1 files changed, 48 insertions, 15 deletions

diff --git a/classes/Calculatable.php b/classes/Calculatable.php
index 5d60704..76f89eb 100644
--- a/classes/Calculatable.php
+++ b/classes/Calculatable.php
@@ -22,35 +22,68 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-define('CALCULATABLE_SUBTOTAL', 1);
-define('CALCULATABLE_VAT', 2);
-define('CALCULATABLE_TOTAL', 3);
-
 /**
- * The calculatable trait, to be used by something of which subtotal, VAT and
- * total can be calculated
+ * The calculatable interface, to be used by something of which subtotal, VAT
+ * and total can be calculated
  */
-trait Calculatable {
+interface Calculatable {
+	const SUBTOTAL = 1;
+	const VAT = 2;
+	const TOTAL = 3;
+
 	/**
 	 * Calculate the subtotal
 	 *
 	 * @return float                        The subtotal
 	 */
-	abstract protected function calculateSubtotal();
+	function calculateSubtotal();
 
 	/**
 	 * Calculate the VAT
 	 *
 	 * @return float                        The VAT
 	 */
-	abstract protected function calculateVAT();
+	function calculateVAT();
+
+	/**
+	 * Calculate the total
+	 *
+	 * @return float                        The total
+	 */
+	function calculateTotal();
+
+	/**
+	 * Calculate and possibly format
+	 *
+	 * Subtotal: the sum of the prices of the assignments excl. VAT
+	 * VAT: the sum of all the VAT from all the assignments
+	 * Total: the sum of subtotal and total
+	 *
+	 * @param int $what                     Any of Calculatable::SUBTOTAL, Calculatable::VAT and Calculatable::TOTAL
+	 * @param int $round                    How many decimals to round the result on
+	 * @param bool $format                  Whether to format the number nicely (for output) or not (for calculations)
+	 *
+	 * @throws PDOException                 If something went wrong with the database
+	 *
+	 * @return float|bool                   The calculated value rounded to $round decimals, or false on incorrect input
+	 */
+	function calculate($what = Calculatable::TOTAL, $round = 2, $format = true);
+}
+
+/**
+ * The calculatable trait, to be used by something of which subtotal, VAT and
+ * total can be calculated
+ */
+trait StandardCalculatable {
+	abstract public function calculateSubtotal();
+	abstract public function calculateVAT();
 
 	/**
 	 * Calculate the total
 	 *
 	 * @return float                        The total
 	 */
-	protected function calculateTotal() {
+	public function calculateTotal() {
 		return $this->calculateSubtotal() + $this->calculateVAT();
 	}
 
@@ -61,7 +94,7 @@ trait Calculatable {
 	 * VAT: the sum of all the VAT from all the assignments
 	 * Total: the sum of subtotal and total
 	 *
-	 * @param int $what                     Any of CALCULATABLE_SUBTOTAL, CALCULATABLE_VAT and CALCULATABLE_TOTAL
+	 * @param int $what                     Any of Calculatable::SUBTOTAL, Calculatable::VAT and Calculatable::TOTAL
 	 * @param int $round                    How many decimals to round the result on
 	 * @param bool $format                  Whether to format the number nicely (for output) or not (for calculations)
 	 *
@@ -69,16 +102,16 @@ trait Calculatable {
 	 *
 	 * @return float|bool                   The calculated value rounded to $round decimals, or false on incorrect input
 	 */
-	public function calculate($what = CALCULATABLE_TOTAL, $round = 2, $format = true) {
+	public function calculate($what = Calculatable::TOTAL, $round = 2, $format = true) {
 		$return = 0;
 		switch ($what) {
-			case CALCULATABLE_SUBTOTAL:
+			case Calculatable::SUBTOTAL:
 				$return = $this->calculateSubtotal();
 				break;
-			case CALCULATABLE_VAT:
+			case Calculatable::VAT:
 				$return = $this->calculateVAT();
 				break;
-			case CALCULATABLE_TOTAL:
+			case Calculatable::TOTAL:
 				$return = $this->calculateTotal();
 				break;
 			default: