/*
 * PyGreSQL - a Python interface for the PostgreSQL database.
 *
 * Large object support - this file is part a of the C extension module.
 *
 * Copyright (c) 2020 by the PyGreSQL Development Team
 *
 * Please see the LICENSE.TXT file for specific restrictions.
 */

/* Deallocate large object. */
static void
large_dealloc(largeObject *self)
{
    if (self->lo_fd >= 0 && self->pgcnx->valid)
        lo_close(self->pgcnx->cnx, self->lo_fd);

    Py_XDECREF(self->pgcnx);
    PyObject_Del(self);
}

/* Return large object as string in human readable form. */
static PyObject *
large_str(largeObject *self)
{
    char str[80];
    sprintf(str, self->lo_fd >= 0 ?
            "Opened large object, oid %ld" :
            "Closed large object, oid %ld", (long) self->lo_oid);
    return PyStr_FromString(str);
}

/* Check validity of large object. */
static int
_check_lo_obj(largeObject *self, int level)
{
    if (!_check_cnx_obj(self->pgcnx))
        return 0;

    if (!self->lo_oid) {
        set_error_msg(IntegrityError, "Object is not valid (null oid)");
        return 0;
    }

    if (level & CHECK_OPEN) {
        if (self->lo_fd < 0) {
            PyErr_SetString(PyExc_IOError, "Object is not opened");
            return 0;
        }
    }

    if (level & CHECK_CLOSE) {
        if (self->lo_fd >= 0) {
            PyErr_SetString(PyExc_IOError, "Object is already opened");
            return 0;
        }
    }

    return 1;
}

/* Get large object attributes. */
static PyObject *
large_getattr(largeObject *self, PyObject *nameobj)
{
    const char *name = PyStr_AsString(nameobj);

    /* list postgreSQL large object fields */

    /* associated pg connection object */
    if (!strcmp(name, "pgcnx")) {
        if (_check_lo_obj(self, 0)) {
            Py_INCREF(self->pgcnx);
            return (PyObject *) (self->pgcnx);
        }
        PyErr_Clear();
        Py_INCREF(Py_None);
        return Py_None;
    }

    /* large object oid */
    if (!strcmp(name, "oid")) {
        if (_check_lo_obj(self, 0))
            return PyInt_FromLong(self->lo_oid);
        PyErr_Clear();
        Py_INCREF(Py_None);
        return Py_None;
    }

    /* error (status) message */
    if (!strcmp(name, "error"))
        return PyStr_FromString(PQerrorMessage(self->pgcnx->cnx));

    /* seeks name in methods (fallback) */
    return PyObject_GenericGetAttr((PyObject *) self, nameobj);
}

/* Get the list of large object attributes. */
static PyObject *
large_dir(largeObject *self, PyObject *noargs)
{
    PyObject *attrs;

    attrs = PyObject_Dir(PyObject_Type((PyObject *) self));
    PyObject_CallMethod(
        attrs, "extend", "[sss]", "oid", "pgcnx", "error");

    return attrs;
}

/* Open large object. */
static char large_open__doc__[] =
"open(mode) -- open access to large object with specified mode\n\n"
"The mode must be one of INV_READ, INV_WRITE (module level constants).\n";

static PyObject *
large_open(largeObject *self, PyObject *args)
{
    int mode, fd;

    /* gets arguments */
    if (!PyArg_ParseTuple(args, "i", &mode)) {
        PyErr_SetString(PyExc_TypeError,
                        "The open() method takes an integer argument");
        return NULL;
    }

    /* check validity */
    if (!_check_lo_obj(self, CHECK_CLOSE)) {
        return NULL;
    }

    /* opens large object */
    if ((fd = lo_open(self->pgcnx->cnx, self->lo_oid, mode)) == -1) {
        PyErr_SetString(PyExc_IOError, "Can't open large object");
        return NULL;
    }
    self->lo_fd = fd;

    /* no error : returns Py_None */
    Py_INCREF(Py_None);
    return Py_None;
}

/* Close large object. */
static char large_close__doc__[] =
"close() -- close access to large object data";

static PyObject *
large_close(largeObject *self, PyObject *noargs)
{
    /* checks validity */
    if (!_check_lo_obj(self, CHECK_OPEN)) {
        return NULL;
    }

    /* closes large object */
    if (lo_close(self->pgcnx->cnx, self->lo_fd)) {
        PyErr_SetString(PyExc_IOError, "Error while closing large object fd");
        return NULL;
    }
    self->lo_fd = -1;

