# Copyright 2015 ksyun.com, Inc. or its affiliates. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"). You
# may not use this file except in compliance with the License. A copy of
# the License is located at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# or in the "license" file accompanying this file. This file is
# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
# ANY KIND, either express or implied. See the License for the specific
# language governing permissions and limitations under the License.
from kscore.docs.method import document_model_driven_method
from kscore.docs.waiter import document_wait_method
from kscore.docs.paginator import document_paginate_method
from kscore.docs.bcdoc.restdoc import DocumentStructure


class LazyLoadedDocstring(str):
    """Used for lazily loading docstrings

    You can instantiate this class and assign it to a __doc__ value.
    The docstring will not be generated till accessed via __doc__ or
    help(). Note that all docstring classes **must** subclass from
    this class. It cannot be used directly as a docstring.
    """
    def __init__(self, *args, **kwargs):
        """
        The args and kwargs are the same as the underlying document
        generation function. These just get proxied to the underlying
        function.
        """
        super(LazyLoadedDocstring, self).__init__()
        self._gen_args = args
        self._gen_kwargs = kwargs
        self._docstring = None

    def __new__(cls, *args, **kwargs):
        # Needed in order to sub class from str with args and kwargs
        return super(LazyLoadedDocstring, cls).__new__(cls)

    def _write_docstring(self, *args, **kwargs):
        raise NotImplementedError(
            '_write_docstring is not implemented. Please subclass from '
            'this class and provide your own _write_docstring method'
        )

    def expandtabs(self, tabsize=8):
        """Expands tabs to spaces

        So this is a big hack in order to get lazy loaded docstring work
        for the ``help()``. In the ``help()`` function, ``pydoc`` and
        ``inspect`` are used. At some point the ``inspect.cleandoc``
        method is called. To clean the docs ``expandtabs`` is called
        and that is where we override the method to generate and return the
        docstrings.
        """
        if self._docstring is None:
            self._generate()
        return self._docstring.expandtabs(tabsize)

    def __str__(self):
        return self._generate()

    # __doc__ of target will use either __repr__ or __str__ of this class.
    __repr__ = __str__

    def _generate(self):
        # Generate the docstring if it is not already cached.
        if self._docstring is None:
            self._docstring = self._create_docstring()
        return self._docstring

    def _create_docstring(self):
        docstring_structure = DocumentStructure('docstring')
        # Call the document method function with the args and kwargs
        # passed to the class.
        self._write_docstring(
            docstring_structure, *self._gen_args,
            **self._gen_kwargs)
        return docstring_structure.flush_structure().decode('utf-8')


class ClientMethodDocstring(LazyLoadedDocstring):
    def _write_docstring(self, *args, **kwargs):
        document_model_driven_method(*args, **kwargs)


class WaiterDocstring(LazyLoadedDocstring):
    def _write_docstring(self, *args, **kwargs):
        document_wait_method(*args, **kwargs)


class PaginatorDocstring(LazyLoadedDocstring):
    def _write_docstring(self, *args, **kwargs):
        document_paginate_method(*args, **kwargs)