Issue #3044185: Add roundDown() to Price Calculator.

modules/price/src/Calculator.php

@@ -200,6 +200,31 @@ public static function round($number, $precision = 0, $mode = PHP_ROUND_HALF_UP)
     return $number;
   }
 
+  /**
+   * Rounds the given number down to the given precision.
+   *
+   * @param string $number
+   *   The number.
+   * @param int $precision
+   *   The number of decimals to round to.
+   *
+   * @return string
+   *   The rounded number.
+   *
+   * @throws \InvalidArgumentException
+   *   Thrown when an invalid (non-numeric or negative) precision is given.
+   */
+  public static function roundDown($number, $precision = 0) {
+    self::assertNumberFormat($number);
+    if (!is_numeric($precision) || $precision < 0) {
+      throw new \InvalidArgumentException('The provided precision should be a positive number');
+    }
+
+    $base = bcpow(10, $precision);
+    return self::divide(self::floor(self::multiply($number, $base, self::getPrecision($number))), $base, $precision);
+
+  }
+
   /**
    * Compares the first number to the second number.
    *
@@ -244,6 +269,23 @@ public static function trim($number) {
     return $number;
   }
 
+  /**
+   * Get the precision of a number.
+   *
+   * @param string $number
+   *   The number to determine precision.
+   *
+   * @return int
+   *   The numbers precision.
+   */
+  public static function getPrecision($number) {
+    $check = explode('.', $number);
+    if (!empty($check[1])) {
+      return strlen($check[1]);
+    }
+    return 0;
+  }
+
   /**
    * Assert that the given number is a numeric string value.
    *

modules/price/tests/src/Unit/CalculatorTest.php

@@ -44,6 +44,7 @@ public function testComparison() {
    * @covers ::ceil
    * @covers ::floor
    * @covers ::round
+   * @covers ::roundDown
    */
   public function testRounding() {
     $this->assertEquals('5', Calculator::ceil('4.4'));
@@ -90,6 +91,15 @@ public function testRounding() {
     foreach ($rounding_data as $item) {
       $this->assertEquals($item[3], Calculator::round($item[0], $item[1], $item[2]));
     }
+
+    $this->assertEquals('1.95', Calculator::roundDown('1.95583', 2));
+  }
+
+  /**
+   * @covers ::getPrecision
+   */
+  public function testPrecision() {
+    $this->assertEquals(2, Calculator::getPrecision('1.99'));
   }
 
 }