From 6b175ba94d056ef29dfbcff9d3d9f621e92f6014 Mon Sep 17 00:00:00 2001
From: Jonathan Hanson <jonathan@jonathan-hanson.org>
Date: Sun, 15 Jan 2017 23:14:24 -0800
Subject: [PATCH 1/4] In order to address difficulties with pull request #64,
 this fix mocks out UnitOfMeasureInterface::isAliasOf() for the
 AbstractPhysicalQuantityTest unit test mock.

---
 tests/AbstractPhysicalQuantityTest.php | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tests/AbstractPhysicalQuantityTest.php b/tests/AbstractPhysicalQuantityTest.php
index 19ce3f2..2936602 100644
--- a/tests/AbstractPhysicalQuantityTest.php
+++ b/tests/AbstractPhysicalQuantityTest.php
@@ -30,6 +30,12 @@ protected function getTestUnitOfMeasure($name, $aliases = [])
             ->willReturn($name);
         $newUnit->method('getAliases')
             ->willReturn($aliases);
+        $newUnit->method('isAliasOf')
+            ->will($this->returnCallback(
+                function ($value) use ($aliases) {
+                    return in_array($value, $aliases);
+                }
+            ));
 
         return $newUnit;
     }

From 8dc6141126f6a32e5bc7d99f15166c8228f04af7 Mon Sep 17 00:00:00 2001
From: pierpaolocira <pierpaolocira@users.noreply.github.com>
Date: Fri, 12 May 2017 10:55:23 +0200
Subject: [PATCH 2/4] Issue 67: Implementation of Power

---
 source/PhysicalQuantity/Power.php    | 32 +++++++++++++++++
 tests/PhysicalQuantity/PowerTest.php | 53 ++++++++++++++++++++++++++++
 2 files changed, 85 insertions(+)
 create mode 100644 source/PhysicalQuantity/Power.php
 create mode 100644 tests/PhysicalQuantity/PowerTest.php

diff --git a/source/PhysicalQuantity/Power.php b/source/PhysicalQuantity/Power.php
new file mode 100644
index 0000000..0ec2a70
--- /dev/null
+++ b/source/PhysicalQuantity/Power.php
@@ -0,0 +1,32 @@
+<?php
+namespace PhpUnitsOfMeasure\PhysicalQuantity;
+
+use PhpUnitsOfMeasure\AbstractPhysicalQuantity;
+use PhpUnitsOfMeasure\UnitOfMeasure;
+use PhpUnitsOfMeasure\HasSIUnitsTrait;
+
+class Power extends AbstractPhysicalQuantity
+{
+    use HasSIUnitsTrait;
+
+    protected static $unitDefinitions;
+
+    protected static function initialize()
+    {
+        // Watt
+        $watt = UnitOfMeasure::nativeUnitFactory('W');
+        $watt->addAlias('watt');
+        $watt->addAlias('watts');
+        static::addUnit($watt);
+
+        static::addMissingSIPrefixedUnits(
+            $watt,
+            1,
+            '%pW',
+            [
+                '%Pwatt',
+                '%Pwatts',
+            ]
+        );
+    }
+}
diff --git a/tests/PhysicalQuantity/PowerTest.php b/tests/PhysicalQuantity/PowerTest.php
new file mode 100644
index 0000000..ca21c2b
--- /dev/null
+++ b/tests/PhysicalQuantity/PowerTest.php
@@ -0,0 +1,53 @@
+<?php
+
+namespace PhpUnitsOfMeasureTest\PhysicalQuantity;
+
+use PhpUnitsOfMeasure\PhysicalQuantity\Power;
+
+class PowerTest extends AbstractPhysicalQuantityTestCase
+{
+    protected $supportedUnitsWithAliases = [
+        'W',
+        'watt',
+        'watts',
+        'µW',
+        'microwatt',
+        'microwatts',
+        'mW',
+        'milliwatt',
+        'milliwatts',
+        'kW',
+        'kilowatt',
+        'kilowatts',
+        'MW',
+        'megawatt',
+        'megawatts',
+        'GW',
+        'gigawatt',
+        'gigawatts',
+        'TW',
+        'terawatt',
+        'terawatts',
+        'PW',
+        'petawatt',
+        'petawatts',
+    ];
+
+    protected function instantiateTestQuantity()
+    {
+        return new Power(1, 'W');
+    }
+
+    public function testToKilowatt()
+    {
+        $quantity = new Energy(1000, 'W');
+        $this->assertEquals(1, $quantity->toUnit('kW'));
+    }
+
+    public function testToWatt()
+    {
+        $quantity = new Energy(1, 'kW');
+        $this->assertEquals(1000, $quantity->toUnit('W'));
+    }
+
+}

