Implement period_archives common context variable

docs/settings.rst

@@ -561,44 +561,47 @@ written over time.
 Example usage::
 
    YEAR_ARCHIVE_SAVE_AS = 'posts/{date:%Y}/index.html'
+   YEAR_ARCHIVE_URL = 'posts/{date:%Y}/'
    MONTH_ARCHIVE_SAVE_AS = 'posts/{date:%Y}/{date:%b}/index.html'
+   MONTH_ARCHIVE_URL = 'posts/{date:%Y}/{date:%b}/'
 
 With these settings, Pelican will create an archive of all your posts for the
 year at (for instance) ``posts/2011/index.html`` and an archive of all your
-posts for the month at ``posts/2011/Aug/index.html``.
+posts for the month at ``posts/2011/Aug/index.html``. These can be accessed
+through the URLs ``posts/2011/`` and ``posts/2011/Aug/``, respectively.
 
 .. note::
     Period archives work best when the final path segment is ``index.html``.
     This way a reader can remove a portion of your URL and automatically arrive
     at an appropriate archive of posts, without having to specify a page name.
 
-.. data:: YEAR_ARCHIVE_URL = ''
-
-   The URL to use for per-year archives of your posts. Used only if you have
-   the ``{url}`` placeholder in ``PAGINATION_PATTERNS``.
-
 .. data:: YEAR_ARCHIVE_SAVE_AS = ''
 
    The location to save per-year archives of your posts.
 
-.. data:: MONTH_ARCHIVE_URL = ''
+.. data:: YEAR_ARCHIVE_URL = ''
 
-   The URL to use for per-month archives of your posts. Used only if you have
-   the ``{url}`` placeholder in ``PAGINATION_PATTERNS``.
+   The URL to use for per-year archives of your posts. You should set this if
+   you enable per-year archives.
 
 .. data:: MONTH_ARCHIVE_SAVE_AS = ''
 
    The location to save per-month archives of your posts.
 
-.. data:: DAY_ARCHIVE_URL = ''
+.. data:: MONTH_ARCHIVE_URL = ''
 
-   The URL to use for per-day archives of your posts. Used only if you have the
-   ``{url}`` placeholder in ``PAGINATION_PATTERNS``.
+   The URL to use for per-month archives of your posts. You should set this if
+   you enable per-month archives.
 
 .. data:: DAY_ARCHIVE_SAVE_AS = ''
 
    The location to save per-day archives of your posts.
 
+.. data:: DAY_ARCHIVE_URL = ''
+
+   The URL to use for per-day archives of your posts. You should set this if
+   you enable per-day archives.
+
 ``DIRECT_TEMPLATES`` work a bit differently than noted above. Only the
 ``_SAVE_AS`` settings are available, but it is available for any direct
 template.

docs/themes.rst

@@ -71,6 +71,8 @@ All templates will receive the variables defined in your settings file, as long
 as they are in all-caps. You can access them directly.
 
 
+.. _common_variables:
+
 Common Variables
 ----------------
 
@@ -92,6 +94,10 @@ dates           The same list of articles, but ordered by date,
                 ascending.
 hidden_articles The list of hidden articles
 drafts          The list of draft articles
+period_archives A dictionary containing elements related to
+                time-period archives (if enabled). See the section
+                :ref:`Listing and Linking to Period Archives
+                <period_archives_variable>` for details.
 authors         A list of (author, articles) tuples, containing all
                 the authors and corresponding articles (values)
 categories      A list of (category, articles) tuples, containing
@@ -348,6 +354,63 @@ period_archives.html template
 <https://github.com/getpelican/pelican/blob/master/pelican/themes/simple/templates/period_archives.html>`_.
 
