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#
# Copyright (c) 2002 Zope Foundation and Contributors.
# All Rights Reserved.
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# 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.
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"""Interface Package Interfaces
"""
__docformat__ = 'restructuredtext'

from zope.interface.interface import Attribute
from zope.interface.interface import Interface
from zope.interface.declarations import implementer


_BLANK = u''

class IElement(Interface):
    """Objects that have basic documentation and tagged values.
    """

    __name__ = Attribute('__name__', 'The object name')
    __doc__  = Attribute('__doc__', 'The object doc string')

    def getTaggedValue(tag):
        """Returns the value associated with `tag`.

        Raise a `KeyError` of the tag isn't set.
        """

    def queryTaggedValue(tag, default=None):
        """Returns the value associated with `tag`.

        Return the default value of the tag isn't set.
        """

    def getTaggedValueTags():
        """Returns a list of all tags."""

    def setTaggedValue(tag, value):
        """Associates `value` with `key`."""


class IAttribute(IElement):
    """Attribute descriptors"""

    interface = Attribute('interface',
                          'Stores the interface instance in which the '
                          'attribute is located.')


class IMethod(IAttribute):
    """Method attributes"""

    def getSignatureInfo():
        """Returns the signature information.

        This method returns a dictionary with the following keys:

        o `positional` - All positional arguments.

        o `required` - A list of all required arguments.

        o `optional` - A list of all optional arguments.

        o `varargs` - The name of the varargs argument.

        o `kwargs` - The name of the kwargs argument.
        """

    def getSignatureString():
        """Return a signature string suitable for inclusion in documentation.

        This method returns the function signature string. For example, if you
        have `func(a, b, c=1, d='f')`, then the signature string is `(a, b,
        c=1, d='f')`.
        """

class ISpecification(Interface):
    """Object Behavioral specifications"""

    def providedBy(object):
        """Test whether the interface is implemented by the object

        Return true of the object asserts that it implements the
        interface, including asserting that it implements an extended
        interface.
        """

    def implementedBy(class_):
        """Test whether the interface is implemented by instances of the class

        Return true of the class asserts that its instances implement the
        interface, including asserting that they implement an extended
        interface.
        """

    def isOrExtends(other):
        """Test whether the specification is or extends another
        """

    def extends(other, strict=True):
        """Test whether a specification extends another

        The specification extends other if it has other as a base
        interface or if one of it's bases extends other.

        If strict is false, then the specification extends itself.
        """

    def weakref(callback=None):
        """Return a weakref to the specification

        This method is, regrettably, needed to allow weakrefs to be
        computed to security-proxied specifications.  While the
        zope.interface package does not require zope.security or
        zope.proxy, it has to be able to coexist with it.

        """

    __bases__ = Attribute("""Base specifications

    A tuple if specifications from which this specification is
    directly derived.

    """)

    __sro__ = Attribute("""Specification-resolution order

    A tuple of the specification and all of it's ancestor
    specifications from most specific to least specific.

    (This is similar to the method-resolution order for new-style classes.)
    """)

    __iro__ = Attribute("""Interface-resolution order

    A tuple of the of the specification's ancestor interfaces from
    most specific to least specific.  The specification itself is
    included if it is an interface.

    (This is similar to the method-resolution order for new-style classes.)
    """)

    def get(name, default=None):
        """Look up the description for a name

        If the named attribute is not defined, the default is
        returned.
        """


class IInterface(ISpecification, IElement):
    """Interface objects

    Interface objects describe the behavior of an object by containing
    useful information about the object.  This information includes:

    - Prose documentation about the object.  In Python terms, this
      is called the "doc string" of the interface.  In this element,
      you describe how the object works in prose language and any
      other useful information about the object.

    - Descriptions of attributes.  Attribute descriptions include
      the name of the attribute and prose documentation describing
      the attributes usage.

    - Descriptions of methods.  Method descriptions can include:

        - Prose "doc string" documentation about the method and its
          usage.

        - A description of the methods arguments; how many arguments
          are expected, optional arguments and their default values,
          the position or arguments in the signature, whether the
          method accepts arbitrary arguments and whether the method
          accepts arbitrary keyword arguments.

