/* Cell object implementation */

#include "Python.h"
#include "internal/mem.h"
#include "internal/pystate.h"

PyObject *
PyCell_New(PyObject *obj)
{
 PyCellObject *op;

 op = (PyCellObject *)PyObject_GC_New(PyCellObject, &PyCell_Type);
 if (op == NULL)
 return NULL;
 op->ob_ref = obj;
 Py_XINCREF(obj);

 _PyObject_GC_TRACK(op);
 return (PyObject *)op;
}

PyObject *
PyCell_Get(PyObject *op)
{
 if (!PyCell_Check(op)) {
 PyErr_BadInternalCall();
 return NULL;
 }
 Py_XINCREF(((PyCellObject*)op)->ob_ref);
 return PyCell_GET(op);
}

int
PyCell_Set(PyObject *op, PyObject *obj)
{
 PyObject* oldobj;
 if (!PyCell_Check(op)) {
 PyErr_BadInternalCall();
 return -1;
 }
 oldobj = PyCell_GET(op);
 Py_XINCREF(obj);
 PyCell_SET(op, obj);
 Py_XDECREF(oldobj);
 return 0;
}

static void
cell_dealloc(PyCellObject *op)
{
 _PyObject_GC_UNTRACK(op);
 Py_XDECREF(op->ob_ref);
 PyObject_GC_Del(op);
}

static PyObject *
cell_richcompare(PyObject *a, PyObject *b, int op)
{
 /* neither argument should be NULL, unless something's gone wrong */
 assert(a != NULL && b != NULL);

 /* both arguments should be instances of PyCellObject */
 if (!PyCell_Check(a) || !PyCell_Check(b)) {
 Py_RETURN_NOTIMPLEMENTED;
 }

 /* compare cells by contents; empty cells come before anything else */
 a = ((PyCellObject *)a)->ob_ref;
 b = ((PyCellObject *)b)->ob_ref;
 if (a != NULL && b != NULL)
 return PyObject_RichCompare(a, b, op);

 Py_RETURN_RICHCOMPARE(b == NULL, a == NULL, op);
}

static PyObject *
cell_repr(PyCellObject *op)
{
 if (op->ob_ref == NULL)
 return PyUnicode_FromFormat("<cell at %p: empty>", op);

 return PyUnicode_FromFormat("<cell at %p: %.80s object at %p>",
 op, op->ob_ref->ob_type->tp_name,
 op->ob_ref);
}

static int
cell_traverse(PyCellObject *op, visitproc visit, void *arg)
{
 Py_VISIT(op->ob_ref);
 return 0;
}

static int
cell_clear(PyCellObject *op)
{
 Py_CLEAR(op->ob_ref);
 return 0;
}

static PyObject *
cell_get_contents(PyCellObject *op, void *closure)
{
 if (op->ob_ref == NULL)
 {
 PyErr_SetString(PyExc_ValueError, "Cell is empty");
 return NULL;
 }
 Py_INCREF(op->ob_ref);
 return op->ob_ref;
}

static int
cell_set_contents(PyCellObject *op, PyObject *obj, void *Py_UNUSED(ignored))
{
 Py_XINCREF(obj);
 Py_XSETREF(op->ob_ref, obj);
 return 0;
}

static PyGetSetDef cell_getsetlist[] = {
 {"cell_contents", (getter)cell_get_contents,
 (setter)cell_set_contents, NULL},
 {NULL} /* sentinel */
};

PyTypeObject PyCell_Type = {
 PyVarObject_HEAD_INIT(&PyType_Type, 0)
 "cell",
 sizeof(PyCellObject),
 0,
 (destructor)cell_dealloc, /* tp_dealloc */
 0, /* tp_print */
 0, /* tp_getattr */
 0, /* tp_setattr */
 0, /* tp_reserved */
 (reprfunc)cell_repr, /* tp_repr */
 0, /* tp_as_number */
 0, /* tp_as_sequence */
 0, /* tp_as_mapping */
 0, /* tp_hash */
 0, /* tp_call */
 0, /* tp_str */
 PyObject_GenericGetAttr, /* tp_getattro */
 0, /* tp_setattro */
 0, /* tp_as_buffer */
 Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC, /* tp_flags */
 0, /* tp_doc */
 (traverseproc)cell_traverse, /* tp_traverse */
 (inquiry)cell_clear, /* tp_clear */
 cell_richcompare, /* tp_richcompare */
 0, /* tp_weaklistoffset */
 0, /* tp_iter */
 0, /* tp_iternext */
 0, /* tp_methods */
 0, /* tp_members */
 cell_getsetlist, /* tp_getset */
};