commit adc1c38d54aed9ad3531183c712a2a20e82f5c4b
Author: Mal <=>
Date:   Mon Aug 17 23:46:58 2020 +0200

    Init

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..617d403
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+data/classes/Setting.php
+data/cache
+data/tmp
+data/qr
+.idea
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..99d1947
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,6 @@
+build:
+	php data/scripts/generate.php
+
+clean:
+	rm -rf data/cache/* data/tmp/*
+
diff --git a/api/v1/index.php b/api/v1/index.php
new file mode 100644
index 0000000..730624f
--- /dev/null
+++ b/api/v1/index.php
@@ -0,0 +1,15 @@
+<?php
+
+require '../../data/classes/core/Autoloader.php';
+
+$autoloader = new Autoloader('../../data/cache/');
+
+$session = new Session();
+
+$router = new Router($_SERVER['REQUEST_URI'], $_SERVER['REQUEST_METHOD']);
+
+if (isset($_SERVER['HTTP_CONTENT_TYPE'])) {
+    $router->setRequestBody($_SERVER['HTTP_CONTENT_TYPE'], file_get_contents('php://input'));
+}
+
+$router->route();
diff --git a/data/classes/api/ApiBadRequestResponse.php b/data/classes/api/ApiBadRequestResponse.php
new file mode 100644
index 0000000..5dd4c05
--- /dev/null
+++ b/data/classes/api/ApiBadRequestResponse.php
@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+class ApiBadRequestResponse extends ApiResponse
+{
+    public function __construct()
+    {
+        parent::__construct();
+        $this->setParameter('success', false);
+        $this->setStatus(self::STATUS_BAD_REQUEST);
+    }
+}
\ No newline at end of file
diff --git a/data/classes/api/ApiJsonResponse.php b/data/classes/api/ApiJsonResponse.php
new file mode 100644
index 0000000..9965eb6
--- /dev/null
+++ b/data/classes/api/ApiJsonResponse.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+final class ApiJsonResponse extends ApiResponse
+{
+    protected string $mimeType = MimeType::JSON;
+
+    public function __construct(int $status = ServerStatus::OK)
+    {
+        parent::__construct($status);
+
+        $this->setParameter('success', true);
+    }
+
+    public function setResult(JsonSerializable $result): void
+    {
+        $this->setParameter('result', $result->jsonSerialize());
+    }
+
+    public function respond(): void
+    {
+        parent::respond();
+
+        echo json_encode($this->parameters);
+    }
+}
\ No newline at end of file
diff --git a/data/classes/api/ApiResponse.php b/data/classes/api/ApiResponse.php
new file mode 100644
index 0000000..827c85b
--- /dev/null
+++ b/data/classes/api/ApiResponse.php
@@ -0,0 +1,77 @@
+<?php
+
+declare(strict_types=1);
+
+class ApiResponse implements JsonSerializable
+{
+    public const STATUS_OK = 200;
+    public const STATUS_FORBIDDEN = 403;
+    public const STATUS_UNAUTHORIZED = 401;
+    public const STATUS_BAD_REQUEST = 400;
+    public const STATUS_NOT_FOUND = 404;
+    public const STATUS_SERVER_ERROR = 500;
+
+    public const MIME_TYPE_PLAINTEXT = 'text/plain';
+    public const MIME_TYPE_JSON = 'application/json';
+    public const MIME_TYPE_SVG = 'image/svg+xml';
+
+    protected int $status = ServerStatus::OK;
+    protected string $mimeType = MimeType::PLAINTEXT;
+    protected array $parameters = [];
+
+    public function __construct(int $status = ServerStatus::OK)
+    {
+        $this->setStatus($status);
+    }
+
+    public function setParameter(string $key, $value): void
+    {
+        $this->parameters[$key] = $value;
+    }
+
+    public function setStatus(int $status): void
+    {
+        $this->status = $status;
+    }
+
+    public function setMessage(string $message): void
+    {
+        $this->setParameter('message', $message);
+    }
+
+    public function setMimeType(string $mimeType): void
+    {
+        $this->mimeType = $mimeType;
+    }
+
+    public function setBody(JsonSerializable $data): void
+    {
+        $this->parameters = $data->jsonSerialize();
+    }
+
+    public function SetMessageIdNotFound(string $instanceName): void
+	{
+		$this->setMessage(sprintf('Die für %s angeforderte ID existiert nicht!', $instanceName));
+	}
+
+    public function getStatus(): int
+    {
+        return $this->status;
+    }
+
+    public function getMimeType(): string
+    {
+        return $this->mimeType;
+    }
+
+    public function jsonSerialize()
+    {
+        return $this->parameters;
+    }
+
+    public function respond(): void
+    {
+        http_response_code($this->status);
+        header('Content-Type: ' . $this->mimeType);
+    }
+}
diff --git a/data/classes/api/ApiSuccessResponse.php b/data/classes/api/ApiSuccessResponse.php
new file mode 100644
index 0000000..7d766b3
--- /dev/null
+++ b/data/classes/api/ApiSuccessResponse.php
@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+class ApiSuccessResponse extends ApiResponse
+{
+    public function __construct(bool $success = true)
+    {
+        parent::__construct();
+        $this->setParameter('success', $success);
+    }
+}
diff --git a/data/classes/api/ApiSvgResponse.php b/data/classes/api/ApiSvgResponse.php
new file mode 100644
index 0000000..c306c96
--- /dev/null
+++ b/data/classes/api/ApiSvgResponse.php
@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+final class ApiSvgResponse extends ApiResponse
+{
+    private string $content;
+    protected string $mimeType = MimeType::SVG;
+
+    public function __construct(int $status = ServerStatus::OK)
+    {
+        parent::__construct($status);
+    }
+
+    public function setContent(string $content): void
+    {
+        $this->content = $content;
+    }
+
+    public function respond(): void
+    {
+        parent::respond();
+        header('Content-Length: ' . strlen($this->content));
+        echo $this->content;
+    }
+}
diff --git a/data/classes/api/ApiUnauthorizedResponse.php b/data/classes/api/ApiUnauthorizedResponse.php
new file mode 100644
index 0000000..b3d1fef
--- /dev/null
+++ b/data/classes/api/ApiUnauthorizedResponse.php
@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+class ApiUnauthorizedResponse extends ApiResponse
+{
+    public function __construct()
+    {
+        parent::__construct();
+        $this->setStatus(self::STATUS_UNAUTHORIZED);
+    }
+}
diff --git a/data/classes/controller/FingerprintGetController.php b/data/classes/controller/FingerprintGetController.php
new file mode 100644
index 0000000..8233261
--- /dev/null
+++ b/data/classes/controller/FingerprintGetController.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+final class FingerprintGetController extends AbstractController
+{
+    protected string $route = '/api/v1/fingerprint/{fingerprintId}';
+
+    private int $fingerprintId;
+
+    public function __construct(string $url)
+    {
+        parent::__construct($url);
+
+        $this->fingerprintId = (int)$this->getUrlParamInt('fingerprintId');
+    }
+
+    public function handle(): void
+    {
+        try {
+            $fingerprint = new Fingerprint($this->fingerprintId);
+
+            $this->response = new ApiJsonResponse();
+            $this->response->setResult($fingerprint->jsonSerialize());
+        } catch (Throwable $e) {
+            $this->response = new ApiJsonResponse(ApiResponse::STATUS_NOT_FOUND);
+            $this->response->setParameter('success', false);
+            $this->response->setMessage(sprintf('No fingerprint with id %d found!', $this->fingerprintId));
