/* XSLT processing functions (requiring libxslt) */
/* John Gray, for Torchbox 2003-04-01 */

#include "postgres.h"
#include "fmgr.h"
#include "executor/spi.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "utils/xml.h"

#ifdef USE_LIBXSLT

/* libxml includes */

#include <libxml/xpath.h>
#include <libxml/tree.h>
#include <libxml/xmlmemory.h>

/* libxslt includes */

#include <libxslt/xslt.h>
#include <libxslt/xsltInternals.h>
#include <libxslt/security.h>
#include <libxslt/transform.h>
#include <libxslt/xsltutils.h>

#endif /* USE_LIBXSLT */


/* externally accessible functions */

Datum		xslt_process(PG_FUNCTION_ARGS);

#ifdef USE_LIBXSLT

/* declarations to come from xpath.c */
extern void pgxml_parser_init(void);

/* local defs */
static void parse_params(const char **params, text *paramstr);

#define MAXPARAMS 20			/* must be even, see parse_params() */

#define GET_STR(textp) DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(textp)))

#endif /* USE_LIBXSLT */


PG_FUNCTION_INFO_V1(xslt_process);

Datum
xslt_process(PG_FUNCTION_ARGS)
{
#ifdef USE_LIBXSLT

	const char *params[MAXPARAMS + 1];	/* +1 for the terminator */
	xsltStylesheetPtr stylesheet = NULL;
	xmlDocPtr	doctree;
	xmlDocPtr	restree;
	xmlDocPtr	ssdoc;
	xsltSecurityPrefsPtr xslt_sec_prefs;
	bool		xslt_sec_prefs_error;
	xsltTransformContextPtr xslt_ctxt;
	xmlChar    *resstr;
	int			resstat;
	int			reslen;

	text	   *doct = PG_GETARG_TEXT_P(0);
	text	   *ssheet = PG_GETARG_TEXT_P(1);
	text	   *paramstr;
	text	   *tres;

	if (fcinfo->nargs == 3)
	{
		paramstr = PG_GETARG_TEXT_P(2);
		parse_params(params, paramstr);
	}
	else
		/* No parameters */
		params[0] = NULL;

	/* Setup parser */
	pgxml_parser_init();

	/* Parse document */
	doctree = xmlParseMemory((char *) VARDATA(doct),
							 VARSIZE(doct) - VARHDRSZ);

	if (doctree == NULL)
		xml_ereport(ERROR, ERRCODE_EXTERNAL_ROUTINE_EXCEPTION,
					"error parsing XML document");

	/* Same for stylesheet */
	ssdoc = xmlParseMemory((char *) VARDATA(ssheet),
						   VARSIZE(ssheet) - VARHDRSZ);

	if (ssdoc == NULL)
	{
		xmlFreeDoc(doctree);
		xml_ereport(ERROR, ERRCODE_EXTERNAL_ROUTINE_EXCEPTION,
					"error parsing stylesheet as XML document");
	}

	/* After this call we need not free ssdoc separately */
	stylesheet = xsltParseStylesheetDoc(ssdoc);

	if (stylesheet == NULL)
	{
		xmlFreeDoc(doctree);
		xsltCleanupGlobals();
		xml_ereport(ERROR, ERRCODE_EXTERNAL_ROUTINE_EXCEPTION,
					"failed to parse stylesheet");
	}

	xslt_ctxt = xsltNewTransformContext(stylesheet, doctree);

	xslt_sec_prefs_error = false;
	if ((xslt_sec_prefs = xsltNewSecurityPrefs()) == NULL)
		xslt_sec_prefs_error = true;

