上篇文章介绍了如何获取用户的在线状态，这篇文章我们记录介绍如何统计用户通话记录。
首先，Teams为了安全，它要求 app 要有 CallRecords.Read.All 权限。然后就可以通过这个api来获取 call record。
GET /communications/callRecords/{id}
这个接口会返回类似如下的数据：
{"@odata.context": "https://graph.microsoft.com/beta/$metadata#communications/callRecords/$entity","version": 1,"type": "groupCall","modalities": ["audio"],"lastModifiedDateTime": "2020-12-25T19:00:24.582757Z","startDateTime": "2020-12-25T18:52:21.321Z","endDateTime": "2020-12-25T19:52:46.123Z","id": "e523d2ed-1111-4b6b-925b-754a88034cc5","organizer": {"user": {"id": "821809f5-0000-0000-0000-3b5136c0e777","displayName": "Abbie Wilkins","tenantId": "dc368399-474c-4d40-900c-6265431fd81f"}},"participants": [{"user": {"id": "821809f5-0000-0000-0000-3b5136c0e777","displayName": "Abbie Wilkins","tenantId": "dc368399-474c-4d40-900c-6265431fd81f"}},...]
}
可以看到，我们能通过 organizer 和 participants 来找到参与这个通过的参与人，我们可以记录下用户的 user id，同时我们还可以通过 startDateTime 和 endDateTime 来取得这次 call 的开始和结束时间。
实际上 Teams 里的 call record 比我们想象的复杂很多，一个call里可能有多个 session 组成，我们用一张官方的数据模型图看一下。
我们可以给上面这个 api 加上参数来获取 session。
GET https://graph.microsoft.com/beta/communications/callRecords/{id}?$expand=sessions
{"@odata.context": "https://graph.microsoft.com/beta/$metadata#communications/callRecords(sessions(segments()))/$entity","startDateTime": "2020-02-25T18:52:21.2169889Z","endDateTime": "2020-02-25T18:52:46.7640013Z","organizer": { ... },"participants": [ ... ],"sessions": [{"modalities": ["audio"],"startDateTime": "2020-02-25T18:52:21.2169889Z","endDateTime": "2020-02-25T18:52:46.7640013Z","id": "e523d2ed-2966-4b6b-925b-754a88034cc5","caller": {"@odata.type": "#microsoft.graph.callRecords.participantEndpoint","userAgent": {"@odata.type": "#microsoft.graph.callRecords.clientUserAgent","headerValue": "RTCC/7.0.0.0 UCWA/7.0.0.0 AndroidLync/6.25.0.27 (SM-G930U Android 8.0.0)","platform": "android","productFamily": "skypeForBusiness"},"identity": {"@odata.type": "#microsoft.graph.identitySet","user": {"id": "821809f5-0000-0000-0000-3b5136c0e777","displayName": "Abbie Wilkins","tenantId": "dc368399-474c-4d40-900c-6265431fd81f"}}},"callee": {"@odata.type": "#microsoft.graph.callRecords.participantEndpoint","userAgent": {"@odata.type": "#microsoft.graph.callRecords.clientUserAgent","headerValue": "UCCAPI/16.0.12527.20122 OC/16.0.12527.20194 (Skype for Business)","platform": "windows","productFamily": "skypeForBusiness"},"identity": {"user": {"id": "f69e2c00-0000-0000-0000-185e5f5f5d8a","displayName": "Owen Franklin","tenantId": "dc368399-474c-4d40-900c-6265431fd81f"}},"feedback": {"rating": "poor","tokens": {"NoSound": false,"OtherNoSound": false,"Echo": false,"Noisy": true,"LowVolume": false,"Stopped": false,"DistortedSound": false,"Interruptions": false}}}}]
}
从上面返回的json可以看到，session里有 startDateTime 和 endDateTime。还有 caller 和 callee，我们用这些数据来进行进一步的深入统计，而且可以看到里面还有每个用户参与这个通话是使用的设备（userAgent.platform），更有意思的是，这里面还有 feedback，里面有这个用户这次通话中音质是好还是差，有没有噪音等等。有了这些信息，相信大家脑海里已经有了大量的可以统计的点了。
各位看到这里，可能会问，上面的接口是获取某一次 call record 的，那我如何获取所有的记录呢？
这里就需要用到 graph api 的订阅功能。
POST https://graph.microsoft.com/beta/subscriptions
{"changeType": "created","notificationUrl": "https://<<your api url>>","resource": "/communications/callRecords","expirationDateTime":"2016-11-20T18:23:45.9356913Z","clientState": "secretClientValue","latestSupportedTlsVersion": "v1_2"
}
上面的 resource 是 /communications/callRecords，表明如果有任何一个call发生，graph api会回调我们的接口。上面的 "notificationUrl": "https://<<your api url>>" 是你的服务的回调 url，我们可以在这个接口里得到相应的 call record id，并且记录下来，等一段时间call 结束后，就可以获取整个call的信息了。
