From 0c3f14c9127e2843814356c9424b583de74a9170 Mon Sep 17 00:00:00 2001
From: Javier Ferrer <javier.mailserio@gmail.com>
Date: Mon, 15 Aug 2016 15:43:35 +0200
Subject: [PATCH 01/10] Rename classes, interfaces, attributes and variables in
 src/ in order to provide Persons semantics

---
 src/Algorithm/F.php                     | 17 ------
 src/Algorithm/FT.php                    | 11 ----
 src/Algorithm/Finder.php                | 70 ++++++++++++++-----------
 src/Algorithm/FinderCriteria.php        | 11 ++++
 src/Algorithm/{Thing.php => Person.php} |  2 +-
 src/Algorithm/PersonsPair.php           | 17 ++++++
 tests/Algorithm/FinderTest.php          | 56 ++++++++++----------
 7 files changed, 97 insertions(+), 87 deletions(-)
 delete mode 100644 src/Algorithm/F.php
 delete mode 100644 src/Algorithm/FT.php
 create mode 100644 src/Algorithm/FinderCriteria.php
 rename src/Algorithm/{Thing.php => Person.php} (96%)
 create mode 100644 src/Algorithm/PersonsPair.php

diff --git a/src/Algorithm/F.php b/src/Algorithm/F.php
deleted file mode 100644
index 3db7792..0000000
--- a/src/Algorithm/F.php
+++ /dev/null
@@ -1,17 +0,0 @@
-<?php
-
-declare(strict_types = 1);
-
-namespace CodelyTV\FinderKata\Algorithm;
-
-final class F
-{
-    /** @var Thing */
-    public $p1;
-
-    /** @var Thing */
-    public $p2;
-
-    /** @var int */
-    public $d;
-}
diff --git a/src/Algorithm/FT.php b/src/Algorithm/FT.php
deleted file mode 100644
index c6bfac2..0000000
--- a/src/Algorithm/FT.php
+++ /dev/null
@@ -1,11 +0,0 @@
-<?php
-
-declare(strict_types = 1);
-
-namespace CodelyTV\FinderKata\Algorithm;
-
-interface FT
-{
-    const ONE = 1;
-    const TWO = 2;
-}
diff --git a/src/Algorithm/Finder.php b/src/Algorithm/Finder.php
index f81550e..1746284 100644
--- a/src/Algorithm/Finder.php
+++ b/src/Algorithm/Finder.php
@@ -6,60 +6,70 @@
 
 final class Finder
 {
-    /** @var Thing[] */
-    private $_p;
+    /** @var Person[] */
+    private $allPersons;
 
-    public function __construct(array $p)
+    public function __construct(array $allPersons)
     {
-        $this->_p = $p;
+        $this->allPersons = $allPersons;
     }
 
-    public function find(int $ft): F
+    public function find(int $finderCriteria): PersonsPair
     {
-        /** @var F[] $tr */
-        $tr = [];
+        /** @var PersonsPair[] $allPersonsPairs */
+        $allPersonsPairs = [];
 
-        for ($i = 0; $i < count($this->_p); $i++) {
-            for ($j = $i + 1; $j < count($this->_p); $j++) {
-                $r = new F();
+        $numberOfPersons = count($this->allPersons);
 
-                if ($this->_p[$i]->birthDate < $this->_p[$j]->birthDate) {
-                    $r->p1 = $this->_p[$i];
-                    $r->p2 = $this->_p[$j];
+        for ($i = 0; $i < $numberOfPersons; $i++) {
+            for ($j = $i + 1; $j < $numberOfPersons; $j++) {
+                $personsPair = new PersonsPair();
+
+                if ($this->allPersons[$i]->birthDate
+                    < $this->allPersons[$j]->birthDate
+                ) {
+                    $personsPair->person1 = $this->allPersons[$i];
+                    $personsPair->person2 = $this->allPersons[$j];
                 } else {
-                    $r->p1 = $this->_p[$j];
-                    $r->p2 = $this->_p[$i];
+                    $personsPair->person1 = $this->allPersons[$j];
+                    $personsPair->person2 = $this->allPersons[$i];
                 }
 
-                $r->d = $r->p2->birthDate->getTimestamp()
-                    - $r->p1->birthDate->getTimestamp();
+                $personsPair->birthDaysDistanceInSeconds =
+                    $personsPair->person2->birthDate->getTimestamp()
+                    - $personsPair->person1->birthDate->getTimestamp();
 
-                $tr[] = $r;
+                $allPersonsPairs[] = $personsPair;
             }
         }
 
-        if (count($tr) < 1) {
-            return new F();
+        $thereAreNoPersonsPairs = count($allPersonsPairs) < 1;
+        if ($thereAreNoPersonsPairs) {
+            return new PersonsPair();
         }
 
-        $answer = $tr[0];
+        $personsPairMatchingCriteria = $allPersonsPairs[0];
 
-        foreach ($tr as $result) {
-            switch ($ft) {
-                case FT::ONE:
-                    if ($result->d < $answer->d) {
-                        $answer = $result;
+        foreach ($allPersonsPairs as $personsPair) {
+            switch ($finderCriteria) {
+                case FinderCriteria::CLOSEST_BIRTHDAYS:
+                    if ($personsPair->birthDaysDistanceInSeconds
+                        < $personsPairMatchingCriteria->birthDaysDistanceInSeconds
+                    ) {
+                        $personsPairMatchingCriteria = $personsPair;
                     }
                     break;
 
-                case FT::TWO:
-                    if ($result->d > $answer->d) {
-                        $answer = $result;
+                case FinderCriteria::FURTHEST_BIRTHDAYS:
+                    if ($personsPair->birthDaysDistanceInSeconds
+                        > $personsPairMatchingCriteria->birthDaysDistanceInSeconds
+                    ) {
+                        $personsPairMatchingCriteria = $personsPair;
                     }
                     break;
             }
         }
 
-        return $answer;
+        return $personsPairMatchingCriteria;
     }
 }
diff --git a/src/Algorithm/FinderCriteria.php b/src/Algorithm/FinderCriteria.php
new file mode 100644
index 0000000..0fc7f8b
--- /dev/null
+++ b/src/Algorithm/FinderCriteria.php
@@ -0,0 +1,11 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace CodelyTV\FinderKata\Algorithm;
+
+interface FinderCriteria
+{
+    const CLOSEST_BIRTHDAYS = 1;
+    const FURTHEST_BIRTHDAYS = 2;
+}
diff --git a/src/Algorithm/Thing.php b/src/Algorithm/Person.php
similarity index 96%
rename from src/Algorithm/Thing.php
rename to src/Algorithm/Person.php
index 3c93163..d0641b7 100644
--- a/src/Algorithm/Thing.php
+++ b/src/Algorithm/Person.php
@@ -6,7 +6,7 @@
 
 use DateTime;
 
-final class Thing
+final class Person
 {
     /** @var string */
     public $name;
diff --git a/src/Algorithm/PersonsPair.php b/src/Algorithm/PersonsPair.php
new file mode 100644
index 0000000..11c9fd2
--- /dev/null
+++ b/src/Algorithm/PersonsPair.php
@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace CodelyTV\FinderKata\Algorithm;
+
+final class PersonsPair
+{
+    /** @var Person */
+    public $person1;
+
+    /** @var Person */
+    public $person2;
+
+    /** @var int */
+    public $birthDaysDistanceInSeconds;
+}
diff --git a/tests/Algorithm/FinderTest.php b/tests/Algorithm/FinderTest.php
index 1a9d996..b8391e0 100644
--- a/tests/Algorithm/FinderTest.php
+++ b/tests/Algorithm/FinderTest.php
@@ -5,39 +5,39 @@
 namespace CodelyTV\FinderKataTest\Algorithm;
 
 use CodelyTV\FinderKata\Algorithm\Finder;
-use CodelyTV\FinderKata\Algorithm\FT;
-use CodelyTV\FinderKata\Algorithm\Thing;
+use CodelyTV\FinderKata\Algorithm\FinderCriteria;
+use CodelyTV\FinderKata\Algorithm\Person;
 use PHPUnit\Framework\TestCase;
 
 final class FinderTest extends TestCase
 {
-    /** @var Thing */
+    /** @var Person */
     private $sue;
 
-    /** @var Thing */
+    /** @var Person */
     private $greg;
 
-    /** @var Thing */
+    /** @var Person */
     private $sarah;
 
-    /** @var Thing */
+    /** @var Person */
     private $mike;
 
     protected function setUp()
     {
-        $this->sue            = new Thing();
+        $this->sue            = new Person();
         $this->sue->name      = "Sue";
         $this->sue->birthDate = new \DateTime("1950-01-01");
 
-        $this->greg            = new Thing();
+        $this->greg            = new Person();
         $this->greg->name      = "Greg";
         $this->greg->birthDate = new \DateTime("1952-05-01");
 
-        $this->sarah            = new Thing();
+        $this->sarah            = new Person();
         $this->sarah->name      = "Sarah";
         $this->sarah->birthDate = new \DateTime("1982-01-01");
 
-        $this->mike            = new Thing();
+        $this->mike            = new Person();
         $this->mike->name      = "Mike";
         $this->mike->birthDate = new \DateTime("1979-01-01");
     }
@@ -48,10 +48,10 @@ public function should_return_empty_when_given_empty_list()
         $list   = [];
         $finder = new Finder($list);
 
-        $result = $finder->find(FT::ONE);
+        $result = $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
 
-        $this->assertEquals(null, $result->p1);
-        $this->assertEquals(null, $result->p2);
+        $this->assertEquals(null, $result->person1);
+        $this->assertEquals(null, $result->person2);
     }
 
     /** @test */
@@ -61,10 +61,10 @@ public function should_return_empty_when_given_one_person()
         $list[] = $this->sue;
         $finder = new Finder($list);
 
-        $result = $finder->find(FT::ONE);
+        $result = $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
 
-        $this->assertEquals(null, $result->p1);
-        $this->assertEquals(null, $result->p2);
+        $this->assertEquals(null, $result->person1);
+        $this->assertEquals(null, $result->person2);
     }
 
     /** @test */
@@ -75,10 +75,10 @@ public function should_return_closest_two_for_two_people()
         $list[] = $this->greg;
         $finder = new Finder($list);
 
