Fix race conditions and add validation for job scheduling

- Reuse duplicate prevention logic in rescheduling to prevent race conditions
- Add queueName validation in plugin initialization and helper function
- Enhanced scheduleEmailProcessingJob to return boolean and accept delay parameter
- Improve error handling: rescheduling failures warn but don't fail current job
- Prevent duplicate jobs when multiple handlers complete simultaneously

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/plugin.ts

@@ -5,7 +5,11 @@ import { createEmailTemplatesCollection } from './collections/EmailTemplates.js'
 import Emails from './collections/Emails.js'
 
 // Helper function to schedule the email processing job
-async function scheduleEmailProcessingJob(payload: any, queueName: string): Promise<void> {
+async function scheduleEmailProcessingJob(payload: any, queueName: string, delayMs: number = 60000): Promise<boolean> {
+  if (!queueName || typeof queueName !== 'string') {
+    throw new Error('Invalid queueName: must be a non-empty string')
+  }
+
   const jobSlug = 'process-email-queue'
 
   // Check if there's already a scheduled job for this task
@@ -36,18 +40,25 @@ async function scheduleEmailProcessingJob(payload: any, queueName: string): Prom
         taskSlug: jobSlug,
         input: {},
         queue: queueName,
-        waitUntil: new Date(Date.now() + 60000), // Start in 1 minute
+        waitUntil: new Date(Date.now() + delayMs),
       },
     })
     console.log(`🔄 Scheduled email processing job in queue: ${queueName}`)
+    return true
   } else {
     console.log(`✅ Email processing job already scheduled in queue: ${queueName}`)
+    return false
   }
 }
 
 export const mailingPlugin = (pluginConfig: MailingPluginConfig) => (config: Config): Config => {
   const queueName = pluginConfig.queue || 'default'
 
+  // Validate queueName
+  if (!queueName || typeof queueName !== 'string') {
+    throw new Error('Invalid queue configuration: queue must be a non-empty string')
+  }
+
   // Handle templates collection configuration
   const templatesConfig = pluginConfig.collections?.templates
   const templatesSlug = typeof templatesConfig === 'string' ? templatesConfig : 'email-templates'
@@ -151,20 +162,18 @@ export const mailingPlugin = (pluginConfig: MailingPluginConfig) => (config: Con
               jobResult = new Error(`Email queue processing failed: ${errorMessage}`)
             }
 
-            // Always reschedule the next job (success or failure)
+            // Always reschedule the next job (success or failure) using duplicate prevention
+            let rescheduled = false
             try {
-              await payload.create({
-                collection: 'payload-jobs',
-                data: {
-                  taskSlug: 'process-email-queue',
-                  input: {},
-                  queue: queueName,
-                  waitUntil: new Date(Date.now() + 300000), // Reschedule in 5 minutes
-                },
-              })
-              console.log(`🔄 Rescheduled next email processing job in ${queueName} queue`)
+              rescheduled = await scheduleEmailProcessingJob(payload, queueName, 300000) // Reschedule in 5 minutes
+              if (rescheduled) {
+                console.log(`🔄 Rescheduled next email processing job in ${queueName} queue`)
+              }
             } catch (rescheduleError) {
               console.error('❌ Failed to reschedule email processing job:', rescheduleError)
+              // If rescheduling fails, we should warn but not fail the current job
+              // since the email processing itself may have succeeded
+              console.warn('⚠️  Email processing completed but next job could not be scheduled')
             }
 
             // Return the original result or throw the error