/*

 * 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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package com.sun.xml.internal.org.jvnet.mimepull;

import java.io.InputStream;

import java.io.IOException;

import java.util.*;

import java.util.logging.Logger;

import java.nio.ByteBuffer;

import java.util.logging.Level;

/**

 * Pull parser for the MIME messages. Applications can use pull API to continue

 * the parsing MIME messages lazily.

 *

 * <pre>

 * for e.g.:

 * <p>

 *

 * MIMEParser parser = ...

 * Iterator<MIMEEvent> it = parser.iterator();

 * while(it.hasNext()) {

 *   MIMEEvent event = it.next();

 *   ...

 * }

 * </pre>

 *

 * @author Jitendra Kotamraju

 */

class MIMEParser implements Iterable<MIMEEvent> {

    private static final Logger LOGGER = Logger.getLogger(MIMEParser.class.getName());

    private static final String HEADER_ENCODING = "ISO8859-1";

    // Actually, the grammar doesn't support whitespace characters

    // after boundary. But the mail implementation checks for it.

    // We will only check for these many whitespace characters after boundary

    private static final int NO_LWSP = 1000;

    private enum STATE {START_MESSAGE, SKIP_PREAMBLE, START_PART, HEADERS, BODY, END_PART, END_MESSAGE}

    private STATE state = STATE.START_MESSAGE;

    private final InputStream in;

    private final byte[] bndbytes;

    private final int bl;

    private final MIMEConfig config;

    private final int[] bcs = new int[128]; // BnM algo: Bad Character Shift table

    private final int[] gss;                // BnM algo : Good Suffix Shift table

    /**

     * Have we parsed the data from our InputStream yet?

     */

    private boolean parsed;

    /*

     * Read and process body partsList until we see the

     * terminating boundary line (or EOF).

     */

    private boolean done = false;

    private boolean eof;

    private final int capacity;

    private byte[] buf;

    private int len;

    private boolean bol;        // beginning of the line

    /*

     * Parses the MIME content. At the EOF, it also closes input stream

     */

    MIMEParser(InputStream in, String boundary, MIMEConfig config) {

        this.in = in;

        this.bndbytes = getBytes("--"+boundary);

        bl = bndbytes.length;

        this.config = config;

        gss = new int[bl];

        compileBoundaryPattern();

        // \r\n + boundary + "--\r\n" + lots of LWSP

        capacity = config.chunkSize+2+bl+4+NO_LWSP;

        createBuf(capacity);

    }

    /**

     * Returns iterator for the parsing events. Use the iterator to advance

     * the parsing.

     *

     * @return iterator for parsing events

     */

    @Override

    public Iterator<MIMEEvent> iterator() {

        return new MIMEEventIterator();

    }

    class MIMEEventIterator implements Iterator<MIMEEvent> {

        @Override

        public boolean hasNext() {

            return !parsed;

        }

        @Override

        public MIMEEvent next() {

            switch(state) {

                case START_MESSAGE :

                    if (LOGGER.isLoggable(Level.FINER)) {LOGGER.log(Level.FINER, "MIMEParser state={0}", STATE.START_MESSAGE);}

                    state = STATE.SKIP_PREAMBLE;

                    return MIMEEvent.START_MESSAGE;

                case SKIP_PREAMBLE :

                    if (LOGGER.isLoggable(Level.FINER)) {LOGGER.log(Level.FINER, "MIMEParser state={0}", STATE.SKIP_PREAMBLE);}

                    skipPreamble();

                    // fall through

                case START_PART :

                    if (LOGGER.isLoggable(Level.FINER)) {LOGGER.log(Level.FINER, "MIMEParser state={0}", STATE.START_PART);}

                    state = STATE.HEADERS;

                    return MIMEEvent.START_PART;

                case HEADERS :

                    if (LOGGER.isLoggable(Level.FINER)) {LOGGER.log(Level.FINER, "MIMEParser state={0}", STATE.HEADERS);}

