Extract getDiscountID()

This is part of a general cleanup to stop passing the form into functions & then checking the form
for a possible property. Instead each form that calls the function has a consistent
(publicly supported) getDiscountID() function that it calls & discountID is passed in.

Note I was actually trying to give getPriceSetID this treatment but discountID was in the
way. In general I'm trying to make some consisent public functions available on forms
for retrieving relevant entity IDs rather than the current property / form
variable patchwork

CRM/Event/Form/Participant.php

@@ -524,8 +524,8 @@ public function setDefaultValues(): array {
 
       $this->_eventTypeId = CRM_Core_DAO::getFieldValue('CRM_Event_DAO_Event', $eventID, 'event_type_id', 'id');
 
-      $this->_discountId = CRM_Core_DAO::getFieldValue('CRM_Event_DAO_Participant', $this->_id, 'discount_id');
-      if ($this->_discountId) {
+      if ($this->getDiscountID()) {
+        // This doesn't seem used....
         $this->set('discountId', $this->_discountId);
       }
     }
@@ -1436,8 +1436,8 @@ public function buildEventFeeForm($form) {
 
       //retrieve custom information
       $form->_values = [];
-      CRM_Event_Form_Registration::initEventFee($form, $event['id'], FALSE);
-      CRM_Event_Form_Registration_Register::buildAmount($form, TRUE, $form->_discountId);
+      CRM_Event_Form_Registration::initEventFee($form, $event['id'], FALSE, $form->getDiscountID());
+      CRM_Event_Form_Registration_Register::buildAmount($form, TRUE, $form->getDiscountID());
       $lineItem = [];
       $totalTaxAmount = 0;
       if (!CRM_Utils_System::isNull($form->_values['line_items'] ?? NULL)) {
@@ -2266,4 +2266,28 @@ protected function sendReceipts($params, $total_amount, array $customFields, arr
     return ['sent' => count($sent), 'not_sent' => count($notSent)];
   }
 
+  /**
+   * Get the discount ID.
+   *
+   * @return int|null
+   *
+   * @api This function will not change in a minor release and is supported for
+   * use outside of core. This annotation / external support for properties
+   * is only given where there is specific test cover.
+   *
+   * @noinspection PhpDocMissingThrowsInspection
+   * @noinspection PhpUnhandledExceptionInspection
+   */
+  public function getDiscountID(): ?int {
+    if ($this->_discountId === NULL) {
+      if ($this->getParticipantID()) {
+        $this->_discountId = (int) CRM_Core_DAO::getFieldValue('CRM_Event_DAO_Participant', $this->getParticipantID(), 'discount_id');
+      }
+      else {
+        CRM_Core_BAO_Discount::findSet($this->getEventID(), 'civicrm_event');
+      }
+    }
+    return $this->_discountId ?: NULL;
+  }
+
 }

CRM/Event/Form/ParticipantFeeSelection.php

@@ -172,7 +172,7 @@ public function buildQuickForm() {
     //retrieve custom information
     $this->_values = [];
 
-    CRM_Event_Form_Registration::initEventFee($this, $event['id'], $this->_action !== CRM_Core_Action::UPDATE);
+    CRM_Event_Form_Registration::initEventFee($this, $event['id'], $this->_action !== CRM_Core_Action::UPDATE, $this->getDiscountID());
     CRM_Event_Form_Registration_Register::buildAmount($this, TRUE);
 
     if (!CRM_Utils_System::isNull($this->_values['line_items'] ?? NULL)) {
@@ -225,6 +225,23 @@ public function buildQuickForm() {
     $this->addFormRule(['CRM_Event_Form_ParticipantFeeSelection', 'formRule'], $this);
   }
 