From 19cca508daf72511168c8b185e2bdf1627b5dd75 Mon Sep 17 00:00:00 2001
From: pierpaolocira <pierpaolocira@users.noreply.github.com>
Date: Fri, 12 May 2017 11:20:02 +0200
Subject: [PATCH 3/4] Fixing test file

---
 tests/PhysicalQuantity/PowerTest.php | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/tests/PhysicalQuantity/PowerTest.php b/tests/PhysicalQuantity/PowerTest.php
index ca21c2b..b66e777 100644
--- a/tests/PhysicalQuantity/PowerTest.php
+++ b/tests/PhysicalQuantity/PowerTest.php
@@ -40,14 +40,13 @@ protected function instantiateTestQuantity()
 
     public function testToKilowatt()
     {
-        $quantity = new Energy(1000, 'W');
+        $quantity = new Power(1000, 'W');
         $this->assertEquals(1, $quantity->toUnit('kW'));
     }
 
     public function testToWatt()
     {
-        $quantity = new Energy(1, 'kW');
+        $quantity = new Power(1, 'kW');
         $this->assertEquals(1000, $quantity->toUnit('W'));
     }
-
 }

From 786a7239d7e8c7e76e5e30a219cdfb0757e9dda0 Mon Sep 17 00:00:00 2001
From: Stephen Clouse <stephen.clouse@noaa.gov>
Date: Mon, 24 Jul 2017 16:27:15 -0500
Subject: [PATCH 4/4] Add caching for unit lookups with getUnit()

---
 source/AbstractPhysicalQuantity.php | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/source/AbstractPhysicalQuantity.php b/source/AbstractPhysicalQuantity.php
index 0d61bbf..029e332 100644
--- a/source/AbstractPhysicalQuantity.php
+++ b/source/AbstractPhysicalQuantity.php
@@ -12,6 +12,23 @@ abstract class AbstractPhysicalQuantity implements PhysicalQuantityInterface
      */
     // protected static $unitDefinitions;
 
+    /**
+     * Static cache for unit lookups.
+     *
+     * @var UnitOfMeasureInterface[]
+     */
+    private static $unitCache = [];
+
+    /**
+     * Create a cache key for the unit lookup cache.
+     *
+     * @var UnitOfMeasureInterface[]
+     */
+    private static function buildUnitCacheKey($unit)
+    {
+        return get_called_class() . '#' . $unit;
+    }
+
     /**
      * Register a new unit of measure for all instances of this this physical quantity.
      *
@@ -47,9 +64,14 @@ public static function getUnit($unit)
             static::initialize();
         }
 
+        $key = static::buildUnitCacheKey($unit);
+        if (isset(self::$unitCache[$key])) {
+            return self::$unitCache[$key];
+        }
+
         foreach (static::$unitDefinitions as $unitOfMeasure) {
             if ($unit === $unitOfMeasure->getName() || $unitOfMeasure->isAliasOf($unit)) {
-                return $unitOfMeasure;
+                return self::$unitCache[$key] = $unitOfMeasure;
             }
         }