/*
    Copyright (C) 2008 Andreas Baumann <abaumann@yahoo.com>

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 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 General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "library/loader.h"

#include "errors.h"

#include "port/sys_internal.h"

#include "port/stdlib.h"		/* for malloc, free */
#include "port/stdio.h"			/* for snprintf */
#include "port/string.h"		/* for strncpy */

#include "i18n/gettext.h"		/* for i18n */

/* check for type of dynamic loading interface */
#if !defined _WIN32
#if !defined HAVE_DLFCN
#error Unkown dynamic loading interface on this platform, port first.
#endif
#endif

#if defined HAVE_DLFCN
#include <dlfcn.h>                      /* for dlopen. dlclose functions */

#if defined NEEDS_LINK_H
//#include <link.h>
#endif     

#endif

#if defined _WIN32
#define WIN32_MEAN_AND_LEAN
#include <windows.h>
#endif

#define INTERNAL_ERRBUF_SIZE 256

struct wolf_library_t {
#if defined HAVE_DLFCN
	void *handle;				/**< the OS handle for a library */
#endif
#if defined _WIN32
	HMODULE handle;				/**< the windows handle for a library */
#endif
	char errbuf[INTERNAL_ERRBUF_SIZE];	/**< internal buffer to hold the error message
						 *   we get with dlerror */
};

wolf_library_p wolf_library_load( const char *name, wolf_error_t *error ) {
	wolf_library_p l;
	int flags = 0;

	l = (struct wolf_library_t *)malloc( sizeof ( struct wolf_library_t ) );
	if( l == NULL ) {
		*error = WOLF_ERR_OUT_OF_MEMORY;
		return NULL;
	}

#if defined HAVE_DLFCN
	/* TODO: Apache has a flags variable and a direct parameter version, find out why..
	 * also make up our mind how many flags we should "leak" to the application layer
	 */
	flags = RTLD_NOW | RTLD_LOCAL;
	l->handle = dlopen( name, flags );
	if( l->handle == NULL ) {
		strncpy( l->errbuf, dlerror( ), INTERNAL_ERRBUF_SIZE );
		*error = WOLF_ERR_INTERNAL;
		return l;
	}
#endif /* defined HAVE_DLFCN */

#if defined _WIN32
	l->handle = LoadLibrary( name );
	if( l->handle == NULL ) {
		wolf_system_error_msg( l->errbuf, INTERNAL_ERRBUF_SIZE );		
		*error = WOLF_ERR_INTERNAL;
		return l;
	}
#endif /* defined _WIN32 */

	*error = WOLF_OK;
	return l;
}

wolf_error_t wolf_library_unload( wolf_library_p l ) {
#if !defined _WIN32
	int res = 0;
#else
	BOOL res = FALSE;
#endif

	if( l == NULL ) {
		return WOLF_OK;
	}

	if( l->handle == NULL ) {
		return WOLF_ERR_INVALID_STATE;
	}

#if defined HAVE_DLFCN
	res = dlclose( l->handle );
	if( res != 0 ) {
		strncpy( l->errbuf, dlerror( ), INTERNAL_ERRBUF_SIZE );
		return WOLF_ERR_INTERNAL;
	}
#endif /* defined HAVE_DLFCN */

#if defined _WIN32
	res = FreeLibrary( l->handle );
	if( !res ) {
		wolf_system_error_msg( l->errbuf, INTERNAL_ERRBUF_SIZE );		
		return WOLF_ERR_INTERNAL;
	}
#endif /* defined _WIN32 */

	free( l );
	l = NULL;

	return WOLF_OK;
}

char *wolf_library_error_msg(  const wolf_library_p library, char *buf, size_t buflen ) {
	strncpy( buf, library->errbuf, buflen );
	return buf;
}

WOLF_LIBRARY_FUNCPTR wolf_library_get( const wolf_library_p l, const char *name, wolf_error_t *error ) {
	WOLF_LIBRARY_FUNCPTR ret;
#if !defined _WIN32
	WOLF_LIBRARY_DLERROR_CONST char *err = NULL;
#endif /* !defined _WIN32 */

#if defined HAVE_DLFCN
	/* clear error state before calling dlsym, so that calling dlsym
	 * can return a NULL as value of a symbol
	 */
	(void)dlerror( ); 

	ret = dlsym( l->handle, name );
	err = dlerror( );
	if( err != NULL ) {
		strncpy( l->errbuf, err, INTERNAL_ERRBUF_SIZE );
		*error = WOLF_ERR_INTERNAL;
		return ret;
	}
#endif /* defined HAVE_DLFCN */

#if defined _WIN32
	ret = GetProcAddress( l->handle, name );
	if( ret == NULL ) {
		wolf_system_error_msg( l->errbuf, INTERNAL_ERRBUF_SIZE );
		*error = WOLF_ERR_INTERNAL;
		return ret;
	}
#endif /* defined _WIN32 */

	*error = WOLF_OK;	
	return ret;
}