+            $this->response->setMimeType(ApiResponse::MIME_TYPE_JSON);
+        }
+    }
+}
\ No newline at end of file
diff --git a/data/classes/controller/FingerprintPostController.php b/data/classes/controller/FingerprintPostController.php
new file mode 100644
index 0000000..77dbc00
--- /dev/null
+++ b/data/classes/controller/FingerprintPostController.php
@@ -0,0 +1,63 @@
+<?php
+
+declare(strict_types=1);
+
+final class FingerprintPostController extends AbstractController
+{
+    protected string $route = '/api/v1/fingerprint';
+    protected array $mandatoryAttributes = [
+        'fingerprint',
+        'userId',
+    ];
+
+    public function __construct(string $url)
+    {
+        parent::__construct($url);
+
+        $this->response = new ApiJsonResponse();
+    }
+
+    public function handle(): void
+    {
+        parent::handle();
+
+        $json = json_decode($this->requestBody);
+        $fingerprint = new Fingerprint();
+
+        try {
+            $fingerprint->setFingerprint($json->fingerprint);
+            $fingerprint->setUserId($json->userId);
+            $fingerprint->Save();
+
+            $qrCode = new QrCode($fingerprint->getFingerprintId(), $fingerprint->getFingerprint());
+            $qrCode->generate();
+            $qrCode->save();
+
+            $this->response->setParameter('fingerprintId', $fingerprint->getFingerprintId());
+        } catch (QrCodeException $e) {
+            $fingerprint->Delete();
+
+            $this->response->setParameter('success', false);
+            $this->response->setStatus(ServerStatus::INTERNAL_ERROR);
+            $this->response->setMessage('An error occured during qr code creation!');
+        } catch (Throwable $e) {
+            $this->catchDatabaseException($e->getMessage(), $json);
+        }
+    }
+
+    private function catchDatabaseException(string $message, object $json): void
+    {
+        $this->response->setParameter('success', false);
+
+        if (substr_count($message, 'foreign key constraint fails') > 0) {
+            $this->response->setMessage(sprintf('User with id %d doesn\'t exist!', $json->userId));
+            $this->response->setStatus(ServerStatus::NOT_FOUND);
+        } elseif (substr_count($message, 'Duplicate entry') > 0) {
+            $this->response->setMessage(sprintf('Fingerprint %s already exists!', $json->fingerprint));
+            $this->response->setStatus(ServerStatus::BAD_REQUEST);
+        } else {
+            $this->response->setMessage($message);
+            $this->response->setStatus(ServerStatus::INTERNAL_ERROR);
+        }
+    }
+}
\ No newline at end of file
diff --git a/data/classes/controller/QrCodeGetController.php b/data/classes/controller/QrCodeGetController.php
new file mode 100644
index 0000000..5a05289
--- /dev/null
+++ b/data/classes/controller/QrCodeGetController.php
@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+final class QrCodeGetController extends AbstractController
+{
+    protected string $route = '/api/v1/fingerprint/{fingerprintId}/qr';
+
+    private int $fingerprintId;
+
+    public function __construct(string $url)
+    {
+        parent::__construct($url);
+
+        $this->fingerprintId = (int)$this->getUrlParamInt('fingerprintId');
+    }
+
+    public function handle(): void
+    {
+        $filename = Setting::PATH_QR_CODES . (string)$this->fingerprintId . '.svg';
+
+        if (!is_file($filename)) {
+            $this->response = new ApiJsonResponse();
+            $this->response->setParameter('success', false);
+            $this->response->setMessage('No QR code for fingerprint id %d found!');
+            $this->response->setMimeType(ApiResponse::MIME_TYPE_JSON);
+        }
+
+        $this->response = new ApiSvgResponse();
+
+        $file = fopen($filename, 'r');
+        $this->response->setContent(fread($file, filesize($filename)));
+        fclose($file);
+    }
+}
\ No newline at end of file
diff --git a/data/classes/controller/UserGetController.php b/data/classes/controller/UserGetController.php
new file mode 100644
index 0000000..2ecf056
--- /dev/null
+++ b/data/classes/controller/UserGetController.php
@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+final class UserGetController extends AbstractController
+{
+    protected string $route = '/api/v1/user/{userId}';
+
+    private int $userId;
+
+    public function __construct(string $url)
+    {
+        parent::__construct($url);
+
+        $this->userId = (int)$this->getUrlParamInt('userId');
+    }
+
+    public function handle(): void
+    {
+        $user = new User($this->userId);
+
+        $this->response = new ApiJsonResponse();
+        $this->response->setResult($user);
+    }
+}
\ No newline at end of file
diff --git a/data/classes/controller/UserLoginPutController.php b/data/classes/controller/UserLoginPutController.php
new file mode 100644
index 0000000..ae30bb5
--- /dev/null
+++ b/data/classes/controller/UserLoginPutController.php
@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types=1);
+
+final class UserLoginPutController extends AbstractController
+{
+    protected string $route = '/api/v1/user/login';
+    protected array $mandatoryAttributes = [
+        'username',
+        'password',
+    ];
+
+    public function handle(): void
+    {
+        parent::handle();
+
+        if ($this->response->getStatus() !== ServerStatus::OK) {
+            return;
+        }
+
+        $json = json_decode($this->requestBody);
+
+        $session = new Session();
+
+        if ($session->IsLoggedIn()) {
+            $this->response = new ApiJsonResponse(ServerStatus::BAD_REQUEST);
+            $this->response->setParameter('success', false);
+            $this->response->setMessage('You are already logged in!');
+
+            return;
+        }
+
+        if (!$session->Login($json->username, $json->password)) {
+            $this->response = new ApiJsonResponse(ServerStatus::UNAUTHORIZED);
+            $this->response->setParameter('success', false);
+            $this->response->setMessage('Login failed!');
+
+            return;
+        }
+
+        $this->response = new ApiJsonResponse();
+    }
+}
\ No newline at end of file
diff --git a/data/classes/controller/UserLogoutPutController.php b/data/classes/controller/UserLogoutPutController.php
new file mode 100644
index 0000000..b7636c3
--- /dev/null
+++ b/data/classes/controller/UserLogoutPutController.php
@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+final class UserLogoutPutController extends AbstractController
+{
+    protected string $route = '/api/v1/user/logout';
+
+    public function handle(): void
+    {
+        parent::handle();
+
+        $session = new Session();
+
+        if (!$session->IsLoggedIn()) {
+            $this->response = new ApiJsonResponse(ServerStatus::BAD_REQUEST);
+            $this->response->setParameter('success', false);
+            $this->response->setMessage('You were not logged in!');
+
+            return;
+        }
+
+        $session->Destroy();
+
+        $this->response = new ApiJsonResponse();
+        $this->response->setParameter('success', true);
+    }
+}
\ No newline at end of file
diff --git a/data/classes/core/AbstractController.php b/data/classes/core/AbstractController.php
new file mode 100644
index 0000000..ea1acef
--- /dev/null
+++ b/data/classes/core/AbstractController.php
