Added custom Sphinx extension for OpenGraph data (#39)

* Added custom Sphinx extension for OpenGraph data

* Updated with """

docs/_ext/ogtag.py

@@ -0,0 +1,106 @@
+"""Automatically generates Open Graph tags for Sphinx html docs.
+Based on https://sphinx-users.jp/cookbook/ogp/index.html
+"""
+
+from docutils import nodes
+from sphinx import addnodes
+from urllib.parse import urljoin
+
+
+class Visitor:
+    def __init__(self, document):
+        self.document = document
+        self.text_list = []
+        self.images = []
+        self.n_sections = 0
+
+    def dispatch_visit(self, node):
+        # Skip toctree
+        if isinstance(node, addnodes.compact_paragraph) and node.get("toctree"):
+            raise nodes.SkipChildren
+
+        # Collect images
+        if isinstance(node, nodes.image):
+            self.images.append(node)
+
+        # Collect text (first three sections)
+        if self.n_sections < 3:
+
+            # Collect paragraphs
+            if isinstance(node, nodes.paragraph):
+                self.text_list.append(node.astext().replace("\n", " "))
+
+            # Include only paragraphs
+            if isinstance(node, nodes.section):
+                self.n_sections += 1
+
+    def dispatch_departure(self, node):
+        pass
+
+    def get_og_description(self):
+        # TODO: Find optimal length for description text
+        text = " ".join(self.text_list)
+        if len(text) > 200:
+            text = text[:197] + "..."
+        return text
+
+    def get_og_image_url(self, page_url):
+        # TODO: Check if picking first image makes sense
+        # TODO: Return fallback image if no image found on page
+        if self.images:
+            return urljoin(page_url, self.images[0]["uri"])
+        else:
+            return None
+
+
+def get_og_tags(context, doctree, config):
+    # page_url
+    site_url = config.og_site_url
+    page_url = urljoin(site_url, context["pagename"] + context["file_suffix"])
+
+    # collection
+    visitor = Visitor(doctree)
+    doctree.walkabout(visitor)
+
+    # og:description
+    og_desc = visitor.get_og_description()
+
+    # og:image
+    og_image = visitor.get_og_image_url(page_url)
+
+    # OGP
+    tags = """
+    <meta name="twitter:card" content="summary" />
+    <meta name="twitter:site" content="{cfg[og_twitter_site]}" />
+    <meta property="og:site_name" content="{ctx[shorttitle]}">
+    <meta property="og:title" content="{ctx[title]}">
+    <meta property="og:description" content="{desc}">
+    <meta property='og:url' content="{page_url}">
+    """.format(
+        ctx=context, desc=og_desc, page_url=page_url, cfg=config
+    )
+    # Add image if present, use default image if no image is found
+    if og_image:
+        tags += f'<meta property="og:image" content="{og_image}">'
+    elif config.og_fallback_image:
+        tags += f'<meta property="og:image" content="{config.og_fallback_image}">'
+    return tags
+
+
+def html_page_context(app, pagename, templatename, context, doctree):
+    if not doctree:
+        return
+
+    context["metatags"] += get_og_tags(context, doctree, app.config)
+
+
+def setup(app):
+    app.add_config_value("og_site_url", None, "html")
+    app.add_config_value("og_twitter_site", None, "html")
+    app.add_config_value("og_fallback_image", None, "html")
+    app.connect("html-page-context", html_page_context)
+    return {
+        "version": "0.1",
+        "parallel_read_safe": True,
+        "parallel_write_safe": True,
+    }

docs/conf.py

@@ -1,15 +1,16 @@
 # -*- coding: utf-8 -*-
-#
-# complexity documentation build configuration file, created by
-# sphinx-quickstart on Tue Jul  9 22:26:36 2013.
-#
-# This file is execfile()d with the current directory set to its containing dir.
-#
-# Note that not all possible configuration values are present in this
-# autogenerated file.
-#
-# All configuration values have a default; values that are commented out
-# serve to show the default.
+
+"""Complexity documentation build configuration file, created by
+sphinx-quickstart on Tue Jul  9 22:26:36 2013.
+
+This file is execfile()d with the current directory set to its containing dir.
+
+Note that not all possible configuration values are present in this
+autogenerated file.
+
+All configuration values have a default; values that are commented out
+serve to show the default.
+"""
 
 import os
 import sys
@@ -23,6 +24,9 @@
 parent = os.path.dirname(cwd)
 sys.path.insert(0, parent)
 
+# Add path for _ext/ogtag.py extension
+sys.path.append(os.path.abspath("_ext"))
+
 import pyzillow  # noqa
 
 # -- General configuration -----------------------------------------------------
@@ -35,6 +39,7 @@
 extensions = [
     "sphinx.ext.autodoc",
     "sphinx.ext.viewcode",
+    "ogtag",
     # "sphinx.ext.autosummary"
 ]
 # autosummary_generate = True
@@ -104,6 +109,11 @@
 
 # -- Options for HTML output ---------------------------------------------------
 
+# Constants for _ext/ogtag.py extension
+og_site_url = "https://pyzillow.readthedocs.io/en/latest/"
+og_twitter_site = "@tcmetzger"
+og_fallback_image = "https://www.tcmetzger.de/STATIC/pyzillow_default.png"
+
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
 html_theme = "sphinx_rtd_theme"