+  /**
+   * Get the discount ID.
+   *
+   * @return int|null
+   *
+   * @api This function will not change in a minor release and is supported for
+   * use outside of core. This annotation / external support for properties
+   * is only given where there is specific test cover.
+   *
+   * @noinspection PhpDocMissingThrowsInspection
+   * @noinspection PhpUnhandledExceptionInspection
+   */
+  public function getDiscountID(): ?int {
+    $discountID = (int) CRM_Core_BAO_Discount::findSet($this->getEventID(), 'civicrm_event');
+    return $discountID ?: NULL;
+  }
+
   /**
    * @param $fields
    * @param $files
@@ -390,4 +407,23 @@ private function emailReceipt(array $params): void {
     CRM_Core_BAO_MessageTemplate::sendTemplate($sendTemplateParams);
   }
 
+  /**
+   * Get the event ID.
+   *
+   * This function is supported for use outside of core.
+   *
+   * @api This function will not change in a minor release and is supported for
+   * use outside of core. This annotation / external support for properties
+   * is only given where there is specific test cover.
+   *
+   * @return int
+   * @throws \CRM_Core_Exception
+   */
+  public function getEventID(): int {
+    if (!$this->_eventId) {
+      $this->_eventId = CRM_Core_DAO::getFieldValue('CRM_Event_DAO_Participant', $this->_participantId, 'event_id');
+    }
+    return $this->_eventId;
+  }
+
 }

CRM/Event/Form/Registration.php

@@ -297,8 +297,9 @@ public function preProcess() {
         ));
         $this->assignPaymentProcessor($isPayLater);
       }
-      //init event fee.
-      self::initEventFee($this, $this->_eventId);
+
+      $discountId = $this->getDiscountID();
+      self::initEventFee($this, $this->_eventId, TRUE, $discountId);
 
       // get the profile ids
       $ufJoinParams = [
@@ -570,18 +571,15 @@ public function buildCustom($id, $name) {
    * @param int $eventID
    * @param bool $doNotIncludeExpiredFields
    *   See CRM-16456.
+   * @param int|null $discountId
+   *   ID of any discount in use.
    *
    * @throws Exception
    */
-  public static function initEventFee(&$form, $eventID, $doNotIncludeExpiredFields = TRUE) {
+  public static function initEventFee(&$form, $eventID, $doNotIncludeExpiredFields = TRUE, $discountId = NULL) {
     // get price info
 
     // retrive all active price set fields.
-    $discountId = CRM_Core_BAO_Discount::findSet($eventID, 'civicrm_event');
-    if (property_exists($form, '_discountId') && $form->_discountId) {
-      $discountId = $form->_discountId;
-    }
-
     if ($discountId) {
       $priceSetId = CRM_Core_DAO::getFieldValue('CRM_Core_BAO_Discount', $discountId, 'price_set_id');
     }
@@ -892,7 +890,7 @@ protected function addParticipant(&$form, $contactID) {
     $participantParams['custom'] = [];
     foreach ($form->_params as $paramName => $paramValue) {
       if (strpos($paramName, 'custom_') === 0) {
-        list($customFieldID, $customValueID) = CRM_Core_BAO_CustomField::getKeyID($paramName, TRUE);
+        [$customFieldID, $customValueID] = CRM_Core_BAO_CustomField::getKeyID($paramName, TRUE);
         CRM_Core_BAO_CustomField::formatCustomField($customFieldID, $participantParams['custom'], $paramValue, 'Participant', $customValueID);
 
       }
@@ -1717,4 +1715,21 @@ private function getInfoPageUrl(): string {
     );
   }
 
+  /**
+   * Get the discount ID.
+   *
+   * @return int|null
+   *
+   * @api This function will not change in a minor release and is supported for
+   * use outside of core. This annotation / external support for properties
+   * is only given where there is specific test cover.
+   *
+   * @noinspection PhpUnhandledExceptionInspection
+   * @noinspection PhpDocMissingThrowsInspection
+   */
+  protected function getDiscountID(): ?int {
+    $id = CRM_Core_BAO_Discount::findSet($this->getEventID(), 'civicrm_event');
+    return $id ?: NULL;
+  }
+
 }