Settings
========

You must declare blocks in a dictionnary setting named
CMS_PLUGIN_BLURP_RENDERERS, each block define a name, a renderer
class and its configuration. The key of the dictionnary define the
slug of each renderer instance, and the value associated to this
slug must be a dictionnary containing at least a key called 'name'
containing the human name of this instance.

Renderer
========

A renderer is a class with the following interface::

      class Renderer(object):
          def __init__(self, slug, config):
            pass

          def render(self, context, instance, placeholder):
              '''Return the context to render the template'''
              pass

          def render_template(self):
              '''Return a template path or a Template object'''
              pass

The render method must return a context which will be passed to its
template, the render_template method must return template path or a
Django Template object.

You can also define the following class method::

    @classmethod
    def check(cls, config)
        '''Validate the config dictionnary and yield an ASCII string for each error'''
         pass

You can raise ImproperlyConfigured when the configuration does not validate.

There is two abstract helper classes:
 - `cmsplugin_blurp.renderers.base.BaseRenderer`
   which provide abstract method for checking that `render()` and
   `render_template()` are properly overriden and a generic
   `check()` method which call the `check_config()` config method
   which must return an iterator yielding strings if errors are
   found
 - `cmsplugin_blurp.renderers.template.TemplateRenderer`
   an abstract subclass of the `BaseRenderer` which provide a
   generic implementation of `render_template()` which extract the
   template path from the configuration dictionnary using the key
   `template_name` and if it is not found return a template parsed from the
   value of the key `template`.

Common configuration keys
=========================

- ``ajax``  if True this key indicate to the base plugin to render the plugin using an AJAX request.

  You must add the ``cmsplugin_blurp.urls`` to your urls::

       ...
       url(r'^cmsplugin_blurp/', include('cmsplugin_blurp.urls')),
       ...

- ``ajax_refresh`` if more than zero it indicates the time between refresh of
  the plugin content using the AJAX request otherwise the content is never
  refreshed after the first loading.

Static renderer
===============

The simplest renderer is the static renderer you can configure one like this::

    CMS_BLURP_RENDERERS = {
        'homepage_text': {
          'name': u'Homepage text',
          'class': 'cmsplugin_blurp.renderers.static.Renderer',
          'content': u'This is the text for the homepage',
          'template': 'homepage_text.html',
        }
    }

The template `homepage_text.html` could look like this::

    {{ config.content }}


Data source renderer
====================

It load one or more local (using a `file://...` URL) or remote file (using
an `http://...` or `https://...` URL) and parses them using the
following parsers:

  - a json parser using the `json` package,
  - an XML parser using the `etree.ElementTree` package,
  - a RSS parser using the `feedparser` package feedparser,
  - a CSV parser using the `csv` package.

The resulting data structure can be cached, in this case loading is
asynchronous using a thread.

The config dictonnary can contain the following keys:
- `name`, the human name of this renderer instance,
- `source`, a list of dictionnary defining the remote files, the
content of the dictionnary is described later,
- `template`, the template in which to render the data sources, it
will receive a variable named `data_sources` in its context
containing property named after the `slug` field of each source.

A source definition is a dictionnary containing the following keys:
    - `slug`, the field name to hold this source parsed value in the
      template, for example with this configuration:


          ...
          'slug': 'source1',
          ...

      you can access it with this template fragment:

