/*###########################################################################
 #
 # Copyright (c) 2003 Zope Foundation and Contributors.
 # All Rights Reserved.
 #
 # This software is subject to the provisions of the Zope Public License,
 # Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
 # THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
 # WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 # WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
 # FOR A PARTICULAR PURPOSE.
 #
 ############################################################################*/

#include "Python.h"
#include "structmember.h"

#define TYPE(O) ((PyTypeObject*)(O))
#define OBJECT(O) ((PyObject*)(O))
#define CLASSIC(O) ((PyClassObject*)(O))
#ifndef PyVarObject_HEAD_INIT
#define PyVarObject_HEAD_INIT(a, b) PyObject_HEAD_INIT(a) b,
#endif
#ifndef Py_TYPE
#define Py_TYPE(o) ((o)->ob_type)
#endif

#if PY_MAJOR_VERSION >= 3
#define PY3K
#endif

static PyObject *str__dict__, *str__implemented__, *strextends;
static PyObject *BuiltinImplementationSpecifications, *str__provides__;
static PyObject *str__class__, *str__providedBy__;
static PyObject *empty, *fallback, *str_implied, *str_cls, *str_implements;
static PyObject *str__conform__, *str_call_conform, *adapter_hooks;
static PyObject *str_uncached_lookup, *str_uncached_lookupAll;
static PyObject *str_uncached_subscriptions;
static PyObject *str_registry, *strro, *str_generation, *strchanged;

static PyTypeObject *Implements;

static int imported_declarations = 0;

static int
import_declarations(void)
{
  PyObject *declarations, *i;

  declarations = PyImport_ImportModule("zope.interface.declarations");
  if (declarations == NULL)
    return -1;

  BuiltinImplementationSpecifications = PyObject_GetAttrString(
                    declarations, "BuiltinImplementationSpecifications");
  if (BuiltinImplementationSpecifications == NULL)
    return -1;

  empty = PyObject_GetAttrString(declarations, "_empty");
  if (empty == NULL)
    return -1;

  fallback = PyObject_GetAttrString(declarations, "implementedByFallback");
  if (fallback == NULL)
    return -1;



  i = PyObject_GetAttrString(declarations, "Implements");
  if (i == NULL)
    return -1;

  if (! PyType_Check(i))
    {
      PyErr_SetString(PyExc_TypeError,
                      "zope.interface.declarations.Implements is not a type");
      return -1;
    }

  Implements = (PyTypeObject *)i;

  Py_DECREF(declarations);

  imported_declarations = 1;
  return 0;
}

static PyTypeObject SpecType;   /* Forward */

static PyObject *
implementedByFallback(PyObject *cls)
{
  if (imported_declarations == 0 && import_declarations() < 0)
    return NULL;

  return PyObject_CallFunctionObjArgs(fallback, cls, NULL);
}

static PyObject *
implementedBy(PyObject *ignored, PyObject *cls)
{
  /* Fast retrieval of implements spec, if possible, to optimize
     common case.  Use fallback code if we get stuck.
  */

  PyObject *dict = NULL, *spec;

  if (PyType_Check(cls))
    {
      dict = TYPE(cls)->tp_dict;
      Py_XINCREF(dict);
    }

  if (dict == NULL)
    dict = PyObject_GetAttr(cls, str__dict__);

  if (dict == NULL)
    {
      /* Probably a security proxied class, use more expensive fallback code */
      PyErr_Clear();
      return implementedByFallback(cls);
    }

  spec = PyObject_GetItem(dict, str__implemented__);
  Py_DECREF(dict);
  if (spec)
    {
      if (imported_declarations == 0 && import_declarations() < 0)
        return NULL;

      if (PyObject_TypeCheck(spec, Implements))
        return spec;

      /* Old-style declaration, use more expensive fallback code */
      Py_DECREF(spec);
      return implementedByFallback(cls);
    }

  PyErr_Clear();

  /* Maybe we have a builtin */
  if (imported_declarations == 0 && import_declarations() < 0)
    return NULL;

  spec = PyDict_GetItem(BuiltinImplementationSpecifications, cls);
  if (spec != NULL)
    {
      Py_INCREF(spec);
      return spec;
    }

  /* We're stuck, use fallback */
  return implementedByFallback(cls);
}

static PyObject *
getObjectSpecification(PyObject *ignored, PyObject *ob)
{
  PyObject *cls, *result;

  result = PyObject_GetAttr(ob, str__provides__);
  if (result != NULL && PyObject_TypeCheck(result, &SpecType))
    return result;

