[scrobbles] Add overlap map

vrobbler/apps/scrobbles/views.py

@@ -331,10 +331,67 @@ class ScrobbleListView(LoginRequiredMixin, ListView):
         self.tag_list = tag_list
         return qs
 
+    def _compute_overlap_groups(self, scrobbles):
+        parent = {}
+
+        def find(x):
+            while parent[x] != x:
+                parent[x] = parent[parent[x]]
+                x = parent[x]
+            return x
+
+        def union(x, y):
+            rx, ry = find(x), find(y)
+            if rx != ry:
+                parent[rx] = ry
+
+        for s in scrobbles:
+            parent[s.pk] = s.pk
+
+        def range_for(s):
+            start = s.timestamp
+            end = s.stop_timestamp
+            if end is None:
+                end = start + datetime.timedelta(hours=12)
+            return start, end
+
+        for i, a in enumerate(scrobbles):
+            a_start, a_end = range_for(a)
+            for b in scrobbles[i + 1 :]:
+                b_start, b_end = range_for(b)
+                if a_start <= b_end and b_start <= a_end:
+                    union(a.pk, b.pk)
+
+        groups = {}
+        for s in scrobbles:
+            root = find(s.pk)
+            groups.setdefault(root, []).append(s.pk)
+
+        overlap_map = {}
+        color_idx = 0
+        COLORS = [
+            "border-start border-3 border-info",
+            "border-start border-3 border-success",
+            "border-start border-3 border-warning",
+            "border-start border-3 border-primary",
+            "border-start border-3 border-danger",
+            "border-start border-3 border-secondary",
+        ]
+        for root, members in groups.items():
+            if len(members) >= 2:
+                color = COLORS[color_idx % len(COLORS)]
+                for pk in members:
+                    overlap_map[pk] = color
+                color_idx += 1
+
+        return overlap_map
+
     def get_context_data(self, **kwargs):
         ctx = super().get_context_data(**kwargs)
         ctx["tags_param"] = self.request.GET.get("tags", "")
         ctx["tag_list"] = getattr(self, "tag_list", [])
+        scrobbles = list(ctx.get("object_list", []))
+        ctx["overlap_map"] = self._compute_overlap_groups(scrobbles)
         return ctx