          {{ data_sources.source1 }}


    - `url`, the URL of the file for this source, the scheme file://,
      http://, and https:// are supported,
    - `auth_mech`, whether an authentication mechanism is required by
      the http[s]:// URL, it can be `hmac-sha1`, `hmac-sha256` or
      `oauth2`. The HMAC mechanism is specified later; the OAuth2
      mechanisme is the classical OAuth2 HTTP bearer authentication
      mechanism but it prequires that you are using django-allauth and
      that an access token for the provider `authentic2` can be
      retrieved for the current user,
    - `signature_key`, when using the HMAC authentication mechanism it
      holds the secret key used to sign the exchanges,
    - `timeout`, a timeout for making the HTTP request, it is optional
      and it default to 10 seconds,
    - `refresh`, how long to cache the parsed value of the source, it
      is optional and it defaults to 3600 seconds,
    - `verify_certificate`, when the scheme of URL is https, it
      indicates whether to check the SSL certificate against configured
      certifate auhtorities, it is optional and defaults to True,
    - `allow_redirects`, whether to follow HTTP redirects when getting
      the data source file, it is optional and defaults to False,
    - `parser_type`, how to parse the loaded file, it can be `json`,
      `xml`, `rss`, 'csv' or 'raw' if you do not want any parsing to be
      done, it is optional and defaults to 'raw',
    - `content_type`, when doing an HTTP request it configures the
      content of the `Accept` header, it is optional and automatically
      set using the `parser_type` value.
    - `limit`, when parsing an RSS file it limits the returned to first
      `limit` entries sorted by date, it is optional and defaults to 0
      meaning no limit,
    - `csv_params`, when parsing a csv file this dictionnary is passed
      as keyword arguments to the `reader()` or `DictReader()`
      constructors, depending on whether the `fieldnames` arguments is
      present,

Exemple with the JSON parser
----------------------------

The configuration::

    CMS_BLURP_RENDERERS = {
        'json': {
             'name': u'My JSON content',
             'class': 'cmsplugin_blurp.renderer.data_source.Renderer',
             'sources': [
                  {
                      'slug': 'json_source',
                      'url': 'http://example.net/file.json',
                      'parser_type': 'json',
                      'auth_mech': 'hmac-sha1',
                      'signature_key': 'abcdefgh0123',
                      'refresh': 600,
                  }
             ]
             'template': 'my-json-block.html',
        }
    }

The `my-json-block.html` template::

    <dl>
    {% for key, value in data_sources.json_source.iteritems %}
        <dt>{{ key }}</dt>
        <dd>{{ value }}</dd>
    {% endfor %}
    </dl>

Exemple with the CSV parser
---------------------------

We suppose that the file `/var/spool/data/timesheet.csv` contains
the following datas::

     Monday,"10-12,14-17"
     Tuesday,"10-12,14-18"
     ....

You can present this file using this configuration::

    CMS_BLURP_RENDERERS = {
        'timesheet': {
            'name': u'Timesheet of our organization',
            'class': 'cmsplugin_blurp.renderer.data_source.Renderer',
            'sources': [
                {
                    'slug': 'timesheet',
                    'url': 'file:///var/spool/data/timesheet.csv',
                    'parser_type': 'csv',
                    'refresh': 86400,
                    'csv_params': {
                        'fieldnames': [
                            'day',
                            'opening_hours',
                        ]
                    }
                }
             ],
             'template': 'timesheet.html',
         }
      }

and the following template::

    <table>
        <thead>
            <tr><td>Day</td><td>Opening hours</td></tr>
        </thead>
        <tbody>
            {% for row in data_sources.timesheet %}
                <tr><td>{{ row.day }}</td><td>{{ row.opening_hours }}</td></tr>
            {% endfor %}
        </tbody>
    </table>

SQL Renderer
============

Configuration::

    CMS_BLURP_RENDERERS = {
        'student_table': {
            'name': u'Table of students',
            'class': 'cmsplugin_blurp.renderer.sql.Renderer',
            'url': 'postgresql://scott:tiger@localhost:5432/mydatabase',
            'views': {
                'students': {
                    'query': 'QUERY name, age, birthdate FROM student WHERE class_id = :class_id',
                    'bindparams': {
                        'class_id': 12
                    }
                }
            }
            'template': 'student-table.html',
        }
   }

Template::

    <!-- student-table.html -->
    <table>
        {% for row in students %}
            <tr>
                <td>{{ row.name }}</td>
                <td>{{ row.age  }}</td>
                <td>{{ row.birthdate }}</td>
            </tr>
        {% endfor %}
    </table>