/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
/*
 *  Authors: Jeffrey Stedfast <fejj@ximian.com>
 *
 *  Copyright (C) 1999-2008 Novell, Inc. (www.novell.com)
 *
 *  This program 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; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 */

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

#include <stdio.h>
#include <string.h>

#include <zlib.h>

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

#define CAMEL_MIME_FILTER_GZIP_GET_PRIVATE(obj) \
	(G_TYPE_INSTANCE_GET_PRIVATE \
	((obj), CAMEL_TYPE_MIME_FILTER_GZIP, CamelMimeFilterGZipPrivate))

/* rfc1952 */

enum {
	GZIP_FLAG_FTEXT     = (1 << 0),
	GZIP_FLAG_FHCRC     = (1 << 1),
	GZIP_FLAG_FEXTRA    = (1 << 2),
	GZIP_FLAG_FNAME     = (1 << 3),
	GZIP_FLAG_FCOMMENT  = (1 << 4),
	GZIP_FLAG_RESERVED0 = (1 << 5),
	GZIP_FLAG_RESERVED1 = (1 << 6),
	GZIP_FLAG_RESERVED2 = (1 << 7)
};

#define GZIP_FLAG_RESERVED (GZIP_FLAG_RESERVED0 | GZIP_FLAG_RESERVED1 | GZIP_FLAG_RESERVED2)

typedef union {
	guchar buf[10];
	struct {
		guint8 id1;
		guint8 id2;
		guint8 cm;
		guint8 flg;
		guint32 mtime;
		guint8 xfl;
		guint8 os;
	} v;
} gzip_hdr_t;

typedef union {
	struct {
		guint16 xlen;
		guint16 xlen_nread;
		guint16 crc16;

		guint8 got_hdr:1;
		guint8 is_valid:1;
		guint8 got_xlen:1;
		guint8 got_fname:1;
		guint8 got_fcomment:1;
		guint8 got_crc16:1;
	} unzip;
	struct {
		guint32 wrote_hdr:1;
	} zip;
} gzip_state_t;

struct _CamelMimeFilterGZipPrivate {

	CamelMimeFilterGZipMode mode;
	gint level;

	z_stream *stream;

	gzip_state_t state;
	gzip_hdr_t hdr;

	guint32 crc32;
	guint32 isize;
};

G_DEFINE_TYPE (CamelMimeFilterGZip, camel_mime_filter_gzip, CAMEL_TYPE_MIME_FILTER)

static void
gzip_filter (CamelMimeFilter *mime_filter,
             const gchar *in,
             gsize len,
             gsize prespace,
             gchar **out,
             gsize *outlen,
             gsize *outprespace,
             gint flush)
{
	CamelMimeFilterGZipPrivate *priv;
	gint retval;

	priv = CAMEL_MIME_FILTER_GZIP_GET_PRIVATE (mime_filter);

	if (!priv->state.zip.wrote_hdr) {
		priv->hdr.v.id1 = 31;
		priv->hdr.v.id2 = 139;
		priv->hdr.v.cm = Z_DEFLATED;
		priv->hdr.v.mtime = 0;
		priv->hdr.v.flg = 0;
		if (priv->level == Z_BEST_COMPRESSION)
			priv->hdr.v.xfl = 2;
		else if (priv->level == Z_BEST_SPEED)
			priv->hdr.v.xfl = 4;
		else
			priv->hdr.v.xfl = 0;
		priv->hdr.v.os = 255;

		camel_mime_filter_set_size (mime_filter, (len * 2) + 22, FALSE);

		memcpy (mime_filter->outbuf, priv->hdr.buf, 10);

		priv->stream->next_out = (Bytef *) mime_filter->outbuf + 10;
		priv->stream->avail_out = mime_filter->outsize - 10;

		priv->state.zip.wrote_hdr = TRUE;
	} else {
		camel_mime_filter_set_size (mime_filter, (len * 2) + 12, FALSE);

		priv->stream->next_out = (Bytef *) mime_filter->outbuf;
		priv->stream->avail_out = mime_filter->outsize;
	}

	priv->stream->next_in = (Bytef *) in;
	priv->stream->avail_in = len;

	do {
		/* FIXME: handle error cases? */
		if ((retval = deflate (priv->stream, flush)) != Z_OK)
			fprintf (stderr, "gzip: %d: %s\n", retval, priv->stream->msg);

		if (flush == Z_FULL_FLUSH) {
			gsize n;

			n = mime_filter->outsize - priv->stream->avail_out;
			camel_mime_filter_set_size (mime_filter, n + (priv->stream->avail_in * 2) + 12, TRUE);
			priv->stream->avail_out = mime_filter->outsize - n;
			priv->stream->next_out = (Bytef *) mime_filter->outbuf + n;

			if (priv->stream->avail_in == 0) {
				guint32 val;

				val = GUINT32_TO_LE (priv->crc32);
				memcpy (priv->stream->next_out, &val, 4);
				priv->stream->avail_out -= 4;
				priv->stream->next_out += 4;

				val = GUINT32_TO_LE (priv->isize);
				memcpy (priv->stream->next_out, &val, 4);
				priv->stream->avail_out -= 4;
				priv->stream->next_out += 4;

				break;
			}
		} else {
			if (priv->stream->avail_in > 0)
				camel_mime_filter_backup (mime_filter, (const gchar *) priv->stream->next_in, priv->stream->avail_in);

			break;
		}
	} while (1);

	priv->crc32 = crc32 (priv->crc32, (guchar *) in, len - priv->stream->avail_in);
	priv->isize += len - priv->stream->avail_in;

