Implemented short code generation based on a provided long URL

composer.json

@@ -18,7 +18,8 @@
         "zendframework/zend-expressive-aurarouter": "^1.0",
         "zendframework/zend-servicemanager": "^3.0",
         "zendframework/zend-expressive-twigrenderer": "^1.0",
-        "doctrine/orm": "^2.5"
+        "doctrine/orm": "^2.5",
+        "guzzlehttp/guzzle": "^6.2"
     },
     "require-dev": {
         "phpunit/phpunit": "^4.8",

src/Entity/ShortUrl.php

@@ -41,7 +41,9 @@ class ShortUrl extends AbstractEntity
      */
     public function __construct()
     {
+        $this->dateCreated = new \DateTime();
         $this->visits = new ArrayCollection();
+        $this->shortCode = '';
     }
 
     /**
@@ -58,7 +60,7 @@ class ShortUrl extends AbstractEntity
      */
     public function setOriginalUrl($originalUrl)
     {
-        $this->originalUrl = $originalUrl;
+        $this->originalUrl = (string) $originalUrl;
         return $this;
     }
 

src/Exception/ExceptionInterface.php

@@ -0,0 +1,6 @@
+<?php
+namespace Acelaya\UrlShortener\Exception;
+
+interface ExceptionInterface
+{
+}

src/Exception/InvalidUrlException.php

@@ -0,0 +1,11 @@
+<?php
+namespace Acelaya\UrlShortener\Exception;
+
+class InvalidUrlException extends RuntimeException
+{
+    public static function fromUrl($url, \Exception $previous = null)
+    {
+        $code = isset($previous) ? $previous->getCode() : -1;
+        return new static(sprintf('Provided URL "%s" is not an exisitng and valid URL', $url), $code, $previous);
+    }
+}

src/Exception/RuntimeException.php

@@ -0,0 +1,6 @@
+<?php
+namespace Acelaya\UrlShortener\Exception;
+
+class RuntimeException extends \RuntimeException implements ExceptionInterface
+{
+}

src/Service/UrlShortener.php

@@ -0,0 +1,131 @@
+<?php
+namespace Acelaya\UrlShortener\Service;
+
+use Acelaya\UrlShortener\Entity\ShortUrl;
+use Acelaya\UrlShortener\Exception\InvalidUrlException;
+use Acelaya\UrlShortener\Exception\RuntimeException;
+use Doctrine\ORM\EntityManagerInterface;
+use Doctrine\ORM\ORMException;
+use GuzzleHttp\ClientInterface;
+use GuzzleHttp\Exception\GuzzleException;
+use Psr\Http\Message\UriInterface;
+
+class UrlShortener implements UrlShortenerInterface
+{
+    const DEFAULT_CHARS = '123456789bcdfghjkmnpqrstvwxyzBCDFGHJKLMNPQRSTVWXYZ';
+
+    /**
+     * @var ClientInterface
+     */
+    private $httpClient;
+    /**
+     * @var EntityManagerInterface
+     */
+    private $em;
+    /**
+     * @var string
+     */
+    private $chars;
+
+    public function __construct(
+        ClientInterface $httpClient,
+        EntityManagerInterface $em,
+        $chars = self::DEFAULT_CHARS
+    ) {
+        $this->httpClient = $httpClient;
+        $this->em = $em;
+        $this->chars = $chars;
+    }
+
+    /**
+     * @param UriInterface $url
+     * @return string
+     * @throws InvalidUrlException
+     * @throws RuntimeException
+     */
+    public function urlToShortCode(UriInterface $url)
+    {
+        // If the url already exists in the database, just return its short code
+        $shortUrl = $this->em->getRepository(ShortUrl::class)->findOneBy([
+            'originalUrl' => $url
+        ]);
+        if (isset($shortUrl)) {
+            return $shortUrl->getShortCode();
+        }
+
+        // Check that the URL exists
+        $this->checkUrlExists($url);
+
+        // Transactionally insert the short url, then generate the short code and finally update the short code
+        try {
+            $this->em->beginTransaction();
+
+            // First, create the short URL with an empty short code
+            $shortUrl = new ShortUrl();
+            $shortUrl->setOriginalUrl($url);
+            $this->em->persist($shortUrl);
+            $this->em->flush();
+
+            // Generate the short code and persist it
+            $shortCode = $this->convertAutoincrementIdToShortCode($shortUrl->getId());
+            $shortUrl->setShortCode($shortCode);
+            $this->em->flush();
+
+            $this->em->commit();
+            return $shortCode;
+        } catch (ORMException $e) {
+            if ($this->em->getConnection()->isTransactionActive()) {
+                $this->em->rollback();
+                $this->em->close();
+            }
+
+            throw new RuntimeException('An error occured while persisting the short URL', -1, $e);
+        }
+    }
+
+    /**
+     * Tries to perform a GET request to provided url, returning true on success and false on failure
+     *
+     * @param UriInterface $url
+     * @return bool
+     */
+    protected function checkUrlExists(UriInterface $url)
+    {
+        try {
+            $this->httpClient->request('GET', $url);
+        } catch (GuzzleException $e) {
+            throw InvalidUrlException::fromUrl($url, $e);
+        }
+    }
+
+    /**
+     * Generates the unique shortcode for an autoincrement ID
+     *
+     * @param int $id
+     * @return string
+     */
+    protected function convertAutoincrementIdToShortCode($id)
+    {
+        $id = intval($id);
+        $length = strlen($this->chars);
+        $code = '';
+
+        while ($id > $length - 1) {
+            // Determine the value of the next higher character in the short code and prepend it
+            $code = $this->chars[fmod($id, $length)] . $code;
+            $id = floor($id / $length);
+        }
+
+        return $this->chars[$id] . $code;
+    }
+
+    /**
+     * @param string $shortCode
+     * @return string
+     */
+    public function shortCodeToUrl($shortCode)
+    {
+        // Validate short code format
+        
+    }
+}

src/Service/UrlShortenerInterface.php

@@ -0,0 +1,23 @@
+<?php
+namespace Acelaya\UrlShortener\Service;
+
+use Acelaya\UrlShortener\Exception\InvalidUrlException;
+use Acelaya\UrlShortener\Exception\RuntimeException;
+use Psr\Http\Message\UriInterface;
+
+interface UrlShortenerInterface
+{
+    /**
+     * @param UriInterface $url
+     * @return string
+     * @throws InvalidUrlException
+     * @throws RuntimeException
+     */
+    public function urlToShortCode(UriInterface $url);
+
+    /**
+     * @param string $shortCode
+     * @return string
+     */
+    public function shortCodeToUrl($shortCode);
+}