Merge pull request #30 from assoconnect/flo_feature_rm_month

Add removeMonth

Author: fguimier

src/TimeTraveler.php

@@ -5,7 +5,7 @@
 namespace AssoConnect\PHPDate;
 
 /**
- * This class addresses corner-case of the modify('+1 month') method
+ * This class addresses corner-case of the ->modify('+/- 1 month') method
  */
 class TimeTraveler
 {
@@ -20,15 +20,32 @@ class TimeTraveler
      */
     public function addMonth(AbsoluteDate $from): AbsoluteDate
     {
-        $expectedMonth = (intval($from->format('n')) % 12) + 1;
+        $currentMonth = intval($from->format('n'));
+        $expectedMonth = $currentMonth + 1 === 13 ? 1 : $currentMonth + 1;
+
         $next = $from->modify('+1 month');
+
         while ($expectedMonth !== intval($next->format('n'))) {
             $next = $next->modify('-1 day');
         }
 
         return $this->modifyForTheLastDayOfThisMonthIfNeedBe($next, $from);
     }
 
+    public function removeMonth(AbsoluteDate $from): AbsoluteDate
+    {
+        $currentMonth = intval($from->format('n'));
+        $expectedMonth = $currentMonth - 1 === 0 ? 12 : $currentMonth - 1;
+
+        $previous = $from->modify('-1 month');
+
+        while ($expectedMonth !== intval($previous->format('n'))) {
+            $previous = $previous->modify('-1 day');
+        }
+
+        return $this->modifyForTheLastDayOfThisMonthIfNeedBe($previous, $from);
+    }
+
     /**
      * Ensures that months calculation are coherent year over year
      *

tests/TimeTravelerTest.php

@@ -35,6 +35,38 @@ public function provideMonths(): iterable
         yield ['2020-06-30', '2020-07-31'];
     }
 
+    /** @dataProvider provideRemoveMonths */
+    public function testRemoveMonth(string $from, string $expected): void
+    {
+        self::assertSame($expected, $this->timeTraveler->removeMonth(new AbsoluteDate($from))->__toString());
+    }
+
+    /** @return iterable<string, array{string, string}> */
+    public function provideRemoveMonths(): iterable
+    {
+        foreach (
+            [
+                '2020-01-01' => '2019-12-01',
+                '2020-01-28' => '2019-12-28',
+                '2020-01-29' => '2019-12-29',
+                '2020-01-30' => '2019-12-30',
+                '2020-01-31' => '2019-12-31',
+                '2020-02-29' => '2020-01-31',
+                '2020-06-30' => '2020-05-31',
+                '2023-10-31' => '2023-09-30',
+                '2023-08-31' => '2023-07-31',
+                '2023-09-30' => '2023-08-31',
+                '2023-03-31' => '2023-02-28',
+                '2024-03-31' => '2024-02-29',
+            ] as $currentMonth => $expectedPreviousMonth
+        ) {
+            yield sprintf('%s: previous month will %s', $currentMonth, $expectedPreviousMonth) => [
+                $currentMonth,
+                $expectedPreviousMonth,
+            ];
+        }
+    }
+
     /** @dataProvider provideMonthsWithReference */
     public function testAddMonthWithReference(string $reference, string $from, string $expected): void
     {