	if (xsltSetSecurityPrefs(xslt_sec_prefs, XSLT_SECPREF_READ_FILE,
							 xsltSecurityForbid) != 0)
		xslt_sec_prefs_error = true;
	if (xsltSetSecurityPrefs(xslt_sec_prefs, XSLT_SECPREF_WRITE_FILE,
							 xsltSecurityForbid) != 0)
		xslt_sec_prefs_error = true;
	if (xsltSetSecurityPrefs(xslt_sec_prefs, XSLT_SECPREF_CREATE_DIRECTORY,
							 xsltSecurityForbid) != 0)
		xslt_sec_prefs_error = true;
	if (xsltSetSecurityPrefs(xslt_sec_prefs, XSLT_SECPREF_READ_NETWORK,
							 xsltSecurityForbid) != 0)
		xslt_sec_prefs_error = true;
	if (xsltSetSecurityPrefs(xslt_sec_prefs, XSLT_SECPREF_WRITE_NETWORK,
							 xsltSecurityForbid) != 0)
		xslt_sec_prefs_error = true;
	if (xsltSetCtxtSecurityPrefs(xslt_sec_prefs, xslt_ctxt) != 0)
		xslt_sec_prefs_error = true;

	if (xslt_sec_prefs_error)
	{
		xsltFreeStylesheet(stylesheet);
		xmlFreeDoc(doctree);
		xsltFreeSecurityPrefs(xslt_sec_prefs);
		xsltFreeTransformContext(xslt_ctxt);
		xsltCleanupGlobals();
		xml_ereport(ERROR, ERRCODE_EXTERNAL_ROUTINE_EXCEPTION,
					"could not set libxslt security preferences");
	}

	restree = xsltApplyStylesheetUser(stylesheet, doctree, params,
									  NULL, NULL, xslt_ctxt);

	if (restree == NULL)
	{
		xsltFreeStylesheet(stylesheet);
		xmlFreeDoc(doctree);
		xsltFreeSecurityPrefs(xslt_sec_prefs);
		xsltFreeTransformContext(xslt_ctxt);
		xsltCleanupGlobals();
		xml_ereport(ERROR, ERRCODE_EXTERNAL_ROUTINE_EXCEPTION,
					"failed to apply stylesheet");
	}

	resstat = xsltSaveResultToString(&resstr, &reslen, restree, stylesheet);

	xsltFreeStylesheet(stylesheet);
	xmlFreeDoc(restree);
	xmlFreeDoc(doctree);
	xsltFreeSecurityPrefs(xslt_sec_prefs);
	xsltFreeTransformContext(xslt_ctxt);

	xsltCleanupGlobals();

	/* XXX this is pretty dubious, really ought to throw error instead */
	if (resstat < 0)
		PG_RETURN_NULL();

	tres = palloc(reslen + VARHDRSZ);
	memcpy(VARDATA(tres), resstr, reslen);
	SET_VARSIZE(tres, reslen + VARHDRSZ);

	if (resstr)
		xmlFree(resstr);

	PG_RETURN_TEXT_P(tres);

#else /* !USE_LIBXSLT */

	ereport(ERROR,
			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
			 errmsg("xslt_process() is not available without libxslt")));
	PG_RETURN_NULL();

#endif /* USE_LIBXSLT */
}

#ifdef USE_LIBXSLT

static void
parse_params(const char **params, text *paramstr)
{
	char	   *pos;
	char	   *pstr;
	int			i;
	char	   *nvsep = "=";
	char	   *itsep = ",";

	pstr = GET_STR(paramstr);

	pos = pstr;

	for (i = 0; i < MAXPARAMS; i++)
	{
		params[i] = pos;
		pos = strstr(pos, nvsep);
		if (pos != NULL)
		{
			*pos = '\0';
			pos++;
		}
		else
		{
			/* No equal sign, so ignore this "parameter" */
			/* We'll reset params[i] to NULL below the loop */
			break;
		}
		/* Value */
		i++;
		/* since MAXPARAMS is even, we still have i < MAXPARAMS */
		params[i] = pos;
		pos = strstr(pos, itsep);
		if (pos != NULL)
		{
			*pos = '\0';
			pos++;
		}
		else
		{
			i++;
			break;
		}
	}

	params[i] = NULL;
}

#endif /* USE_LIBXSLT */