Fix incrementing logic on new cohort names

Author: cjqian

frontend/src/components/experiment_dashboard/cohort_list.ts

@@ -134,8 +134,8 @@ export class Component extends MobxLitElement {
   }
 
   private renderHeader() {
-    const getCohortName = (length: number) => {
-      return this.experimentManager.getNextCohortName(length);
+    const getCohortName = (offset: number) => {
+      return this.experimentManager.getNextCohortName(offset);
     };
 
     return html`
@@ -155,9 +155,7 @@ export class Component extends MobxLitElement {
               ?loading=${this.experimentManager.isWritingCohort}
               @click=${() => {
                 this.analyticsService.trackButtonClick(ButtonClick.COHORT_ADD);
-                const name = getCohortName(
-                  this.experimentManager.cohortList.length,
-                );
+                const name = getCohortName(0);
                 this.experimentManager.createCohort({}, name);
               }}
             >
@@ -170,12 +168,11 @@ export class Component extends MobxLitElement {
               variant="tonal"
               ?loading=${this.experimentManager.isWritingCohort}
               @click=${() => {
-                const numCohorts = this.experimentManager.cohortList.length;
                 [...Array(5).keys()].forEach((key) => {
                   this.analyticsService.trackButtonClick(
                     ButtonClick.COHORT_ADD,
                   );
-                  const name = getCohortName(numCohorts + key);
+                  const name = getCohortName(key);
                   this.experimentManager.createCohort({}, name);
                 });
               }}
@@ -189,12 +186,11 @@ export class Component extends MobxLitElement {
               variant="tonal"
               ?loading=${this.experimentManager.isWritingCohort}
               @click=${() => {
-                const numCohorts = this.experimentManager.cohortList.length;
                 [...Array(10).keys()].forEach((key) => {
                   this.analyticsService.trackButtonClick(
                     ButtonClick.COHORT_ADD,
                   );
-                  const name = getCohortName(numCohorts + key);
+                  const name = getCohortName(key);
                   this.experimentManager.createCohort({}, name);
                 });
               }}

frontend/src/services/experiment.manager.ts

@@ -369,14 +369,27 @@ export class ExperimentManager extends Service {
   }
 
   // Return name for next cohort based on number of cohorts
-  getNextCohortName(numCohorts = this.cohortList.length) {
+  getNextCohortName(offset = 0) {
     const hasTransfer = this.sp.experimentService.stages.find(
       (stage) => stage.kind === StageKind.TRANSFER,
     );
-    if (numCohorts > 0 || !hasTransfer) {
-      return `Cohort ${String(numCohorts).padStart(2, '0')}`;
+
+    if (this.cohortList.length === 0 && hasTransfer) {
+      return 'Lobby';
     }
-    return 'Lobby';
+
+    let maxNum = -1;
+    this.cohortList.forEach((cohort) => {
+      const match = cohort.metadata.name.match(/^Cohort (\d+)$/);
+      if (match) {
+        const num = parseInt(match[1], 10);
+        if (!isNaN(num) && num > maxNum) {
+          maxNum = num;
+        }
+      }
+    });
+
+    return `Cohort ${String(maxNum + 1 + offset).padStart(2, '0')}`;
   }
 
   isFullCohort(cohort: CohortConfig) {