@@ -0,0 +1,83 @@
+<?php
+
+declare(strict_types=1);
+
+abstract class AbstractController
+{
+    protected string $route;
+    protected ApiResponse $response;
+
+    protected string $requestUrl;
+    protected ?string $requestBody = null;
+    protected ?string $contentType = null;
+    protected array $mandatoryAttributes = [];
+
+    public function __construct(string $url)
+    {
+        $this->requestUrl = $url;
+        $this->response = new ApiResponse();
+    }
+
+    public function setRequestBody(string $contentType, string $content): void
+    {
+        $this->requestBody = $content;
+        $this->contentType = $contentType;
+    }
+
+    public function getResponse(): ApiResponse
+    {
+        return $this->response;
+    }
+
+    public function handle(): void
+    {
+        if (!$this->validateJsonBody()) {
+            $this->response = new ApiJsonResponse(ServerStatus::BAD_REQUEST);
+            $this->response->setParameter('success', false);
+            $this->response->setMessage('The request body has not the required json attributes!');
+        }
+    }
+
+    protected function getUrlParam(string $name): ?string
+    {
+        foreach (explode('/', $this->route) as $index => $fragment) {
+            if ($fragment === '{' . $name . '}') {
+                return explode('/', $this->requestUrl)[$index];
+            }
+        }
+
+        return null;
+    }
+
+    protected function getUrlParamInt(string $name): ?int
+    {
+        $param = $this->getUrlParam($name);
+
+        return $param !== null ? (int)$param : null;
+    }
+
+    protected function validateJsonBody(): bool
+    {
+        if (count($this->mandatoryAttributes) === 0) {
+            return true;
+        }
+
+        if ($this->contentType === MimeType::JSON && $this->requestBody === null) {
+            return false;
+        }
+
+        try {
+            $json = json_decode($this->requestBody);
+
+            foreach ($this->mandatoryAttributes as $attribute) {
+                if (!isset($json->{$attribute})) {
+                    return false;
+                }
+            }
+
+            return true;
+        } catch (Throwable $e) {
+            return false;
+        }
+    }
+}
diff --git a/data/classes/core/Autoloader.php b/data/classes/core/Autoloader.php
new file mode 100644
index 0000000..6fa7e6f
--- /dev/null
+++ b/data/classes/core/Autoloader.php
@@ -0,0 +1,245 @@
+<?php
+
+declare(strict_types=1);
+
+class Autoloader
+{
+    private const PATH_CLASSES = 'data/classes';
+    private const PATH_CONTROLLERS = self::PATH_CLASSES . '/controller';
+    private const PATH_CACHE = 'data/cache/';
+
+    public function __construct(string $cachePath = self::PATH_CACHE)
+    {
+    	if ($cachePath !== self::PATH_CACHE) {
+    		$cachePath = substr($cachePath, -1) === '/' ? $cachePath : $cachePath . '/';
+		}
+
+        $routesFound = @include($cachePath . 'routes.php');
+        $classesFound = @include($cachePath . 'classes.php');
+
+        if (!$routesFound || !$classesFound) {
+            throw new Exception(
+                sprintf(
+                    'Autoloader cache not found! Please generate it with %s::BuildCache() at first!',
+                    self::class
+                )
+            );
+        }
+
+        spl_autoload_register(
+            function (string $className) {
+                if (!$this->loadClass($className)) {
+                    throw new Exception(sprintf('Class %s couldn\'t be loaded!', $className));
+                }
+            }
+        );
+    }
+
+    public static function BuildCache(): void
+    {
+        self::BuildClassCache();
+        self::BuildRouteCache();
+    }
+
+    public static function BuildClassCache(): void
+    {
+        $classesResult = self::scanForClasses();
+
+        $cacheContent = '';
+
+        foreach ($classesResult as $className => $path) {
+            $cacheContent .= sprintf("\t\t'%s' => '%s',\n", $className, $path);
+        }
+
+        $cacheContent .= "\t]\n);";
+
+        self::buildCacheFile($cacheContent, 'classes');
+    }
+
+    private function loadClass(string $className): bool
+    {
+        if (!isset(CLASSES[$className]) || !@include(CLASSES[$className])) {
+            return false;
+        }
+
+        return true;
+    }
+
+    public static function BuildRouteCache(): void
+    {
+        $controllersResult = self::scanForControllers();
+        $controllerMethods = [
+            'GET' => [],
+            'POST' => [],
+            'PUT' => [],
+        ];
+
+        foreach ($controllersResult as $className => $path) {
+            $file = fopen($path, 'r');
+            $content = fread($file, filesize($path));
+            fclose($file);
+
+            preg_match_all('/(?<=private )\w+ \$\w+(?=;)/', $content, $matches);
+
+            $params = [];
+
+            foreach ($matches[0] as $match) {
+                $parts = explode(' ', $match);
+                $params[] = [
+                    'type' => $parts[0],
+                    'name' => $parts[1],
+                ];
+            }
+
+            preg_match('/(?<=protected string \$route = \').*(?=\';)/', $content, $matches);
+            $route = $matches[0];
+
+            preg_match('/[A-Z][a-z]+(?=Controller)/', $className, $matches);
+            $method = strtoupper($matches[0]);
+
+            $controllerMethods[$method][$route] = [
+                'name' => $className,
+                'params' => $params,
+            ];
+        }
+
+        $cacheContent = '';
+
+        foreach ($controllerMethods as $method => $controllers) {
+            $cacheContent .= self::createRoutesForMethod($method, $controllers);
+        }
+
+        $cacheContent .= "\t]\n);";
+
+        self::buildCacheFile($cacheContent, 'routes');
+    }
+
+    private static function createRoutesForMethod(string $method, array $routes): string
+    {
+        krsort($routes);
+        $stringRoutes = '';
+
+        foreach ($routes as $route => $params) {
+            $stringRoutes .= sprintf(
+                "'%s' => [
+                    'controller' => %s::class,
+                    'params' => [
+                        %s
+                    ],
+                ],
+                ",
+                $route,
+                $params['name'],
+                self::createRouteParams($params['params'])
+            );
+        }
+
+        return sprintf(
+            "
+                '%s' => [
+                    %s
+                ],
+            ",
+            $method,
+            $stringRoutes,
+        );
+    }
+
+    private static function createRouteParams(array $params): string
+    {
+        $string = '';
+
+        foreach ($params as $param) {
+            $string .= sprintf(
+                "
+                    '%s' => [
+                        'type' => '%s',
+                    ],
+                ",
+                str_replace('$', '', $param['name']),
+                $param['type']
+            );
+        }
+
+        return $string;
+    }
+
+    private static function reformatCacheFileContent(string $content): string
+    {
+        $depth = 0;
+        $reformatted = '';
+        $replace = '';
+
+        // Removing indents
+        foreach (explode("\n", $content) as $line) {
+            $trim = trim($line);
+
+            if ($trim !== '') {
+                $replace .= $trim . "\n";
+            }
+        }
+
+        for ($i = 0; $i < strlen($replace); $i++) {
+            if (in_array($replace[$i], [')', ']'])) {
+                $depth--;
+            }
+
+            if ($replace[$i - 1] === "\n") {
+                $reformatted .= str_repeat("\t", $depth);
+            }
+
+            $reformatted .= $replace[$i];
+
+            if (in_array($replace[$i], ['(', '['])) {
+                $depth++;
+            }
+        }
+
+        return $reformatted;
+    }
+
+    private static function buildCacheFile(string $content, string $cacheName): void
+    {
+        $cacheContent = sprintf(
+            "<?php\n\n/*\n * This file was auto generated on %s\n */\n\ndefine(\n\t'%s',\n\t[\n",
+            (new DateTime())->format('Y-m-d H:i:s'),
+            strtoupper($cacheName)
+        );
+
+        $cacheContent .= $content;
+
+        $file = fopen(getcwd() . '/' . self::PATH_CACHE . $cacheName . '.php', 'w');
+        fwrite($file, self::reformatCacheFileContent($cacheContent));
+        fclose($file);
+    }
+
+    private static function scanForFiles(string $folder): array
+    {
+        $folder = substr($folder, -1) === '/' ? substr($folder, 0, -1) : $folder;
+        $files = [];
+        $handler = opendir($folder);
+
+        while ($file = readdir($handler)) {
+            $path = $folder . '/' . $file;
+
+            if (is_dir($path) && $file !== '.' && $file !== '..') {
+                $files = array_merge($files, self::scanForFiles($path));
+            } elseif (is_file($path) && substr($path, -4) === '.php') {
+                $className = substr($file, 0, -4);
+                $files[$className] = $path;
+            }
+        }
+
+        return $files;
+    }
+
+    private static function scanForClasses(): array
+    {
+        return self::scanForFiles(getcwd() . '/' . self::PATH_CLASSES);
+    }
+
+    private static function scanForControllers(): array
+    {
+        return self::scanForFiles(getcwd() . '/' . self::PATH_CONTROLLERS);
+    }
+}
diff --git a/data/classes/core/DatabaseInterface.php b/data/classes/core/DatabaseInterface.php
new file mode 100644
index 0000000..795ab51
--- /dev/null
+++ b/data/classes/core/DatabaseInterface.php
@@ -0,0 +1,60 @@
+<?php
+
+interface DatabaseInterface
+{
+    public const ORDER_ASC = true;
+    public const ORDER_DESC = false;
+
+    /**
+     * Has to close the connection.
+     */
+    public function __destruct();
+
+    /**
+     * Sends an sql query to the database.
+     */
+    public function Query(string $query, array $params = []): void;
+
+    /**
+     * @return array
+     */
+    public function getResult(): array;
+
+    /**
+     * Selects data from a table.
+     */
+    public function Select(
+        string $tableName,
+        array $fields = [],
+        array $conditions = [],
+        int $limit = 0,
+        array $orderBy = [],
+        bool $asc = true,
+        int $offset = 0
+    ): array;
+
+    /**
+     * Deletes rows from a table.
+     */
+    public function Delete(string $table, array $conditions): void;
+
+    /**
+     * Inserts a new row into the table.
+     */
+    public function Insert(string $table, array $fields): ?int;
+
+    /**
+     * Edits data inside a table.
+     */
+    public function Update(string $table, array $fields, array $conditions): void;
+
+    /**
+     * Returns the number of entries found.
+     */
+    public function Count(string $table, array $conditions = []): int;
+
+    /**
+     * Returns the primary key from the last inserted row.
+     */
+    public function GetLastInsertedId(): int;
+}
\ No newline at end of file
diff --git a/data/classes/core/MimeType.php b/data/classes/core/MimeType.php
new file mode 100644
index 0000000..6c9f252
--- /dev/null
+++ b/data/classes/core/MimeType.php
@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+final class MimeType
+{
+    public const PLAINTEXT = 'text/plain';
+    public const JSON = 'application/json';
+    public const SVG = 'image/svg+xml';
+}
diff --git a/data/classes/core/MySqlDatabase.php b/data/classes/core/MySqlDatabase.php
new file mode 100644
index 0000000..5fe4533
--- /dev/null
+++ b/data/classes/core/MySqlDatabase.php
@@ -0,0 +1,262 @@
+<?php
+
+declare(strict_types=1);
+
+class MySqlDatabase implements DatabaseInterface
+{
+	private const CHARS_ALLOWED_IN_TABLE_NAMES = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890_-';
+
+	private ?PDO $connection;
+	private ?PDOStatement $cursor;
+
+	public function __construct(
+		string $hostname = Setting::MYSQL_HOST,
+		string $user = Setting::MYSQL_USER,
+		string $password = Setting::MYSQL_PASSWORD,
+		string $database = Setting::MYSQL_DATABASE
+	) {
+	    $this->connection = new PDO("mysql:host=$hostname;dbname=$database", $user, $password);
+	}
+
+	public function __destruct()
+	{
+		$this->connection = null;
+	}
+
+    /**
+     * {@inheritDoc}
+     */
+	public function Query(string $query, array $params = []): void
+	{
+		$this->cursor = $this->connection->prepare($query);
+
+		if (!$this->cursor) {
+			throw new Exception('Initialization of database cursor failed');
+		}
+
+		foreach ($params as $key => $param) {
+		    if (is_bool($param)) {
+		        $param = (int)$param;
+            }
+
+			$this->cursor->bindValue(':' . $key, $param);
+		}
+
+		if (!$this->cursor->execute()) {
+            throw new Exception($this->cursor->errorInfo()[2]);
+        }
+	}
+
+    /**
+     * {@inheritDoc}
+     */
+	public function getResult(): array
+	{
+		$result = [];
+
+		while ($fetch = $this->cursor->fetchObject()) {
+			$row = [];
+
+			foreach (get_object_vars($fetch) as $key => $value) {
+				$row[$key] = $value;
+			}
+
+			$result[] = $row;
+		}
+
+		return $result;
+	}
+
+    /**
+     * Selects data from a table.
+     */
+    public function Select(
+		string $tableName,
+		array $fields = [],
+		array $conditions = [],
+		int $limit = 0,
+		array $orderBy = [],
+		bool $asc = true,
+        int $offset = 0
+	): array {
+		if (!self::isValidTableName($tableName)) {
+			[];
+		}
+
+		if (count($fields) === 0) {
+			$fieldsExpression = '*';
+		} else {
+			$fieldsExpression = implode(',', $fields);
+		}
+
+		$conditionsExpression = '';
+		$conditionPairs = [];
+
+		foreach ($conditions as $field => $value) {
+			$conditionPairs[] = sprintf('%s = :%s ', $field, $field);
+		}
+
+		if (count($conditions) > 0) {
+			$conditionsExpression = 'WHERE ';
+			$conditionsExpression .= implode(' AND ', $conditionPairs);
+		}
+
+		$orderStatement = '';
+
+		if (count($orderBy) > 0) {
+			$orderStatement = 'ORDER BY ' . implode(',', $orderBy);
+
+			if (!$asc) {
+				$orderStatement .= ' DESC';
+			}
+		}
+
+		$limitStatement = '';
+
+		if ($limit > 0) {
+			$limitStatement = 'LIMIT ' . $limit;
+		}
+
+		$offsetStatement = '';
+
+		if ($offset > 0) {
+		    $offsetStatement = 'OFFSET ' . $offset;
+        }
+
+		$query = sprintf(
+			'SELECT %s FROM %s %s %s %s %s',
+			$fieldsExpression,
+			$tableName,
+			$conditionsExpression,
+			$orderStatement,
+			$limitStatement,
+            $offsetStatement
+		);
+
+        try {
+            $this->Query($query, $conditions);
+        } catch (Throwable $e) {
+            return [];
+        }
+
+        return $this->getResult();
+	}
+
+    /**
+     * Deletes rows from a table.
