feat(billing): add billions unit formatting for token display

Generated-By: PostHog Code

Author: MattPua

packages/core/src/billing/spendAnalysisFormat.test.ts

@@ -0,0 +1,17 @@
+import { describe, expect, it } from "vitest";
+import { formatTokens } from "./spendAnalysisFormat";
+
+describe("formatTokens", () => {
+  it.each([
+    [0, "0"],
+    [999, "999"],
+    [1_000, "1k"],
+    [108_400, "108k"],
+    [1_500_000, "1.5M"],
+    [999_949_999, "999.9M"],
+    [1_000_000_000, "1.0B"],
+    [2_449_300_000, "2.4B"],
+  ])("formats %d as %s", (input, expected) => {
+    expect(formatTokens(input)).toBe(expected);
+  });
+});

packages/core/src/billing/spendAnalysisFormat.ts

@@ -6,6 +6,7 @@ export function formatUsd(amount: number): string {
 }
 
 export function formatTokens(n: number): string {
+  if (n >= 1_000_000_000) return `${(n / 1_000_000_000).toFixed(1)}B`;
   if (n >= 1_000_000) return `${(n / 1_000_000).toFixed(1)}M`;
   if (n >= 1_000) return `${(n / 1_000).toFixed(0)}k`;
   return n.toString();