From 03e9da57a1f09ca4f15dce73ccfcc50849e11226 Mon Sep 17 00:00:00 2001
From: Jake Howard <git@theorangeone.net>
Date: Fri, 1 Jul 2022 09:25:57 +0100
Subject: [PATCH] Add anchor links to headers

---
 static/src/scss/_content.scss                  | 10 ++++++++++
 website/common/models.py                       |  6 +++++-
 .../common/templates/common/content_page.html  |  4 ++--
 website/common/utils.py                        | 18 ++++++++++++++++--
 4 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/static/src/scss/_content.scss b/static/src/scss/_content.scss
index f9a86e3..51ec8a8 100644
--- a/static/src/scss/_content.scss
+++ b/static/src/scss/_content.scss
@@ -1,6 +1,16 @@
 section.content {
   font-size: 1.25rem;
   padding-top: 0.5rem;
+
+  h2,
+  h3,
+  h4,
+  h5,
+  h6 {
+    .heading-anchor {
+      margin-right: 0.5rem;
+    }
+  }
 }
 
 .content-details {
diff --git a/website/common/models.py b/website/common/models.py
index 38b2c43..592a4eb 100644
--- a/website/common/models.py
+++ b/website/common/models.py
@@ -10,7 +10,7 @@ from wagtail.images import get_image_model_string
 from wagtail.models import Page
 
 from .streamfield import get_blocks, get_html, get_word_count, truncate_streamfield
-from .utils import TocEntry, get_table_of_contents
+from .utils import TocEntry, add_heading_anchors, get_table_of_contents
 
 
 class BasePage(Page):
@@ -68,6 +68,10 @@ class BaseContentMixin(models.Model):
     def summary(self) -> str:
         return truncate_streamfield(self.body, 50)
 
+    @cached_property
+    def body_html(self):
+        return add_heading_anchors(str(self.body))
+
 
 class ContentPage(BasePage, BaseContentMixin):  # type: ignore[misc]
     subpage_types: list[Any] = []
diff --git a/website/common/templates/common/content_page.html b/website/common/templates/common/content_page.html
index e580c42..6a92e9b 100644
--- a/website/common/templates/common/content_page.html
+++ b/website/common/templates/common/content_page.html
@@ -1,13 +1,13 @@
 {% extends "wagtail_base.html" %}
 
-{% load wagtailcore_tags static %}
+{% load static %}
 
 {% block content %}
 
 {% include "common/hero.html" %}
 
 <section class="container content">
-  {% include_block page.body %}
+  {{ page.body_html|safe }}
 </section>
 
 {% endblock %}
diff --git a/website/common/utils.py b/website/common/utils.py
index 1fefd08..c57586f 100644
--- a/website/common/utils.py
+++ b/website/common/utils.py
@@ -5,9 +5,12 @@ from typing import Type
 from bs4 import BeautifulSoup
 from django.conf import settings
 from django.http.request import HttpRequest
+from django.utils.text import slugify
 from wagtail.models import Page
 from wagtail.models import get_page_models as get_wagtail_page_models
 
+HEADER_TAGS = ["h2", "h3", "h4", "h5", "h6"]
+
 
 @dataclass
 class TocEntry:
@@ -20,10 +23,10 @@ class TocEntry:
 def get_table_of_contents(html: str) -> list[TocEntry]:
     soup = BeautifulSoup(html, "lxml")
 
-    headings = soup.find_all(["h2", "h3", "h4", "h5", "h6"])
+    headings = soup.find_all(HEADER_TAGS)
 
     heading_levels = [
-        TocEntry(tag.text, tag.text, int(tag.name[1]), []) for tag in headings
+        TocEntry(tag.text, slugify(tag.text), int(tag.name[1]), []) for tag in headings
     ]
 
     # Abort if there are no headings
@@ -53,6 +56,17 @@ def get_table_of_contents(html: str) -> list[TocEntry]:
     return root.children
 
 
+def add_heading_anchors(html: str) -> str:
+    soup = BeautifulSoup(html, "lxml")
+    for tag in soup.find_all(HEADER_TAGS):
+        slug = slugify(tag.text)
+        anchor = soup.new_tag("a", href="#" + slug, id=slug)
+        anchor.string = "#"
+        anchor.attrs["class"] = "heading-anchor"
+        tag.insert(0, anchor)
+    return str(soup)
+
+
 def get_page_models() -> list[Type[Page]]:
     page_models = get_wagtail_page_models().copy()
     page_models.remove(Page)