    - Optional tagged data.  Interface objects (and their attributes and
      methods) can have optional, application specific tagged data
      associated with them.  Examples uses for this are examples,
      security assertions, pre/post conditions, and other possible
      information you may want to associate with an Interface or its
      attributes.

    Not all of this information is mandatory.  For example, you may
    only want the methods of your interface to have prose
    documentation and not describe the arguments of the method in
    exact detail.  Interface objects are flexible and let you give or
    take any of these components.

    Interfaces are created with the Python class statement using
    either `zope.interface.Interface` or another interface, as in::

      from zope.interface import Interface

      class IMyInterface(Interface):
        '''Interface documentation'''

        def meth(arg1, arg2):
            '''Documentation for meth'''

        # Note that there is no self argument

     class IMySubInterface(IMyInterface):
        '''Interface documentation'''

        def meth2():
            '''Documentation for meth2'''

    You use interfaces in two ways:

    - You assert that your object implement the interfaces.

      There are several ways that you can assert that an object
      implements an interface:

      1. Call `zope.interface.implements` in your class definition.

      2. Call `zope.interfaces.directlyProvides` on your object.

      3. Call `zope.interface.classImplements` to assert that instances
         of a class implement an interface.

         For example::

           from zope.interface import classImplements

           classImplements(some_class, some_interface)

         This approach is useful when it is not an option to modify
         the class source.  Note that this doesn't affect what the
         class itself implements, but only what its instances
         implement.

    - You query interface meta-data. See the IInterface methods and
      attributes for details.

    """

    def names(all=False):
        """Get the interface attribute names

        Return a sequence of the names of the attributes, including
        methods, included in the interface definition.

        Normally, only directly defined attributes are included. If
        a true positional or keyword argument is given, then
        attributes defined by base classes will be included.
        """

    def namesAndDescriptions(all=False):
        """Get the interface attribute names and descriptions

        Return a sequence of the names and descriptions of the
        attributes, including methods, as name-value pairs, included
        in the interface definition.

        Normally, only directly defined attributes are included. If
        a true positional or keyword argument is given, then
        attributes defined by base classes will be included.
        """

    def __getitem__(name):
        """Get the description for a name

        If the named attribute is not defined, a `KeyError` is raised.
        """

    def direct(name):
        """Get the description for the name if it was defined by the interface

        If the interface doesn't define the name, returns None.
        """

    def validateInvariants(obj, errors=None):
        """Validate invariants

        Validate object to defined invariants.  If errors is None,
        raises first Invalid error; if errors is a list, appends all errors
        to list, then raises Invalid with the errors as the first element
        of the "args" tuple."""

    def __contains__(name):
        """Test whether the name is defined by the interface"""

    def __iter__():
        """Return an iterator over the names defined by the interface

        The names iterated include all of the names defined by the
        interface directly and indirectly by base interfaces.
        """

    __module__ = Attribute("""The name of the module defining the interface""")

class IDeclaration(ISpecification):
    """Interface declaration

    Declarations are used to express the interfaces implemented by
    classes or provided by objects.
    """

    def __contains__(interface):
        """Test whether an interface is in the specification

        Return true if the given interface is one of the interfaces in
        the specification and false otherwise.
        """

    def __iter__():
        """Return an iterator for the interfaces in the specification
        """

    def flattened():
        """Return an iterator of all included and extended interfaces

        An iterator is returned for all interfaces either included in
        or extended by interfaces included in the specifications
        without duplicates. The interfaces are in "interface
        resolution order". The interface resolution order is such that
        base interfaces are listed after interfaces that extend them
        and, otherwise, interfaces are included in the order that they
        were defined in the specification.
        """

    def __sub__(interfaces):
        """Create an interface specification with some interfaces excluded

        The argument can be an interface or an interface
        specifications.  The interface or interfaces given in a
        specification are subtracted from the interface specification.

        Removing an interface that is not in the specification does
        not raise an error. Doing so has no effect.

        Removing an interface also removes sub-interfaces of the interface.

        """