	*out = mime_filter->outbuf;
	*outlen = mime_filter->outsize - priv->stream->avail_out;
	*outprespace = mime_filter->outpre;
}

static void
gunzip_filter (CamelMimeFilter *mime_filter,
               const gchar *in,
               gsize len,
               gsize prespace,
               gchar **out,
               gsize *outlen,
               gsize *outprespace,
               gint flush)
{
	CamelMimeFilterGZipPrivate *priv;
	guint16 need, val;
	gint retval;

	priv = CAMEL_MIME_FILTER_GZIP_GET_PRIVATE (mime_filter);

	if (!priv->state.unzip.got_hdr) {
		if (len < 10) {
			camel_mime_filter_backup (mime_filter, in, len);
			return;
		}

		memcpy (priv->hdr.buf, in, 10);
		priv->state.unzip.got_hdr = TRUE;
		len -= 10;
		in += 10;

		priv->state.unzip.is_valid = (priv->hdr.v.id1 == 31 &&
					      priv->hdr.v.id2 == 139 &&
					      priv->hdr.v.cm == Z_DEFLATED);
	}

	if (!priv->state.unzip.is_valid)
		return;

	if (priv->hdr.v.flg & GZIP_FLAG_FEXTRA) {
		if (!priv->state.unzip.got_xlen) {
			if (len < 2) {
				camel_mime_filter_backup (mime_filter, in, len);
				return;
			}

			memcpy (&val, in, 2);
			priv->state.unzip.xlen = GUINT16_FROM_LE (val);
			priv->state.unzip.got_xlen = TRUE;
			len -= 2;
			in += 2;
		}

		if (priv->state.unzip.xlen_nread < priv->state.unzip.xlen) {
			need = priv->state.unzip.xlen - priv->state.unzip.xlen_nread;

			if (need < len) {
				priv->state.unzip.xlen_nread += need;
				len -= need;
				in += need;
			} else {
				priv->state.unzip.xlen_nread += len;
				return;
			}
		}
	}

	if ((priv->hdr.v.flg & GZIP_FLAG_FNAME) && !priv->state.unzip.got_fname) {
		while (*in && len > 0) {
			len--;
			in++;
		}

		if (*in == '\0' && len > 0) {
			priv->state.unzip.got_fname = TRUE;
			len--;
			in++;
		} else {
			return;
		}
	}

	if ((priv->hdr.v.flg & GZIP_FLAG_FCOMMENT) && !priv->state.unzip.got_fcomment) {
		while (*in && len > 0) {
			len--;
			in++;
		}

		if (*in == '\0' && len > 0) {
			priv->state.unzip.got_fcomment = TRUE;
			len--;
			in++;
		} else {
			return;
		}
	}

	if ((priv->hdr.v.flg & GZIP_FLAG_FHCRC) && !priv->state.unzip.got_crc16) {
		if (len < 2) {
			camel_mime_filter_backup (mime_filter, in, len);
			return;
		}

		memcpy (&val, in, 2);
		priv->state.unzip.crc16 = GUINT16_FROM_LE (val);
		len -= 2;
		in += 2;
	}

	if (len == 0)
		return;

	camel_mime_filter_set_size (mime_filter, (len * 2) + 12, FALSE);

	priv->stream->next_in = (Bytef *) in;
	priv->stream->avail_in = len - 8;

	priv->stream->next_out = (Bytef *) mime_filter->outbuf;
	priv->stream->avail_out = mime_filter->outsize;

	do {
		/* FIXME: handle error cases? */
		if ((retval = inflate (priv->stream, flush)) != Z_OK)
			fprintf (stderr, "gunzip: %d: %s\n", retval, priv->stream->msg);

		if (flush == Z_FULL_FLUSH) {
			gsize n;

			if (priv->stream->avail_in == 0) {
				/* FIXME: extract & compare calculated crc32 and isize values? */
				break;
			}

			n = mime_filter->outsize - priv->stream->avail_out;
			camel_mime_filter_set_size (mime_filter, n + (priv->stream->avail_in * 2) + 12, TRUE);
			priv->stream->avail_out = mime_filter->outsize - n;
			priv->stream->next_out = (Bytef *) mime_filter->outbuf + n;
		} else {
			priv->stream->avail_in += 8;

			if (priv->stream->avail_in > 0)
				camel_mime_filter_backup (mime_filter, (gchar *) priv->stream->next_in, priv->stream->avail_in);

			break;
		}
	} while (1);

	/* FIXME: if we keep this, we could check that the gzip'd
	 * stream is sane, but how would we tell our consumer if it
	 * was/wasn't? */
	/*priv->crc32 = crc32 (priv->crc32, in, len - priv->stream->avail_in - 8);
	  priv->isize += len - priv->stream->avail_in - 8;*/

