From 0f767ffa668bed98b5be9249f9b5e970b3245397 Mon Sep 17 00:00:00 2001
From: Mark Trolley <marktrolley@gmail.com>
Date: Sun, 28 Jun 2020 16:04:29 -0400
Subject: [PATCH] fetchart: Use Cover Art Archive thumbnails

The Cover Art Archive API offers pre-resized thumbnails of cover
art. If the `maxwidth` option of `fetchart` matches one of the
supported Cover Art Archive thumbnail sizes, and a thumbnail of
that size exists in the Cover Art Archive, fetch it directly
instead of fetching the full size image then resizing it.
---
 beetsplug/fetchart.py | 27 +++++++++++++++++++++++----
 docs/changelog.rst    |  3 +++
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/beetsplug/fetchart.py b/beetsplug/fetchart.py
index 70477a624..86c5b958f 100644
--- a/beetsplug/fetchart.py
+++ b/beetsplug/fetchart.py
@@ -305,6 +305,7 @@ class RemoteArtSource(ArtSource):
 class CoverArtArchive(RemoteArtSource):
     NAME = u"Cover Art Archive"
     VALID_MATCHING_CRITERIA = ['release', 'releasegroup']
+    VALID_THUMBNAIL_SIZES = [250, 500, 1200]
 
     if util.SNI_SUPPORTED:
         URL = 'https://coverartarchive.org/release/{mbid}/front'
@@ -317,13 +318,31 @@ class CoverArtArchive(RemoteArtSource):
         """Return the Cover Art Archive and Cover Art Archive release group URLs
         using album MusicBrainz release ID and release group ID.
         """
+        release_url = self.URL.format(mbid=album.mb_albumid)
+        release_group_url = self.GROUP_URL.format(mbid=album.mb_releasegroupid)
+
+        # Cover Art Archive API offers pre-resized thumbnails at several sizes.
+        # If the maxwidth config matches one of the already available sizes
+        # fetch it directly intead of fetching the full sized image and
+        # resizing it.
+        size_suffix = None
+        if plugin.maxwidth in self.VALID_THUMBNAIL_SIZES:
+            size_suffix = "-" + str(plugin.maxwidth)
+
         if 'release' in self.match_by and album.mb_albumid:
-            yield self._candidate(url=self.URL.format(mbid=album.mb_albumid),
+            if size_suffix:
+                release_thumbnail_url = release_url + size_suffix
+                yield self._candidate(url=release_thumbnail_url,
+                                      match=Candidate.MATCH_EXACT)
+            yield self._candidate(url=release_url,
                                   match=Candidate.MATCH_EXACT)
         if 'releasegroup' in self.match_by and album.mb_releasegroupid:
-            yield self._candidate(
-                url=self.GROUP_URL.format(mbid=album.mb_releasegroupid),
-                match=Candidate.MATCH_FALLBACK)
+            if size_suffix:
+                release_group_thumbnail_url = release_group_url + size_suffix
+                yield self._candidate(url=release_group_thumbnail_url,
+                                      match=Candidate.MATCH_FALLBACK)
+            yield self._candidate(url=release_group_url,
+                                  match=Candidate.MATCH_FALLBACK)
 
 
 class Amazon(RemoteArtSource):
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 73cd89fb8..b6904bb71 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -217,6 +217,9 @@ Fixes:
   results or fetched lyrics
   :bug:`2805`
 * Adapt to breaking changes in Python's ``ast`` module in 3.8
+* :doc:`/plugins/fetchart`: Attempt to fetch pre-resized thumbnails from Cover
+  Art Archive if the ``maxwidth`` option matches one of the sizes supported by
+  the Cover Art Archive API.
 
 For plugin developers: