Add PDO repository (#2)

* Add PDO repository

* Make file storage path configurable

* Name username query property required

* Add special exception class

src/CounterPdoRepository.php

@@ -0,0 +1,51 @@
+<?php
+
+/*
+ * This file is part of GitHub Profile Views Counter.
+ *
+ * (c) Anton Komarev <anton@komarev.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace Komarev\GitHubProfileViewsCounter;
+
+use Contracts\Komarev\GitHubProfileViewsCounter\CounterRepositoryInterface;
+use PDO;
+
+final class CounterPdoRepository implements CounterRepositoryInterface
+{
+    private PDO $connection;
+
+    public function __construct(PDO $connection)
+    {
+        $this->connection = $connection;
+    }
+
+    public function getCountByUsername(string $username): int
+    {
+        $statement = $this->connection->prepare(
+            'SELECT COUNT(*)
+               FROM page_views
+              WHERE username = :username;'
+        );
+        $statement->bindParam('username', $username);
+        $statement->execute();
+
+        return (int) $statement->fetchColumn(0);
+    }
+
+    public function incrementCountByUsername(string $username): void
+    {
+        $statement = $this->connection->prepare(
+            'INSERT INTO page_views
+                         (username, created_at)
+                  VALUES (:username, NOW());'
+        );
+        $statement->bindParam('username', $username);
+        $statement->execute();
+    }
+}