                    InternetHeaders ih = readHeaders();

                    state = STATE.BODY;

                    bol = true;

                    return new MIMEEvent.Headers(ih);

                case BODY :

                    if (LOGGER.isLoggable(Level.FINER)) {LOGGER.log(Level.FINER, "MIMEParser state={0}", STATE.BODY);}

                    ByteBuffer buf = readBody();

                    bol = false;

                    return new MIMEEvent.Content(buf);

                case END_PART :

                    if (LOGGER.isLoggable(Level.FINER)) {LOGGER.log(Level.FINER, "MIMEParser state={0}", STATE.END_PART);}

                    if (done) {

                        state = STATE.END_MESSAGE;

                    } else {

                        state = STATE.START_PART;

                    }

                    return MIMEEvent.END_PART;

                case END_MESSAGE :

                    if (LOGGER.isLoggable(Level.FINER)) {LOGGER.log(Level.FINER, "MIMEParser state={0}", STATE.END_MESSAGE);}

                    parsed = true;

                    return MIMEEvent.END_MESSAGE;

                default :

                    throw new MIMEParsingException("Unknown Parser state = "+state);

            }

        }

        @Override

        public void remove() {

            throw new UnsupportedOperationException();

        }

    }

    /**

     * Collects the headers for the current part by parsing mesage stream.

     *

     * @return headers for the current part

     */

    private InternetHeaders readHeaders() {

        if (!eof) {

            fillBuf();

        }

        return new InternetHeaders(new LineInputStream());

    }

    /**

     * Reads and saves the part of the current attachment part's content.

     * At the end of this method, buf should have the remaining data

     * at index 0.

     *

     * @return a chunk of the part's content

     *

     */

    private ByteBuffer readBody() {

        if (!eof) {

            fillBuf();

        }

        int start = match(buf, 0, len);     // matches boundary

        if (start == -1) {

            // No boundary is found

            assert eof || len >= config.chunkSize;

            int chunkSize = eof ? len : config.chunkSize;

            if (eof) {

                done = true;

                throw new MIMEParsingException("Reached EOF, but there is no closing MIME boundary.");

            }

            return adjustBuf(chunkSize, len-chunkSize);

        }

        // Found boundary.

        // Is it at the start of a line ?

        int chunkLen = start;

        if (bol && start == 0) {

            // nothing to do

        } else if (start > 0 && (buf[start-1] == '\n' || buf[start-1] =='\r')) {

            --chunkLen;

            if (buf[start-1] == '\n' && start >1 && buf[start-2] == '\r') {

                --chunkLen;

            }

        } else {

           return adjustBuf(start+1, len-start-1);  // boundary is not at beginning of a line

        }

        if (start+bl+1 < len && buf[start+bl] == '-' && buf[start+bl+1] == '-') {

            state = STATE.END_PART;

            done = true;

            return adjustBuf(chunkLen, 0);

        }

        // Consider all the whitespace in boundary+whitespace+"\r\n"

        int lwsp = 0;

        for(int i=start+bl; i < len && (buf[i] == ' ' || buf[i] == '\t'); i++) {

            ++lwsp;

        }

        // Check for \n or \r\n in boundary+whitespace+"\n" or boundary+whitespace+"\r\n"

        if (start+bl+lwsp < len && buf[start+bl+lwsp] == '\n') {

            state = STATE.END_PART;

            return adjustBuf(chunkLen, len-start-bl-lwsp-1);

        } else if (start+bl+lwsp+1 < len && buf[start+bl+lwsp] == '\r' && buf[start+bl+lwsp+1] == '\n') {

            state = STATE.END_PART;

            return adjustBuf(chunkLen, len-start-bl-lwsp-2);

        } else if (start+bl+lwsp+1 < len) {

            return adjustBuf(chunkLen+1, len-chunkLen-1);       // boundary string in a part data

        } else if (eof) {

            done = true;

            throw new MIMEParsingException("Reached EOF, but there is no closing MIME boundary.");

        }

        // Some more data needed to determine if it is indeed a proper boundary

        return adjustBuf(chunkLen, len-chunkLen);

    }

    /**

     * Returns a chunk from the original buffer. A new buffer is

     * created with the remaining bytes.

