[Experimental] Added a new "Similar" radio based on users history (suggested by @gordon)

api/funkwhale_api/radios/radios.py

@@ -1,7 +1,7 @@
 import random
 
 from django.core.exceptions import ValidationError
-from django.db.models import Count
+from django.db import connection
 from rest_framework import serializers
 from taggit.models import Tag
 
@@ -43,8 +43,7 @@ class SessionRadio(SimpleRadio):
         return self.session
 
     def get_queryset(self, **kwargs):
-        qs = Track.objects.annotate(uploads_count=Count("uploads"))
-        return qs.filter(uploads_count__gt=0)
+        return Track.objects.all()
 
     def get_queryset_kwargs(self):
         return {}
@@ -56,6 +55,10 @@ class SessionRadio(SimpleRadio):
             queryset = self.filter_from_session(queryset)
             if kwargs.pop("filter_playable", True):
                 queryset = queryset.playable_by(self.session.user.actor)
+        queryset = self.filter_queryset(queryset)
+        return queryset
+
+    def filter_queryset(self, queryset):
         return queryset
 
     def filter_from_session(self, queryset):
@@ -153,6 +156,74 @@ class TagRadio(RelatedObjectRadio):
         return qs.filter(tags__in=[self.session.related_object])
 
 
+def weighted_choice(choices):
+    total = sum(w for c, w in choices)
+    r = random.uniform(0, total)
+    upto = 0
+    for c, w in choices:
+        if upto + w >= r:
+            return c
+        upto += w
+    assert False, "Shouldn't get here"
+
+
+class NextNotFound(Exception):
+    pass
+
+
+@registry.register(name="similar")
+class SimilarRadio(RelatedObjectRadio):
+    model = Track
+
+    def filter_queryset(self, queryset):
+        queryset = super().filter_queryset(queryset)
+        seeds = list(
+            self.session.session_tracks.all()
+            .values_list("track_id", flat=True)
+            .order_by("-id")[:3]
+        ) + [self.session.related_object.pk]
+        for seed in seeds:
+            try:
+                return queryset.filter(pk=self.find_next_id(queryset, seed))
+            except NextNotFound:
+                continue
+
+        return queryset.none()
+
+    def find_next_id(self, queryset, seed):
+        with connection.cursor() as cursor:
+            query = """
+            SELECT next, count(next) AS c
+            FROM (
+                SELECT
+                    track_id,
+                    creation_date,
+                    LEAD(track_id) OVER (
+                        PARTITION by user_id order by creation_date asc
+                    ) AS next
+                FROM history_listening
+                INNER JOIN users_user ON (users_user.id = user_id)
+                WHERE users_user.privacy_level = 'instance' OR users_user.privacy_level = 'everyone' OR user_id = %s
+                ORDER BY creation_date ASC
+            ) t WHERE track_id = %s AND next != %s GROUP BY next ORDER BY c DESC;
+            """
+            cursor.execute(query, [self.session.user_id, seed, seed])
+            next_candidates = list(cursor.fetchall())
+
+        if not next_candidates:
+            raise NextNotFound()
+
+        matching_tracks = list(
+            queryset.filter(pk__in=[c[0] for c in next_candidates]).values_list(
+                "id", flat=True
+            )
+        )
+        next_candidates = [n for n in next_candidates if n[0] in matching_tracks]
+        if not next_candidates:
+            raise NextNotFound()
+        return weighted_choice(next_candidates)
+
+
 @registry.register(name="artist")
 class ArtistRadio(RelatedObjectRadio):
     model = Artist