/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
/*
 * Copyright (C) 1999-2008 Novell, Inc. (www.novell.com)
 *
 * This library is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation.
 *
 * This library 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 Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library. If not, see <http://www.gnu.org/licenses/>.
 *
 * Authors: Jeffrey Stedfast <fejj@ximian.com>
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <string.h>

#include "camel-mime-filter-yenc.h"

#define CAMEL_MIME_FILTER_YENC_GET_PRIVATE(obj) \
	(G_TYPE_INSTANCE_GET_PRIVATE \
	((obj), CAMEL_TYPE_MIME_FILTER_YENC, CamelMimeFilterYencPrivate))

struct _CamelMimeFilterYencPrivate {

	CamelMimeFilterYencDirection direction;

	gint part;

	gint state;
	guint32 pcrc;
	guint32 crc;
};

G_DEFINE_TYPE (CamelMimeFilterYenc, camel_mime_filter_yenc, CAMEL_TYPE_MIME_FILTER)

/* here we do all of the basic yEnc filtering */
static void
mime_filter_yenc_filter (CamelMimeFilter *mime_filter,
                         const gchar *in,
                         gsize len,
                         gsize prespace,
                         gchar **out,
                         gsize *outlen,
                         gsize *outprespace)
{
	CamelMimeFilterYencPrivate *priv;
	gsize newlen = 0;

	priv = CAMEL_MIME_FILTER_YENC_GET_PRIVATE (mime_filter);

	switch (priv->direction) {
		case CAMEL_MIME_FILTER_YENC_DIRECTION_ENCODE:
			/* won't go to more than 2 * (x + 2) + 62 */
			camel_mime_filter_set_size (
				mime_filter, (len + 2) * 2 + 62, FALSE);
			newlen = camel_yencode_step (
				(const guchar *) in, len,
				(guchar *) mime_filter->outbuf, &priv->state,
				&priv->pcrc, &priv->crc);
			g_return_if_fail (newlen <= (len + 2) * 2 + 62);
			break;
		case CAMEL_MIME_FILTER_YENC_DIRECTION_DECODE:
			if (!(priv->state & CAMEL_MIME_YDECODE_STATE_DECODE)) {
				const gchar *inptr, *inend;
				gsize left;

				inptr = in;
				inend = inptr + len;

				/* we cannot start decoding until we have found an =ybegin line */
				if (!(priv->state & CAMEL_MIME_YDECODE_STATE_BEGIN)) {
					while (inptr < inend) {
						left = inend - inptr;
						if (left < 8) {
							if (!strncmp (inptr, "=ybegin ", left))
								camel_mime_filter_backup (mime_filter, inptr, left);
							break;
						} else if (!strncmp (inptr, "=ybegin ", 8)) {
							for (in = inptr; inptr < inend && *inptr != '\n'; inptr++);
							if (inptr < inend) {
								inptr++;
								priv->state |= CAMEL_MIME_YDECODE_STATE_BEGIN;
								/* we can start ydecoding if the next line isn't
								 * a ypart... */
								in = inptr;
								len = inend - in;
							} else {
								/* we don't have enough... */
								camel_mime_filter_backup (mime_filter, in, left);
							}
							break;
						}

						/* go to the next line */
						while (inptr < inend && *inptr != '\n')
							inptr++;

						if (inptr < inend)
							inptr++;
					}
				}

				left = inend - inptr;
				if ((priv->state & CAMEL_MIME_YDECODE_STATE_BEGIN) && left > 0) {
					/* we have found an '=ybegin' line but we may yet have an "=ypart" line to
					 * yield before decoding the content */
					if (left < 7 && !strncmp (inptr, "=ypart ", left)) {
						camel_mime_filter_backup (mime_filter, inptr, left);
					} else if (!strncmp (inptr, "=ypart ", 7)) {
						for (in = inptr; inptr < inend && *inptr != '\n'; inptr++);
						if (inptr < inend) {
							inptr++;
							priv->state |= CAMEL_MIME_YDECODE_STATE_PART | CAMEL_MIME_YDECODE_STATE_DECODE;
							in = inptr;
							len = inend - in;
						} else {
							camel_mime_filter_backup (mime_filter, in, left);
						}
					} else {
						/* guess it doesn't have a =ypart line */
						priv->state |= CAMEL_MIME_YDECODE_STATE_DECODE;
					}
				}
			}

			if ((priv->state & CAMEL_MIME_YDECODE_STATE_DECODE) && !(priv->state & CAMEL_MIME_YDECODE_STATE_END)) {
				/* all yEnc headers have been found so we can now start decoding */
				camel_mime_filter_set_size (
					mime_filter, len + 3, FALSE);
				newlen = camel_ydecode_step (
					(const guchar *) in, len,
					(guchar *) mime_filter->outbuf,
					&priv->state, &priv->pcrc, &priv->crc);
				g_return_if_fail (newlen <= len + 3);
			} else {
				newlen = 0;
			}
			break;
	}

