#include <Python.h>

static PyObject *sha1_callback = NULL;

static void manipulate(uint8_t *key)
{
   uint64_t temp = key[0x38] << 56| 
      key[0x39] << 48|
      key[0x3a] << 40|
      key[0x3b] << 32|
      key[0x3c] << 24|
      key[0x3d] << 16|
      key[0x3e] <<  8|
      key[0x3f];
   temp++;
   key[0x38] = (temp >> 56) & 0xff;
   key[0x39] = (temp >> 48) & 0xff;
   key[0x3a] = (temp >> 40) & 0xff;
   key[0x3b] = (temp >> 32) & 0xff;
   key[0x3c] = (temp >> 24) & 0xff;
   key[0x3d] = (temp >> 16) & 0xff;
   key[0x3e] = (temp >>  8) & 0xff;
   key[0x3f] = (temp >>  0) & 0xff;
}

static PyObject* pkg_crypt(PyObject *self, PyObject *args)
{
   uint8_t *key, *input, *ret;
   int key_length, input_length, length;
   int remaining, i, offset=0;

   PyObject *arglist;
   PyObject *result;

   if (!PyArg_ParseTuple(args, "s#s#i", &key, &key_length, &input, &input_length, &length))
      return NULL;
   ret       = malloc(length);
   remaining = length;

   while (remaining > 0)
   {
      int outHash_length;
      uint8_t *outHash; 
      int bytes_to_dump = remaining;
      if (bytes_to_dump > 0x10) 
         bytes_to_dump = 0x10;

      arglist = Py_BuildValue("(s#)", key, 0x40);
      result  = PyObject_CallObject(sha1_callback, arglist);
      Py_DECREF(arglist);
      if (!result)
         return NULL;
      if (!PyArg_Parse(result, "s#", &outHash, &outHash_length))
         return NULL;

      for(i = 0; i < bytes_to_dump; i++)
      {
         ret[offset] = outHash[i] ^ input[offset];
         offset++;
      }
      Py_DECREF(result);
      manipulate(key);
      remaining -= bytes_to_dump;
   }

   /* Return the encrypted data */
   PyObject *py_ret = Py_BuildValue("s#", ret, length);
   free(ret);
   return py_ret;
}

static PyObject *register_sha1_callback(PyObject *self, PyObject *args)
{
   PyObject *result = NULL;
   PyObject *temp;

   if (PyArg_ParseTuple(args, "O:set_callback", &temp))
   {
      if (!PyCallable_Check(temp))
      {
         PyErr_SetString(PyExc_TypeError, "parameter must be callable");
         return NULL;
      }
      Py_XINCREF(temp);         /* Add a reference to new callback */
      Py_XDECREF(sha1_callback);  /* Dispose of previous callback */
      sha1_callback = temp;       /* Remember new callback */
      /* Boilerplate to return "None" */
      Py_INCREF(Py_None);
      result = Py_None;
   }
   return result;
}

static PyMethodDef cryptMethods[] = {
	{"pkgcrypt", pkg_crypt, METH_VARARGS, "C implementation of pkg.py's crypt function"},
	{"register_sha1_callback", register_sha1_callback, METH_VARARGS, "Register a callback to python's SHA1 function, so we don't have to bother with creating our own implementation."},
	{NULL, NULL, 0, NULL}
};

PyMODINIT_FUNC initpkgcrypt(void)
{
   (void) Py_InitModule("pkgcrypt", cryptMethods);
}


