/***********************************************************
Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam,
The Netherlands.

                        All Rights Reserved

Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the names of Stichting Mathematisch
Centrum or CWI or Corporation for National Research Initiatives or
CNRI not be used in advertising or publicity pertaining to
distribution of the software without specific, written prior
permission.

While CWI is the initial source for this software, a modified version
is made available by the Corporation for National Research Initiatives
(CNRI) at the Internet address ftp://ftp.python.org.

STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH
CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.

******************************************************************/

/* Return the initial module search path. */
/* Used by DOS, OS/2, Windows 3.1, Windows 95/98, Windows NT. */

#include "Python.h"
#include "osdefs.h"

#ifdef MS_WIN32
#include <windows.h>
extern BOOL PyWin_IsWin32s();
#endif

#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>

#if HAVE_UNISTD_H
#include <unistd.h>
#endif /* HAVE_UNISTD_H */

/* Search in some common locations for the associated Python libraries.
 *
 * Py_GetPath() tries to return a sensible Python module search path.
 *
 * The approach is an adaptation for Windows of the strategy used in
 * ../Modules/getpath.c; it uses the Windows Registry as one of its
 * information sources.
 */

#ifndef LANDMARK
#define LANDMARK "lib\\string.py"
#endif

static char prefix[MAXPATHLEN+1];
static char progpath[MAXPATHLEN+1];
static char *module_search_path = NULL;


static int
is_sep(ch)	/* determine if "ch" is a separator character */
	char ch;
{
#ifdef ALTSEP
	return ch == SEP || ch == ALTSEP;
#else
	return ch == SEP;
#endif
}


static void
reduce(dir)
	char *dir;
{
	int i = strlen(dir);
	while (i > 0 && !is_sep(dir[i]))
		--i;
	dir[i] = '\0';
}
	

static int
exists(filename)
	char *filename;
{
	struct stat buf;
	return stat(filename, &buf) == 0;
}


static int
ismodule(filename)	/* Is module -- check for .pyc/.pyo too */
	char *filename;
{
	if (exists(filename))
		return 1;

	/* Check for the compiled version of prefix. */
	if (strlen(filename) < MAXPATHLEN) {
		strcat(filename, Py_OptimizeFlag ? "o" : "c");
		if (exists(filename))
			return 1;
	}
	return 0;
}


static void
join(buffer, stuff)
	char *buffer;
	char *stuff;
{
	int n, k;
	if (is_sep(stuff[0]))
		n = 0;
	else {
		n = strlen(buffer);
		if (n > 0 && !is_sep(buffer[n-1]) && n < MAXPATHLEN)
			buffer[n++] = SEP;
	}
	k = strlen(stuff);
	if (n + k > MAXPATHLEN)
		k = MAXPATHLEN - n;
	strncpy(buffer+n, stuff, k);
	buffer[n+k] = '\0';
}


static int
gotlandmark(landmark)
	char *landmark;
{
	int n, ok;

	n = strlen(prefix);
	join(prefix, landmark);
	ok = ismodule(prefix);
	prefix[n] = '\0';
	return ok;
}


static int
search_for_prefix(argv0_path, landmark)
	char *argv0_path;
	char *landmark;
{

	/* Search from argv0_path, until landmark is found */
	strcpy(prefix, argv0_path);
	do {
		if (gotlandmark(landmark))
			return 1;
		reduce(prefix);
	} while (prefix[0]);
	return 0;
}

#ifdef MS_WIN32

#ifndef BUILD_LANDMARK
#define BUILD_LANDMARK "PC\\getpathp.c"
#endif

#include "malloc.h" // for alloca - see comments below!
extern const char *PyWin_DLLVersionString; // a string loaded from the DLL at startup.


/* Load a PYTHONPATH value from the registry.
   Load from either HKEY_LOCAL_MACHINE or HKEY_CURRENT_USER.

