Adding roman converters

README.md

@@ -57,6 +57,19 @@ echo Number::ordinal(1002); // "nd"
 echo Number::ordinal(-111); // "th"
 ```
 
+**Roman numbers**
+```php
+use PHPHumanizer\Number;
+
+echo Number::toRoman(1); // "I"
+echo Number::toRoman(5); // "V"
+echo Number::toRoman(1300); // "MCCC"
+
+echo Number::fromRoman("MMMCMXCIX"); // 3999
+echo Number::fromRoman("V"); // 5
+echo Number::fromRoman("CXXV"); // 125
+```
+
 **Binary Suffix**
 
 ```php

spec/PHPHumanizer/NumberSpec.php

@@ -75,4 +75,38 @@ function it_throw_exception_when_converting_to_string_with_metric_suffix_non_num
         $this->shouldThrow(new \InvalidArgumentException("Metric suffix converter accept only numeric values."))
             ->during('metricSuffix', array('as12'));
     }
+
+    function it_converts_numbers_to_roman()
+    {
+        $this->toRoman(1)->shouldReturn("I");
+        $this->toRoman(5)->shouldReturn("V");
+        $this->toRoman(9)->shouldReturn("IX");
+        $this->toRoman(10)->shouldReturn("X");
+        $this->toRoman(125)->shouldReturn("CXXV");
+        $this->toRoman(1300)->shouldReturn("MCCC");
+        $this->toRoman(3999)->shouldReturn("MMMCMXCIX");
+    }
+
+    function it_throws_exception_when_converting_number_is_out_of_range()
+    {
+        $this->shouldThrow(new \InvalidArgumentException())->during('toRoman', array(-1));
+        $this->shouldThrow(new \InvalidArgumentException())->during('toRoman', array(4000));
+    }
+
+    function it_converts_roman_numbers_to_arabic()
+    {
+        $this->fromRoman("I")->shouldReturn(1);
+        $this->fromRoman("V")->shouldReturn(5);
+        $this->fromRoman("IX")->shouldReturn(9);
+        $this->fromRoman("CXXV")->shouldReturn(125);
+        $this->fromRoman("MCCC")->shouldReturn(1300);
+        $this->fromRoman("MMMCMXCIX")->shouldReturn(3999);
+    }
+
+    function it_throws_exception_when_converting_roman_number_is_invalid()
+    {
+        $this->shouldThrow(new \InvalidArgumentException())->during('fromRoman', array(1234));
+        $this->shouldThrow(new \InvalidArgumentException())->during('fromRoman', array(""));
+        $this->shouldThrow(new \InvalidArgumentException())->during('fromRoman', array("foobar"));
+    }
 }

src/PHPHumanizer/Number.php

@@ -3,6 +3,7 @@
 namespace PHPHumanizer;
 
 use PHPHumanizer\Number\Ordinal;
+use PHPHumanizer\Number\RomanNumeral;
 use PHPHumanizer\String\BinarySuffix;
 use PHPHumanizer\String\MetricSuffix;
 
@@ -29,4 +30,16 @@ public static function metricSuffix($number, $locale = 'en')
         $binarySuffix = new MetricSuffix($number, $locale);
         return $binarySuffix->convert();
     }
+
+    public static function toRoman($number)
+    {
+        $romanNumeral = new RomanNumeral();
+        return $romanNumeral->toRoman($number);
+    }
+
+    public function fromRoman($number)
+    {
+        $romanNumeral = new RomanNumeral();
+        return $romanNumeral->fromRoman($number);
+    }
 }

src/PHPHumanizer/Number/RomanNumeral.php

@@ -0,0 +1,90 @@
+<?php
+
+namespace PHPHumanizer\Number;
+
+class RomanNumeral
+{
+    const MIN_VALUE = 1;
+    const MAX_VALUE = 3999;
+    const ROMAN_STRING_MATCHER = "/^M{0,4}(CM|CD|D?C{0,3})(XC|XL|L?X{0,3})(IX|IV|V?I{0,3})$/";
+
+    private $map = array(
+        'M'  => 1000,
+        'CM' => 900,
+        'D'  => 500,
+        'CD' => 400,
+        'C'  => 100,
+        'XC' => 90,
+        'L'  => 50,
+        'XL' => 40,
+        'X'  => 10,
+        'IX' => 9,
+        'V'  => 5,
+        'IV' => 4,
+        'I'  => 1
+    );
+
+
+    /**
+     * @param $number
+     * @return string
+     * @throws \InvalidArgumentException
+     */
+    public function toRoman($number)
+    {
+        if (($number < self::MIN_VALUE) || ($number > self::MAX_VALUE)) {
+            throw new \InvalidArgumentException();
+        }
+
+        $romanString = '';
+
+        while($number > 0)
+        {
+            foreach($this->map as $key => $value)
+            {
+                if($number >= $value)
+                {
+                    $romanString .= $key;
+                    $number -= $value;
+                    break;
+                }
+            }
+        }
+
+        return $romanString;
+    }
+
+    /**
+     * @param $string
+     * @return int
+     * @throws \InvalidArgumentException
+     */
+    public function fromRoman($string)
+    {
+        if (strlen($string) === 0 || 0 === preg_match(self::ROMAN_STRING_MATCHER, $string)) {
+            throw new \InvalidArgumentException();
+        }
+
+        $total = 0;
+        $i     = strlen($string);
+
+        while ($i > 0)
+        {
+            $digit = $this->map[$string{--$i}];
+
+            if ($i > 0) {
+                $previousDigit = $this->map[$string{$i - 1}];
+
+                if ($previousDigit < $digit) {
+                    $digit -= $previousDigit;
+                    $i--;
+                }
+            }
+
+            $total += $digit;
+        }
+
+        return $total;
+    }
+
+}