"""Sphinx documentation plugin used to document tasks.

Introduction
============

Usage
-----

The Celery extension for Sphinx requires Sphinx 2.0 or later.

Add the extension to your :file:`docs/conf.py` configuration module:

.. code-block:: python

    extensions = (...,
                  'celery.contrib.sphinx')

If you'd like to change the prefix for tasks in reference documentation
then you can change the ``celery_task_prefix`` configuration value:

.. code-block:: python

    celery_task_prefix = '(task)'  # < default

With the extension installed `autodoc` will automatically find
task decorated objects (e.g. when using the automodule directive)
and generate the correct (as well as add a ``(task)`` prefix),
and you can also refer to the tasks using `:task:proj.tasks.add`
syntax.

Use ``.. autotask::`` to alternatively manually document a task.

Sphinx 9.0+ Compatibility
-------------------------

Sphinx 9.0 introduced a rewritten autodoc implementation. The Celery
extension requires the legacy class-based autodoc mode to function
correctly. When using Sphinx 9.0 or later, add the following to your
:file:`conf.py`:

.. code-block:: python

    autodoc_use_legacy_class_based = True

The extension will automatically enable this setting if not configured,
but it is recommended to set it explicitly to avoid warnings.
"""
import warnings
from inspect import signature

from docutils import nodes
from sphinx.domains.python import PyFunction
from sphinx.ext.autodoc import FunctionDocumenter

from celery.app.task import BaseTask


class TaskDocumenter(FunctionDocumenter):
    """Document task definitions."""

    objtype = 'task'
    member_order = 11

    @classmethod
    def can_document_member(cls, member, membername, isattr, parent):
        return isinstance(member, BaseTask) and getattr(member, '__wrapped__')

    def format_args(self):
        wrapped = getattr(self.object, '__wrapped__', None)
        if wrapped is not None:
            sig = signature(wrapped)
            if "self" in sig.parameters or "cls" in sig.parameters:
                sig = sig.replace(parameters=list(sig.parameters.values())[1:])
            return str(sig)
        return ''

    def document_members(self, all_members=False):
        pass

    def check_module(self):
        # Normally checks if *self.object* is really defined in the module
        # given by *self.modname*. But since functions decorated with the @task
        # decorator are instances living in the celery.local, we have to check
        # the wrapped function instead.
        wrapped = getattr(self.object, '__wrapped__', None)
        if wrapped and getattr(wrapped, '__module__') == self.modname:
            return True
        return super().check_module()


class TaskDirective(PyFunction):
    """Sphinx task directive."""

    def get_signature_prefix(self, sig):
        return [nodes.Text(self.env.config.celery_task_prefix)]


def autodoc_skip_member_handler(app, what, name, obj, skip, options):
    """Handler for autodoc-skip-member event."""
    # Celery tasks created with the @task decorator have the property
    # that *obj.__doc__* and *obj.__class__.__doc__* are equal, which
    # trips up the logic in sphinx.ext.autodoc that is supposed to
    # suppress repetition of class documentation in an instance of the
    # class. This overrides that behavior.
    if isinstance(obj, BaseTask) and getattr(obj, '__wrapped__'):
        if skip:
            return False
    return None


def setup(app):
    """Setup Sphinx extension."""
    import sphinx

    app.setup_extension('sphinx.ext.autodoc')

    # Sphinx 9.0+ rewrote autodoc; TaskDocumenter requires legacy mode.
    # See: https://www.sphinx-doc.org/en/master/usage/extensions/autodoc.html
    sphinx_version = tuple(int(x) for x in sphinx.__version__.split('.')[:2])
    if sphinx_version >= (9, 0):
        if not getattr(app.config, 'autodoc_use_legacy_class_based', False):
            warnings.warn(
                "Sphinx 9.0+ detected. celery.contrib.sphinx requires "
                "'autodoc_use_legacy_class_based = True' in conf.py. "
                "Enabling it automatically.",
                UserWarning,
                stacklevel=2
            )
            app.config.autodoc_use_legacy_class_based = True

    app.add_autodocumenter(TaskDocumenter)
    app.add_directive_to_domain('py', 'task', TaskDirective)
    app.add_config_value('celery_task_prefix', '(task)', True)
    app.connect('autodoc-skip-member', autodoc_skip_member_handler)

    return {
        'parallel_read_safe': True
    }
