Nikola plugin for embedding content from popular sites with micawber and Noembed

noembed.plugin

[Core]
name = rest_noembed
module = noembed

[Nikola]
compiler = rest
plugincategory = CompilerExtension

[Documentation]
author = Christopher Arndt
version = 0.1
website = https://github.com/SpotlightKid/nikola-plugin-noembed
description = Directive to support oembed via micawber using NoEmbed provider

noembed.py

# -*- coding: utf-8 -*-
"""Nikola plugin for embedding content from popular sites with micawber_ and
Noembed_.

Provides a ReST directive and a generic Nikola shortcode.

ReST directive usage example::

    .. noembed:: http://soundcloud.com/myuser/my-track

Shortcode usage example::

    {{% noembed http://soundcloud.com/myuser/my-track %}}

.. _micawber: https://github.com/coleifer/micawber/
.. _noembed: http://www.noembed.com/

When you use this directive / shortcode in a post or story and generate the
output, the plugin will download the list of OEmbed Providers from noembed.com
and then use the provider matching the URL you specified to download the HTML
snippet to include in your post / story to embed the content the URL is
pointing to. Both the list of providers and the embedding HTML code are cashed
locally in files below your site's cache directory. So when you re-generate
your site and you haven't changed or added any noembed directives / shortcodes,
no internet connection is needed for the plugin. You can safely delete the
cache files by running `nikola clean`.

"""

import shelve

from os.path import join

from docutils import nodes
from docutils.parsers.rst import Directive, directives

try:
    import micawber
except ImportError:
    micawber = None  # NOQA

from nikola.plugin_categories import RestExtension
from nikola.utils import req_missing


class Plugin(RestExtension):
    """Plugin for noembed reST directive and generic Nikola shortcode."""

    name = "rest_noembed"

    def set_site(self, site):
        """Set Nikola site."""
        self.site = site
        directives.register_directive('noembed', Noembed(plugin=self))
        self.site.register_shortcode('noembed', self.gen_noembed)
        self.cachefn = join(site.config['CACHE_FOLDER'], "noembed.cache")
        return super(Plugin, self).set_site(site)

    def get_providers(self):
        try:
            with shelve.open(self.cachefn) as cache:
                providers = cache['_providers']
        except (OSError, IOError, KeyError):
            providers = micawber.bootstrap_noembed()
            with shelve.open(self.cachefn, 'w') as cache:
                cache['_providers'] = providers

        return providers

    def gen_noembed(self, url, *args, **kw):
        try:
            with shelve.open(self.cachefn) as cache:
                text = cache[url]
        except (OSError, IOError, KeyError):
            if micawber is None:
                msg = req_missing(['micawber'], 'use the noembed directive',
                                  optional=True)
                text = '<div class="text-error">{0}</div>'.format(msg)
            else:
                text = micawber.parse_text(url, self.get_providers())

            with shelve.open(self.cachefn, 'w') as cache:
                cache[url] = text

        return text


class Noembed(Directive):
    """ReST extension for embedding content from popular sites using micawber
    and Noembed."""

    has_content = False
    required_arguments = 1
    optional_arguments = 999

    def __init__(self, *args, **kw):
        self.plugin = kw.pop('plugin', None)

    # XXX: ugly hack to be able to receive state:
    #      instead of a class object, we pass an instance of Noembed to
    #      docutils' register_directive, which already has some dynamic state
    #      set (the 'plugin' attribute referencing our plugin instance).
    #      When docutils calls the instance (normally it would instantiate the
    #      class) the '__call__' method is called and the delayed
    #      initialization of the superclass is carried out.
    def __call__(self, *args, **kw):
        super().__init__(*args, **kw)
        return self

    def run(self):
        """Run noembed directive."""
        html = self.plugin.gen_noembed(" ".join(self.arguments))
        return [nodes.raw('', html, format='html')]