+     */
+    public function Delete(string $table, array $conditions): void
+    {
+        if (count($conditions) === 0) {
+            $conditionsStatement = '1';
+        } else {
+            $conditionPairs = [];
+
+            foreach ($conditions as $field => $value) {
+                $conditionPairs[] = sprintf('%s=:Condition%s', $field, $field);
+                $conditions['Condition' . $field] = $value;
+                unset($conditions[$field]);
+            }
+
+            $conditionsStatement = implode(' AND ', $conditionPairs);
+        }
+
+        $query = sprintf('DELETE FROM %s WHERE %s', $table, $conditionsStatement);
+
+        $this->Query($query, $conditions);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function Insert(string $table, array $fields): ?int
+    {
+        if (count($fields) === 0) {
+           throw new Exception('Row to insert is empty!');
+        }
+
+        $fieldNames = implode(',', array_keys($fields));
+        $fieldPlaceholder = [];
+
+        foreach ($fields as $name => $value) {
+            $fieldPlaceholder[] = ':' . $name;
+        }
+
+        $query = sprintf(
+            'INSERT INTO %s (%s) VALUES (%s)', $table, $fieldNames, implode(',', $fieldPlaceholder)
+        );
+
+        $this->Query($query, $fields);
+
+        $lastInsertedId = $this->GetLastInsertedId();
+
+        if ((int)$lastInsertedId === 0) {
+            return null;
+        }
+
+        return $lastInsertedId;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function Update(string $table, array $fields, array $conditions): void
+    {
+        $conditionPairs = [];
+
+        foreach ($conditions as $field => $value) {
+            $conditionPairs[] = sprintf('%s=:Condition%s', $field, $field);
+            $conditions['Condition' . $field] = $value;
+            unset($conditions[$field]);
+        }
+
+        $conditionsStatement = implode(' AND ', $conditionPairs);
+
+        $fieldPairs = [];
+
+        foreach ($fields as $field => $value) {
+            $fieldPairs[] = sprintf('%s=:%s', $field, $field);
+        }
+
+        $fieldsStatement = implode(',', $fieldPairs);
+
+        $query = sprintf('UPDATE %s SET %s WHERE %s', $table, $fieldsStatement, $conditionsStatement);
+
+
+        $this->Query($query, array_merge($fields, $conditions));
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function Count(string $table, array $conditions = []): int
+    {
+        $result = $this->Select($table, ['count(*)'], $conditions);
+
+        return (int)$result[0]['count(*)'];
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function GetLastInsertedId(): int
+    {
+        $this->Query('SELECT LAST_INSERT_ID() as ID');
+
+        return (int)$this->getResult()[0]['ID'];
+    }
+
+    /**
+     * Does a check if the given table name contains forbidden chars.
+     */
+	private static function isValidTableName(string $tableName): bool
+	{
+		foreach (str_split($tableName) as $char) {
+			if (substr_count(self::CHARS_ALLOWED_IN_TABLE_NAMES, $char) === 0) {
+				return false;
+			}
+		}
+
+		return true;
+	}
+}
diff --git a/data/classes/core/MySqlTable.php b/data/classes/core/MySqlTable.php
new file mode 100644
index 0000000..2e176af
--- /dev/null
+++ b/data/classes/core/MySqlTable.php
@@ -0,0 +1,18 @@
+<?php
+
+class MySqlTable extends Table
+{
+    public function __construct(string $tableName, $id = null, DatabaseInterface &$database = null)
+    {
+        self::EnsureConnection($database);
+
+        parent::__construct($tableName, $id, $database);
+    }
+
+    public static function EnsureConnection(?DatabaseInterface & $database): void
+    {
+        if (!($database instanceof MySqlDatabase)) {
+            $database = new MySqlDatabase();
+        }
+    }
+}
\ No newline at end of file
diff --git a/data/classes/core/Password.php b/data/classes/core/Password.php
new file mode 100644
index 0000000..755ba5a
--- /dev/null
+++ b/data/classes/core/Password.php
@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+class Password
+{
+    public static function IsValid(string $password, string $hash): bool
+    {
+        return password_verify($password, $hash);
+    }
+
+    public static function GetHash(string $password): string
+	{
+		return password_hash($password, PASSWORD_BCRYPT);
+	}
+}
\ No newline at end of file
diff --git a/data/classes/core/QrCode.php b/data/classes/core/QrCode.php
new file mode 100644
index 0000000..4e41c9e
--- /dev/null
+++ b/data/classes/core/QrCode.php
@@ -0,0 +1,67 @@
+<?php
+
+declare(strict_types=1);
+
+final class QrCode
+{
+    private int $fingerprintId;
+    private string $fingerprint;
+    private string $temporaryFilename;
+
+    public function __construct(int $fingerprintId, string $fingerprint)
+    {
+        $this->fingerprintId = $fingerprintId;
+        $this->fingerprint = $fingerprint;
+    }
+
+    public function save(): void
+    {
+        if (!is_file($this->temporaryFilename)) {
+            throw new QrCodeException(
+                sprintf('Temporary QR file %s couldn\'t be found!', $this->temporaryFilename)
+            );
+        }
+
+        $returnCode = 0;
+
+        $path = substr(Setting::PATH_QR_CODES, -1) === '/'
+            ? Setting::PATH_QR_CODES
+            : Setting::PATH_QR_CODES . '/';
+
+        $filename = $path . $this->fingerprintId . '.svg';
+
+        passthru(
+            sprintf('mv %s %s', $this->temporaryFilename, $filename),
+            $returnCode
+        );
+
+        if ($returnCode !== 0 || !is_file($filename)) {
+            throw new QrCodeException(
+                sprintf('QR code for fingerprint %d couldn\'t be created!', $this->fingerprintId)
+            );
+        }
+    }
+
+    public function generate(): bool
+    {
+        $returnCode = 0;
+
+        $path = substr(Setting::PATH_TMP, -1) === '/' ? Setting::PATH_TMP : Setting::PATH_TMP . '/';
+
+        $this->temporaryFilename = $path . $this->generateTemporaryFilename() . '.svg';
