From 157ce1c9042d03a337d91b97a42bd70ae616dd75 Mon Sep 17 00:00:00 2001
From: smhg <sam@strictlyphp.com>
Date: Tue, 21 Oct 2014 09:10:26 +0200
Subject: [PATCH] trim returns a copy

---
 src/Timespan/Timespan.php | 22 ++++++++++++++++------
 test/Timespan.php         | 33 +++++++++++++++++++++++++--------
 2 files changed, 41 insertions(+), 14 deletions(-)

diff --git a/src/Timespan/Timespan.php b/src/Timespan/Timespan.php
index 7abe4b7..51aa4a9 100644
--- a/src/Timespan/Timespan.php
+++ b/src/Timespan/Timespan.php
@@ -101,19 +101,29 @@ public function merge(Timespan $span)
      * Trim timespan to fit within boundaries
      * @param  DateTime $start
      * @param  DateTime $end
-     * @return Timespan
+     * @return Timespan A new, trimmed, timespan
      */
     public function trim(DateTime $start, DateTime $end)
     {
-        if ($this->start < $start) {
-            $this->start = $start;
+        $trimmed = clone $this;
+
+        if ($start > $trimmed->end || $end < $trimmed->start) {
+            return;
+        }
+
+        if ($trimmed->start < $start) {
+            $trimmed->start = $start;
+        }
+
+        if ($trimmed->end > $end) {
+            $trimmed->end = $end;
         }
 
-        if ($this->end > $end) {
-            $this->end = $end;
+        if ($trimmed->start == $trimmed->end) {
+            return;
         }
 
-        return $this;
+        return $trimmed;
     }
 
     /**
diff --git a/test/Timespan.php b/test/Timespan.php
index c0658b3..10ccf22 100644
--- a/test/Timespan.php
+++ b/test/Timespan.php
@@ -184,17 +184,34 @@ public function testMerge($span)
      */
     public function testTrim($span)
     {
-        $tmp = clone $span;
-        $start = clone $tmp->start;
+        $start = clone $span->start;
         $start->modify('+1 day');
-        $tmp->trim($start, $tmp->end);
-        $this->assertEquals($start, $tmp->start);
+        $trimmed = $span->trim($start, $span->end);
+        $this->assertTrue($trimmed !== $span, 'Trim should not mutate the original span, but return a new one.');
+        $this->assertEquals($start, $trimmed->start);
+        $this->assertNotEquals($span->start, $trimmed->start);
 
-        $tmp = clone $span;
-        $end = clone $tmp->end;
+        $end = clone $span->end;
         $end->modify('-1 day');
-        $tmp->trim($tmp->start, $end);
-        $this->assertEquals($end, $tmp->end);
+        $trimmed = $span->trim($span->start, $end);
+        $this->assertEquals($end, $trimmed->end);
+        $this->assertNotEquals($span->end, $trimmed->end);
+
+        $start = clone $span->start;
+        $start->modify('+2 week');
+        $end = clone $span->end;
+        $end->modify('+2 week');
+        $this->assertTrue(!$span->trim($start, $end), 'Trim should not return anything if no time is left inside the span.');
+
+        $start = clone $span->start;
+        $start->modify('-2 week');
+        $end = clone $span->end;
+        $end->modify('-2 week');
+        $this->assertTrue(!$span->trim($start, $end), 'Trim should not return anything if no time is left inside the span.');
+
+        $start = clone $span->start;
+        $start->modify('+1 day');
+        $this->assertTrue(!$span->trim($start, $start), 'Trim should not return anything if no time is left inside the span.');
     }
 
     /**