    /* no error : returns Py_None */
    Py_INCREF(Py_None);
    return Py_None;
}

/* Read from large object. */
static char large_read__doc__[] =
"read(size) -- read from large object to sized string\n\n"
"Object must be opened in read mode before calling this method.\n";

static PyObject *
large_read(largeObject *self, PyObject *args)
{
    int size;
    PyObject *buffer;

    /* gets arguments */
    if (!PyArg_ParseTuple(args, "i", &size)) {
        PyErr_SetString(PyExc_TypeError,
                        "Method read() takes an integer argument");
        return NULL;
    }

    if (size <= 0) {
        PyErr_SetString(PyExc_ValueError,
                        "Method read() takes a positive integer as argument");
        return NULL;
    }

    /* checks validity */
    if (!_check_lo_obj(self, CHECK_OPEN)) {
        return NULL;
    }

    /* allocate buffer and runs read */
    buffer = PyBytes_FromStringAndSize((char *) NULL, size);

    if ((size = lo_read(self->pgcnx->cnx, self->lo_fd,
        PyBytes_AS_STRING((PyBytesObject *) (buffer)), (size_t) size)) == -1)
    {
        PyErr_SetString(PyExc_IOError, "Error while reading");
        Py_XDECREF(buffer);
        return NULL;
    }

    /* resize buffer and returns it */
    _PyBytes_Resize(&buffer, size);
    return buffer;
}

/* Write to large object. */
static char large_write__doc__[] =
"write(string) -- write sized string to large object\n\n"
"Object must be opened in read mode before calling this method.\n";

static PyObject *
large_write(largeObject *self, PyObject *args)
{
    char *buffer;
    int size;
    Py_ssize_t bufsize;

    /* gets arguments */
    if (!PyArg_ParseTuple(args, "s#", &buffer, &bufsize)) {
        PyErr_SetString(PyExc_TypeError,
                        "Method write() expects a sized string as argument");
        return NULL;
    }

    /* checks validity */
    if (!_check_lo_obj(self, CHECK_OPEN)) {
        return NULL;
    }

    /* sends query */
    if ((size = lo_write(self->pgcnx->cnx, self->lo_fd, buffer,
                         (size_t) bufsize)) != bufsize)
    {
        PyErr_SetString(PyExc_IOError, "Buffer truncated during write");
        return NULL;
    }

    /* no error : returns Py_None */
    Py_INCREF(Py_None);
    return Py_None;
}

/* Go to position in large object. */
static char large_seek__doc__[] =
"seek(offset, whence) -- move to specified position\n\n"
"Object must be opened before calling this method. The whence option\n"
"can be SEEK_SET, SEEK_CUR or SEEK_END (module level constants).\n";

static PyObject *
large_seek(largeObject *self, PyObject *args)
{
    /* offset and whence are initialized to keep compiler happy */
    int ret, offset = 0, whence = 0;

    /* gets arguments */
    if (!PyArg_ParseTuple(args, "ii", &offset, &whence)) {
        PyErr_SetString(PyExc_TypeError,
                        "Method lseek() expects two integer arguments");
        return NULL;
    }

    /* checks validity */
    if (!_check_lo_obj(self, CHECK_OPEN)) {
        return NULL;
    }

    /* sends query */
    if ((ret = lo_lseek(
        self->pgcnx->cnx, self->lo_fd, offset, whence)) == -1)
    {
        PyErr_SetString(PyExc_IOError, "Error while moving cursor");
        return NULL;
    }

    /* returns position */
    return PyInt_FromLong(ret);
}

/* Get large object size. */
static char large_size__doc__[] =
"size() -- return large object size\n\n"
"The object must be opened before calling this method.\n";

static PyObject *
large_size(largeObject *self, PyObject *noargs)
{
    int start, end;

    /* checks validity */
    if (!_check_lo_obj(self, CHECK_OPEN)) {
        return NULL;
    }

    /* gets current position */
    if ((start = lo_tell(self->pgcnx->cnx, self->lo_fd)) == -1) {
        PyErr_SetString(PyExc_IOError, "Error while getting current position");
        return NULL;
    }

    /* gets end position */
    if ((end = lo_lseek(self->pgcnx->cnx, self->lo_fd, 0, SEEK_END)) == -1) {
        PyErr_SetString(PyExc_IOError, "Error while getting end position");
        return NULL;
    }

    /* move back to start position */
    if ((start = lo_lseek(
        self->pgcnx->cnx, self->lo_fd, start, SEEK_SET)) == -1)
    {
        PyErr_SetString(PyExc_IOError,
                        "Error while moving back to first position");
        return NULL;
    }