+
+        passthru(
+            sprintf('qrencode -o %s -t SVG "%s"', $this->temporaryFilename, $this->fingerprint),
+            $returnCode
+        );
+
+        return !(bool)$returnCode;
+    }
+
+    private function generateTemporaryFilename(): string
+    {
+        $hash = hash('md5', (new DateTime())->format('U') . $this->fingerprint);
+
+        return sprintf('%s.svg', $hash);
+    }
+}
\ No newline at end of file
diff --git a/data/classes/core/Router.php b/data/classes/core/Router.php
new file mode 100644
index 0000000..de16905
--- /dev/null
+++ b/data/classes/core/Router.php
@@ -0,0 +1,57 @@
+<?php
+
+declare(strict_types=1);
+
+final class Router
+{
+    private string $route;
+    private string $method;
+    private ?string $requestBody = null;
+    private ?string $contentType = null;
+
+    public function __construct(string $route, string $method)
+    {
+        $this->route = $route;
+        $this->method = $method;
+    }
+
+    public function setRequestBody(string $contentType, string $content): void
+    {
+        $this->contentType = $contentType;
+        $this->requestBody = $content;
+    }
+
+    public function route(): void
+    {
+        foreach (ROUTES[$this->method] as $route => $params) {
+            preg_match_all($this->createRegex($route, $params['params']), $this->route, $matches);
+
+            if (count($matches[0]) > 0) {
+                $class = new ReflectionClass($params['controller']);
+
+                $controller = $class->newInstance($matches[0][0]);
+
+                if ($this->requestBody !== null && $this->contentType !== null) {
+                    $controller->setRequestBody($this->contentType, $this->requestBody);
+                }
+
+                $controller->handle();
+                $controller->getResponse()->respond();
+
+                return;
+            }
+        }
+    }
+
+    private function createRegex(string $route, array $params): string
+    {
+        foreach ($params as $param => $values) {
+            switch ($values['type']) {
+                case 'int':
+                    $route = str_replace('{' . $param . '}', '[0-9]+', $route);
+            }
+        }
+
+        return '/' . str_replace('/', '\\/', $route) . '/';
+    }
+}
\ No newline at end of file
diff --git a/data/classes/core/ServerStatus.php b/data/classes/core/ServerStatus.php
new file mode 100644
index 0000000..2cff70f
--- /dev/null
+++ b/data/classes/core/ServerStatus.php
@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+class ServerStatus
+{
+    public const OK = 200;
+    public const FORBIDDEN = 403;
+    public const UNAUTHORIZED = 401;
+    public const BAD_REQUEST = 400;
+    public const NOT_FOUND = 404;
+    public const INTERNAL_ERROR = 500;
+}
diff --git a/data/classes/core/Session.php b/data/classes/core/Session.php
new file mode 100644
index 0000000..00fb91d
--- /dev/null
+++ b/data/classes/core/Session.php
@@ -0,0 +1,108 @@
+<?php
+
+declare(strict_types=1);
+
+final class Session
+{
+    public const TYPE_INT = 1;
+    public const TYPE_STRING = 2;
+    public const TYPE_BOOL = 3;
+
+    private const IS_LOGGED_IN = 'is_logged_in';
+    private const USER_ID = 'account_id';
+    private const USERNAME = 'username';
+	private const PERMISSION = 'permission';
+    private const EMAIL = 'email';
+    private const JABBER_ADDRESS = 'jabber';
+
+    public function __construct()
+    {
+        @session_start();
+
+        if (!$this->HasValue(self::IS_LOGGED_IN)) {
+            $this->SetBool(self::IS_LOGGED_IN, false);
+        }
+    }
+
+    public function Destroy(): void
+    {
+        session_unset();
+        session_destroy();
+    }
+
+    public function Login(string $usernameOrEmail, string $password): bool
+    {
+        try {
+            $user = User::getFromUsername($usernameOrEmail);
+        } catch (Throwable $e) {
+            $user = User::getFromEmail($usernameOrEmail);
+        }
+
+        if ($user === null || !Password::IsValid($password, $user->getPassword())) {
+            return false;
+        }
+
+        $this->SetBool(self::IS_LOGGED_IN, true);
+        $this->SetInt(self::USER_ID, $user->getPrimaryKey());
+		$this->SetString(self::USERNAME, $user->getUsername());
+        $this->SetString(self::EMAIL, $user->getEmail());
+        $this->SetString(self::JABBER_ADDRESS, $user->getJabberAddress());
+
+        return true;
+    }
+
+    public function HasValue(string $key): bool
+    {
+        return self::HasSession() && isset($_SESSION[$key]);
+    }
+
+    public function SetBool(string $key, bool $value): void
+    {
+        $_SESSION[$key] = $value;
+    }
+
+    public function SetString(string $key, string $value): void
+    {
+        $_SESSION[$key] = $value;
+    }
+
+    public function SetInt(string $key, int $value): void
+    {
+        $_SESSION[$key] = $value;
+    }
+
+    public function IsLoggedIn(): bool
+    {
+        return self::HasSession() && $this->GetBool(self::IS_LOGGED_IN);
+    }
+
+    public function GetInt(string $key): ?int
+    {
+        return $this->HasValue($key) ? (int)$_SESSION[$key] : null;
+    }
+
+    public function GetString(string $key): ?string
+    {
+        return $this->HasValue($key) ? (string)$_SESSION[$key] : null;
+    }
+
+    public function GetBool(string $key): ?bool
+    {
+        return $this->HasValue($key) ? (bool)$_SESSION[$key] : null;
+    }
+
+	public function GetAccountId(): ?int
+	{
+		return $this->GetInt(self::USER_ID);
+	}
+
+	public function GetPermission(): ?int
+	{
+		return $this->GetInt(self::PERMISSION);
+	}
+
+    public static function HasSession(): bool
+    {
+        return isset($_SESSION);
+    }
+}
\ No newline at end of file
diff --git a/data/classes/core/Table.php b/data/classes/core/Table.php
new file mode 100644
index 0000000..1464659
--- /dev/null
+++ b/data/classes/core/Table.php
@@ -0,0 +1,284 @@
+<?php
+
+/**
+ * Basic object to load a mysql table inside an object.