   Returns NULL, or a pointer that should be freed.
*/

static char *
getpythonregpath(HKEY keyBase)
{
	HKEY newKey = 0;
	DWORD nameSize = 0;
	DWORD dataSize = 0;
	DWORD numEntries = 0;
	LONG rc;
	char *retval = NULL;
	char *dataBuf;
	const char keyPrefix[] = "Software\\Python\\PythonCore\\";
	const char keySuffix[] = "\\PythonPath";
	int versionLen;
	char *keyBuf;

	// Tried to use sysget("winver") but here is too early :-(
	versionLen = strlen(PyWin_DLLVersionString);
	// alloca == no free required, but memory only local to fn.
	// also no heap fragmentation!  Am I being silly?
	keyBuf = alloca(sizeof(keyPrefix)-1 + versionLen + sizeof(keySuffix)); // chars only, plus 1 NULL.
	// lots of constants here for the compiler to optimize away :-)
	memcpy(keyBuf, keyPrefix, sizeof(keyPrefix)-1);
	memcpy(keyBuf+sizeof(keyPrefix)-1, PyWin_DLLVersionString, versionLen);
	memcpy(keyBuf+sizeof(keyPrefix)-1+versionLen, keySuffix, sizeof(keySuffix)); // NULL comes with this one!

	rc=RegOpenKey(keyBase,
		      keyBuf,
		      &newKey);
	if (rc==ERROR_SUCCESS) {
		RegQueryInfoKey(newKey, NULL, NULL, NULL, NULL, NULL, NULL, 
		                &numEntries, &nameSize, &dataSize, NULL, NULL);
	}
	if (numEntries) {
		/* Loop over all subkeys. */
		/* Win32s doesnt know how many subkeys, so we do
		   it twice */
		char keyBuf[MAX_PATH+1];
		int index = 0;
		int off = 0;
		for(index=0;;index++) {
			long reqdSize = 0;
			DWORD rc = RegEnumKey(newKey,
					      index, keyBuf, MAX_PATH+1);
			if (rc) break;
			rc = RegQueryValue(newKey, keyBuf, NULL, &reqdSize);
			if (rc) break;
			dataSize += reqdSize + 1; /* 1 for the ";" */
		}
		dataBuf = malloc(dataSize+1);
		if (dataBuf==NULL)
			return NULL; /* pretty serious?  Raise error? */
		/* Now loop over, grabbing the paths.
		   Subkeys before main library */
		for(index=0;;index++) {
			int adjust;
			long reqdSize = dataSize;
			DWORD rc = RegEnumKey(newKey,
					      index, keyBuf,MAX_PATH+1);
			if (rc) break;
			rc = RegQueryValue(newKey,
					   keyBuf, dataBuf+off, &reqdSize);
			if (rc) break;
			if (reqdSize>1) {
				/* If Nothing, or only '\0' copied. */
				adjust = strlen(dataBuf+off);
				dataSize -= adjust;
				off += adjust;
				dataBuf[off++] = ';';
				dataBuf[off] = '\0';
				dataSize--;
			}
		}
		/* Additionally, win32s doesnt work as expected, so
		   the specific strlen() is required for 3.1. */
		rc = RegQueryValue(newKey, "", dataBuf+off, &dataSize);
		if (rc==ERROR_SUCCESS) {
			if (strlen(dataBuf)==0)
				free(dataBuf);
			else
				retval = dataBuf; /* caller will free */
		}
		else
			free(dataBuf);
	}

	if (newKey)
		RegCloseKey(newKey);
	return retval;
}
#endif /* MS_WIN32 */

static void
get_progpath()
{
	extern char *Py_GetProgramName();
	char *path = getenv("PATH");
	char *prog = Py_GetProgramName();

#ifdef MS_WIN32
	if (GetModuleFileName(NULL, progpath, MAXPATHLEN))
		return;
#endif
	if (prog == NULL || *prog == '\0')
		prog = "python";

	/* If there is no slash in the argv0 path, then we have to
	 * assume python is on the user's $PATH, since there's no
	 * other way to find a directory to start the search from.  If
	 * $PATH isn't exported, you lose.
	 */
#ifdef ALTSEP
	if (strchr(prog, SEP) || strchr(prog, ALTSEP))
#else
	if (strchr(prog, SEP))
#endif
		strcpy(progpath, prog);
	else if (path) {
		while (1) {
			char *delim = strchr(path, DELIM);

			if (delim) {
				int len = delim - path;
				strncpy(progpath, path, len);
				*(progpath + len) = '\0';
			}
			else
				strcpy(progpath, path);

			join(progpath, prog);
			if (exists(progpath))
				break;

			if (!delim) {
				progpath[0] = '\0';
				break;
			}
			path = delim + 1;
		}
	}
	else
		progpath[0] = '\0';
}

static void
calculate_path()
{
	char argv0_path[MAXPATHLEN+1];
	char *buf;
	int bufsz;
	char *pythonhome = Py_GetPythonHome();
	char *envpath = getenv("PYTHONPATH");