-        $result = $finder->find(FT::ONE);
+        $result = $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
 
-        $this->assertEquals($this->sue, $result->p1);
-        $this->assertEquals($this->greg, $result->p2);
+        $this->assertEquals($this->sue, $result->person1);
+        $this->assertEquals($this->greg, $result->person2);
     }
 
     /** @test */
@@ -89,10 +89,10 @@ public function should_return_furthest_two_for_two_people()
         $list[] = $this->greg;
         $finder = new Finder($list);
 
-        $result = $finder->find(FT::TWO);
+        $result = $finder->find(FinderCriteria::FURTHEST_BIRTHDAYS);
 
-        $this->assertEquals($this->greg, $result->p1);
-        $this->assertEquals($this->mike, $result->p2);
+        $this->assertEquals($this->greg, $result->person1);
+        $this->assertEquals($this->mike, $result->person2);
     }
 
     /** @test */
@@ -105,10 +105,10 @@ public function should_return_furthest_two_for_four_people()
         $list[] = $this->greg;
         $finder = new Finder($list);
 
-        $result = $finder->find(FT::TWO);
+        $result = $finder->find(FinderCriteria::FURTHEST_BIRTHDAYS);
 
-        $this->assertEquals($this->sue, $result->p1);
-        $this->assertEquals($this->sarah, $result->p2);
+        $this->assertEquals($this->sue, $result->person1);
+        $this->assertEquals($this->sarah, $result->person2);
     }
 
     /**
@@ -123,9 +123,9 @@ public function should_return_closest_two_for_four_people()
         $list[] = $this->greg;
         $finder = new Finder($list);
 
-        $result = $finder->find(FT::ONE);
+        $result = $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
 
-        $this->assertEquals($this->sue, $result->p1);
-        $this->assertEquals($this->greg, $result->p2);
+        $this->assertEquals($this->sue, $result->person1);
+        $this->assertEquals($this->greg, $result->person2);
     }
 }

From 99b77f946ad3091320e5c774d1ee4e1751ceef34 Mon Sep 17 00:00:00 2001
From: Javier Ferrer <javier.mailserio@gmail.com>
Date: Mon, 15 Aug 2016 15:48:19 +0200
Subject: [PATCH 02/10] Rename variables in tests/ in order to provide Persons
 semantics

---
 tests/Algorithm/FinderTest.php | 41 +++++++++++-----------------------
 1 file changed, 13 insertions(+), 28 deletions(-)

diff --git a/tests/Algorithm/FinderTest.php b/tests/Algorithm/FinderTest.php
index b8391e0..391b7a9 100644
--- a/tests/Algorithm/FinderTest.php
+++ b/tests/Algorithm/FinderTest.php
@@ -45,8 +45,8 @@ protected function setUp()
     /** @test */
     public function should_return_empty_when_given_empty_list()
     {
-        $list   = [];
-        $finder = new Finder($list);
+        $allPersons = [];
+        $finder     = new Finder($allPersons);
 
         $result = $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
 
@@ -57,9 +57,8 @@ public function should_return_empty_when_given_empty_list()
     /** @test */
     public function should_return_empty_when_given_one_person()
     {
-        $list   = [];
-        $list[] = $this->sue;
-        $finder = new Finder($list);
+        $allPersons = [$this->sue];
+        $finder     = new Finder($allPersons);
 
         $result = $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
 
@@ -70,10 +69,8 @@ public function should_return_empty_when_given_one_person()
     /** @test */
     public function should_return_closest_two_for_two_people()
     {
-        $list   = [];
-        $list[] = $this->sue;
-        $list[] = $this->greg;
-        $finder = new Finder($list);
+        $allPersons = [$this->sue, $this->greg];
+        $finder     = new Finder($allPersons);
 
         $result = $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
 
@@ -84,10 +81,8 @@ public function should_return_closest_two_for_two_people()
     /** @test */
     public function should_return_furthest_two_for_two_people()
     {
-        $list   = [];
-        $list[] = $this->mike;
-        $list[] = $this->greg;
-        $finder = new Finder($list);
+        $allPersons = [$this->mike, $this->greg];
+        $finder     = new Finder($allPersons);
 
         $result = $finder->find(FinderCriteria::FURTHEST_BIRTHDAYS);
 
@@ -98,12 +93,8 @@ public function should_return_furthest_two_for_two_people()
     /** @test */
     public function should_return_furthest_two_for_four_people()
     {
-        $list   = [];
-        $list[] = $this->sue;
-        $list[] = $this->sarah;
-        $list[] = $this->mike;
-        $list[] = $this->greg;
-        $finder = new Finder($list);
+        $allPersons = [$this->sue, $this->sarah, $this->mike, $this->greg];
+        $finder     = new Finder($allPersons);
 
         $result = $finder->find(FinderCriteria::FURTHEST_BIRTHDAYS);
 
@@ -111,17 +102,11 @@ public function should_return_furthest_two_for_four_people()
         $this->assertEquals($this->sarah, $result->person2);
     }
 
-    /**
-     * @test
-     */
+    /** @test */
     public function should_return_closest_two_for_four_people()
     {
-        $list   = [];
-        $list[] = $this->sue;
-        $list[] = $this->sarah;
-        $list[] = $this->mike;
-        $list[] = $this->greg;
-        $finder = new Finder($list);
+        $allPersons = [$this->sue, $this->sarah, $this->mike, $this->greg];
+        $finder     = new Finder($allPersons);
 
         $result = $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
 

From ad0aa8adb69acf5fed53c51f3fe4e037b6301d09 Mon Sep 17 00:00:00 2001
From: Javier Ferrer <javier.mailserio@gmail.com>
Date: Mon, 15 Aug 2016 16:09:14 +0200
Subject: [PATCH 03/10] * Make `Person` and `PersonsPair` attributes private *
 Create constructor for `Person` and `PersonsPair` classes and remove setters
 * Remove the get prefix from getters * Move the responsibility of calculating
 the `birthDaysDistanceInSeconds` from the `Finder` to the `PersonsPair` *
 Throw an exception `NotEnoughPersonsException` in case of receiving not
 enough persons in order to find a pair. * Refactor the test in order to
 expect the new exception instead of an empty/inconsistent `PersonsPair`

---
 src/Algorithm/Finder.php                    | 31 ++++++-----
 src/Algorithm/NotEnoughPersonsException.php |  8 +++
 src/Algorithm/Person.php                    | 20 +++----
 src/Algorithm/PersonsPair.php               | 33 ++++++++++--
 tests/Algorithm/FinderTest.php              | 59 +++++++++------------
 5 files changed, 85 insertions(+), 66 deletions(-)
 create mode 100644 src/Algorithm/NotEnoughPersonsException.php

diff --git a/src/Algorithm/Finder.php b/src/Algorithm/Finder.php
index 1746284..6a582ab 100644
--- a/src/Algorithm/Finder.php
+++ b/src/Algorithm/Finder.php
@@ -23,29 +23,26 @@ public function find(int $finderCriteria): PersonsPair
 
         for ($i = 0; $i < $numberOfPersons; $i++) {
             for ($j = $i + 1; $j < $numberOfPersons; $j++) {
-                $personsPair = new PersonsPair();
 
-                if ($this->allPersons[$i]->birthDate
-                    < $this->allPersons[$j]->birthDate
+                if ($this->allPersons[$i]->birthDate()
+                    < $this->allPersons[$j]->birthDate()
                 ) {
-                    $personsPair->person1 = $this->allPersons[$i];
-                    $personsPair->person2 = $this->allPersons[$j];
+                    $personsPair = new PersonsPair(
+                        $this->allPersons[$i], $this->allPersons[$j]
+                    );
                 } else {
-                    $personsPair->person1 = $this->allPersons[$j];
-                    $personsPair->person2 = $this->allPersons[$i];
+                    $personsPair = new PersonsPair(
+                        $this->allPersons[$j], $this->allPersons[$i]
+                    );
                 }
 
-                $personsPair->birthDaysDistanceInSeconds =
-                    $personsPair->person2->birthDate->getTimestamp()
-                    - $personsPair->person1->birthDate->getTimestamp();
-
                 $allPersonsPairs[] = $personsPair;
             }
         }
 
         $thereAreNoPersonsPairs = count($allPersonsPairs) < 1;
         if ($thereAreNoPersonsPairs) {
-            return new PersonsPair();
+            throw new NotEnoughPersonsException();
         }
 
         $personsPairMatchingCriteria = $allPersonsPairs[0];
@@ -53,16 +50,18 @@ public function find(int $finderCriteria): PersonsPair
         foreach ($allPersonsPairs as $personsPair) {
             switch ($finderCriteria) {
                 case FinderCriteria::CLOSEST_BIRTHDAYS:
-                    if ($personsPair->birthDaysDistanceInSeconds
-                        < $personsPairMatchingCriteria->birthDaysDistanceInSeconds
+                    if ($personsPair->birthDaysDistanceInSeconds()
+                        < $personsPairMatchingCriteria->birthDaysDistanceInSeconds(
+                        )
                     ) {
                         $personsPairMatchingCriteria = $personsPair;
                     }
                     break;
 
                 case FinderCriteria::FURTHEST_BIRTHDAYS:
-                    if ($personsPair->birthDaysDistanceInSeconds
-                        > $personsPairMatchingCriteria->birthDaysDistanceInSeconds
+                    if ($personsPair->birthDaysDistanceInSeconds()
+                        > $personsPairMatchingCriteria->birthDaysDistanceInSeconds(
+                        )
                     ) {
                         $personsPairMatchingCriteria = $personsPair;
                     }
diff --git a/src/Algorithm/NotEnoughPersonsException.php b/src/Algorithm/NotEnoughPersonsException.php
new file mode 100644
index 0000000..22a6f0f
--- /dev/null
+++ b/src/Algorithm/NotEnoughPersonsException.php
@@ -0,0 +1,8 @@
+<?php
+
+namespace CodelyTV\FinderKata\Algorithm;
+
+final class NotEnoughPersonsException extends \InvalidArgumentException
+{
+    protected $message = "You have not specified enough persons in order to find a pair.";
+}
diff --git a/src/Algorithm/Person.php b/src/Algorithm/Person.php
index d0641b7..748d458 100644
--- a/src/Algorithm/Person.php
+++ b/src/Algorithm/Person.php
@@ -9,28 +9,24 @@
 final class Person
 {
     /** @var string */
-    public $name;
+    private $name;
 
