/* The zstdw object.
 *
 * This is an rsyslog object wrapper around zstd.
 *
 * Copyright 2022 Rainer Gerhards and Adiscon GmbH.
 *
 * This file is part of the rsyslog runtime library.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *       -or-
 *       see COPYING.ASL20 in the source distribution
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "config.h"
#include <string.h>
#include <assert.h>
#include <zstd.h>

#include "rsyslog.h"
#include "errmsg.h"
#include "stream.h"
#include "module-template.h"
#include "obj.h"
#include "zstdw.h"

MODULE_TYPE_LIB
MODULE_TYPE_NOKEEP

/* static data */
DEFobjStaticHelpers


/* finish buffer, to be called before closing the zstd file. */
static rsRetVal
zstd_doCompressFinish(strm_t *pThis,
	rsRetVal (*strmPhysWrite)(strm_t *pThis, uchar *pBuf, size_t lenBuf) )
{
	size_t remaining = 0;
	DEFiRet;
	assert(pThis != NULL);

	if(!pThis->bzInitDone)
		goto done;

	char dummybuf; /* not sure if we can pass in NULL as buffer address in this special case */
	ZSTD_inBuffer input = { &dummybuf, 0, 0 };

	do {
		ZSTD_outBuffer output = { pThis->pZipBuf, pThis->sIOBufSize, 0 };
		remaining = ZSTD_compressStream2(pThis->zstd.cctx, &output , &input, ZSTD_e_end);
		if(ZSTD_isError(remaining)) {
			LogError(0, RS_RET_ZLIB_ERR,
				"error returned from ZSTD_compressStream2(): %s\n",
				ZSTD_getErrorName(remaining));
			ABORT_FINALIZE(RS_RET_ZLIB_ERR);
		}

		CHKiRet(strmPhysWrite(pThis, (uchar*)pThis->pZipBuf, output.pos));

	} while (remaining != 0);

finalize_it:
done:	RETiRet;
}


static rsRetVal
zstd_doStrmWrite(strm_t *pThis, uchar *const pBuf, const size_t lenBuf, const int bFlush,
	rsRetVal (*strmPhysWrite)(strm_t *pThis, uchar *pBuf, size_t lenBuf) )
{
	DEFiRet;
	assert(pThis != NULL);
	assert(pBuf != NULL);
	if(!pThis->bzInitDone) {
		pThis->zstd.cctx = (void*) ZSTD_createCCtx();
		if(pThis->zstd.cctx == NULL) {
			LogError(0, RS_RET_ZLIB_ERR, "error creating zstd context (ZSTD_createCCtx failed, "
				"that's all we know");
			ABORT_FINALIZE(RS_RET_ZLIB_ERR);
		}

		ZSTD_CCtx_setParameter(pThis->zstd.cctx, ZSTD_c_compressionLevel, pThis->iZipLevel);
		ZSTD_CCtx_setParameter(pThis->zstd.cctx, ZSTD_c_checksumFlag, 1);
		if(pThis->zstd.num_wrkrs > 0) {
			ZSTD_CCtx_setParameter(pThis->zstd.cctx, ZSTD_c_nbWorkers,
				pThis->zstd.num_wrkrs);
		}
		pThis->bzInitDone = RSTRUE;
	}

	/* now doing the compression */
	ZSTD_inBuffer input = { pBuf, lenBuf, 0 };

	// This following needs to be configurable? It's possibly sufficient to use e_flush
	// only, as this can also be controlled by veryRobustZip. However, testbench will than
	// not be able to check when all file lines are complete.
	ZSTD_EndDirective const mode = bFlush ? ZSTD_e_flush : ZSTD_e_continue;
	size_t remaining;
	do {
		ZSTD_outBuffer output = { pThis->pZipBuf, 128, 0 };
		remaining = ZSTD_compressStream2(pThis->zstd.cctx, &output , &input, mode);
		if(ZSTD_isError(remaining)) {
			LogError(0, RS_RET_ZLIB_ERR, "error returned from ZSTD_compressStream2(): %s",
				ZSTD_getErrorName(remaining));
			ABORT_FINALIZE(RS_RET_ZLIB_ERR);
		}

		CHKiRet(strmPhysWrite(pThis, (uchar*)pThis->pZipBuf, output.pos));

	} while ( mode == ZSTD_e_end ? (remaining != 0) : (input.pos != input.size));

finalize_it:
	if(pThis->bzInitDone && pThis->bVeryReliableZip) {
		zstd_doCompressFinish(pThis, strmPhysWrite);
	}
	RETiRet;
}

/* destruction of caller's zstd ressources */
static rsRetVal
zstd_Destruct(strm_t *const pThis)
{
	DEFiRet;
	assert(pThis != NULL);

	if(!pThis->bzInitDone)
		goto done;

	const int result = ZSTD_freeCCtx(pThis->zstd.cctx);
	if(ZSTD_isError(result)) {
		LogError(0, RS_RET_ZLIB_ERR, "error from ZSTD_freeCCtx(): %s",
			ZSTD_getErrorName(result));
	}

	pThis->bzInitDone = 0;
done:	RETiRet;
}


/* queryInterface function
 * rgerhards, 2008-03-05
 */
BEGINobjQueryInterface(zstdw)
CODESTARTobjQueryInterface(zstdw)
	if(pIf->ifVersion != zstdwCURR_IF_VERSION) { /* check for current version, increment on each change */
		ABORT_FINALIZE(RS_RET_INTERFACE_NOT_SUPPORTED);
	}
	pIf->doStrmWrite  = zstd_doStrmWrite;
	pIf->doCompressFinish  = zstd_doCompressFinish;
	pIf->Destruct  = zstd_Destruct;
finalize_it:
ENDobjQueryInterface(zstdw)


/* Initialize the zstdw class. Must be called as the very first method
 * before anything else is called inside this class.
 * rgerhards, 2008-02-19
 */
BEGINAbstractObjClassInit(zstdw, 1, OBJ_IS_LOADABLE_MODULE) /* class, version */
ENDObjClassInit(zstdw)


/* --------------- here now comes the plumbing that makes as a library module --------------- */


BEGINmodExit
CODESTARTmodExit
ENDmodExit


BEGINqueryEtryPt
CODESTARTqueryEtryPt
CODEqueryEtryPt_STD_LIB_QUERIES
ENDqueryEtryPt


BEGINmodInit()
CODESTARTmodInit
	*ipIFVersProvided = CURR_MOD_IF_VERSION; /* we only support the current interface specification */
	CHKiRet(zstdwClassInit(pModInfo));
ENDmodInit