 
+.. _period_archives_variable:
+
+Listing and Linking to Period Archives
+""""""""""""""""""""""""""""""""""""""
+
+The ``period_archives`` variable can be used to generate a list of links to
+the set of period archives that Pelican generates. As a :ref:`common variable
+<common_variables>`, it is available for use in any template, so you
+can implement such an index in a custom direct template, or in a sidebar
+visible across different site pages.
+
+``period_archives`` is a dict that may contain ``year``, ``month``, and/or
+``day`` keys, depending on which ``*_ARCHIVE_SAVE_AS`` settings are enabled.
+The corresponding value is a list of dicts, where each dict in turn represents
+a time period (ordered according to the ``NEWEST_FIRST_ARCHIVES`` setting)
+with the following keys and values:
+
+===================     ===================================================
+Key                     Value
+===================     ===================================================
+period                  The same tuple as described in
+                        ``period_archives.html``, e.g.
+                        ``(2023, 'June', 18)``.
+period_num              The same tuple as described in
+                        ``period_archives.html``, e.g. ``(2023, 6, 18)``.
+url                     The URL to the period archive page, e.g.
+                        ``posts/2023/06/18/``. This is controlled by the
+                        corresponding ``*_ARCHIVE_URL`` setting.
+save_as                 The path to the save location of the period archive
+                        page file, e.g. ``posts/2023/06/18/index.html``.
+                        This is used internally by Pelican and is usually
+                        not relevant to themes.
+articles                A list of :ref:`Article <object-article>` objects
+                        that fall under the time period.
+dates                   Same list as ``articles``, but ordered according
+                        to the ``NEWEST_FIRST_ARCHIVES`` setting.
+===================     ===================================================
+
+Here is an example of how ``period_archives`` can be used in a template:
+
+.. code-block:: html+jinja
+
+    <ul>
+    {% for archive in period_archives.month %}
+        <li>
+            <a href="{{ SITEURL }}/{{ archive.url }}">
+                {{ archive.period | reverse | join(' ') }} ({{ archive.articles|count }})
+            </a>
+        </li>
+    {% endfor %}
+    </ul>
+
+You can change ``period_archives.month`` in the ``for`` statement to
+``period_archives.year`` or ``period_archives.day`` as appropriate, depending
+on the time period granularity desired.
+
+
 Objects
 =======
 

pelican/generators.py

@@ -295,6 +295,7 @@ def __init__(self, *args, **kwargs):
         self.drafts = []                   # only drafts in default language
         self.drafts_translations = []
         self.dates = {}
+        self.period_archives = defaultdict(list)
         self.tags = defaultdict(list)
         self.categories = defaultdict(list)
         self.related_posts = []
@@ -483,64 +484,17 @@ def generate_period_archives(self, write):
         except PelicanTemplateNotFound:
             template = self.get_template('archives')
 
-        period_save_as = {
-            'year': self.settings['YEAR_ARCHIVE_SAVE_AS'],
-            'month': self.settings['MONTH_ARCHIVE_SAVE_AS'],
-            'day': self.settings['DAY_ARCHIVE_SAVE_AS'],
-        }
-
-        period_url = {
-            'year': self.settings['YEAR_ARCHIVE_URL'],
-            'month': self.settings['MONTH_ARCHIVE_URL'],
-            'day': self.settings['DAY_ARCHIVE_URL'],
-        }
-
-        period_date_key = {
-            'year': attrgetter('date.year'),
-            'month': attrgetter('date.year', 'date.month'),
-            'day': attrgetter('date.year', 'date.month', 'date.day')
-        }
+        for granularity in self.period_archives:
+            for period in self.period_archives[granularity]:
 
-        def _generate_period_archives(dates, key, save_as_fmt, url_fmt):
-            """Generate period archives from `dates`, grouped by
-            `key` and written to `save_as`.
-            """
-            # `dates` is already sorted by date
-            for _period, group in groupby(dates, key=key):
-                archive = list(group)
-                articles = [a for a in self.articles if a in archive]
-                # arbitrarily grab the first date so that the usual
-                # format string syntax can be used for specifying the
-                # period archive dates
-                date = archive[0].date
-                save_as = save_as_fmt.format(date=date)
-                url = url_fmt.format(date=date)
                 context = self.context.copy()
+                context['period'] = period['period']
+                context['period_num'] = period['period_num']
 
