refactor: optimize credit-service imports with lazy loading (calcom#25091)

* refactor: optimize credit-service imports with lazy loading

- Remove top-level imports of heavy modules (reminderScheduler, email services, i18n, billing services)
- Implement dynamic imports for modules only when needed:
  - reminderScheduler: loaded only when SMS credit limit reached
  - email services: loaded only when sending credit notifications
  - getTranslation: loaded only when handling low credit balance
  - InternalTeamBilling: loaded only in getMonthlyCredits method
  - billing singleton: loaded only when calculating warning limits
- Break circular dependency: credit-service → reminderScheduler → ... → credit-service
- Update tests to mock StripeBillingService for dynamic imports
- All 30 tests passing, no type errors, lint clean

This reduces baseline import cost by deferring:
- Stripe SDK initialization (loaded twice before)
- 557KB+ i18n English translation file
- Email template classes
- Workflow reminder scheduler

Verified with madge: circular dependency successfully resolved

Co-Authored-By: morgan@cal.com <morgan@cal.com>

* fix: add null checks for billing.getPrice() return value

Co-Authored-By: morgan@cal.com <morgan@cal.com>

---------

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: ThyMinimalDev

packages/features/ee/billing/credit-service.test.ts

@@ -101,6 +101,20 @@ vi.mock("../workflows/lib/reminders/reminderScheduler", () => ({
 vi.mock("@calcom/lib/getOrgIdFromMemberOrTeamId", () => ({
   default: vi.fn().mockResolvedValue(null),
 }));
+vi.mock("@calcom/features/ee/billing/stripe-billing-service", () => {
+  return {
+    StripeBillingService: vi.fn().mockImplementation(() => ({
+      getPrice: async (priceId: string) => {
+        const stripe = (await import("@calcom/features/ee/payments/server/stripe")).default;
+        return stripe.prices.retrieve(priceId);
+      },
+      checkoutSessionIsPaid: vi.fn(),
+      handleSubscriptionCancel: vi.fn(),
+      handleSubscriptionCreation: vi.fn(),
+      handleSubscriptionUpdate: vi.fn(),
+    })),
+  };
+});
 
 const creditService = new CreditService();
 

packages/features/ee/billing/credit-service.ts

@@ -1,19 +1,11 @@
 import type { TFunction } from "i18next";
 
 import dayjs from "@calcom/dayjs";
-import {
-  sendCreditBalanceLimitReachedEmails,
-  sendCreditBalanceLowWarningEmails,
-} from "@calcom/emails/billing-email-service";
-import { StripeBillingService } from "@calcom/features/ee/billing/stripe-billing-service";
-import { InternalTeamBilling } from "@calcom/features/ee/billing/teams/internal-team-billing";
 import { TeamRepository } from "@calcom/features/ee/teams/repositories/TeamRepository";
-import { cancelScheduledMessagesAndScheduleEmails } from "@calcom/features/ee/workflows/lib/reminders/reminderScheduler";
 import { MembershipRepository } from "@calcom/features/membership/repositories/MembershipRepository";
 import { IS_SMS_CREDITS_ENABLED } from "@calcom/lib/constants";
 import getOrgIdFromMemberOrTeamId from "@calcom/lib/getOrgIdFromMemberOrTeamId";
 import logger from "@calcom/lib/logger";
-import { getTranslation } from "@calcom/lib/server/i18n";
 import { CreditsRepository } from "@calcom/lib/server/repository/credits";
 import { prisma, type PrismaTransaction } from "@calcom/prisma";
 import { CreditUsageType, CreditType } from "@calcom/prisma/enums";
@@ -474,9 +466,9 @@ export class CreditService {
       const { totalMonthlyCredits } = await this._getAllCreditsForTeam({ teamId, tx });
       warningLimit = totalMonthlyCredits * 0.2;
     } else if (userId) {
-      const billingService = new StripeBillingService();
-      const teamMonthlyPrice = await billingService.getPrice(process.env.STRIPE_TEAM_MONTHLY_PRICE_ID || "");
-      const pricePerSeat = teamMonthlyPrice.unit_amount ?? 0;
+      const billing = (await import("@calcom/features/ee/billing")).default;
+      const teamMonthlyPrice = await billing.getPrice(process.env.STRIPE_TEAM_MONTHLY_PRICE_ID || "");
+      const pricePerSeat = teamMonthlyPrice?.unit_amount ?? 0;
       warningLimit = (pricePerSeat / 2) * 0.2;
     }
 
@@ -495,6 +487,8 @@ export class CreditService {
         return null; // user has limit already reached or team has already reached limit this month
       }
 
+      const { getTranslation } = await import("@calcom/lib/server/i18n");
+
       const teamWithAdmins = creditBalance?.team
         ? {
             ...creditBalance.team,
@@ -591,6 +585,10 @@ export class CreditService {
 
     try {
       if (result.type === "LIMIT_REACHED") {
+        const { sendCreditBalanceLimitReachedEmails } = await import(
+          "@calcom/emails/billing-email-service"
+        );
+
         const promises: Promise<unknown>[] = [
           sendCreditBalanceLimitReachedEmails({
             team: result.team,
@@ -602,6 +600,9 @@ export class CreditService {
         ];
 
         if (!result.creditFor || result.creditFor === CreditUsageType.SMS) {
+          const { cancelScheduledMessagesAndScheduleEmails } = await import(
+            "@calcom/features/ee/workflows/lib/reminders/reminderScheduler"
+          );
           promises.push(
             cancelScheduledMessagesAndScheduleEmails({ teamId: result.teamId, userId: result.userId }).catch(
               (error) => {
@@ -613,6 +614,7 @@ export class CreditService {
 
         await Promise.all(promises);
       } else if (result.type === "WARNING") {
+        const { sendCreditBalanceLowWarningEmails } = await import("@calcom/emails/billing-email-service");
         await sendCreditBalanceLowWarningEmails({
           balance: result.balance,
           team: result.team,
@@ -653,6 +655,7 @@ export class CreditService {
 
     if (!team) return 0;
 
+    const { InternalTeamBilling } = await import("@calcom/features/ee/billing/teams/internal-team-billing");
     const teamBillingService = new InternalTeamBilling(team);
     const subscriptionStatus = await teamBillingService.getSubscriptionStatus();
 
@@ -668,15 +671,19 @@ export class CreditService {
       return activeMembers * creditsPerSeat;
     }
 
-    const billingService = new StripeBillingService();
+    const billing = (await import("@calcom/features/ee/billing")).default;
     const priceId = process.env.STRIPE_TEAM_MONTHLY_PRICE_ID;
 
     if (!priceId) {
       log.warn("Monthly price ID not configured", { teamId });
       return 0;
     }
 
-    const monthlyPrice = await billingService.getPrice(priceId);
+    const monthlyPrice = await billing.getPrice(priceId);
+    if (!monthlyPrice) {
+      log.warn("Failed to retrieve monthly price", { teamId, priceId });
+      return 0;
+    }
     const pricePerSeat = monthlyPrice.unit_amount ?? 0;
     const creditsPerSeat = pricePerSeat * 0.5;