From ce4553b367beb905fcf81d2efab9e7d265c52402 Mon Sep 17 00:00:00 2001
From: Joachim <joachim.robert@protonmail.com>
Date: Tue, 3 Aug 2021 17:45:52 +0200
Subject: [PATCH] Add simple tag to provide fallback if original image doesn't
 exist

---
 bookwyrm/templates/snippets/book_cover.html | 86 +++++++++++++++------
 bookwyrm/templatetags/utilities.py          | 11 +++
 2 files changed, 73 insertions(+), 24 deletions(-)

diff --git a/bookwyrm/templates/snippets/book_cover.html b/bookwyrm/templates/snippets/book_cover.html
index 8068051d1..84303015a 100644
--- a/bookwyrm/templates/snippets/book_cover.html
+++ b/bookwyrm/templates/snippets/book_cover.html
@@ -3,6 +3,7 @@
 {% load i18n %}
 {% load static %}
 {% load imagekit %}
+{% load utilities %}
 
 {% if book.cover %}
     <picture class="cover-container {{ cover_class }}">
@@ -21,93 +22,130 @@
                     <source
                         media="(max-width: 768px)"
                         type="image/webp"
-                        srcset="{{ book.cover_bw_book_xsmall_webp.url }}"
+                        srcset="{% get_book_cover_thumbnail book=book size='xsmall' ext='webp' %}"
                     />
                     <source
                         media="(max-width: 768px)"
                         type="image/jpg"
-                        srcset="{{ book.cover_bw_book_xsmall_jpg.url }}"
+                        srcset="{% get_book_cover_thumbnail book=book size='xsmall' ext='jpg' %}"
                     />
                 {% elif size_mobile == 'small' %}
                     <source
                         media="(max-width: 768px)"
                         type="image/webp"
-                        srcset="{{ book.cover_bw_book_small_webp.url }}"
+                        srcset="{% get_book_cover_thumbnail book=book size='small' ext='webp' %}"
                     />
                     <source
                         media="(max-width: 768px)"
                         type="image/jpg"
-                        srcset="{{ book.cover_bw_book_small_jpg.url }}"
+                        srcset="{% get_book_cover_thumbnail book=book size='small' ext='jpg' %}"
                     />
                 {% elif size_mobile == 'medium' %}
                     <source
                         media="(max-width: 768px)"
                         type="image/webp"
-                        srcset="{{ book.cover_bw_book_medium_webp.url }}"
+                        srcset="{% get_book_cover_thumbnail book=book size='medium' ext='webp' %}"
                     />
                     <source
                         media="(max-width: 768px)"
                         type="image/jpg"
-                        srcset="{{ book.cover_bw_book_medium_jpg.url }}"
+                        srcset="{% get_book_cover_thumbnail book=book size='medium' ext='jpg' %}"
                     />
                 {% elif size_mobile == 'large' %}
                     <source
                         media="(max-width: 768px)"
                         type="image/webp"
-                        srcset="{{ book.cover_bw_book_large_webp.url }}"
+                        srcset="{% get_book_cover_thumbnail book=book size='large' ext='webp' %}"
                     />
                     <source
                         media="(max-width: 768px)"
                         type="image/jpg"
-                        srcset="{{ book.cover_bw_book_large_jpg.url }}"
+                        srcset="{% get_book_cover_thumbnail book=book size='large' ext='jpg' %}"
                     />
                 {% elif size_mobile == 'xlarge' %}
                     <source
                         media="(max-width: 768px)"
                         type="image/webp"
-                        srcset="{{ book.cover_bw_book_xlarge_webp.url }}"
+                        srcset="{% get_book_cover_thumbnail book=book size='xlarge' ext='webp' %}"
                     />
                     <source
                         media="(max-width: 768px)"
                         type="image/jpg"
-                        srcset="{{ book.cover_bw_book_xlarge_jpg.url }}"
+                        srcset="{% get_book_cover_thumbnail book=book size='xlarge' ext='jpg' %}"
                     />
                 {% elif size_mobile == 'xxlarge' %}
                     <source
                         media="(max-width: 768px)"
                         type="image/webp"
-                        srcset="{{ book.cover_bw_book_xxlarge_webp.url }}"
+                        srcset="{% get_book_cover_thumbnail book=book size='xxlarge' ext='webp' %}"
                     />
                     <source
                         media="(max-width: 768px)"
                         type="image/jpg"
-                        srcset="{{ book.cover_bw_book_xxlarge_jpg.url }}"
+                        srcset="{% get_book_cover_thumbnail book=book size='xxlarge' ext='jpg' %}"
                     />
                 {% endif %}
 