	*out = mime_filter->outbuf;
	*outlen = newlen;
	*outprespace = mime_filter->outpre;
}

static void
mime_filter_yenc_complete (CamelMimeFilter *mime_filter,
                           const gchar *in,
                           gsize len,
                           gsize prespace,
                           gchar **out,
                           gsize *outlen,
                           gsize *outprespace)
{
	CamelMimeFilterYencPrivate *priv;
	gsize newlen = 0;

	priv = CAMEL_MIME_FILTER_YENC_GET_PRIVATE (mime_filter);

	switch (priv->direction) {
	case CAMEL_MIME_FILTER_YENC_DIRECTION_ENCODE:
			/* won't go to more than 2 * (x + 2) + 62 */
			camel_mime_filter_set_size (
				mime_filter, (len + 2) * 2 + 62, FALSE);
			newlen = camel_yencode_close (
				(const guchar *) in, len,
				(guchar *) mime_filter->outbuf,
				&priv->state, &priv->pcrc, &priv->crc);
			g_return_if_fail (newlen <= (len + 2) * 2 + 62);
			break;
		case CAMEL_MIME_FILTER_YENC_DIRECTION_DECODE:
			if ((priv->state & CAMEL_MIME_YDECODE_STATE_DECODE) &&
				!(priv->state & CAMEL_MIME_YDECODE_STATE_END)) {
				/* all yEnc headers have been found so we
				 * can now start decoding */
				camel_mime_filter_set_size (
					mime_filter, len + 3, FALSE);
				newlen = camel_ydecode_step (
					(const guchar *) in, len,
					(guchar *) mime_filter->outbuf,
					&priv->state, &priv->pcrc, &priv->crc);
				g_return_if_fail (newlen <= len + 3);
			} else {
				newlen = 0;
			}
			break;
	}

	*out = mime_filter->outbuf;
	*outlen = newlen;
	*outprespace = mime_filter->outpre;
}

/* should this 'flush' outstanding state/data bytes? */
static void
mime_filter_yenc_reset (CamelMimeFilter *mime_filter)
{
	CamelMimeFilterYencPrivate *priv;

	priv = CAMEL_MIME_FILTER_YENC_GET_PRIVATE (mime_filter);

	switch (priv->direction) {
		case CAMEL_MIME_FILTER_YENC_DIRECTION_ENCODE:
			priv->state = CAMEL_MIME_YENCODE_STATE_INIT;
			break;
		case CAMEL_MIME_FILTER_YENC_DIRECTION_DECODE:
			priv->state = CAMEL_MIME_YDECODE_STATE_INIT;
			break;
	}

	priv->pcrc = CAMEL_MIME_YENCODE_CRC_INIT;
	priv->crc = CAMEL_MIME_YENCODE_CRC_INIT;
}

static void
camel_mime_filter_yenc_class_init (CamelMimeFilterYencClass *class)
{
	CamelMimeFilterClass *mime_filter_class;

	g_type_class_add_private (class, sizeof (CamelMimeFilterYencPrivate));

	mime_filter_class = CAMEL_MIME_FILTER_CLASS (class);
	mime_filter_class->filter = mime_filter_yenc_filter;
	mime_filter_class->complete = mime_filter_yenc_complete;
	mime_filter_class->reset = mime_filter_yenc_reset;
}

static void
camel_mime_filter_yenc_init (CamelMimeFilterYenc *filter)
{
	filter->priv = CAMEL_MIME_FILTER_YENC_GET_PRIVATE (filter);

	filter->priv->part = 0;
	filter->priv->pcrc = CAMEL_MIME_YENCODE_CRC_INIT;
	filter->priv->crc = CAMEL_MIME_YENCODE_CRC_INIT;
}

