/*

 pathencode.c - efficient path name encoding

 Copyright 2012 Facebook

 This software may be used and distributed according to the terms of

 the GNU General Public License, incorporated herein by reference.

*/

#include <Python.h>

#include <assert.h>

#include <ctype.h>

#include <stdlib.h>

#include <string.h>

#include "util.h"

/* state machine for dir-encoding */

enum dir_state {

	DDOT,

	DH,

	DHGDI,

	DDEFAULT,

};

static inline void charcopy(char *dest, Py_ssize_t *destlen, size_t destsize,

                            char c)

{

	if (dest) {

		assert(*destlen < destsize);

		dest[*destlen] = c;

	}

	(*destlen)++;

}

static inline void memcopy(char *dest, Py_ssize_t *destlen, size_t destsize,

                           const void *src, Py_ssize_t len)

{

	if (dest) {

		assert(*destlen + len < destsize);

		memcpy((void *)&dest[*destlen], src, len);

	}

	*destlen += len;

}

static Py_ssize_t _encodedir(char *dest, size_t destsize,

                             const char *src, Py_ssize_t len)

{

	enum dir_state state = DDEFAULT;

	Py_ssize_t i = 0, destlen = 0;

	while (i < len) {

		switch (state) {

		case DDOT:

			switch (src[i]) {

			case 'd':

			case 'i':

				state = DHGDI;

				charcopy(dest, &destlen, destsize, src[i++]);

				break;

			case 'h':

				state = DH;

				charcopy(dest, &destlen, destsize, src[i++]);

				break;

			default:

				state = DDEFAULT;

				break;

			}

			break;

		case DH:

			if (src[i] == 'g') {

				state = DHGDI;

				charcopy(dest, &destlen, destsize, src[i++]);

			}

			else state = DDEFAULT;

			break;

		case DHGDI:

			if (src[i] == '/') {

				memcopy(dest, &destlen, destsize, ".hg", 3);

				charcopy(dest, &destlen, destsize, src[i++]);

			}

			state = DDEFAULT;

			break;

		case DDEFAULT:

			if (src[i] == '.')

				state = DDOT;

			charcopy(dest, &destlen, destsize, src[i++]);

			break;

		}

	}

	return destlen;

}

PyObject *encodedir(PyObject *self, PyObject *args)

{

	Py_ssize_t len, newlen;

	PyObject *pathobj, *newobj;

	char *path;

	if (!PyArg_ParseTuple(args, "O:encodedir", &pathobj))

		return NULL;

	if (PyString_AsStringAndSize(pathobj, &path, &len) == -1) {

		PyErr_SetString(PyExc_TypeError, "expected a string");

		return NULL;

	}

	newlen = len ? _encodedir(NULL, 0, path, len + 1) : 1;

	if (newlen == len + 1) {

		Py_INCREF(pathobj);

		return pathobj;

	}

	newobj = PyString_FromStringAndSize(NULL, newlen);

	if (newobj) {

		PyString_GET_SIZE(newobj)--;

		_encodedir(PyString_AS_STRING(newobj), newlen, path,

			   len + 1);

	}

	return newobj;

}