     /** @var DateTime */
-    public $birthDate;
+    private $birthDate;
 
-    public function getName(): string
+    public function __construct(string $aName, DateTime $aBirthDate)
     {
-        return $this->name;
+        $this->name      = $aName;
+        $this->birthDate = $aBirthDate;
     }
 
-    public function setName(string $name)
+    public function name(): string
     {
-        $this->name = $name;
+        return $this->name;
     }
 
-    public function getBirthDate(): DateTime
+    public function birthDate(): DateTime
     {
         return $this->birthDate;
     }
-
-    public function setBirthDate(DateTime $birthDate)
-    {
-        $this->birthDate = $birthDate;
-    }
 }
diff --git a/src/Algorithm/PersonsPair.php b/src/Algorithm/PersonsPair.php
index 11c9fd2..6dc0674 100644
--- a/src/Algorithm/PersonsPair.php
+++ b/src/Algorithm/PersonsPair.php
@@ -7,11 +7,38 @@
 final class PersonsPair
 {
     /** @var Person */
-    public $person1;
+    private $person1;
 
     /** @var Person */
-    public $person2;
+    private $person2;
 
     /** @var int */
-    public $birthDaysDistanceInSeconds;
+    private $birthDaysDistanceInSeconds;
+
+    public function __construct(Person $aPerson1, Person $aPerson2)
+    {
+        $this->person1                    = $aPerson1;
+        $this->person2                    = $aPerson2;
+        $this->birthDaysDistanceInSeconds = $this->calculateBirthDaysDistanceInSeconds();
+    }
+
+    public function person1(): Person
+    {
+        return $this->person1;
+    }
+
+    public function person2(): Person
+    {
+        return $this->person2;
+    }
+
+    public function birthDaysDistanceInSeconds(): int
+    {
+        return $this->birthDaysDistanceInSeconds;
+    }
+
+    private function calculateBirthDaysDistanceInSeconds(): int
+    {
+        return $this->person2()->birthDate()->getTimestamp() - $this->person1()->birthDate()->getTimestamp();
+    }
 }
diff --git a/tests/Algorithm/FinderTest.php b/tests/Algorithm/FinderTest.php
index 391b7a9..fc73248 100644
--- a/tests/Algorithm/FinderTest.php
+++ b/tests/Algorithm/FinderTest.php
@@ -6,6 +6,7 @@
 
 use CodelyTV\FinderKata\Algorithm\Finder;
 use CodelyTV\FinderKata\Algorithm\FinderCriteria;
+use CodelyTV\FinderKata\Algorithm\NotEnoughPersonsException;
 use CodelyTV\FinderKata\Algorithm\Person;
 use PHPUnit\Framework\TestCase;
 
@@ -25,45 +26,33 @@ final class FinderTest extends TestCase
 
     protected function setUp()
     {
-        $this->sue            = new Person();
-        $this->sue->name      = "Sue";
-        $this->sue->birthDate = new \DateTime("1950-01-01");
-
-        $this->greg            = new Person();
-        $this->greg->name      = "Greg";
-        $this->greg->birthDate = new \DateTime("1952-05-01");
-
-        $this->sarah            = new Person();
-        $this->sarah->name      = "Sarah";
-        $this->sarah->birthDate = new \DateTime("1982-01-01");
-
-        $this->mike            = new Person();
-        $this->mike->name      = "Mike";
-        $this->mike->birthDate = new \DateTime("1979-01-01");
+        $this->sue   = new Person("Sue", new \DateTime("1950-01-01"));
+        $this->greg  = new Person("Greg", new \DateTime("1952-05-01"));
+        $this->sarah = new Person("Sarah", new \DateTime("1982-01-01"));
+        $this->mike  = new Person("Mike", new \DateTime("1979-01-01"));
     }
 
     /** @test */
-    public function should_return_empty_when_given_empty_list()
+    public function should_throw_not_enough_persons_exception_when_given_empty_list(
+    )
     {
         $allPersons = [];
         $finder     = new Finder($allPersons);
 
-        $result = $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
+        $this->expectException(NotEnoughPersonsException::class);
 
-        $this->assertEquals(null, $result->person1);
-        $this->assertEquals(null, $result->person2);
+        $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
     }
 
     /** @test */
-    public function should_return_empty_when_given_one_person()
+    public function should_throw_not_enough_persons_when_given_one_person()
     {
         $allPersons = [$this->sue];
         $finder     = new Finder($allPersons);
 
-        $result = $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
+        $this->expectException(NotEnoughPersonsException::class);
 
-        $this->assertEquals(null, $result->person1);
-        $this->assertEquals(null, $result->person2);
+        $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
     }
 
     /** @test */
@@ -72,10 +61,10 @@ public function should_return_closest_two_for_two_people()
         $allPersons = [$this->sue, $this->greg];
         $finder     = new Finder($allPersons);
 
-        $result = $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
+        $personsPairFound = $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
 
-        $this->assertEquals($this->sue, $result->person1);
-        $this->assertEquals($this->greg, $result->person2);
+        $this->assertEquals($this->sue, $personsPairFound->person1());
+        $this->assertEquals($this->greg, $personsPairFound->person2());
     }
 
     /** @test */
@@ -84,10 +73,10 @@ public function should_return_furthest_two_for_two_people()
         $allPersons = [$this->mike, $this->greg];
         $finder     = new Finder($allPersons);
 
-        $result = $finder->find(FinderCriteria::FURTHEST_BIRTHDAYS);
+        $personsPairFound = $finder->find(FinderCriteria::FURTHEST_BIRTHDAYS);
 
-        $this->assertEquals($this->greg, $result->person1);
-        $this->assertEquals($this->mike, $result->person2);
+        $this->assertEquals($this->greg, $personsPairFound->person1());
+        $this->assertEquals($this->mike, $personsPairFound->person2());
     }
 
     /** @test */
@@ -96,10 +85,10 @@ public function should_return_furthest_two_for_four_people()
         $allPersons = [$this->sue, $this->sarah, $this->mike, $this->greg];
         $finder     = new Finder($allPersons);
 
-        $result = $finder->find(FinderCriteria::FURTHEST_BIRTHDAYS);
+        $personsPairFound = $finder->find(FinderCriteria::FURTHEST_BIRTHDAYS);
 
-        $this->assertEquals($this->sue, $result->person1);
-        $this->assertEquals($this->sarah, $result->person2);
+        $this->assertEquals($this->sue, $personsPairFound->person1());
+        $this->assertEquals($this->sarah, $personsPairFound->person2());
     }
 
     /** @test */
@@ -108,9 +97,9 @@ public function should_return_closest_two_for_four_people()
         $allPersons = [$this->sue, $this->sarah, $this->mike, $this->greg];
         $finder     = new Finder($allPersons);
 
-        $result = $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
+        $personsPairFound = $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
 
-        $this->assertEquals($this->sue, $result->person1);
-        $this->assertEquals($this->greg, $result->person2);
+        $this->assertEquals($this->sue, $personsPairFound->person1());
+        $this->assertEquals($this->greg, $personsPairFound->person2());
     }
 }

From d5397c6e262820cd898c3a72a262eeb215e5d919 Mon Sep 17 00:00:00 2001
From: Javier Ferrer <javier.mailserio@gmail.com>
Date: Mon, 15 Aug 2016 16:20:43 +0200
Subject: [PATCH 04/10] Moderate `FinderCriteria` as a Value Object instead of
 a plain `interface` with two `const`

---
 src/Algorithm/Finder.php         | 32 ++++++++++-------------
 src/Algorithm/FinderCriteria.php | 44 +++++++++++++++++++++++++++++---
 tests/Algorithm/FinderTest.php   | 12 ++++-----
 3 files changed, 60 insertions(+), 28 deletions(-)

diff --git a/src/Algorithm/Finder.php b/src/Algorithm/Finder.php
index 6a582ab..de9e4fa 100644
--- a/src/Algorithm/Finder.php
+++ b/src/Algorithm/Finder.php
@@ -14,7 +14,7 @@ public function __construct(array $allPersons)
         $this->allPersons = $allPersons;
     }
 
-    public function find(int $finderCriteria): PersonsPair
+    public function find(FinderCriteria $finderCriteria): PersonsPair
     {
         /** @var PersonsPair[] $allPersonsPairs */
         $allPersonsPairs = [];
@@ -48,24 +48,18 @@ public function find(int $finderCriteria): PersonsPair
         $personsPairMatchingCriteria = $allPersonsPairs[0];
 
         foreach ($allPersonsPairs as $personsPair) {
-            switch ($finderCriteria) {
-                case FinderCriteria::CLOSEST_BIRTHDAYS:
-                    if ($personsPair->birthDaysDistanceInSeconds()
-                        < $personsPairMatchingCriteria->birthDaysDistanceInSeconds(
-                        )
-                    ) {
-                        $personsPairMatchingCriteria = $personsPair;
-                    }
-                    break;
-
-                case FinderCriteria::FURTHEST_BIRTHDAYS:
-                    if ($personsPair->birthDaysDistanceInSeconds()
-                        > $personsPairMatchingCriteria->birthDaysDistanceInSeconds(
-                        )
-                    ) {
-                        $personsPairMatchingCriteria = $personsPair;
-                    }
-                    break;
+            if ($finderCriteria->isByClosestBirthDates()) {
+                if ($personsPair->birthDaysDistanceInSeconds()
+                    < $personsPairMatchingCriteria->birthDaysDistanceInSeconds()
+                ) {
+                    $personsPairMatchingCriteria = $personsPair;
+                }
+            } elseif ($finderCriteria->isByFurthestBirthDates()) {
+                if ($personsPair->birthDaysDistanceInSeconds()
+                    > $personsPairMatchingCriteria->birthDaysDistanceInSeconds()
+                ) {
+                    $personsPairMatchingCriteria = $personsPair;
+                }
             }
         }
 
diff --git a/src/Algorithm/FinderCriteria.php b/src/Algorithm/FinderCriteria.php
index 0fc7f8b..84786a3 100644
--- a/src/Algorithm/FinderCriteria.php
+++ b/src/Algorithm/FinderCriteria.php
@@ -4,8 +4,46 @@
 
 namespace CodelyTV\FinderKata\Algorithm;
 