/**
 * camel_mime_filter_yenc_new:
 * @direction: encode direction
 *
 * Create a new #CamelMimeFilterYenc filter object.
 *
 * Returns: a new #CamelMimeFilterYenc object
 **/
CamelMimeFilter *
camel_mime_filter_yenc_new (CamelMimeFilterYencDirection direction)
{
	CamelMimeFilter *filter;
	CamelMimeFilterYencPrivate *priv;

	filter = g_object_new (CAMEL_TYPE_MIME_FILTER_YENC, NULL);
	priv = CAMEL_MIME_FILTER_YENC_GET_PRIVATE (filter);

	priv->direction = direction;

	switch (direction) {
		case CAMEL_MIME_FILTER_YENC_DIRECTION_ENCODE:
			priv->state = CAMEL_MIME_YENCODE_STATE_INIT;
			break;
		case CAMEL_MIME_FILTER_YENC_DIRECTION_DECODE:
			priv->state = CAMEL_MIME_YDECODE_STATE_INIT;
			break;
		default:
			g_warn_if_reached ();
	}

	return filter;
}

/**
 * camel_mime_filter_yenc_set_state:
 * @yenc: a #CamelMimeFilterYenc object
 * @state: encode/decode state
 *
 * Sets the current state of the yencoder/ydecoder
 **/
void
camel_mime_filter_yenc_set_state (CamelMimeFilterYenc *yenc,
                                  gint state)
{
	g_return_if_fail (CAMEL_IS_MIME_FILTER_YENC (yenc));

	yenc->priv->state = state;
}

/**
 * camel_mime_filter_yenc_set_crc:
 * @yenc: a #CamelMimeFilterYenc object
 * @crc: crc32 value
 *
 * Sets the current crc32 value on the yEnc filter @yenc to @crc.
 **/
void
camel_mime_filter_yenc_set_crc (CamelMimeFilterYenc *yenc,
                                guint32 crc)
{
	g_return_if_fail (CAMEL_IS_MIME_FILTER_YENC (yenc));

	yenc->priv->crc = crc;
}

/**
 * camel_mime_filter_yenc_get_pcrc:
 * @yenc: a #CamelMimeFilterYenc object
 *
 * Get the computed part crc or (#guint32) %-1 on fail.
 *
 * Returns: the computed part crc or (#guint32) %-1 on fail.
 **/
guint32
camel_mime_filter_yenc_get_pcrc (CamelMimeFilterYenc *yenc)
{
	g_return_val_if_fail (CAMEL_IS_MIME_FILTER_YENC (yenc), -1);

	return CAMEL_MIME_YENCODE_CRC_FINAL (yenc->priv->pcrc);
}

/**
 * camel_mime_filter_yenc_get_crc:
 * @yenc: a #CamelMimeFiletrYenc object
 *
 * Get the computed crc or (#guint32) -1 on fail.
 *
 * Returns: the computed crc or (#guint32) -1 on fail.
 **/
guint32
camel_mime_filter_yenc_get_crc (CamelMimeFilterYenc *yenc)
{
	g_return_val_if_fail (CAMEL_IS_MIME_FILTER_YENC (yenc), -1);

	return CAMEL_MIME_YENCODE_CRC_FINAL (yenc->priv->crc);
}

static const gint yenc_crc_table[256] = {
	0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
	0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
	0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
	0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
	0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
	0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
	0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
	0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
	0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
	0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
	0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
	0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
	0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
	0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
	0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
	0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
	0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
	0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
	0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
	0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
	0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
	0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
	0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
	0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
	0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
	0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
	0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
	0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
	0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
	0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
	0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
	0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
};

#define yenc_crc_add(crc, c) (yenc_crc_table[(((gint) (crc)) ^ ((guchar) (c))) & 0xff] ^ ((((gint) (crc)) >> 8) & 0x00ffffff))

#define YENC_NEWLINE_ESCAPE (CAMEL_MIME_YDECODE_STATE_EOLN | CAMEL_MIME_YDECODE_STATE_ESCAPE)

/**
 * camel_ydecode_step:
 * @in: input buffer
 * @inlen: input buffer length
 * @out: output buffer
 * @state: ydecode state
 * @pcrc: part crc state
 * @crc: crc state
 *
 * Performs a 'decode step' on a chunk of yEncoded data of length
 * @inlen pointed to by @in and writes to @out. Assumes the =ybegin
 * and =ypart lines have already been stripped off.
 *
 * To get the crc32 value of the part, use #CAMEL_MIME_YENCODE_CRC_FINAL
 * (@pcrc). If there are more parts, you should reuse @crc without
 * re-initializing. Once all parts have been decoded, you may get the
 * combined crc32 value of all the parts using #CAMEL_MIME_YENCODE_CRC_FINAL
 * (@crc).
 *
 * Returns: the number of bytes decoded
 **/
gsize
camel_ydecode_step (const guchar *in,
                    gsize inlen,
                    guchar *out,
                    gint *state,
                    guint32 *pcrc,
                    guint32 *crc)
{
	register const guchar *inptr;
	register guchar *outptr;
	const guchar *inend;
	guchar ch;
	gint ystate;

