/*###########################################################################
 #
 # 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"

#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-parameter"
#pragma clang diagnostic ignored "-Wmissing-field-initializers"
#endif

#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
#define PyNative_FromString PyUnicode_FromString
#else
#define PyNative_FromString PyString_FromString
#endif

static PyObject *str__dict__, *str__implemented__, *strextends;
static PyObject *BuiltinImplementationSpecifications, *str__provides__;
static PyObject *str__class__, *str__providedBy__;
static PyObject *empty, *fallback;
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 PyObject *str__self__;
static PyObject *str__module__;
static PyObject *str__name__;
static PyObject *str__adapt__;
static PyObject *str_CALL_CUSTOM_ADAPT;

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 SpecificationBaseType;   /* 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 (PyObject_TypeCheck(cls, &PySuper_Type))
  {
      // Let merging be handled by Python.
      return implementedByFallback(cls);
  }

  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)
  {
      if (!PyErr_ExceptionMatches(PyExc_AttributeError))
      {
          /* Propagate non AttributeError exceptions. */
          return NULL;
      }
      PyErr_Clear();
  }
  else
  {
      int is_instance = -1;
      is_instance = PyObject_IsInstance(result, (PyObject*)&SpecificationBaseType);
      if (is_instance < 0)
      {
          /* Propagate all errors */
          return NULL;
      }
      if (is_instance)
      {
          return result;
      }
  }

  /* We do a getattr here so as not to be defeated by proxies */
  cls = PyObject_GetAttr(ob, str__class__);
  if (cls == NULL)
  {
      if (!PyErr_ExceptionMatches(PyExc_AttributeError))
      {
          /* Propagate non-AttributeErrors */
          return 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;
  int is_instance = -1;
  result = NULL;

  is_instance = PyObject_IsInstance(ob, (PyObject*)&PySuper_Type);
  if (is_instance < 0)
  {
      if (!PyErr_ExceptionMatches(PyExc_AttributeError))
      {
          /* Propagate non-AttributeErrors */
          return NULL;
      }
      PyErr_Clear();
  }
  if (is_instance)
  {
      return implementedBy(NULL, ob);
  }

  result = PyObject_GetAttr(ob, str__providedBy__);

  if (result == NULL)
  {
      if (!PyErr_ExceptionMatches(PyExc_AttributeError))
      {
          return 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, &SpecificationBaseType)
      ||
      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;
}

typedef struct {
    PyObject_HEAD
    PyObject* weakreflist;
    /*
      In the past, these fields were stored in the __dict__
      and were technically allowed to contain any Python object, though
      other type checks would fail or fall back to generic code paths if
      they didn't have the expected type. We preserve that behaviour and don't
      make any assumptions about contents.
    */
    PyObject* _implied;
    /*
      The remainder aren't used in C code but must be stored here
      to prevent instance layout conflicts.
    */
    PyObject* _dependents;
    PyObject* _bases;
    PyObject* _v_attrs;
    PyObject* __iro__;
    PyObject* __sro__;
} Spec;

/*
  We know what the fields are *supposed* to define, but