[NO QA] Add random reportID generation and method for creating optimistic reports

src/libs/ReportUtils.js

@@ -510,6 +510,19 @@ function navigateToDetailsPage(report) {
     Navigation.navigate(ROUTES.getReportParticipantsRoute(report.reportID));
 }
 
+/**
+ * Generate a random reportID between 98000000 (the number of reports before the switch from sequential to random)
+ * and the maximum safe integer of js (53 bits aka 9,007,199,254,740,991)
+ *
+ * In a test of 500M reports (28 years of reports at our current max rate) we got 20-40 collisions meaning that
+ * this is more than random enough for our needs.
+ *
+ * @returns {Number}
+ */
+function generateReportID() {
+    return Math.floor(Math.random() * (Number.MAX_SAFE_INTEGER - 98000000)) + 98000000;
+}
+
 export {
     getReportParticipantsTitle,
     isReportMessageAttachment,
@@ -538,4 +551,5 @@ export {
     getDisplayNamesWithTooltips,
     getReportName,
     navigateToDetailsPage,
+    generateReportID,
 };

src/libs/actions/Report.js

@@ -820,6 +820,39 @@ function fetchAllReports(
         });
 }
 
+/**
+ * Creates an optimistic report with a randomly generated reportID and as much information as we currently have
+ *
+ * @param {Array} participantList
+ * @returns {Object}
+ */
+function createOptimisticReport(participantList) {
+    return {
+        chatType: '',
+        hasOutstandingIOU: false,
+        isOwnPolicyExpenseChat: false,
+        isPinned: false,
+        lastActorEmail: '',
+        lastMessageHtml: '',
+        lastMessageText: null,
+        lastReadSequenceNumber: undefined,
+        lastMessageTimestamp: 0,
+        lastVisitedTimestamp: 0,
+        maxSequenceNumber: 0,
+        notificationPreference: '',
+        oldPolicyName: '',
+        ownerEmail: '__FAKE__',
+        participants: participantList,
+        policyID: '_FAKE_',
+        reportID: ReportUtils.generateReportID(),
+        reportName: 'Chat Report',
+        stateNum: 0,
+        statusNum: 0,
+        unreadActionCount: 0,
+        visibility: undefined,
+    };
+}
+
 /**
  * @param {Number} reportID
  * @param {String} [text]
@@ -1663,4 +1696,5 @@ export {
     readNewestAction,
     openReport,
     openPaymentDetailsPage,
+    createOptimisticReport,
 };