-interface FinderCriteria
+final class FinderCriteria
 {
-    const CLOSEST_BIRTHDAYS = 1;
-    const FURTHEST_BIRTHDAYS = 2;
+    const CLOSEST_BIRTH_DATES = 1;
+    const FURTHEST_BIRTH_DATES = 2;
+
+    const VALID_FINDER_CRITERIA = [
+        self::CLOSEST_BIRTH_DATES,
+        self::FURTHEST_BIRTH_DATES
+    ];
+
+    private $rawFinderCriteria;
+
+    private function __construct(int $aRawFinderCriteria)
+    {
+        if (!in_array($aRawFinderCriteria, self::VALID_FINDER_CRITERIA, true)) {
+            throw new \InvalidArgumentException(
+                "You have specified an invalid finder criteria value: <$aRawFinderCriteria>"
+            );
+        }
+
+        $this->rawFinderCriteria = $aRawFinderCriteria;
+    }
+
+    public static function closestBirthDates()
+    {
+        return new self(self::CLOSEST_BIRTH_DATES);
+    }
+
+    public static function furthestBirthDates()
+    {
+        return new self(self::FURTHEST_BIRTH_DATES);
+    }
+
+    public function isByClosestBirthDates()
+    {
+        return $this->rawFinderCriteria === self::CLOSEST_BIRTH_DATES;
+    }
+
+    public function isByFurthestBirthDates()
+    {
+        return $this->rawFinderCriteria === self::FURTHEST_BIRTH_DATES;
+    }
 }
diff --git a/tests/Algorithm/FinderTest.php b/tests/Algorithm/FinderTest.php
index fc73248..d111e59 100644
--- a/tests/Algorithm/FinderTest.php
+++ b/tests/Algorithm/FinderTest.php
@@ -41,7 +41,7 @@ public function should_throw_not_enough_persons_exception_when_given_empty_list(
 
         $this->expectException(NotEnoughPersonsException::class);
 
-        $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
+        $finder->find(FinderCriteria::closestBirthDates());
     }
 
     /** @test */
@@ -52,7 +52,7 @@ public function should_throw_not_enough_persons_when_given_one_person()
 
         $this->expectException(NotEnoughPersonsException::class);
 
-        $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
+        $finder->find(FinderCriteria::closestBirthDates());
     }
 
     /** @test */
@@ -61,7 +61,7 @@ public function should_return_closest_two_for_two_people()
         $allPersons = [$this->sue, $this->greg];
         $finder     = new Finder($allPersons);
 
-        $personsPairFound = $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
+        $personsPairFound = $finder->find(FinderCriteria::closestBirthDates());
 
         $this->assertEquals($this->sue, $personsPairFound->person1());
         $this->assertEquals($this->greg, $personsPairFound->person2());
@@ -73,7 +73,7 @@ public function should_return_furthest_two_for_two_people()
         $allPersons = [$this->mike, $this->greg];
         $finder     = new Finder($allPersons);
 
-        $personsPairFound = $finder->find(FinderCriteria::FURTHEST_BIRTHDAYS);
+        $personsPairFound = $finder->find(FinderCriteria::furthestBirthDates());
 
         $this->assertEquals($this->greg, $personsPairFound->person1());
         $this->assertEquals($this->mike, $personsPairFound->person2());
@@ -85,7 +85,7 @@ public function should_return_furthest_two_for_four_people()
         $allPersons = [$this->sue, $this->sarah, $this->mike, $this->greg];
         $finder     = new Finder($allPersons);
 
-        $personsPairFound = $finder->find(FinderCriteria::FURTHEST_BIRTHDAYS);
+        $personsPairFound = $finder->find(FinderCriteria::furthestBirthDates());
 
         $this->assertEquals($this->sue, $personsPairFound->person1());
         $this->assertEquals($this->sarah, $personsPairFound->person2());
@@ -97,7 +97,7 @@ public function should_return_closest_two_for_four_people()
         $allPersons = [$this->sue, $this->sarah, $this->mike, $this->greg];
         $finder     = new Finder($allPersons);
 
-        $personsPairFound = $finder->find(FinderCriteria::CLOSEST_BIRTHDAYS);
+        $personsPairFound = $finder->find(FinderCriteria::closestBirthDates());
 
         $this->assertEquals($this->sue, $personsPairFound->person1());
         $this->assertEquals($this->greg, $personsPairFound->person2());

From e7cd5054593aa0e7d3a09db900e1b924eb8d6a1d Mon Sep 17 00:00:00 2001
From: Javier Ferrer <javier.mailserio@gmail.com>
Date: Mon, 15 Aug 2016 16:34:09 +0200
Subject: [PATCH 05/10] Improve `Finder` class readability: * Extract private
 methods from the `Finder::find` public one * Replace `$i` and `$j` index by
 the more semantic ones `$currentPersonIteration` and `$personToPairIteration`
 * Extract  `$currentPerson` and `$personToPair` explanatory variables

---
 src/Algorithm/Finder.php | 81 ++++++++++++++++++++++++++++++++--------
 1 file changed, 66 insertions(+), 15 deletions(-)

diff --git a/src/Algorithm/Finder.php b/src/Algorithm/Finder.php
index de9e4fa..9997ef7 100644
--- a/src/Algorithm/Finder.php
+++ b/src/Algorithm/Finder.php
@@ -14,37 +14,88 @@ public function __construct(array $allPersons)
         $this->allPersons = $allPersons;
     }
 
+    /**
+     * @param FinderCriteria $finderCriteria
+     *
+     * @return PersonsPair The pair of persons matching the specified
+     *                     $finderCriteria
+     *
+     * @throws NotEnoughPersonsException
+     */
     public function find(FinderCriteria $finderCriteria): PersonsPair
     {
-        /** @var PersonsPair[] $allPersonsPairs */
+        $allPersonsPairs = $this->pairAllPersons($this->allPersons);
+
+        $this->validateThereAreEnoughPersonsPairs($allPersonsPairs);
+
+        $personsPairMatchingCriteria = $this->findPersonsPairMatchingCriteria(
+            $finderCriteria,
+            $allPersonsPairs
+        );
+
+        return $personsPairMatchingCriteria;
+    }
+
+    /**
+     * @param Person[] $allPersons
+     *
+     * @return PersonsPair[]
+     */
+    private function pairAllPersons(array $allPersons): array
+    {
         $allPersonsPairs = [];
 
-        $numberOfPersons = count($this->allPersons);
+        $numberOfPersons = count($allPersons);
 
-        for ($i = 0; $i < $numberOfPersons; $i++) {
-            for ($j = $i + 1; $j < $numberOfPersons; $j++) {
+        for ($currentPersonIteration = 0;
+            $currentPersonIteration < $numberOfPersons;
+            $currentPersonIteration++) {
+            for ($personToPairIteration = $currentPersonIteration + 1;
+                $personToPairIteration < $numberOfPersons;
+                $personToPairIteration++) {
 
-                if ($this->allPersons[$i]->birthDate()
-                    < $this->allPersons[$j]->birthDate()
-                ) {
-                    $personsPair = new PersonsPair(
-                        $this->allPersons[$i], $this->allPersons[$j]
-                    );
+                $currentPerson = $this->allPersons[$currentPersonIteration];
+                $personToPair  = $this->allPersons[$personToPairIteration];
+
+                if ($currentPerson->birthDate() < $personToPair->birthDate()) {
+                    $allPersonsPairs[] =
+                        new PersonsPair($currentPerson, $personToPair);
                 } else {
-                    $personsPair = new PersonsPair(
-                        $this->allPersons[$j], $this->allPersons[$i]
-                    );
+                    $allPersonsPairs[] =
+                        new PersonsPair($personToPair, $currentPerson);
                 }
-
-                $allPersonsPairs[] = $personsPair;
             }
         }
 
+        return $allPersonsPairs;
+    }
+
+    /**
+     * @param PersonsPair[] $allPersonsPairs
+     *
+     * @return void
+     *
+     * @throws NotEnoughPersonsException
+     */
+    private function validateThereAreEnoughPersonsPairs(array $allPersonsPairs)
+    {
         $thereAreNoPersonsPairs = count($allPersonsPairs) < 1;
         if ($thereAreNoPersonsPairs) {
             throw new NotEnoughPersonsException();
         }
+    }
 
+    /**
+     * @param FinderCriteria $finderCriteria
+     * @param PersonsPair[]  $allPersonsPairs
+     *
+     * @return PersonsPair
+     */
+    private function findPersonsPairMatchingCriteria(
+        FinderCriteria $finderCriteria,
+        array $allPersonsPairs
+    ): PersonsPair
+    {
         $personsPairMatchingCriteria = $allPersonsPairs[0];
 
         foreach ($allPersonsPairs as $personsPair) {

From 8fba6ef71588c750041d551e41019005860dd20e Mon Sep 17 00:00:00 2001
From: Javier Ferrer <javier.mailserio@gmail.com>
Date: Mon, 15 Aug 2016 16:56:47 +0200
Subject: [PATCH 06/10] Make the Finder OCP (Open/Closed SOLID Principle)
 compliant * Refactor the `FinderCriteria` Value Object into an `interface`
 and implement it from two different models `ClosestBirthDateCriteria` and
 `FurthestBirthDateCriteria`. This classes implement the logic to determine
 which `PersonsPair` `hasMorePriority`. So if we want to add another different
 criteria, we just need to implement the `PersonsPairCriteria` interface and
 pass it to the `Finder:: find` method without modifying any `switch` nor
 `if`/`elseif`.

