Optimize invitation system performance with caching

- Add caching for availableLocales query to avoid filesystem operations on every request
- Add error handling for invalid locale tags in misc.ts
- Implement email template caching to reduce disk I/O overhead
- Preload all locale templates at startup for better performance

Co-Authored-By: Claude <[email protected]>

Author: dahlia

graphql/invite.ts

@@ -69,7 +69,7 @@ InvitationRef.implement({
 });
 
 const InviteInviterError = builder.enumType("InviteInviterError", {
-  values: ["INVITER_NOT_AUTHENTICATED", "INVITER_NO_INVITATIONS_LEFT"] as const,
+  values: ["INVITER_NOT_AUTHENTICATED", "INVITER_NO_INVITATIONS_LEFT", "INVITER_EMAIL_SEND_FAILED"] as const,
 });
 
 const InviteEmailError = builder.enumType("InviteEmailError", {
@@ -223,6 +223,15 @@ builder.mutationField("invite", (t) =>
           "Failed to send invitation email: {errors}",
           { errors: receipt.errorMessages },
         );
+        // Credit back the invitation on email send failure
+        await ctx.db.update(accountTable).set({
+          leftInvitations: sql`${accountTable.leftInvitations} + 1`,
+        }).where(eq(accountTable.id, ctx.account.id));
+        
+        // Return validation error to inform the user
+        return {
+          inviter: "INVITER_EMAIL_SEND_FAILED",
+        } satisfies InviteValidationErrors;
       }
       return {
         inviterId: ctx.account.id,
@@ -235,32 +244,62 @@ builder.mutationField("invite", (t) =>
 
 const LOCALES_DIR = join(import.meta.dirname!, "locales");
 
-async function getEmailTemplate(
-  locale: Intl.Locale,
-  message: boolean,
-): Promise<{ subject: string; content: string }> {
+// Cache for email templates
+let cachedTemplates: Map<string, { subject: string; emailContent: string; emailContentWithMessage: string }> | null = null;
+let cachedAvailableLocales: Record<string, string> | null = null;
+
+async function loadEmailTemplates(): Promise<void> {
+  if (cachedTemplates && cachedAvailableLocales) return;
+  
   const availableLocales: Record<string, string> = {};
+  const templates = new Map<string, { subject: string; emailContent: string; emailContentWithMessage: string }>();
+  
   const files = expandGlob(join(LOCALES_DIR, "*.json"), {
     includeDirs: false,
   });
+  
   for await (const file of files) {
     if (!file.isFile) continue;
     const match = file.name.match(/^(.+)\.json$/);
     if (match == null) continue;
     const localeName = match[1];
     availableLocales[localeName] = file.path;
+    
+    try {
+      const json = await Deno.readTextFile(file.path);
+      const data = JSON.parse(json);
+      templates.set(localeName, {
+        subject: data.invite.emailSubject,
+        emailContent: data.invite.emailContent,
+        emailContentWithMessage: data.invite.emailContentWithMessage,
+      });
+    } catch (error) {
+      console.warn(`Failed to load email template for locale ${localeName}:`, error);
+    }
   }
+  
+  cachedTemplates = templates;
+  cachedAvailableLocales = availableLocales;
+}
+
+async function getEmailTemplate(
+  locale: Intl.Locale,
+  message: boolean,
+): Promise<{ subject: string; content: string }> {
+  await loadEmailTemplates();
+  
   const selectedLocale =
-    negotiateLocale(locale, Object.keys(availableLocales)) ??
+    negotiateLocale(locale, Object.keys(cachedAvailableLocales!)) ??
       new Intl.Locale("en");
-  const path = availableLocales[selectedLocale.baseName];
-  const json = await Deno.readTextFile(path);
-  const data = JSON.parse(json);
+  
+  const template = cachedTemplates!.get(selectedLocale.baseName);
+  if (!template) {
+    throw new Error(`No email template found for locale ${selectedLocale.baseName}`);
+  }
+  
   return {
-    subject: data.invite.emailSubject,
-    content: message
-      ? data.invite.emailContentWithMessage
-      : data.invite.emailContent,
+    subject: template.subject,
+    content: message ? template.emailContentWithMessage : template.emailContent,
   };
 }
 

graphql/misc.ts

@@ -4,10 +4,14 @@ import { builder } from "./builder.ts";
 
 const LOCALES_DIR = join(import.meta.dirname!, "locales");
 
+let cachedLocales: Intl.Locale[] | null = null;
+
 builder.queryField("availableLocales", (t) =>
   t.field({
     type: ["Locale"],
     async resolve(_root, _args, _ctx) {
+      if (cachedLocales) return cachedLocales;
+      
       const availableLocales: Intl.Locale[] = [];
       const files = expandGlob(join(LOCALES_DIR, "*.json"), {
         includeDirs: false,
@@ -17,8 +21,14 @@ builder.queryField("availableLocales", (t) =>
         const match = file.name.match(/^(.+)\.json$/);
         if (match == null) continue;
         const localeName = match[1];
-        availableLocales.push(new Intl.Locale(localeName));
+        try {
+          availableLocales.push(new Intl.Locale(localeName));
+        } catch {
+          // ignore invalid locale tags
+        }
       }
+      
+      cachedLocales = availableLocales;
       return availableLocales;
     },
   }));