-                if key == period_date_key['year']:
-                    context["period"] = (_period,)
-                    context["period_num"] = (_period,)
-                else:
-                    month_name = calendar.month_name[_period[1]]
-                    if key == period_date_key['month']:
-                        context["period"] = (_period[0],
-                                             month_name)
-                    else:
-                        context["period"] = (_period[0],
-                                             month_name,
-                                             _period[2])
-                    context["period_num"] = tuple(_period)
-
-                write(save_as, template, context, articles=articles,
-                      dates=archive, template_name='period_archives',
-                      blog=True, url=url, all_articles=self.articles)
-
-        for period in 'year', 'month', 'day':
-            save_as = period_save_as[period]
-            url = period_url[period]
-            if save_as:
-                key = period_date_key[period]
-                _generate_period_archives(self.dates, key, save_as, url)
+                write(period['save_as'], template, context,
+                      articles=period['articles'], dates=period['dates'],
+                      template_name='period_archives', blog=True,
+                      url=period['url'], all_articles=self.articles)
 
     def generate_direct_templates(self, write):
         """Generate direct templates pages"""
@@ -680,6 +634,9 @@ def _process(arts):
         self.dates.sort(key=attrgetter('date'),
                         reverse=self.context['NEWEST_FIRST_ARCHIVES'])
 
+        self.period_archives = self._build_period_archives(
+            self.dates, self.articles, self.settings)
+
         # and generate the output :)
 
         # order the categories per name
@@ -694,10 +651,80 @@ def _process(arts):
             'articles', 'drafts', 'hidden_articles',
             'dates', 'tags', 'categories',
             'authors', 'related_posts'))
+        # _update_context flattens dicts, which should not happen to
+        # period_archives, so we update the context directly for it:
+        self.context['period_archives'] = self.period_archives
         self.save_cache()
         self.readers.save_cache()
         signals.article_generator_finalized.send(self)
 
+    def _build_period_archives(self, sorted_articles, articles, settings):
+        """
+        Compute the groupings of articles, with related attributes, for
+        per-year, per-month, and per-day archives.
+        """
+
+        period_archives = defaultdict(list)
+
+        period_archives_settings = {
+            'year': {
+                'save_as': settings['YEAR_ARCHIVE_SAVE_AS'],
+                'url': settings['YEAR_ARCHIVE_URL'],
+            },
+            'month': {
+                'save_as': settings['MONTH_ARCHIVE_SAVE_AS'],
+                'url': settings['MONTH_ARCHIVE_URL'],
+            },
+            'day': {
+                'save_as': settings['DAY_ARCHIVE_SAVE_AS'],
+                'url': settings['DAY_ARCHIVE_URL'],
+            },
+        }
+
+        granularity_key_func = {
+            'year': attrgetter('date.year'),
+            'month': attrgetter('date.year', 'date.month'),
+            'day': attrgetter('date.year', 'date.month', 'date.day'),
+        }
+
+        for granularity in 'year', 'month', 'day':
+            save_as_fmt = period_archives_settings[granularity]['save_as']
+            url_fmt = period_archives_settings[granularity]['url']
+            key_func = granularity_key_func[granularity]
+
+            if not save_as_fmt:
+                # the archives for this period granularity are not needed
+                continue
+
+            for period, group in groupby(sorted_articles, key=key_func):
+                archive = {}
+
+                dates = list(group)
+                archive['dates'] = dates
+                archive['articles'] = [a for a in articles if a in dates]
+
+                # use the first date to specify the period archive URL
+                # and save_as; the specific date used does not matter as
+                # they all belong to the same period
+                d = dates[0].date
+                archive['save_as'] = save_as_fmt.format(date=d)
+                archive['url'] = url_fmt.format(date=d)
+
+                if granularity == 'year':
+                    archive['period'] = (period,)
+                    archive['period_num'] = (period,)
+                else:
+                    month_name = calendar.month_name[period[1]]
+                    if granularity == 'month':
+                        archive['period'] = (period[0], month_name)
+                    else:
+                        archive['period'] = (period[0], month_name, period[2])
+                    archive['period_num'] = tuple(period)
+
+                period_archives[granularity].append(archive)
+
+        return period_archives
+
     def generate_output(self, writer):
         self.generate_feeds(writer)
         self.generate_pages(writer)