#ifdef MS_WIN32
	int skiphome = 0;
	char *machinepath = NULL;
	char *userpath = NULL;
#endif

	get_progpath();
	strcpy(argv0_path, progpath);
	reduce(argv0_path);
	if (pythonhome == NULL || *pythonhome == '\0') {
		if (search_for_prefix(argv0_path, LANDMARK))
			pythonhome = prefix;
		else
			pythonhome = NULL;
	}
	else
		strcpy(prefix, pythonhome);

	if (envpath && *envpath == '\0')
		envpath = NULL;


#ifdef MS_WIN32
	if (!gotlandmark(BUILD_LANDMARK)) {
		machinepath = getpythonregpath(HKEY_LOCAL_MACHINE);
		userpath = getpythonregpath(HKEY_CURRENT_USER);
	}
#endif

	/* We need to construct a path from the following parts.
	   (1) the PYTHONPATH environment variable, if set;
	   (2) for Win32, the machinepath and userpath, if set;
	   (3) the PYTHONPATH config macro, with the leading "."
	       of each component replaced with pythonhome, if set;
	   (4) the directory containing the executable (argv0_path).
	   The length calculation calculates #3 first.
	   Extra rules:
	   - If PYTHONHOME is set (in any way) item (2) is ignored.
	   - If registry values are used, (3) and (4) are ignored.
	*/

	/* Calculate size of return buffer */
	if (pythonhome != NULL) {
		char *p;
		bufsz = 1;	
		for (p = PYTHONPATH; *p; p++) {
			if (*p == DELIM)
				bufsz++; /* number of DELIM plus one */
		}
		bufsz *= strlen(pythonhome);
	}
	else
		bufsz = 0;
	bufsz += strlen(PYTHONPATH) + 1;
	bufsz += strlen(argv0_path) + 1;
#ifdef MS_WIN32
	if (userpath)
		bufsz += strlen(userpath) + 1;
	if (machinepath)
		bufsz += strlen(machinepath) + 1;
#endif
	if (envpath != NULL)
		bufsz += strlen(envpath) + 1;

	module_search_path = buf = malloc(bufsz);
	if (buf == NULL) {
		/* We can't exit, so print a warning and limp along */
		fprintf(stderr, "Can't malloc dynamic PYTHONPATH.\n");
		if (envpath) {
			fprintf(stderr, "Using environment $PYTHONPATH.\n");
			module_search_path = envpath;
		}
		else {
			fprintf(stderr, "Using default static path.\n");
			module_search_path = PYTHONPATH;
		}
#ifdef MS_WIN32
		if (machinepath)
			free(machinepath);
		if (userpath)
			free(userpath);
#endif /* MS_WIN32 */
		return;
	}

	if (envpath) {
		strcpy(buf, envpath);
		buf = strchr(buf, '\0');
		*buf++ = DELIM;
	}
#ifdef MS_WIN32
	if (userpath) {
		strcpy(buf, userpath);
		buf = strchr(buf, '\0');
		*buf++ = DELIM;
		free(userpath);
		skiphome = 1;
	}
	if (machinepath) {
		strcpy(buf, machinepath);
		buf = strchr(buf, '\0');
		*buf++ = DELIM;
		free(machinepath);
		skiphome = 1;
	}
	if (skiphome) {
		*buf = 0;
		return;
	}
#endif
	if (pythonhome == NULL) {
		strcpy(buf, PYTHONPATH);
		buf = strchr(buf, '\0');
	}
	else {
		char *p = PYTHONPATH;
		char *q;
		int n;
		for (;;) {
			q = strchr(p, DELIM);
			if (q == NULL)
				n = strlen(p);
			else
				n = q-p;
			if (p[0] == '.' && is_sep(p[1])) {
				strcpy(buf, pythonhome);
				buf = strchr(buf, '\0');
				p++;
				n--;
			}
			strncpy(buf, p, n);
			buf += n;
			if (q == NULL)
				break;
			*buf++ = DELIM;
			p = q+1;
		}
	}
	if (argv0_path) {
		*buf++ = DELIM;
		strcpy(buf, argv0_path);
		buf = strchr(buf, '\0');
	}
	*buf = '\0';
}


/* External interface */

char *
Py_GetPath()
{
	if (!module_search_path)
		calculate_path();
	return module_search_path;
}

char *
Py_GetPrefix()
{
	if (!module_search_path)
		calculate_path();
	return prefix;
}

char *
Py_GetExecPrefix()
{
	return Py_GetPrefix();
}

char *
Py_GetProgramFullPath()
{
	if (!module_search_path)
		calculate_path();
	return progpath;
}