+ */
+abstract class Table
+{
+	public const TYPE_STRING = 1;
+	public const TYPE_INTEGER = 2;
+	public const TYPE_FLOAT = 3;
+	public const TYPE_DATETIME = 4;
+	public const TYPE_BOOL = 5;
+
+	protected const VALUE = 'value';
+	protected const TYPE = 'type';
+
+	protected ?DatabaseInterface $database;
+	protected string $tableName;
+	protected array $fields;
+	protected string $primaryKey;
+    protected bool $isPrimKeyManual = false;
+
+	public function __construct(string $tableName, $id, ?DatabaseInterface & $database)
+	{
+		$this->tableName = $tableName;
+		$this->fields = [];
+
+        $this->database = $database;
+
+        $this->database->Query(sprintf('DESCRIBE %s', $tableName));
+
+        $result = $this->database->getResult();
+
+		foreach ($result as $field) {
+            $sqlType = substr_count(
+                $field['Type'], '(') === 0 ? $field['Type'] : strstr($field['Type'],
+                '(',
+                true
+            );
+
+			switch ($sqlType) {
+				case 'varchar':
+				case 'char':
+				case 'text':
+				case 'longtext':
+				case 'mediumtext':
+				case 'tinytext':
+					$type = self::TYPE_STRING;
+					break;
+				case 'int':
+				case 'smallint':
+				case 'mediumint':
+				case 'bigint':
+					$type = self::TYPE_INTEGER;
+					break;
+				case 'float':
+				case 'decimal':
+				case 'double':
+				case 'real':
+					$type = self::TYPE_FLOAT;
+					break;
+				case 'datetime':
+                case 'date':
+					$type = self::TYPE_DATETIME;
+					break;
+                case 'tinyint':
+                    $type = self::TYPE_BOOL;
+                    break;
+				default:
+					throw new Exception(sprintf('Type %s of field %s couldn\'t be handled', $sqlType, $field['Field']));
+			}
+
+            $this->addField($field['Field'], $type);
+
+            if ($field['Key'] === 'PRI') {
+				$this->primaryKey = $field['Field'];
+			}
+		}
+
+		if (!$this->isPrimKeyManual && $id !== null) {
+    		$this->loadById($id);
+        }
+    }
+
+    public function getPrimaryKey()
+    {
+        if ($this->primaryKey === null) {
+            return null;
+        }
+
+        return $this->getField($this->primaryKey);
+    }
+
+	protected function addField(string $name, int $type): void
+	{
+		if (!self::IsValidType($type)) {
+			throw new Exception(
+			    sprintf('Field %s has invalid type of %s!', $name, $type)
+            );
+		}
+
+		$this->fields[$name] = [self::VALUE => null, self::TYPE => $type];
+	}
+
+    protected function loadById($id): void
+	{
+        try {
+            $this->database->Query(
+                sprintf('SELECT * FROM %s WHERE %s = :id', $this->tableName, $this->primaryKey),
+                ['id' => $id]
+            );
+        } catch (Throwable $e) {
+            throw new Exception();
+        }
+
+		$result = $this->database->getResult();
+
+		if (count($result) === 0) {
+			throw new Exception('No table entry with id ' . $id . ' found!');
+		}
+
+		foreach ($result[0] as $field => $value) {
+			$this->setField($field, $value);
+		}
+	}
+
+	public function Flush(): void
+    {
+        $this->database->Delete($this->tableName, []);
+    }
+
+    public function Delete(): void
+    {
+        try {
+            $this->database->Delete($this->tableName, [$this->primaryKey => $this->getPrimaryKey()]);
+        } catch (Throwable $e) {
+            throw new Exception();
+        }
+
+        foreach ($this->GetAllFieldNames() as $field) {
+            $this->fields[$field][self::VALUE] = null;
+        }
+    }
+
+	protected function getField(string $name)
+	{
+		if (!array_key_exists($name, $this->fields)) {
+			return null;
+		}
+
+		return $this->fields[$name][self::VALUE];
+	}
+
+    /**
+     * Sets the value for the given field inside the database.
+     */
+	protected function setField(string $name, $value): void
+	{
+		if (!$this->HasField($name)) {
+			throw new Exception(sprintf('Field %s doesn\'t exist!', $name));
+		}
+
+		if ($value === null) {
+			$this->fields[$name][self::VALUE] = null;
+			return;
+		}
+
+		switch ($this->fields[$name][self::TYPE]) {
+			case self::TYPE_STRING:
+				$this->fields[$name][self::VALUE] = (string)$value;
+				return;
+			case self::TYPE_INTEGER:
+				$this->fields[$name][self::VALUE] = (int)$value;
+				return;
+			case self::TYPE_FLOAT:
+				$this->fields[$name][self::VALUE] = (float)$value;
+				return;
+			case self::TYPE_DATETIME:
+				try {
+				    $this->fields[$name][self::VALUE] = new DateTime((string)$value);
+                } catch (Exception $e) {
+                    throw new Exception();
+                }
+				return;
+            case self::TYPE_BOOL:
+                $this->fields[$name][self::VALUE] = (bool)$value;
+		}
+	}
+
+	/**
+     * Checks if the table has the given column.
+	 */
+	public function HasField(string $name): bool
+	{
+		return array_key_exists($name, $this->fields);
+	}
+
+    /**
+     * Saves the whole object into the database.
+     */
+	public function Save(): void
+	{
+		$fields = [];
+
+		foreach ($this->GetAllFieldNames() as $fieldName) {
+            $field = $this->getField($fieldName);
+
+            if ($field instanceof DateTime) {
+			    $fields[$fieldName] = $field->format('Y-m-d H:i:s');
+            } else if (is_bool($field)) {
+                $fields[$fieldName] = (int)$field;
+            } else {
+			    $fields[$fieldName] = $field;
+            }
+		}
+
+		if ($this->isPrimKeyManual) {
+            $this->saveWithManualId($fields);
+        } else {
+	        $this->saveWithPrimaryKey($fields);
+        }
+	}
+
+	/**
+	 * @return string[]
+	 */
+	public function GetAllFieldNames(): array
+	{
+		$fieldNames = [];
+
+		foreach ($this->fields as $name => $field) {
+			$fieldNames[] = $name;
+		}
+
+		return $fieldNames;
+	}
+
+    /**
+     * Checks if the index is a valid data type.
+     */
+	public static function IsValidType(int $type): bool
+	{
+		$validTypes = [
+			self::TYPE_STRING,
+			self::TYPE_INTEGER,
+			self::TYPE_FLOAT,
+			self::TYPE_DATETIME,
+            self::TYPE_BOOL,
+		];
+
+		return in_array($type, $validTypes);
+	}
+
+	protected function saveWithManualId(array $fields): void
+    {
+        if ($this->getField($this->primaryKey) === null) {
+            throw new Exception('Manual primary key must not be null!');
+        }
+
+        $hasKey = (bool)$this->database->Count(
+            $this->tableName,
+            [$this->primaryKey => $this->getField($this->primaryKey)]
+        );
+
+        if ($hasKey) {
+            $this->database->Update(
+                $this->tableName, $fields, [$this->primaryKey => $this->getField($this->primaryKey)]
+            );
+        } else {
+            $this->database->Insert($this->tableName, $fields);
+        }
+    }
+
+    protected function saveWithPrimaryKey(array $fields): void
+    {
+        if ($this->getField($this->primaryKey) !== null) {
+            $this->database->Update(
+                $this->tableName, $fields, [$this->primaryKey => $this->getField($this->primaryKey)]
+            );
+        } else {
+            $this->setField($this->primaryKey, $this->database->Insert($this->tableName, $fields));
+        }
+    }
+}
diff --git a/data/classes/database/Fingerprint.php b/data/classes/database/Fingerprint.php
new file mode 100644
index 0000000..aa2d6c4
--- /dev/null
+++ b/data/classes/database/Fingerprint.php
@@ -0,0 +1,53 @@
+<?php
+
+declare(strict_types=1);
+
+final class Fingerprint extends MySqlTable implements JsonSerializable
+{
+    public const FIELD_ID = 'FingerprintId';
+    public const FIELD_FINGERPRINT = 'Fingerprint';
+    public const FIELD_USER = 'UserId';