	if (*state & CAMEL_MIME_YDECODE_STATE_END)
		return 0;

	ystate = *state;

	inend = in + inlen;
	outptr = out;

	inptr = in;
	while (inptr < inend) {
		ch = *inptr++;

		if ((ystate & YENC_NEWLINE_ESCAPE) == YENC_NEWLINE_ESCAPE) {
			ystate &= ~CAMEL_MIME_YDECODE_STATE_EOLN;

			if (ch == 'y') {
				/* we probably have a =yend here */
				ystate |= CAMEL_MIME_YDECODE_STATE_END;
				break;
			}
		}

		if (ch == '\n') {
			ystate |= CAMEL_MIME_YDECODE_STATE_EOLN;
			continue;
		}

		if (ystate & CAMEL_MIME_YDECODE_STATE_ESCAPE) {
			ystate &= ~CAMEL_MIME_YDECODE_STATE_ESCAPE;
			ch -= 64;
		} else if (ch == '=') {
			ystate |= CAMEL_MIME_YDECODE_STATE_ESCAPE;
			continue;
		}

		ystate &= ~CAMEL_MIME_YDECODE_STATE_EOLN;

		*outptr++ = ch -= 42;

		*pcrc = yenc_crc_add (*pcrc, ch);
		*crc = yenc_crc_add (*crc, ch);
	}

	*state = ystate;

	return outptr - out;
}

/**
 * camel_yencode_step:
 * @in: input buffer
 * @inlen: input buffer length
 * @out: output buffer
 * @state: yencode state
 * @pcrc: part crc state
 * @crc: crc state
 *
 * Performs an yEncode 'encode step' on a chunk of raw data of length
 * @inlen pointed to by @in and writes to @out.
 *
 * @state should be initialized to #CAMEL_MIME_YENCODE_STATE_INIT before
 * beginning making the first call to this function. Subsequent calls
 * should reuse @state.
 *
 * Along the same lines, @pcrc and @crc should be initialized to
 * #CAMEL_MIME_YENCODE_CRC_INIT before using.
 *
 * Returns: the number of bytes encoded
 **/
gsize
camel_yencode_step (const guchar *in,
                    gsize inlen,
                    guchar *out,
                    gint *state,
                    guint32 *pcrc,
                    guint32 *crc)
{
	register const guchar *inptr;
	register guchar *outptr;
	const guchar *inend;
	register gint already;
	guchar ch;

	inend = in + inlen;
	outptr = out;

	already = *state;

	inptr = in;
	while (inptr < inend) {
		ch = (*inptr++);

		*pcrc = yenc_crc_add (*pcrc, ch);
		*crc = yenc_crc_add (*crc, ch);

		ch += 42;

		if (ch == '\0' || ch == '\t' || ch == '\r' || ch == '\n' || ch == '=') {
			*outptr++ = '=';
			*outptr++ = ch + 64;
			already += 2;
		} else {
			*outptr++ = ch;
			already++;
		}

		if (already >= 128) {
			*outptr++ = '\n';
			already = 0;
		}
	}

	*state = already;

	return outptr - out;
}

/**
 * camel_yencode_close:
 * @in: input buffer
 * @inlen: input buffer length
 * @out: output buffer
 * @state: yencode state
 * @pcrc: part crc state
 * @crc: crc state
 *
 * Call this function when finished encoding data with
 * camel_yencode_step() to flush off the remaining state.
 *
 * #CAMEL_MIME_YENCODE_CRC_FINAL (@pcrc) will give you the crc32 of the
 * encoded "part". If there are more "parts" to encode, you should
 * re-use @crc when encoding the next "parts" and then use
 * #CAMEL_MIME_YENCODE_CRC_FINAL (@crc) to get the combined crc32 value of
 * all the parts.
 *
 * Returns: the number of bytes encoded.
 **/
gsize
camel_yencode_close (const guchar *in,
                     gsize inlen,
                     guchar *out,
                     gint *state,
                     guint32 *pcrc,
                     guint32 *crc)
{
	register guchar *outptr;

	outptr = out;

	if (inlen)
		outptr += camel_yencode_step (in, inlen, out, state, pcrc, crc);

	if (*state)
		*outptr++ = '\n';

	*state = CAMEL_MIME_YENCODE_STATE_INIT;

	return outptr - out;
}