    /* returns size */
    return PyInt_FromLong(end);
}

/* Get large object cursor position. */
static char large_tell__doc__[] =
"tell() -- give current position in large object\n\n"
"The object must be opened before calling this method.\n";

static PyObject *
large_tell(largeObject *self, PyObject *noargs)
{
    int start;

    /* checks validity */
    if (!_check_lo_obj(self, CHECK_OPEN)) {
        return NULL;
    }

    /* gets current position */
    if ((start = lo_tell(self->pgcnx->cnx, self->lo_fd)) == -1) {
        PyErr_SetString(PyExc_IOError, "Error while getting position");
        return NULL;
    }

    /* returns size */
    return PyInt_FromLong(start);
}

/* Export large object as unix file. */
static char large_export__doc__[] =
"export(filename) -- export large object data to specified file\n\n"
"The object must be closed when calling this method.\n";

static PyObject *
large_export(largeObject *self, PyObject *args)
{
    char *name;

    /* checks validity */
    if (!_check_lo_obj(self, CHECK_CLOSE)) {
        return NULL;
    }

    /* gets arguments */
    if (!PyArg_ParseTuple(args, "s", &name)) {
        PyErr_SetString(PyExc_TypeError,
                        "The method export() takes a filename as argument");
        return NULL;
    }

    /* runs command */
    if (lo_export(self->pgcnx->cnx, self->lo_oid, name) != 1) {
        PyErr_SetString(PyExc_IOError, "Error while exporting large object");
        return NULL;
    }

    Py_INCREF(Py_None);
    return Py_None;
}

/* Delete a large object. */
static char large_unlink__doc__[] =
"unlink() -- destroy large object\n\n"
"The object must be closed when calling this method.\n";

static PyObject *
large_unlink(largeObject *self, PyObject *noargs)
{
    /* checks validity */
    if (!_check_lo_obj(self, CHECK_CLOSE)) {
        return NULL;
    }

    /* deletes the object, invalidate it on success */
    if (lo_unlink(self->pgcnx->cnx, self->lo_oid) != 1) {
        PyErr_SetString(PyExc_IOError, "Error while unlinking large object");
        return NULL;
    }
    self->lo_oid = 0;

    Py_INCREF(Py_None);
    return Py_None;
}

/* Large object methods */
static struct PyMethodDef large_methods[] = {
    {"__dir__", (PyCFunction) large_dir,  METH_NOARGS, NULL},
    {"open", (PyCFunction) large_open, METH_VARARGS, large_open__doc__},
    {"close", (PyCFunction) large_close, METH_NOARGS, large_close__doc__},
    {"read", (PyCFunction) large_read, METH_VARARGS, large_read__doc__},
    {"write", (PyCFunction) large_write, METH_VARARGS, large_write__doc__},
    {"seek", (PyCFunction) large_seek, METH_VARARGS, large_seek__doc__},
    {"size", (PyCFunction) large_size, METH_NOARGS, large_size__doc__},
    {"tell", (PyCFunction) large_tell, METH_NOARGS, large_tell__doc__},
    {"export",(PyCFunction) large_export, METH_VARARGS, large_export__doc__},
    {"unlink",(PyCFunction) large_unlink, METH_NOARGS, large_unlink__doc__},
    {NULL, NULL}
};

static char large__doc__[] = "PostgreSQL large object";

/* Large object type definition */
static PyTypeObject largeType = {
    PyVarObject_HEAD_INIT(NULL, 0)
    "pg.LargeObject",              /* tp_name */
    sizeof(largeObject),           /* tp_basicsize */
    0,                             /* tp_itemsize */

    /* methods */
    (destructor) large_dealloc,    /* tp_dealloc */
    0,                             /* tp_print */
    0,                             /* tp_getattr */
    0,                             /* tp_setattr */
    0,                             /* tp_compare */
    0,                             /* tp_repr */
    0,                             /* tp_as_number */
    0,                             /* tp_as_sequence */
    0,                             /* tp_as_mapping */
    0,                             /* tp_hash */
    0,                             /* tp_call */
    (reprfunc) large_str,          /* tp_str */
    (getattrofunc) large_getattr,  /* tp_getattro */
    0,                             /* tp_setattro */
    0,                             /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT,            /* tp_flags */
    large__doc__,                  /* tp_doc */
    0,                             /* tp_traverse */
    0,                             /* tp_clear */
    0,                             /* tp_richcompare */
    0,                             /* tp_weaklistoffset */
    0,                             /* tp_iter */
    0,                             /* tp_iternext */
    large_methods,                 /* tp_methods */
};