3 datetime type (#12)

* Add datetime type

* Update type list in readme

Author: Christian Blank

README.md

@@ -69,6 +69,7 @@ Currently the following types are supported:
  * String
  * Object
  * List
+ * Datetime
 
 There are some open issues with ideas for more types. Feel free to send pull requests.
 

spec/Type/DatetimeTypeSpec.php

@@ -0,0 +1,35 @@
+<?php
+
+namespace spec\StructureCheck\Type;
+
+use StructureCheck\Type\DatetimeType;
+use PhpSpec\ObjectBehavior;
+use Prophecy\Argument;
+
+class DatetimeTypeSpec extends ObjectBehavior
+{
+    function it_is_initializable()
+    {
+        $this->beConstructedWith('d-m-Y h:m:s', 'UTC');
+        $this->shouldHaveType(DatetimeType::class);
+    }
+
+    function it_should_return_valid_for_correct_values()
+    {
+        $this->beConstructedWith('d-m-Y h:m:s', 'Europe/Berlin');
+
+        $this->check('12-12-2012 12:12:10')->isValid()->shouldBe(true);
+    }
+
+    function it_should_return_invalid_for_others()
+    {
+        $this->beConstructedWith('d-m-Y h:m:s', 'Europe/Berlin');
+
+        $this->check(null)->isValid()->shouldBe(false);
+        $this->check('foo')->isValid()->shouldBe(false);
+        $this->check([])->isValid()->shouldBe(false);
+        $this->check(1.234)->isValid()->shouldBe(false);
+        $this->check(true)->isValid()->shouldBe(false);
+        $this->check(false)->isValid()->shouldBe(false);
+    }
+}

src/Type/DatetimeType.php

@@ -0,0 +1,69 @@
+<?php
+
+namespace StructureCheck\Type;
+
+use DateTime;
+use DateTimeZone;
+use StructureCheck\Result;
+use StructureCheck\ResultInterface;
+
+/**
+ * Class DatetimeType
+ * @package StructureCheck\Type
+ */
+class DatetimeType
+{
+    /**
+     * @var string
+     */
+    private static $errorMessage = 'The value %s is not a valid datetime.';
+
+    /**
+     * @var string
+     */
+    private $datetimeFormat;
+
+    /**
+     * @var string
+     */
+    private $datetimeZone;
+
+    /**
+     * DatetimeType constructor.
+     *
+     * @param string $format
+     * @param string $datetimeZone
+     */
+    public function __construct($format, $datetimeZone)
+    {
+        $this->datetimeFormat = $format;
+        $this->datetimeZone = $datetimeZone;
+    }
+
+    /**
+     * @param mixed $value
+     *
+     * @return ResultInterface
+     */
+    public function check($value)
+    {
+        $checkResult = is_string($value) && $this->isValidDatetime($value);
+
+        return new Result(
+            $checkResult,
+            !$checkResult ? [sprintf(self::$errorMessage, json_encode($value))] : []
+        );
+    }
+
+    /**
+     * @param string $value
+     *
+     * @return bool
+     */
+    private function isValidDatetime($value) {
+        $date = DateTime::createFromFormat($this->datetimeFormat, $value, new DateTimeZone($this->datetimeZone));
+        $errors = DateTime::getLastErrors()["warning_count"];
+
+        return $date && $errors["warning_count"] == 0 && $errors["error_count"] == 0;
+    }
+}