refactor answer code into one location

lib/session/call-session.js

@@ -443,7 +443,7 @@ class CallSession extends Emitter {
       if (!task.earlyMedia || this.dlg) return this.ep;
 
       // we are going from an early media connection to answer
-      await answerCall();
+      await this.propagateAnswer();
       return this.ep;
     }
 
@@ -459,7 +459,7 @@ class CallSession extends Emitter {
           this.res.send(183, {body: ep.local.sdp});
           return ep;
         }
-        answerCall();
+        this.propagateAnswer();
       }
       else {
         // outbound call TODO
@@ -541,6 +541,36 @@ class CallSession extends Emitter {
     return this.ms;
   }
 
+  /**
+   * Answer the call, if it has not already been answered.
+   * 
+   * NB: This should be the one and only place we generate 200 OK to incoming INVITEs
+   */
+  async propagateAnswer() {
+    if (!this.dlg) {
+      assert(this.ep);
+      this.dlg = await this.srf.createUAS(this.req, this.res, {localSdp: this.ep.local.sdp});
+      this.dlg.on('destroy', this._callerHungup.bind(this));
+      this.wrapDialog(this.dlg);
+      this.dlg.callSid = this.callSid;
+      this.emit('callStatusChange', {sipStatus: 200, callStatus: CallStatus.InProgress});
+
+      this.dlg.on('modify', this._onReinvite.bind(this));
+
+      this.logger.debug(`CallSession:propagateAnswer - answered callSid ${this.callSid}`);
+    }
+  }
+
+  async _onReinvite(req, res) {
+    try {
+      const newSdp = await this.ep.modify(req.body);
+      res.send(200, {body: newSdp});
+      this.logger.info({offer: req.body, answer: newSdp}, 'handling reINVITE');
+    } catch (err) {
+      this.logger.error(err, 'Error handling reinvite');
+    }
+  }
+
   /**
    * create and endpoint if we don't have one; otherwise simply return
    * the current media server and endpoint that are associated with this call

lib/session/inbound-call-session.js

@@ -43,20 +43,6 @@ class InboundCallSession extends CallSession {
     }
   }
 
-  /**
-   * Answer the call, if it has not already been answered.
-   */
-  async propagateAnswer() {
-    if (!this.dlg) {
-      assert(this.ep);
-      this.dlg = await this.srf.createUAS(this.req, this.res, {localSdp: this.ep.local.sdp});
-      this.wrapDialog(this.dlg);
-      this.dlg.on('destroy', this._callerHungup.bind(this));
-      this.emit('callStatusChange', {sipStatus: 200, callStatus: CallStatus.InProgress});
-      this.logger.debug(`CallSession:propagateAnswer - answered callSid ${this.callSid}`);
-    }
-  }
-
   /**
    * This is invoked when the caller hangs up, in order to calculate the call duration.
    */