---
 src/Algorithm/Finder.php                      | 38 +++++++-------
 src/Algorithm/FinderCriteria.php              | 49 -------------------
 .../PersonsPair/ClosestBirthDateCriteria.php  | 18 +++++++
 .../PersonsPair/FurthestBirthDateCriteria.php | 18 +++++++
 .../Model/PersonsPair/PersonsPairCriteria.php | 23 +++++++++
 tests/Algorithm/FinderTest.php                | 33 ++++++++++---
 6 files changed, 102 insertions(+), 77 deletions(-)
 delete mode 100644 src/Algorithm/FinderCriteria.php
 create mode 100644 src/Domain/Model/PersonsPair/ClosestBirthDateCriteria.php
 create mode 100644 src/Domain/Model/PersonsPair/FurthestBirthDateCriteria.php
 create mode 100644 src/Domain/Model/PersonsPair/PersonsPairCriteria.php

diff --git a/src/Algorithm/Finder.php b/src/Algorithm/Finder.php
index 9997ef7..917d0f5 100644
--- a/src/Algorithm/Finder.php
+++ b/src/Algorithm/Finder.php
@@ -4,6 +4,8 @@
 
 namespace CodelyTV\FinderKata\Algorithm;
 
+use CodelyTV\FinderKata\Domain\Model\PersonsPair\PersonsPairCriteria;
+
 final class Finder
 {
     /** @var Person[] */
@@ -15,14 +17,14 @@ public function __construct(array $allPersons)
     }
 
     /**
-     * @param FinderCriteria $finderCriteria
+     * @param PersonsPairCriteria $finderCriteria
      *
      * @return PersonsPair The pair of persons matching the specified
      *                     $finderCriteria
      *
      * @throws NotEnoughPersonsException
      */
-    public function find(FinderCriteria $finderCriteria): PersonsPair
+    public function find(PersonsPairCriteria $finderCriteria): PersonsPair
     {
         $allPersonsPairs = $this->pairAllPersons($this->allPersons);
 
@@ -86,34 +88,28 @@ private function validateThereAreEnoughPersonsPairs(array $allPersonsPairs)
     }
 
     /**
-     * @param FinderCriteria $finderCriteria
-     * @param PersonsPair[]  $allPersonsPairs
+     * @param PersonsPairCriteria $personsPairPriorityCriteria
+     * @param PersonsPair[]       $allPersonsPairs
      *
      * @return PersonsPair
      */
     private function findPersonsPairMatchingCriteria(
-        FinderCriteria $finderCriteria,
+        PersonsPairCriteria $personsPairPriorityCriteria,
         array $allPersonsPairs
     ): PersonsPair
     {
-        $personsPairMatchingCriteria = $allPersonsPairs[0];
-
-        foreach ($allPersonsPairs as $personsPair) {
-            if ($finderCriteria->isByClosestBirthDates()) {
-                if ($personsPair->birthDaysDistanceInSeconds()
-                    < $personsPairMatchingCriteria->birthDaysDistanceInSeconds()
-                ) {
-                    $personsPairMatchingCriteria = $personsPair;
-                }
-            } elseif ($finderCriteria->isByFurthestBirthDates()) {
-                if ($personsPair->birthDaysDistanceInSeconds()
-                    > $personsPairMatchingCriteria->birthDaysDistanceInSeconds()
-                ) {
-                    $personsPairMatchingCriteria = $personsPair;
-                }
+        $bestPersonsPair = $allPersonsPairs[0];
+
+        foreach ($allPersonsPairs as $personsPairCandidate) {
+            if ($personsPairPriorityCriteria->hasMorePriority(
+                $bestPersonsPair,
+                $personsPairCandidate
+            )
+            ) {
+                $bestPersonsPair = $personsPairCandidate;
             }
         }
 
-        return $personsPairMatchingCriteria;
+        return $bestPersonsPair;
     }
 }
diff --git a/src/Algorithm/FinderCriteria.php b/src/Algorithm/FinderCriteria.php
deleted file mode 100644
index 84786a3..0000000
--- a/src/Algorithm/FinderCriteria.php
+++ /dev/null
@@ -1,49 +0,0 @@
-<?php
-
-declare(strict_types = 1);
-
-namespace CodelyTV\FinderKata\Algorithm;
-
-final class FinderCriteria
-{
-    const CLOSEST_BIRTH_DATES = 1;
-    const FURTHEST_BIRTH_DATES = 2;
-
-    const VALID_FINDER_CRITERIA = [
-        self::CLOSEST_BIRTH_DATES,
-        self::FURTHEST_BIRTH_DATES
-    ];
-
-    private $rawFinderCriteria;
-
-    private function __construct(int $aRawFinderCriteria)
-    {
-        if (!in_array($aRawFinderCriteria, self::VALID_FINDER_CRITERIA, true)) {
-            throw new \InvalidArgumentException(
-                "You have specified an invalid finder criteria value: <$aRawFinderCriteria>"
-            );
-        }
-
-        $this->rawFinderCriteria = $aRawFinderCriteria;
-    }
-
-    public static function closestBirthDates()
-    {
-        return new self(self::CLOSEST_BIRTH_DATES);
-    }
-
-    public static function furthestBirthDates()
-    {
-        return new self(self::FURTHEST_BIRTH_DATES);
-    }
-
-    public function isByClosestBirthDates()
-    {
-        return $this->rawFinderCriteria === self::CLOSEST_BIRTH_DATES;
-    }
-
-    public function isByFurthestBirthDates()
-    {
-        return $this->rawFinderCriteria === self::FURTHEST_BIRTH_DATES;
-    }
-}
diff --git a/src/Domain/Model/PersonsPair/ClosestBirthDateCriteria.php b/src/Domain/Model/PersonsPair/ClosestBirthDateCriteria.php
new file mode 100644
index 0000000..c104b17
--- /dev/null
+++ b/src/Domain/Model/PersonsPair/ClosestBirthDateCriteria.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace CodelyTV\FinderKata\Domain\Model\PersonsPair;
+
+use CodelyTV\FinderKata\Algorithm\PersonsPair;
+
+final class ClosestBirthDateCriteria implements PersonsPairCriteria
+{
+    /** @{InheritDoc} */
+    public function hasMorePriority(
+        PersonsPair $basePersonsPair,
+        PersonsPair $candidatePersonsPair
+    ): bool
+    {
+        return $candidatePersonsPair->birthDaysDistanceInSeconds()
+        < $basePersonsPair->birthDaysDistanceInSeconds();
+    }
+}
diff --git a/src/Domain/Model/PersonsPair/FurthestBirthDateCriteria.php b/src/Domain/Model/PersonsPair/FurthestBirthDateCriteria.php
new file mode 100644
index 0000000..ac955cf
--- /dev/null
+++ b/src/Domain/Model/PersonsPair/FurthestBirthDateCriteria.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace CodelyTV\FinderKata\Domain\Model\PersonsPair;
+
+use CodelyTV\FinderKata\Algorithm\PersonsPair;
+
+final class FurthestBirthDateCriteria implements PersonsPairCriteria
+{
+    /** @{InheritDoc} */
+    public function hasMorePriority(
+        PersonsPair $basePersonsPair,
+        PersonsPair $candidatePersonsPair
+    ): bool
+    {
+        return $candidatePersonsPair->birthDaysDistanceInSeconds()
+        > $basePersonsPair->birthDaysDistanceInSeconds();
+    }
+}
diff --git a/src/Domain/Model/PersonsPair/PersonsPairCriteria.php b/src/Domain/Model/PersonsPair/PersonsPairCriteria.php
new file mode 100644
index 0000000..1b20d4a
--- /dev/null
+++ b/src/Domain/Model/PersonsPair/PersonsPairCriteria.php
@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace CodelyTV\FinderKata\Domain\Model\PersonsPair;
+
+use CodelyTV\FinderKata\Algorithm\PersonsPair;
+
+interface PersonsPairCriteria
+{
+    /**
+     * Determines if the $candidatePersonsPair has more priority than the $basePersonsPair based on a priority criteria.
+     *
+     * @param PersonsPair $basePersonsPair
+     * @param PersonsPair $candidatePersonsPair
+     *
+     * @return bool
+     */
+    public function hasMorePriority(
+        PersonsPair $basePersonsPair,
+        PersonsPair $candidatePersonsPair
+    ): bool;
+}
diff --git a/tests/Algorithm/FinderTest.php b/tests/Algorithm/FinderTest.php
index d111e59..61809b2 100644
--- a/tests/Algorithm/FinderTest.php
+++ b/tests/Algorithm/FinderTest.php
@@ -5,9 +5,10 @@
 namespace CodelyTV\FinderKataTest\Algorithm;
 
 use CodelyTV\FinderKata\Algorithm\Finder;
-use CodelyTV\FinderKata\Algorithm\FinderCriteria;
 use CodelyTV\FinderKata\Algorithm\NotEnoughPersonsException;
 use CodelyTV\FinderKata\Algorithm\Person;
+use CodelyTV\FinderKata\Domain\Model\PersonsPair\ClosestBirthDateCriteria;
+use CodelyTV\FinderKata\Domain\Model\PersonsPair\FurthestBirthDateCriteria;
 use PHPUnit\Framework\TestCase;
 
 final class FinderTest extends TestCase
@@ -41,7 +42,9 @@ public function should_throw_not_enough_persons_exception_when_given_empty_list(
 
         $this->expectException(NotEnoughPersonsException::class);
 
-        $finder->find(FinderCriteria::closestBirthDates());
+        $closestBirthDatePersonsPairsCriteria = new ClosestBirthDateCriteria();
+
+        $finder->find($closestBirthDatePersonsPairsCriteria);
     }
 
     /** @test */
@@ -52,7 +55,9 @@ public function should_throw_not_enough_persons_when_given_one_person()
 
         $this->expectException(NotEnoughPersonsException::class);
 
-        $finder->find(FinderCriteria::closestBirthDates());
+        $closestBirthDatePersonsPairsCriteria = new ClosestBirthDateCriteria();
+
+        $finder->find($closestBirthDatePersonsPairsCriteria);
     }
 
     /** @test */
@@ -61,7 +66,10 @@ public function should_return_closest_two_for_two_people()
         $allPersons = [$this->sue, $this->greg];
         $finder     = new Finder($allPersons);
 
-        $personsPairFound = $finder->find(FinderCriteria::closestBirthDates());
+        $closestBirthDatePersonsPairsCriteria = new ClosestBirthDateCriteria();
+
+        $personsPairFound =
+            $finder->find($closestBirthDatePersonsPairsCriteria);
 
         $this->assertEquals($this->sue, $personsPairFound->person1());
         $this->assertEquals($this->greg, $personsPairFound->person2());
@@ -73,7 +81,11 @@ public function should_return_furthest_two_for_two_people()
         $allPersons = [$this->mike, $this->greg];
         $finder     = new Finder($allPersons);
 
