add earlyaccess code generation

booking.earlyaccess_admin.inc

@@ -38,4 +38,59 @@ function booking_earlyaccess_admin() {
 	$output .= theme('table', array('header' => $header, 'rows' => $rows, 'attributes' => $attributes));
 
 	return $output;
+}
+
+/**
+ * Function to generate early access codes for the current event
+ */
+function booking_earlyaccess_generate_codes() {
+  global $event;
+  $num_codes_to_add = 0;
+  $num_codes_available = 0;
+  $code_length = 6;
+
+  //determine number of currently available access codes for this event
+	$codecount_query = db_query("SELECT count(*) as num_codes FROM {booking_regn_earlyaccess_codes} where booking_eventid = :eventid and booking_regn_earlyaccess_code_avail = 'Y'",
+	  array(':eventid' => $event->eid))
+		->fetchObject();
+  $num_codes_available = $codecount_query->num_codes;
+  //get the number of codes we need to have available from variable_get('booking_earlyaccess_codes_count')
+  $num_codes_to_add = variable_get('booking_earlyaccess_codes_count', 0) - $num_codes_available;
+  //add required number of codes to database table
+
+	//use the multi-insert query type at https://drupal.org/node/310079
+	$insert_query = db_insert('booking_regn_earlyaccess_codes')
+    ->fields(array(
+      'booking_eventid',
+      'booking_regn_earlyaccess_code', 
+			'booking_regn_earlyaccess_code_avail',
+  ));	
+	
+  for ($i = 0; $i < $num_codes_to_add; $i++) {
+    $insert_query->values(array(
+      'booking_eventid' => $event->eid,
+      'booking_regn_earlyaccess_code' => booking_getToken(code_length),
+      'booking_regn_earlyaccess_code_avail' => 'Y',
+    ));
+  }
+	$insert_query->execute();
+}
+
+/**
+ * Function to calculate unique code
+ * @see https://stackoverflow.com/questions/1846202/php-how-to-generate-a-random-unique-alphanumeric-string
+ * Requires PHP7
+ */
+function booking_getToken($length){
+  $token = "";
+  $codeAlphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+  //$codeAlphabet.= "abcdefghijklmnopqrstuvwxyz";
+  $codeAlphabet.= "0123456789";
+  $max = strlen($codeAlphabet); // edited
+
+  for ($i=0; $i < $length; $i++) {
+    $token .= $codeAlphabet[random_int(0, $max-1)];
+  }
+
+  return $token;
 }