                 {% if size == 'xsmall' %}
-                    <source type="image/webp" srcset="{{ book.cover_bw_book_xsmall_webp.url }}"/>
-                    <source type="image/jpg" srcset="{{ book.cover_bw_book_xsmall_jpg.url }}"/>
+                    <source
+                        type="image/webp"
+                        srcset="{% get_book_cover_thumbnail book=book size='xsmall' ext='webp' %}"
+                    />
+                    <source
+                        type="image/jpg"
+                        srcset="{% get_book_cover_thumbnail book=book size='xsmall' ext='jpg' %}"
+                    />
                 {% elif size == 'small' %}
-                    <source type="image/webp" srcset="{{ book.cover_bw_book_small_webp.url }}"/>
-                    <source type="image/jpg" srcset="{{ book.cover_bw_book_small_jpg.url }}"/>
+                    <source
+                        type="image/webp"
+                        srcset="{% get_book_cover_thumbnail book=book size='small' ext='webp' %}"
+                    />
+                    <source
+                        type="image/jpg"
+                        srcset="{% get_book_cover_thumbnail book=book size='small' ext='jpg' %}"
+                    />
                 {% elif size == 'medium' %}
-                    <source type="image/webp" srcset="{{ book.cover_bw_book_medium_webp.url }}"/>
-                    <source type="image/jpg" srcset="{{ book.cover_bw_book_medium_jpg.url }}"/>
+                    <source
+                        type="image/webp"
+                        srcset="{% get_book_cover_thumbnail book=book size='medium' ext='webp' %}"
+                    />
+                    <source
+                        type="image/jpg"
+                        srcset="{% get_book_cover_thumbnail book=book size='medium' ext='jpg' %}"
+                    />
                 {% elif size == 'large' %}
-                    <source type="image/webp" srcset="{{ book.cover_bw_book_large_webp.url }}"/>
-                    <source type="image/jpg" srcset="{{ book.cover_bw_book_large_jpg.url }}"/>
+                    <source
+                        type="image/webp"
+                        srcset="{% get_book_cover_thumbnail book=book size='large' ext='webp' %}"
+                    />
+                    <source
+                        type="image/jpg"
+                        srcset="{% get_book_cover_thumbnail book=book size='large' ext='jpg' %}"
+                    />
                 {% elif size == 'xlarge' %}
-                    <source type="image/webp" srcset="{{ book.cover_bw_book_xlarge_webp.url }}"/>
-                    <source type="image/jpg" srcset="{{ book.cover_bw_book_xlarge_jpg.url }}"/>
+                    <source
+                        type="image/webp"
+                        srcset="{% get_book_cover_thumbnail book=book size='xlarge' ext='webp' %}"
+                    />
+                    <source
+                        type="image/jpg"
+                        srcset="{% get_book_cover_thumbnail book=book size='xlarge' ext='jpg' %}"
+                    />
                 {% elif size == 'xxlarge' %}
-                    <source type="image/webp" srcset="{{ book.cover_bw_book_xxlarge_webp.url }}"/>
-                    <source type="image/jpg" srcset="{{ book.cover_bw_book_xxlarge_jpg.url }}"/>
+                    <source
+                        type="image/webp"
+                        srcset="{% get_book_cover_thumbnail book=book size='xxlarge' ext='webp' %}"
+                    />
+                    <source
+                        type="image/jpg"
+                        srcset="{% get_book_cover_thumbnail book=book size='xxlarge' ext='jpg' %}"
+                    />
                 {% endif %}
 
             {% endif %}
 
             <img
+                alt="{{ book.alt_text|default:'' }}"
                 class="book-cover"
                 itemprop="thumbnailUrl"
                 src="{% if img_path is None %}{% get_media_prefix %}{% else %}{{ img_path }}{% endif %}{{ book.cover }}"
diff --git a/bookwyrm/templatetags/utilities.py b/bookwyrm/templatetags/utilities.py
index 23b6685d6..1be660496 100644
--- a/bookwyrm/templatetags/utilities.py
+++ b/bookwyrm/templatetags/utilities.py
@@ -3,6 +3,7 @@ import os
 from uuid import uuid4
 from django import template
 from django.utils.translation import gettext_lazy as _
+from django.templatetags.static import static
 
 
 register = template.Library()
@@ -50,3 +51,13 @@ def truncatepath(value, arg):
     except ValueError:  # invalid literal for int()
         return path_list[-1]  # Fail silently.
     return "%s/…%s" % (path_list[0], path_list[-1][-length:])
+
+
+@register.simple_tag(takes_context=False)
+def get_book_cover_thumbnail(book, size, ext):
+    """Returns a book thumbnail at the specified size and extension, with fallback if needed"""
+    try:
+        cover_thumbnail = getattr(book, "cover_bw_book_%s_%s" % (size, ext))
+        return cover_thumbnail.url
+    except OSError:
+        return static("images/no_cover.jpg")