-        $personsPairFound = $finder->find(FinderCriteria::furthestBirthDates());
+        $furthestBirthDatePersonsPairsCriteria =
+            new FurthestBirthDateCriteria();
+
+        $personsPairFound =
+            $finder->find($furthestBirthDatePersonsPairsCriteria);
 
         $this->assertEquals($this->greg, $personsPairFound->person1());
         $this->assertEquals($this->mike, $personsPairFound->person2());
@@ -85,7 +97,11 @@ public function should_return_furthest_two_for_four_people()
         $allPersons = [$this->sue, $this->sarah, $this->mike, $this->greg];
         $finder     = new Finder($allPersons);
 
-        $personsPairFound = $finder->find(FinderCriteria::furthestBirthDates());
+        $furthestBirthDatePersonsPairsCriteria =
+            new FurthestBirthDateCriteria();
+
+        $personsPairFound =
+            $finder->find($furthestBirthDatePersonsPairsCriteria);
 
         $this->assertEquals($this->sue, $personsPairFound->person1());
         $this->assertEquals($this->sarah, $personsPairFound->person2());
@@ -97,7 +113,10 @@ public function should_return_closest_two_for_four_people()
         $allPersons = [$this->sue, $this->sarah, $this->mike, $this->greg];
         $finder     = new Finder($allPersons);
 
-        $personsPairFound = $finder->find(FinderCriteria::closestBirthDates());
+        $closestBirthDatePersonsPairsCriteria = new ClosestBirthDateCriteria();
+
+        $personsPairFound =
+            $finder->find($closestBirthDatePersonsPairsCriteria);
 
         $this->assertEquals($this->sue, $personsPairFound->person1());
         $this->assertEquals($this->greg, $personsPairFound->person2());

From 597457661c5bf6d0336d05b417c268026afd83bd Mon Sep 17 00:00:00 2001
From: Javier Ferrer <javier.mailserio@gmail.com>
Date: Mon, 15 Aug 2016 17:03:47 +0200
Subject: [PATCH 07/10] Move the `$allPersons` input array from the `Finder`
 constructor to the `find` method. This way we don't need to create 2
 different `Finder` instances in order to execute the algorithm with 2
 different inputs, and more importantly, we leave the constructor ready in
 order to only receive collaborator as parameters

---
 src/Algorithm/Finder.php       | 22 ++++++++--------------
 tests/Algorithm/FinderTest.php | 24 ++++++++++++------------
 2 files changed, 20 insertions(+), 26 deletions(-)

diff --git a/src/Algorithm/Finder.php b/src/Algorithm/Finder.php
index 917d0f5..f0cda6d 100644
--- a/src/Algorithm/Finder.php
+++ b/src/Algorithm/Finder.php
@@ -8,25 +8,19 @@
 
 final class Finder
 {
-    /** @var Person[] */
-    private $allPersons;
-
-    public function __construct(array $allPersons)
-    {
-        $this->allPersons = $allPersons;
-    }
-
     /**
+     * @param Person[]            $allPersons
      * @param PersonsPairCriteria $finderCriteria
      *
      * @return PersonsPair The pair of persons matching the specified
      *                     $finderCriteria
-     *
-     * @throws NotEnoughPersonsException
      */
-    public function find(PersonsPairCriteria $finderCriteria): PersonsPair
+    public function find(
+        array $allPersons,
+        PersonsPairCriteria $finderCriteria
+    ): PersonsPair
     {
-        $allPersonsPairs = $this->pairAllPersons($this->allPersons);
+        $allPersonsPairs = $this->pairAllPersons($allPersons);
 
         $this->validateThereAreEnoughPersonsPairs($allPersonsPairs);
 
@@ -56,8 +50,8 @@ private function pairAllPersons(array $allPersons): array
                 $personToPairIteration < $numberOfPersons;
                 $personToPairIteration++) {
 
-                $currentPerson = $this->allPersons[$currentPersonIteration];
-                $personToPair  = $this->allPersons[$personToPairIteration];
+                $currentPerson = $allPersons[$currentPersonIteration];
+                $personToPair  = $allPersons[$personToPairIteration];
 
                 if ($currentPerson->birthDate() < $personToPair->birthDate()) {
                     $allPersonsPairs[] =
diff --git a/tests/Algorithm/FinderTest.php b/tests/Algorithm/FinderTest.php
index 61809b2..b88aace 100644
--- a/tests/Algorithm/FinderTest.php
+++ b/tests/Algorithm/FinderTest.php
@@ -38,38 +38,38 @@ public function should_throw_not_enough_persons_exception_when_given_empty_list(
     )
     {
         $allPersons = [];
-        $finder     = new Finder($allPersons);
+        $finder     = new Finder();
 
         $this->expectException(NotEnoughPersonsException::class);
 
         $closestBirthDatePersonsPairsCriteria = new ClosestBirthDateCriteria();
 
-        $finder->find($closestBirthDatePersonsPairsCriteria);
+        $finder->find($allPersons, $closestBirthDatePersonsPairsCriteria);
     }
 
     /** @test */
     public function should_throw_not_enough_persons_when_given_one_person()
     {
         $allPersons = [$this->sue];
-        $finder     = new Finder($allPersons);
+        $finder     = new Finder();
 
         $this->expectException(NotEnoughPersonsException::class);
 
         $closestBirthDatePersonsPairsCriteria = new ClosestBirthDateCriteria();
 
-        $finder->find($closestBirthDatePersonsPairsCriteria);
+        $finder->find($allPersons, $closestBirthDatePersonsPairsCriteria);
     }
 
     /** @test */
     public function should_return_closest_two_for_two_people()
     {
         $allPersons = [$this->sue, $this->greg];
-        $finder     = new Finder($allPersons);
+        $finder     = new Finder();
 
         $closestBirthDatePersonsPairsCriteria = new ClosestBirthDateCriteria();
 
         $personsPairFound =
-            $finder->find($closestBirthDatePersonsPairsCriteria);
+            $finder->find($allPersons, $closestBirthDatePersonsPairsCriteria);
 
         $this->assertEquals($this->sue, $personsPairFound->person1());
         $this->assertEquals($this->greg, $personsPairFound->person2());
@@ -79,13 +79,13 @@ public function should_return_closest_two_for_two_people()
     public function should_return_furthest_two_for_two_people()
     {
         $allPersons = [$this->mike, $this->greg];
-        $finder     = new Finder($allPersons);
+        $finder     = new Finder();
 
         $furthestBirthDatePersonsPairsCriteria =
             new FurthestBirthDateCriteria();
 
         $personsPairFound =
-            $finder->find($furthestBirthDatePersonsPairsCriteria);
+            $finder->find($allPersons, $furthestBirthDatePersonsPairsCriteria);
 
         $this->assertEquals($this->greg, $personsPairFound->person1());
         $this->assertEquals($this->mike, $personsPairFound->person2());
@@ -95,13 +95,13 @@ public function should_return_furthest_two_for_two_people()
     public function should_return_furthest_two_for_four_people()
     {
         $allPersons = [$this->sue, $this->sarah, $this->mike, $this->greg];
-        $finder     = new Finder($allPersons);
+        $finder     = new Finder();
 
         $furthestBirthDatePersonsPairsCriteria =
             new FurthestBirthDateCriteria();
 
         $personsPairFound =
-            $finder->find($furthestBirthDatePersonsPairsCriteria);
+            $finder->find($allPersons, $furthestBirthDatePersonsPairsCriteria);
 
         $this->assertEquals($this->sue, $personsPairFound->person1());
         $this->assertEquals($this->sarah, $personsPairFound->person2());
@@ -111,12 +111,12 @@ public function should_return_furthest_two_for_four_people()
     public function should_return_closest_two_for_four_people()
     {
         $allPersons = [$this->sue, $this->sarah, $this->mike, $this->greg];
-        $finder     = new Finder($allPersons);
+        $finder     = new Finder();
 
         $closestBirthDatePersonsPairsCriteria = new ClosestBirthDateCriteria();
 
         $personsPairFound =
-            $finder->find($closestBirthDatePersonsPairsCriteria);
+            $finder->find($allPersons, $closestBirthDatePersonsPairsCriteria);
 
         $this->assertEquals($this->sue, $personsPairFound->person1());
         $this->assertEquals($this->greg, $personsPairFound->person2());

From 4b014cbbe3253af0fcfde1d7c07a1031fcbca840 Mon Sep 17 00:00:00 2001
From: Javier Ferrer <javier.mailserio@gmail.com>
Date: Mon, 15 Aug 2016 17:19:50 +0200
Subject: [PATCH 08/10] Extract the responsibility of pair all the `Person`
 received as the `Finder::find` input into the new `PersonsPairer` interface
 allowing also OCP applications on that end

---
 src/Algorithm/Finder.php                      | 45 +++++--------------
 .../PersonsPair/ClosestBirthDateCriteria.php  |  1 -
 .../PersonsPair/FurthestBirthDateCriteria.php |  1 -
 .../Service/PersonsPair/PersonsPairer.php     | 18 ++++++++
 .../PersonsPair/SequentialPersonsPairer.php   | 37 +++++++++++++++
 tests/Algorithm/FinderTest.php                | 27 ++++++++---
 6 files changed, 85 insertions(+), 44 deletions(-)
 create mode 100644 src/Domain/Service/PersonsPair/PersonsPairer.php
 create mode 100644 src/Domain/Service/PersonsPair/SequentialPersonsPairer.php

diff --git a/src/Algorithm/Finder.php b/src/Algorithm/Finder.php
index f0cda6d..1bc71c5 100644
--- a/src/Algorithm/Finder.php
+++ b/src/Algorithm/Finder.php
@@ -5,9 +5,18 @@
 namespace CodelyTV\FinderKata\Algorithm;
 
 use CodelyTV\FinderKata\Domain\Model\PersonsPair\PersonsPairCriteria;
+use CodelyTV\FinderKata\Domain\Service\PersonsPair\PersonsPairer;
 
 final class Finder
 {
+    /** @var PersonsPairer */
+    private $personsPairer;
+
+    public function __construct(PersonsPairer $aPersonsPairer)
+    {
+        $this->personsPairer = $aPersonsPairer;
+    }
+
     /**
      * @param Person[]            $allPersons
      * @param PersonsPairCriteria $finderCriteria
@@ -20,7 +29,7 @@ public function find(
         PersonsPairCriteria $finderCriteria
     ): PersonsPair
     {
-        $allPersonsPairs = $this->pairAllPersons($allPersons);
+        $allPersonsPairs = $this->personsPairer->pair($allPersons);
 