     *

     * @param chunkSize create a chunk with these many bytes

     * @param remaining bytes from the end of the buffer that need to be copied to

     *        the beginning of the new buffer

     * @return chunk

     */

    private ByteBuffer adjustBuf(int chunkSize, int remaining) {

        assert buf != null;

        assert chunkSize >= 0;

        assert remaining >= 0;

        byte[] temp = buf;

        // create a new buf and adjust it without this chunk

        createBuf(remaining);

        System.arraycopy(temp, len-remaining, buf, 0, remaining);

        len = remaining;

        return ByteBuffer.wrap(temp, 0, chunkSize);

    }

    private void createBuf(int min) {

        buf = new byte[min < capacity ? capacity : min];

    }

    /**

     * Skips the preamble to find the first attachment part

     */

    private void skipPreamble() {

        while(true) {

            if (!eof) {

                fillBuf();

            }

            int start = match(buf, 0, len);     // matches boundary

            if (start == -1) {

                // No boundary is found

                if (eof) {

                    throw new MIMEParsingException("Missing start boundary");

                } else {

                    adjustBuf(len-bl+1, bl-1);

                    continue;

                }

            }

            if (start > config.chunkSize) {

                adjustBuf(start, len-start);

                continue;

            }

            // Consider all the whitespace boundary+whitespace+"\r\n"

            int lwsp = 0;

            for(int i=start+bl; i < len && (buf[i] == ' ' || buf[i] == '\t'); i++) {

                ++lwsp;

            }

            // Check for \n or \r\n

            if (start+bl+lwsp < len && (buf[start+bl+lwsp] == '\n' || buf[start+bl+lwsp] == '\r') ) {

                if (buf[start+bl+lwsp] == '\n') {

                    adjustBuf(start+bl+lwsp+1, len-start-bl-lwsp-1);

                    break;

                } else if (start+bl+lwsp+1 < len && buf[start+bl+lwsp+1] == '\n') {

                    adjustBuf(start+bl+lwsp+2, len-start-bl-lwsp-2);

                    break;

                }

            }

            adjustBuf(start+1, len-start-1);

        }

        if (LOGGER.isLoggable(Level.FINE)) {LOGGER.log(Level.FINE, "Skipped the preamble. buffer len={0}", len);}

    }

    private static byte[] getBytes(String s) {

        char [] chars= s.toCharArray();

        int size = chars.length;

        byte[] bytes = new byte[size];

        for (int i = 0; i < size;) {

            bytes[i] = (byte) chars[i++];

        }

        return bytes;

    }

        /**

     * Boyer-Moore search method. Copied from java.util.regex.Pattern.java

     *

     * Pre calculates arrays needed to generate the bad character

     * shift and the good suffix shift. Only the last seven bits

     * are used to see if chars match; This keeps the tables small

     * and covers the heavily used ASCII range, but occasionally

     * results in an aliased match for the bad character shift.

     */

    private void compileBoundaryPattern() {

        int i, j;

        // Precalculate part of the bad character shift

        // It is a table for where in the pattern each

        // lower 7-bit value occurs

        for (i = 0; i < bndbytes.length; i++) {

            bcs[bndbytes[i]&0x7F] = i + 1;

        }

        // Precalculate the good suffix shift

        // i is the shift amount being considered

NEXT:   for (i = bndbytes.length; i > 0; i--) {

            // j is the beginning index of suffix being considered

            for (j = bndbytes.length - 1; j >= i; j--) {

                // Testing for good suffix

                if (bndbytes[j] == bndbytes[j-i]) {

                    // src[j..len] is a good suffix

                    gss[j-1] = i;

                } else {

                    // No match. The array has already been

                    // filled up with correct values before.

                    continue NEXT;

                }

            }

            // This fills up the remaining of optoSft

            // any suffix can not have larger shift amount

            // then its sub-suffix. Why???

            while (j > 0) {

                gss[--j] = i;

            }

        }

        // Set the guard value because of unicode compression

        gss[bndbytes.length -1] = 1;

    }

    /**

     * Finds the boundary in the given buffer using Boyer-Moore algo.

