Add playback success rate to /api/v1/stats (#4085)

* Add stats-based /videoplayback blockage status

* Count when YouTube returns wrong video as failure

* Cast playback stats hash type prior to return

* Bump stats refresh timer to 10 minutes

src/invidious/helpers/helpers.cr

@@ -208,3 +208,20 @@ def proxy_file(response, env)
     IO.copy response.body_io, env.response
   end
 end
+
+# Fetch the playback requests tracker from the statistics endpoint.
+#
+# Creates a new tracker when unavailable.
+def get_playback_statistic
+  if (tracker = Invidious::Jobs::StatisticsRefreshJob::STATISTICS["playback"]) && tracker.as(Hash).empty?
+    tracker = {
+      "totalRequests"      => 0_i64,
+      "successfulRequests" => 0_i64,
+      "ratio"              => 0_f64,
+    }
+
+    Invidious::Jobs::StatisticsRefreshJob::STATISTICS["playback"] = tracker
+  end
+
+  return tracker.as(Hash(String, Int64 | Float64))
+end