         $this->validateThereAreEnoughPersonsPairs($allPersonsPairs);
 
@@ -32,40 +41,6 @@ public function find(
         return $personsPairMatchingCriteria;
     }
 
-    /**
-     * @param Person[] $allPersons
-     *
-     * @return PersonsPair[]
-     */
-    private function pairAllPersons(array $allPersons): array
-    {
-        $allPersonsPairs = [];
-
-        $numberOfPersons = count($allPersons);
-
-        for ($currentPersonIteration = 0;
-            $currentPersonIteration < $numberOfPersons;
-            $currentPersonIteration++) {
-            for ($personToPairIteration = $currentPersonIteration + 1;
-                $personToPairIteration < $numberOfPersons;
-                $personToPairIteration++) {
-
-                $currentPerson = $allPersons[$currentPersonIteration];
-                $personToPair  = $allPersons[$personToPairIteration];
-
-                if ($currentPerson->birthDate() < $personToPair->birthDate()) {
-                    $allPersonsPairs[] =
-                        new PersonsPair($currentPerson, $personToPair);
-                } else {
-                    $allPersonsPairs[] =
-                        new PersonsPair($personToPair, $currentPerson);
-                }
-            }
-        }
-
-        return $allPersonsPairs;
-    }
-
     /**
      * @param PersonsPair[] $allPersonsPairs
      *
diff --git a/src/Domain/Model/PersonsPair/ClosestBirthDateCriteria.php b/src/Domain/Model/PersonsPair/ClosestBirthDateCriteria.php
index c104b17..4ecee0c 100644
--- a/src/Domain/Model/PersonsPair/ClosestBirthDateCriteria.php
+++ b/src/Domain/Model/PersonsPair/ClosestBirthDateCriteria.php
@@ -6,7 +6,6 @@
 
 final class ClosestBirthDateCriteria implements PersonsPairCriteria
 {
-    /** @{InheritDoc} */
     public function hasMorePriority(
         PersonsPair $basePersonsPair,
         PersonsPair $candidatePersonsPair
diff --git a/src/Domain/Model/PersonsPair/FurthestBirthDateCriteria.php b/src/Domain/Model/PersonsPair/FurthestBirthDateCriteria.php
index ac955cf..bc14017 100644
--- a/src/Domain/Model/PersonsPair/FurthestBirthDateCriteria.php
+++ b/src/Domain/Model/PersonsPair/FurthestBirthDateCriteria.php
@@ -6,7 +6,6 @@
 
 final class FurthestBirthDateCriteria implements PersonsPairCriteria
 {
-    /** @{InheritDoc} */
     public function hasMorePriority(
         PersonsPair $basePersonsPair,
         PersonsPair $candidatePersonsPair
diff --git a/src/Domain/Service/PersonsPair/PersonsPairer.php b/src/Domain/Service/PersonsPair/PersonsPairer.php
new file mode 100644
index 0000000..052012e
--- /dev/null
+++ b/src/Domain/Service/PersonsPair/PersonsPairer.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace CodelyTV\FinderKata\Domain\Service\PersonsPair;
+
+use CodelyTV\FinderKata\Algorithm\Person;
+use CodelyTV\FinderKata\Algorithm\PersonsPair;
+
+interface PersonsPairer
+{
+    /**
+     * Returns an array of PersonsPair based on a criteria.
+     *
+     * @param Person[] $allPersons
+     *
+     * @return PersonsPair[]
+     */
+    public function pair(array $allPersons): array;
+}
diff --git a/src/Domain/Service/PersonsPair/SequentialPersonsPairer.php b/src/Domain/Service/PersonsPair/SequentialPersonsPairer.php
new file mode 100644
index 0000000..aea3b85
--- /dev/null
+++ b/src/Domain/Service/PersonsPair/SequentialPersonsPairer.php
@@ -0,0 +1,37 @@
+<?php
+
+namespace CodelyTV\FinderKata\Domain\Service\PersonsPair;
+
+use CodelyTV\FinderKata\Algorithm\PersonsPair;
+
+final class SequentialPersonsPairer implements PersonsPairer
+{
+    public function pair(array $allPersons): array {
+        $allPersonsPairs = [];
+
+        $numberOfPersons = count($allPersons);
+
+        for ($currentPersonIteration = 0;
+            $currentPersonIteration < $numberOfPersons;
+            $currentPersonIteration++) {
+
+            for ($personToPairIteration = $currentPersonIteration + 1;
+                $personToPairIteration < $numberOfPersons;
+                $personToPairIteration++) {
+
+                $currentPerson = $allPersons[$currentPersonIteration];
+                $personToPair  = $allPersons[$personToPairIteration];
+
+                if ($currentPerson->birthDate() < $personToPair->birthDate()) {
+                    $allPersonsPairs[] =
+                        new PersonsPair($currentPerson, $personToPair);
+                } else {
+                    $allPersonsPairs[] =
+                        new PersonsPair($personToPair, $currentPerson);
+                }
+            }
+        }
+
+        return $allPersonsPairs;
+    }
+}
diff --git a/tests/Algorithm/FinderTest.php b/tests/Algorithm/FinderTest.php
index b88aace..32dfde8 100644
--- a/tests/Algorithm/FinderTest.php
+++ b/tests/Algorithm/FinderTest.php
@@ -9,6 +9,7 @@
 use CodelyTV\FinderKata\Algorithm\Person;
 use CodelyTV\FinderKata\Domain\Model\PersonsPair\ClosestBirthDateCriteria;
 use CodelyTV\FinderKata\Domain\Model\PersonsPair\FurthestBirthDateCriteria;
+use CodelyTV\FinderKata\Domain\Service\PersonsPair\SequentialPersonsPairer;
 use PHPUnit\Framework\TestCase;
 
 final class FinderTest extends TestCase
@@ -37,8 +38,10 @@ protected function setUp()
     public function should_throw_not_enough_persons_exception_when_given_empty_list(
     )
     {
+        $sequentialPersonsPairer = new SequentialPersonsPairer();
+        $finder                  = new Finder($sequentialPersonsPairer);
+
         $allPersons = [];
-        $finder     = new Finder();
 
         $this->expectException(NotEnoughPersonsException::class);
 
@@ -50,8 +53,10 @@ public function should_throw_not_enough_persons_exception_when_given_empty_list(
     /** @test */
     public function should_throw_not_enough_persons_when_given_one_person()
     {
+        $sequentialPersonsPairer = new SequentialPersonsPairer();
+        $finder                  = new Finder($sequentialPersonsPairer);
+
         $allPersons = [$this->sue];
-        $finder     = new Finder();
 
         $this->expectException(NotEnoughPersonsException::class);
 
@@ -63,8 +68,10 @@ public function should_throw_not_enough_persons_when_given_one_person()
     /** @test */
     public function should_return_closest_two_for_two_people()
     {
+        $sequentialPersonsPairer = new SequentialPersonsPairer();
+        $finder                  = new Finder($sequentialPersonsPairer);
+
         $allPersons = [$this->sue, $this->greg];
-        $finder     = new Finder();
 
         $closestBirthDatePersonsPairsCriteria = new ClosestBirthDateCriteria();
 
@@ -78,8 +85,10 @@ public function should_return_closest_two_for_two_people()
     /** @test */
     public function should_return_furthest_two_for_two_people()
     {
+        $sequentialPersonsPairer = new SequentialPersonsPairer();
+        $finder                  = new Finder($sequentialPersonsPairer);
+
         $allPersons = [$this->mike, $this->greg];
-        $finder     = new Finder();
 
         $furthestBirthDatePersonsPairsCriteria =
             new FurthestBirthDateCriteria();
@@ -94,8 +103,10 @@ public function should_return_furthest_two_for_two_people()
     /** @test */
     public function should_return_furthest_two_for_four_people()
     {
+        $sequentialPersonsPairer = new SequentialPersonsPairer();
+        $finder                  = new Finder($sequentialPersonsPairer);
+
         $allPersons = [$this->sue, $this->sarah, $this->mike, $this->greg];
-        $finder     = new Finder();
 
         $furthestBirthDatePersonsPairsCriteria =
             new FurthestBirthDateCriteria();
@@ -110,9 +121,11 @@ public function should_return_furthest_two_for_four_people()
     /** @test */
     public function should_return_closest_two_for_four_people()
     {
-        $allPersons = [$this->sue, $this->sarah, $this->mike, $this->greg];
-        $finder     = new Finder();
+        $sequentialPersonsPairer = new SequentialPersonsPairer();
+        $finder                  = new Finder($sequentialPersonsPairer);
 
+        $allPersons = [$this->sue, $this->sarah, $this->mike, $this->greg];
+        
         $closestBirthDatePersonsPairsCriteria = new ClosestBirthDateCriteria();
 
         $personsPairFound =

From 097b1b93af5d406221e54f8a1b40cfea13000c3a Mon Sep 17 00:00:00 2001
From: Javier Ferrer <javier.mailserio@gmail.com>
Date: Mon, 15 Aug 2016 17:35:06 +0200
Subject: [PATCH 09/10] Extract the responsibility of constructing the
 `PersonsPair` from the `PersonsPairer` to its own `PersonsPairFactory`. This
 way we can mix different `PersonsPairer` implementations without repeating
 the `PersonsPair` construction logic