     * Copied from java.util.regex.Pattern.java

     *

     * @param mybuf boundary to be searched in this mybuf

     * @param off start index in mybuf

     * @param len number of bytes in mybuf

     *

     * @return -1 if there is no match or index where the match starts

     */

    private int match(byte[] mybuf, int off, int len) {

        int last = len - bndbytes.length;

        // Loop over all possible match positions in text

NEXT:   while (off <= last) {

            // Loop over pattern from right to left

            for (int j = bndbytes.length - 1; j >= 0; j--) {

                byte ch = mybuf[off+j];

                if (ch != bndbytes[j]) {

                    // Shift search to the right by the maximum of the

                    // bad character shift and the good suffix shift

                    off += Math.max(j + 1 - bcs[ch&0x7F], gss[j]);

                    continue NEXT;

                }

            }

            // Entire pattern matched starting at off

            return off;

        }

        return -1;

    }

    /**

     * Fills the remaining buf to the full capacity

     */

    private void fillBuf() {

        if (LOGGER.isLoggable(Level.FINER)) {LOGGER.log(Level.FINER, "Before fillBuf() buffer len={0}", len);}

        assert !eof;

        while(len < buf.length) {

            int read;

            try {

                read = in.read(buf, len, buf.length-len);

            } catch(IOException ioe) {

                throw new MIMEParsingException(ioe);

            }

            if (read == -1) {

                eof = true;

                try {

                    if (LOGGER.isLoggable(Level.FINE)) {LOGGER.fine("Closing the input stream.");}

                    in.close();

                } catch(IOException ioe) {

                    throw new MIMEParsingException(ioe);

                }

                break;

            } else {

                len += read;

            }

        }

        if (LOGGER.isLoggable(Level.FINER)) {LOGGER.log(Level.FINER, "After fillBuf() buffer len={0}", len);}

    }

    private void doubleBuf() {

        byte[] temp = new byte[2*len];

        System.arraycopy(buf, 0, temp, 0, len);

        buf = temp;

        if (!eof) {

            fillBuf();

        }

    }

    class LineInputStream {

        private int offset;

        /*

         * Read a line containing only ASCII characters from the input

         * stream. A line is terminated by a CR or NL or CR-NL sequence.

         * A common error is a CR-CR-NL sequence, which will also terminate

         * a line.

         * The line terminator is not returned as part of the returned

         * String. Returns null if no data is available. <p>

         *

         * This class is similar to the deprecated

         * <code>DataInputStream.readLine()</code>

         */

        public String readLine() throws IOException {

            int hdrLen = 0;

            int lwsp = 0;

            while(offset+hdrLen < len) {

                if (buf[offset+hdrLen] == '\n') {

                    lwsp = 1;

                    break;

                }

                if (offset+hdrLen+1 == len) {

                    doubleBuf();

                }

                if (offset+hdrLen+1 >= len) {   // No more data in the stream

                    assert eof;

                    return null;

                }

                if (buf[offset+hdrLen] == '\r' && buf[offset+hdrLen+1] == '\n') {

                    lwsp = 2;

                    break;

                }

                ++hdrLen;

            }

            if (hdrLen == 0) {

                adjustBuf(offset+lwsp, len-offset-lwsp);

                return null;

            }

            String hdr = new String(buf, offset, hdrLen, HEADER_ENCODING);

            offset += hdrLen+lwsp;

            return hdr;

        }

    }

}