  PyErr_Clear();

  /* We do a getattr here so as not to be defeated by proxies */
  cls = PyObject_GetAttr(ob, str__class__);
  if (cls == NULL)
    {
      PyErr_Clear();
      if (imported_declarations == 0 && import_declarations() < 0)
        return NULL;
      Py_INCREF(empty);
      return empty;
    }

  result = implementedBy(NULL, cls);
  Py_DECREF(cls);

  return result;
}

static PyObject *
providedBy(PyObject *ignored, PyObject *ob)
{
  PyObject *result, *cls, *cp;

  result = PyObject_GetAttr(ob, str__providedBy__);
  if (result == NULL)
    {
      PyErr_Clear();
      return getObjectSpecification(NULL, ob);
    }


  /* We want to make sure we have a spec. We can't do a type check
     because we may have a proxy, so we'll just try to get the
     only attribute.
  */
  if (PyObject_TypeCheck(result, &SpecType)
      ||
      PyObject_HasAttr(result, strextends)
      )
    return result;

  /*
    The object's class doesn't understand descriptors.
    Sigh. We need to get an object descriptor, but we have to be
    careful.  We want to use the instance's __provides__,l if
    there is one, but only if it didn't come from the class.
  */
  Py_DECREF(result);

  cls = PyObject_GetAttr(ob, str__class__);
  if (cls == NULL)
    return NULL;

  result = PyObject_GetAttr(ob, str__provides__);
  if (result == NULL)
    {
      /* No __provides__, so just fall back to implementedBy */
      PyErr_Clear();
      result = implementedBy(NULL, cls);
      Py_DECREF(cls);
      return result;
    }

  cp = PyObject_GetAttr(cls, str__provides__);
  if (cp == NULL)
    {
      /* The the class has no provides, assume we're done: */
      PyErr_Clear();
      Py_DECREF(cls);
      return result;
    }

  if (cp == result)
    {
      /*
        Oops, we got the provides from the class. This means
        the object doesn't have it's own. We should use implementedBy
      */
      Py_DECREF(result);
      result = implementedBy(NULL, cls);
    }

  Py_DECREF(cls);
  Py_DECREF(cp);

  return result;
}

/*
   Get an attribute from an inst dict. Return a borrowed reference.

   This has a number of advantages:

   - It avoids layers of Python api

   - It doesn't waste time looking for descriptors

   - It fails wo raising an exception, although that shouldn't really
     matter.

*/
static PyObject *
inst_attr(PyObject *self, PyObject *name)
{
  PyObject **dictp, *v;

  dictp = _PyObject_GetDictPtr(self);
  if (dictp && *dictp && (v = PyDict_GetItem(*dictp, name)))
    return v;
  PyErr_SetObject(PyExc_AttributeError, name);
  return NULL;
}


static PyObject *
Spec_extends(PyObject *self, PyObject *other)
{
  PyObject *implied;

  implied = inst_attr(self, str_implied);
  if (implied == NULL)
    return NULL;

#ifdef Py_True
  if (PyDict_GetItem(implied, other) != NULL)
    {
      Py_INCREF(Py_True);
      return Py_True;
    }
  Py_INCREF(Py_False);
  return Py_False;
#else
  return PyInt_FromLong(PyDict_GetItem(implied, other) != NULL);
#endif
}

static char Spec_extends__doc__[] =
"Test whether a specification is or extends another"
;

static char Spec_providedBy__doc__[] =
"Test whether an interface is implemented by the specification"
;

static PyObject *
Spec_call(PyObject *self, PyObject *args, PyObject *kw)
{
  PyObject *spec;

  if (! PyArg_ParseTuple(args, "O", &spec))
    return NULL;
  return Spec_extends(self, spec);
}

static PyObject *
Spec_providedBy(PyObject *self, PyObject *ob)
{
  PyObject *decl, *item;

  decl = providedBy(NULL, ob);
  if (decl == NULL)
    return NULL;

  if (PyObject_TypeCheck(decl, &SpecType))
    item = Spec_extends(decl, self);
  else
    /* decl is probably a security proxy.  We have to go the long way
       around.
    */
    item = PyObject_CallFunctionObjArgs(decl, self, NULL);

  Py_DECREF(decl);
  return item;
}


static char Spec_implementedBy__doc__[] =
"Test whether the specification is implemented by a class or factory.\n"
"Raise TypeError if argument is neither a class nor a callable."
;