	*out = mime_filter->outbuf;
	*outlen = mime_filter->outsize - priv->stream->avail_out;
	*outprespace = mime_filter->outpre;
}

static void
mime_filter_gzip_finalize (GObject *object)
{
	CamelMimeFilterGZipPrivate *priv;

	priv = CAMEL_MIME_FILTER_GZIP_GET_PRIVATE (object);

	if (priv->mode == CAMEL_MIME_FILTER_GZIP_MODE_ZIP)
		deflateEnd (priv->stream);
	else
		inflateEnd (priv->stream);

	g_free (priv->stream);

	/* Chain up to parent's finalize() method. */
	G_OBJECT_CLASS (camel_mime_filter_gzip_parent_class)->finalize (object);
}

static void
mime_filter_gzip_filter (CamelMimeFilter *mime_filter,
                         const gchar *in,
                         gsize len,
                         gsize prespace,
                         gchar **out,
                         gsize *outlen,
                         gsize *outprespace)
{
	CamelMimeFilterGZipPrivate *priv;

	priv = CAMEL_MIME_FILTER_GZIP_GET_PRIVATE (mime_filter);

	if (priv->mode == CAMEL_MIME_FILTER_GZIP_MODE_ZIP)
		gzip_filter (
			mime_filter, in, len, prespace,
			out, outlen, outprespace, Z_SYNC_FLUSH);
	else
		gunzip_filter (
			mime_filter, in, len, prespace,
			out, outlen, outprespace, Z_SYNC_FLUSH);
}

static void
mime_filter_gzip_complete (CamelMimeFilter *mime_filter,
                           const gchar *in,
                           gsize len,
                           gsize prespace,
                           gchar **out,
                           gsize *outlen,
                           gsize *outprespace)
{
	CamelMimeFilterGZipPrivate *priv;

	priv = CAMEL_MIME_FILTER_GZIP_GET_PRIVATE (mime_filter);

	if (priv->mode == CAMEL_MIME_FILTER_GZIP_MODE_ZIP)
		gzip_filter (
			mime_filter, in, len, prespace,
			out, outlen, outprespace, Z_FULL_FLUSH);
	else
		gunzip_filter (
			mime_filter, in, len, prespace,
			out, outlen, outprespace, Z_FULL_FLUSH);
}

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

	priv = CAMEL_MIME_FILTER_GZIP_GET_PRIVATE (mime_filter);

	memset (&priv->state, 0, sizeof (priv->state));

	if (priv->mode == CAMEL_MIME_FILTER_GZIP_MODE_ZIP)
		deflateReset (priv->stream);
	else
		inflateReset (priv->stream);

	priv->crc32 = crc32 (0, Z_NULL, 0);
	priv->isize = 0;
}

static void
camel_mime_filter_gzip_class_init (CamelMimeFilterGZipClass *class)
{
	GObjectClass *object_class;
	CamelMimeFilterClass *mime_filter_class;

	g_type_class_add_private (class, sizeof (CamelMimeFilterGZipPrivate));

	object_class = G_OBJECT_CLASS (class);
	object_class->finalize = mime_filter_gzip_finalize;

	mime_filter_class = CAMEL_MIME_FILTER_CLASS (class);
	mime_filter_class->filter = mime_filter_gzip_filter;
	mime_filter_class->complete = mime_filter_gzip_complete;
	mime_filter_class->reset = mime_filter_gzip_reset;
}

static void
camel_mime_filter_gzip_init (CamelMimeFilterGZip *mime_filter)
{
	mime_filter->priv = CAMEL_MIME_FILTER_GZIP_GET_PRIVATE (mime_filter);
	mime_filter->priv->stream = g_new0 (z_stream, 1);
	mime_filter->priv->crc32 = crc32 (0, Z_NULL, 0);
}

/**
 * camel_mime_filter_gzip_new:
 * @mode: zip or unzip
 * @level: compression level
 *
 * Creates a new gzip (or gunzip) filter.
 *
 * Returns: a new gzip (or gunzip) filter.
 **/
CamelMimeFilter *
camel_mime_filter_gzip_new (CamelMimeFilterGZipMode mode, gint level)
{
	CamelMimeFilter *new;
	CamelMimeFilterGZipPrivate *priv;
	gint retval;

	new = g_object_new (CAMEL_TYPE_MIME_FILTER_GZIP, NULL);
	priv = CAMEL_MIME_FILTER_GZIP_GET_PRIVATE (new);

	priv->mode = mode;
	priv->level = level;

	if (mode == CAMEL_MIME_FILTER_GZIP_MODE_ZIP)
		retval = deflateInit2 (priv->stream, level, Z_DEFLATED, -MAX_WBITS, MAX_MEM_LEVEL, Z_DEFAULT_STRATEGY);
	else
		retval = inflateInit2 (priv->stream, -MAX_WBITS);

	if (retval != Z_OK) {
		g_object_unref (new);
		return NULL;
	}

	return new;
}
