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();
    }
}