---
 .../PersonsPair/PersonsPairFactory.php        | 11 +++++++
 .../PersonsPair/SequentialPersonsPairer.php   | 24 ++++++++-------
 .../YoungerFirstPersonsPairFactory.php        | 18 ++++++++++++
 tests/Algorithm/FinderTest.php                | 29 ++++++++++++++-----
 4 files changed, 64 insertions(+), 18 deletions(-)
 create mode 100644 src/Domain/Service/PersonsPair/PersonsPairFactory.php
 create mode 100644 src/Domain/Service/PersonsPair/YoungerFirstPersonsPairFactory.php

diff --git a/src/Domain/Service/PersonsPair/PersonsPairFactory.php b/src/Domain/Service/PersonsPair/PersonsPairFactory.php
new file mode 100644
index 0000000..407e49f
--- /dev/null
+++ b/src/Domain/Service/PersonsPair/PersonsPairFactory.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace CodelyTV\FinderKata\Domain\Service\PersonsPair;
+
+use CodelyTV\FinderKata\Algorithm\Person;
+use CodelyTV\FinderKata\Algorithm\PersonsPair;
+
+interface PersonsPairFactory
+{
+    public function __invoke(Person $person1, Person $person2): PersonsPair;
+}
diff --git a/src/Domain/Service/PersonsPair/SequentialPersonsPairer.php b/src/Domain/Service/PersonsPair/SequentialPersonsPairer.php
index aea3b85..d5deef5 100644
--- a/src/Domain/Service/PersonsPair/SequentialPersonsPairer.php
+++ b/src/Domain/Service/PersonsPair/SequentialPersonsPairer.php
@@ -2,11 +2,18 @@
 
 namespace CodelyTV\FinderKata\Domain\Service\PersonsPair;
 
-use CodelyTV\FinderKata\Algorithm\PersonsPair;
-
 final class SequentialPersonsPairer implements PersonsPairer
 {
-    public function pair(array $allPersons): array {
+    /** @var PersonsPairFactory */
+    private $personsPairFactory;
+
+    public function __construct(PersonsPairFactory $aPersonsPairFactory)
+    {
+        $this->personsPairFactory = $aPersonsPairFactory;
+    }
+
+    public function pair(array $allPersons): array
+    {
         $allPersonsPairs = [];
 
         $numberOfPersons = count($allPersons);
@@ -22,13 +29,10 @@ public function pair(array $allPersons): array {
                 $currentPerson = $allPersons[$currentPersonIteration];
                 $personToPair  = $allPersons[$personToPairIteration];
 
-                if ($currentPerson->birthDate() < $personToPair->birthDate()) {
-                    $allPersonsPairs[] =
-                        new PersonsPair($currentPerson, $personToPair);
-                } else {
-                    $allPersonsPairs[] =
-                        new PersonsPair($personToPair, $currentPerson);
-                }
+                $allPersonsPairs[] = $this->personsPairFactory->__invoke(
+                    $currentPerson,
+                    $personToPair
+                );
             }
         }
 
diff --git a/src/Domain/Service/PersonsPair/YoungerFirstPersonsPairFactory.php b/src/Domain/Service/PersonsPair/YoungerFirstPersonsPairFactory.php
new file mode 100644
index 0000000..fe3e44f
--- /dev/null
+++ b/src/Domain/Service/PersonsPair/YoungerFirstPersonsPairFactory.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace CodelyTV\FinderKata\Domain\Service\PersonsPair;
+
+use CodelyTV\FinderKata\Algorithm\Person;
+use CodelyTV\FinderKata\Algorithm\PersonsPair;
+
+final class YoungerFirstPersonsPairFactory implements PersonsPairFactory
+{
+    public function __invoke(Person $person1, Person $person2): PersonsPair
+    {
+        if ($person1->birthDate() < $person2->birthDate()) {
+            return new PersonsPair($person1, $person2);
+        } else {
+            return new PersonsPair($person2, $person1);
+        }
+    }
+}
diff --git a/tests/Algorithm/FinderTest.php b/tests/Algorithm/FinderTest.php
index 32dfde8..1816f58 100644
--- a/tests/Algorithm/FinderTest.php
+++ b/tests/Algorithm/FinderTest.php
@@ -10,6 +10,7 @@
 use CodelyTV\FinderKata\Domain\Model\PersonsPair\ClosestBirthDateCriteria;
 use CodelyTV\FinderKata\Domain\Model\PersonsPair\FurthestBirthDateCriteria;
 use CodelyTV\FinderKata\Domain\Service\PersonsPair\SequentialPersonsPairer;
+use CodelyTV\FinderKata\Domain\Service\PersonsPair\YoungerFirstPersonsPairFactory;
 use PHPUnit\Framework\TestCase;
 
 final class FinderTest extends TestCase
@@ -38,8 +39,10 @@ protected function setUp()
     public function should_throw_not_enough_persons_exception_when_given_empty_list(
     )
     {
-        $sequentialPersonsPairer = new SequentialPersonsPairer();
-        $finder                  = new Finder($sequentialPersonsPairer);
+        $youngerFirstPersonsPairFactory = new YoungerFirstPersonsPairFactory();
+        $sequentialPersonsPairer        =
+            new SequentialPersonsPairer($youngerFirstPersonsPairFactory);
+        $finder                         = new Finder($sequentialPersonsPairer);
 
         $allPersons = [];
 
@@ -53,7 +56,9 @@ public function should_throw_not_enough_persons_exception_when_given_empty_list(
     /** @test */
     public function should_throw_not_enough_persons_when_given_one_person()
     {
-        $sequentialPersonsPairer = new SequentialPersonsPairer();
+        $youngerFirstPersonsPairFactory = new YoungerFirstPersonsPairFactory();
+        $sequentialPersonsPairer        =
+            new SequentialPersonsPairer($youngerFirstPersonsPairFactory);
         $finder                  = new Finder($sequentialPersonsPairer);
 
         $allPersons = [$this->sue];
@@ -68,7 +73,9 @@ public function should_throw_not_enough_persons_when_given_one_person()
     /** @test */
     public function should_return_closest_two_for_two_people()
     {
-        $sequentialPersonsPairer = new SequentialPersonsPairer();
+        $youngerFirstPersonsPairFactory = new YoungerFirstPersonsPairFactory();
+        $sequentialPersonsPairer        =
+            new SequentialPersonsPairer($youngerFirstPersonsPairFactory);
         $finder                  = new Finder($sequentialPersonsPairer);
 
         $allPersons = [$this->sue, $this->greg];
@@ -85,7 +92,9 @@ public function should_return_closest_two_for_two_people()
     /** @test */
     public function should_return_furthest_two_for_two_people()
     {
-        $sequentialPersonsPairer = new SequentialPersonsPairer();
+        $youngerFirstPersonsPairFactory = new YoungerFirstPersonsPairFactory();
+        $sequentialPersonsPairer        =
+            new SequentialPersonsPairer($youngerFirstPersonsPairFactory);
         $finder                  = new Finder($sequentialPersonsPairer);
 
         $allPersons = [$this->mike, $this->greg];
@@ -103,7 +112,9 @@ public function should_return_furthest_two_for_two_people()
     /** @test */
     public function should_return_furthest_two_for_four_people()
     {
-        $sequentialPersonsPairer = new SequentialPersonsPairer();
+        $youngerFirstPersonsPairFactory = new YoungerFirstPersonsPairFactory();
+        $sequentialPersonsPairer        =
+            new SequentialPersonsPairer($youngerFirstPersonsPairFactory);
         $finder                  = new Finder($sequentialPersonsPairer);
 
         $allPersons = [$this->sue, $this->sarah, $this->mike, $this->greg];
@@ -121,11 +132,13 @@ public function should_return_furthest_two_for_four_people()
     /** @test */
     public function should_return_closest_two_for_four_people()
     {
-        $sequentialPersonsPairer = new SequentialPersonsPairer();
+        $youngerFirstPersonsPairFactory = new YoungerFirstPersonsPairFactory();
+        $sequentialPersonsPairer        =
+            new SequentialPersonsPairer($youngerFirstPersonsPairFactory);
         $finder                  = new Finder($sequentialPersonsPairer);
 
         $allPersons = [$this->sue, $this->sarah, $this->mike, $this->greg];
-        
+
         $closestBirthDatePersonsPairsCriteria = new ClosestBirthDateCriteria();
 
         $personsPairFound =

From 178f30d31a6491149e9f619cf336900bacba2631 Mon Sep 17 00:00:00 2001
From: Javier Ferrer <javier.mailserio@gmail.com>
Date: Mon, 15 Aug 2016 17:37:17 +0200
Subject: [PATCH 10/10] Rename `PersonsPairer::pair` method to
 `PersonsPairer::__invoke` for consistency. We don't need the method name
 semantics. We're doing little pieces so the semantics could be in the
 interface or class name by its own

---
 src/Algorithm/Finder.php                                   | 2 +-
 src/Domain/Service/PersonsPair/PersonsPairer.php           | 2 +-
 src/Domain/Service/PersonsPair/SequentialPersonsPairer.php | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/Algorithm/Finder.php b/src/Algorithm/Finder.php
index 1bc71c5..ac79175 100644
--- a/src/Algorithm/Finder.php
+++ b/src/Algorithm/Finder.php
@@ -29,7 +29,7 @@ public function find(
         PersonsPairCriteria $finderCriteria
     ): PersonsPair
     {
-        $allPersonsPairs = $this->personsPairer->pair($allPersons);
+        $allPersonsPairs = $this->personsPairer->__invoke($allPersons);
 
         $this->validateThereAreEnoughPersonsPairs($allPersonsPairs);
 
diff --git a/src/Domain/Service/PersonsPair/PersonsPairer.php b/src/Domain/Service/PersonsPair/PersonsPairer.php
index 052012e..5318a7a 100644
--- a/src/Domain/Service/PersonsPair/PersonsPairer.php
+++ b/src/Domain/Service/PersonsPair/PersonsPairer.php
@@ -14,5 +14,5 @@ interface PersonsPairer
      *
      * @return PersonsPair[]
      */
-    public function pair(array $allPersons): array;
+    public function __invoke(array $allPersons): array;
 }
diff --git a/src/Domain/Service/PersonsPair/SequentialPersonsPairer.php b/src/Domain/Service/PersonsPair/SequentialPersonsPairer.php
index d5deef5..c55249c 100644
--- a/src/Domain/Service/PersonsPair/SequentialPersonsPairer.php
+++ b/src/Domain/Service/PersonsPair/SequentialPersonsPairer.php
@@ -12,7 +12,7 @@ public function __construct(PersonsPairFactory $aPersonsPairFactory)
         $this->personsPairFactory = $aPersonsPairFactory;
     }
 
-    public function pair(array $allPersons): array
+    public function __invoke(array $allPersons): array
     {
         $allPersonsPairs = [];