feat(handlers): add per-phone index for CSV bulk messages

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: AchoArnold

api/pkg/handlers/bulk_message_handler.go

@@ -89,21 +89,30 @@ func (h *BulkMessageHandler) Store(c *fiber.Ctx) error {
 	wg := sync.WaitGroup{}
 	count := atomic.Int64{}
 
-	for index, message := range messages {
+	// Compute per-phone index for rate-based dispatch delay
+	phoneIndexCounter := make(map[string]int)
+
+	for _, message := range messages {
 		wg.Add(1)
+		var perPhoneIndex int
+		if message.SendTime == nil {
+			perPhoneIndex = phoneIndexCounter[message.FromPhoneNumber]
+			phoneIndexCounter[message.FromPhoneNumber]++
+		}
+
 		go func(message *requests.BulkMessage, index int) {
 			count.Add(1)
 			_, err = h.messageService.SendMessage(
 				ctx,
-				message.ToMessageSendParams(h.userIDFomContext(c), requestID, c.OriginalURL()),
+				message.ToMessageSendParams(h.userIDFomContext(c), requestID, c.OriginalURL(), index),
 			)
 			if err != nil {
 				count.Add(-1)
 				msg := fmt.Sprintf("cannot send message with paylod [%s] at index [%d]", spew.Sdump(message), index)
 				ctxLogger.Error(stacktrace.Propagate(err, msg))
 			}
 			wg.Done()
-		}(message, index)
+		}(message, perPhoneIndex)
 	}
 
 	wg.Wait()

api/pkg/requests/bulk_message_request.go

@@ -38,7 +38,7 @@ func (input *BulkMessage) Sanitize() *BulkMessage {
 }
 
 // ToMessageSendParams converts BulkMessage to services.MessageSendParams
-func (input *BulkMessage) ToMessageSendParams(userID entities.UserID, requestID uuid.UUID, source string) services.MessageSendParams {
+func (input *BulkMessage) ToMessageSendParams(userID entities.UserID, requestID uuid.UUID, source string, index int) services.MessageSendParams {
 	from, _ := phonenumbers.Parse(input.FromPhoneNumber, phonenumbers.UNKNOWN_REGION)
 
 	return services.MessageSendParams{
@@ -51,5 +51,6 @@ func (input *BulkMessage) ToMessageSendParams(userID entities.UserID, requestID
 		Contact:           input.sanitizeAddress(input.ToPhoneNumber),
 		Content:           input.Content,
 		Attachments:       input.removeEmptyStrings(strings.Split(input.AttachmentURLs, ",")),
+		Index:             index,
 	}
 }