Add webrtc metric to OTel (#974)

* stats: Add summery report

---------

Co-authored-by: David Baker <dave@matrix.org>

src/otel/ObjectFlattener.ts

@@ -0,0 +1,97 @@
+/*
+Copyright 2023 New Vector Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+import { Attributes } from "@opentelemetry/api";
+import { GroupCallStatsReport } from "matrix-js-sdk/src/webrtc/groupCall";
+import {
+  ByteSentStatsReport,
+  ConnectionStatsReport,
+  SummaryStatsReport,
+} from "matrix-js-sdk/src/webrtc/stats/statsReport";
+
+export class ObjectFlattener {
+  public static flattenConnectionStatsReportObject(
+    statsReport: GroupCallStatsReport<ConnectionStatsReport>
+  ): Attributes {
+    const flatObject = {};
+    ObjectFlattener.flattenObjectRecursive(
+      statsReport.report,
+      flatObject,
+      "matrix.stats.conn.",
+      0
+    );
+    return flatObject;
+  }
+
+  public static flattenByteSentStatsReportObject(
+    statsReport: GroupCallStatsReport<ByteSentStatsReport>
+  ): Attributes {
+    const flatObject = {};
+    ObjectFlattener.flattenObjectRecursive(
+      statsReport.report,
+      flatObject,
+      "matrix.stats.bytesSent.",
+      0
+    );
+    return flatObject;
+  }
+
+  static flattenSummaryStatsReportObject(
+    statsReport: GroupCallStatsReport<SummaryStatsReport>
+  ) {
+    const flatObject = {};
+    ObjectFlattener.flattenObjectRecursive(
+      statsReport.report,
+      flatObject,
+      "matrix.stats.summary.",
+      0
+    );
+    return flatObject;
+  }
+
+  public static flattenObjectRecursive(
+    obj: Object,
+    flatObject: Attributes,
+    prefix: string,
+    depth: number
+  ): void {
+    if (depth > 10)
+      throw new Error(
+        "Depth limit exceeded: aborting VoipEvent recursion. Prefix is " +
+          prefix
+      );
+    let entries;
+    if (obj instanceof Map) {
+      entries = obj.entries();
+    } else {
+      entries = Object.entries(obj);
+    }
+    for (const [k, v] of entries) {
+      if (["string", "number", "boolean"].includes(typeof v) || v === null) {
+        let value;
+        value = v === null ? "null" : v;
+        value = typeof v === "number" && Number.isNaN(v) ? "NaN" : value;
+        flatObject[prefix + k] = value;
+      } else if (typeof v === "object") {
+        ObjectFlattener.flattenObjectRecursive(
+          v,
+          flatObject,
+          prefix + k + ".",
+          depth + 1
+        );
+      }
+    }
+  }
+}