+
+    public function __construct($id = null, DatabaseInterface &$database = null)
+    {
+        parent::__construct(self::class, $id, $database);
+    }
+
+    public function getFingerprintId(): ?int
+    {
+        if ($this->getPrimaryKey() === null) {
+            return null;
+        }
+
+        return (int)$this->getPrimaryKey();
+    }
+
+    public function getFingerprint(): string
+    {
+        return $this->getField(self::FIELD_FINGERPRINT);
+    }
+
+    public function getUserId(): int
+    {
+        return $this->getField(self::FIELD_USER);
+    }
+
+    public function setFingerprint(string $fingerprint): void
+    {
+        $this->setField(self::FIELD_FINGERPRINT, $fingerprint);
+    }
+
+    public function setUserId(int $userId): void
+    {
+        $this->setField(self::FIELD_USER, $userId);
+    }
+
+    public function jsonSerialize(): array
+    {
+        return [
+            'fingerprintId' => $this->getFingerprintId(),
+            'fingerprint' => $this->getFingerprint(),
+            'userId' => $this->getUserId()
+        ];
+    }
+}
diff --git a/data/classes/database/Sharing.php b/data/classes/database/Sharing.php
new file mode 100644
index 0000000..d9b4999
--- /dev/null
+++ b/data/classes/database/Sharing.php
@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types=1);
+
+final class Sharing extends MySqlTable
+{
+    public const FIELD_USER = 'User';
+    public const FIELD_USER_SHARED = 'UserShared';
+
+    public function __construct($id = null, DatabaseInterface &$database = null)
+    {
+        parent::__construct(self::class, $id, $database);
+    }
+
+    public function getSharingId(): ?int
+    {
+        if ($this->getPrimaryKey() === null) {
+            return null;
+        }
+
+        return (int)$this->getPrimaryKey();
+    }
+
+    public function getUserId(): int
+    {
+        return $this->getField(self::FIELD_USER);
+    }
+
+    public function getUserShared(): int
+    {
+        return $this->getField(self::FIELD_USER_SHARED);
+    }
+
+    public function setUserId(int $userId): void
+    {
+        $this->setField(self::FIELD_USER, $userId);
+    }
+
+    public function setUserShared(int $userShared): void
+    {
+        $this->setField(self::FIELD_USER_SHARED, $userShared);
+    }
+}
diff --git a/data/classes/database/User.php b/data/classes/database/User.php
new file mode 100644
index 0000000..f3e4f61
--- /dev/null
+++ b/data/classes/database/User.php
@@ -0,0 +1,133 @@
+<?php
+
+declare(strict_types=1);
+
+final class User extends MySqlTable implements JsonSerializable
+{
+    public const FIELD_ID = 'UserId';
+    public const FIELD_USERNAME = 'Username';
+    public const FIELD_PASSWORD = 'Password';
+    public const FIELD_EMAIL = 'Email';
+    public const FIELD_JABBER_ADDRESS = 'JabberAddress';
+
+    public function __construct($id = null, DatabaseInterface &$database = null)
+    {
+        parent::__construct(self::class, $id, $database);
+    }
+
+    public function getUserId(): ?int
+    {
+        if ($this->getPrimaryKey() === null) {
+            return null;
+        }
+
+        return (int)$this->getPrimaryKey();
+    }
+
+    public function getUsername(): string
+    {
+        return $this->getField(self::FIELD_USERNAME);
+    }
+
+    public function getPassword(): string
+    {
+        return $this->getField(self::FIELD_PASSWORD);
+    }
+
+    public function getEmail(): string
+    {
+        return $this->getField(self::FIELD_EMAIL);
+    }
+
+    public function getJabberAddress(): string
+    {
+        return $this->getField(self::FIELD_JABBER_ADDRESS);
+    }
+
+    public function setUsername(string $username): void
+    {
+        $this->setField(self::FIELD_USERNAME, $username);
+    }
+
+    public function setPassword(string $password): void
+    {
+        $this->setField(self::FIELD_PASSWORD, $password);
+    }
+
+    public function setEmail(string $email): void
+    {
+        $this->setField(self::FIELD_EMAIL, $email);
+    }
+
+    public function setJabberAddress(string $jabberAddress): void
+    {
+        $this->setField(self::FIELD_JABBER_ADDRESS, $jabberAddress);
+    }
+
+    public static function getFromUsername(string $username, DatabaseInterface &$database = null): self
+    {
+        $databaseGiven = true;
+
+        if ($database === null) {
+            $database = new MySqlDatabase();
+            $databaseGiven = false;
+        }
+
+        if ($database->Count(self::class) === 0) {
+            throw new UserException(sprintf('No user with name %s found!', $username));
+        }
+
+        $id = $database->Select(self::class, [self::FIELD_ID], [self::FIELD_USERNAME => $username]);
+
+        $user = $databaseGiven ? new User((int)$id, $database) : new User((int)$id);
+
+        return $user;
+    }
+
+    public static function getFromEmail(string $email, DatabaseInterface &$database = null): self
+    {
+        $databaseGiven = true;
+
+        if ($database === null) {
+            $database = new MySqlDatabase();
+            $databaseGiven = false;
+        }
+
+        if ($database->Count(self::class) === 0) {
+            throw new UserException(sprintf('No user with email %s found!', $email));
+        }
+
+        $id = $database->Select(self::class, [self::FIELD_ID], [self::FIELD_EMAIL => $email])[0][self::FIELD_ID];
+
+        $user = $databaseGiven ? new User((int)$id, $database) : new User((int)$id);
+
+        return $user;
+    }
+
+    public function getFingerprintIds(): array
+    {
+        $result = $this->database->Select(
+            Fingerprint::class,
+            [Fingerprint::FIELD_ID],
+            [Fingerprint::FIELD_USER => $this->getUserId()]
+        );
+
+        $ids = [];
+
+        foreach ($result as $record) {
+            $ids[] = (int)$record[Fingerprint::FIELD_ID];
+        }
+
+        return $ids;
+    }
+
+    public function jsonSerialize()
+    {
+        return [
+            'userId' => $this->getUserId(),
+            'username' => $this->getUsername(),
+            'jabberAddress' => $this->getJabberAddress(),
+            'fingerprintIds' => $this->getFingerprintIds()
+        ];
+    }
+}
diff --git a/data/classes/exception/DatabaseException.php b/data/classes/exception/DatabaseException.php
new file mode 100644
index 0000000..c33d8cd
--- /dev/null
+++ b/data/classes/exception/DatabaseException.php
@@ -0,0 +1,7 @@
+<?php
+
+declare(strict_types=1);
+
+class DatabaseException extends Exception
+{
+}
\ No newline at end of file
diff --git a/data/classes/exception/QrCodeException.php b/data/classes/exception/QrCodeException.php
new file mode 100644
index 0000000..cc9d8ea
--- /dev/null
+++ b/data/classes/exception/QrCodeException.php
@@ -0,0 +1,7 @@
+<?php
+
+declare(strict_types=1);
+
+class QrCodeException extends Exception
+{
+}
\ No newline at end of file
diff --git a/data/classes/exception/UserException.php b/data/classes/exception/UserException.php
new file mode 100644
index 0000000..042a573
--- /dev/null
+++ b/data/classes/exception/UserException.php
@@ -0,0 +1,7 @@
+<?php
+
+declare(strict_types=1);
+
+final class UserException extends Exception
+{
+}
\ No newline at end of file
diff --git a/data/scripts/generate.php b/data/scripts/generate.php
new file mode 100644
index 0000000..10d7916
--- /dev/null
+++ b/data/scripts/generate.php
@@ -0,0 +1,5 @@
+<?php
+
+require 'data/classes/core/Autoloader.php';
+
+Autoloader::BuildCache();
diff --git a/docs/api/v1.yaml b/docs/api/v1.yaml
new file mode 100644
index 0000000..e69de29
diff --git a/index.php b/index.php
new file mode 100644
index 0000000..757ca80
--- /dev/null
+++ b/index.php
@@ -0,0 +1,5 @@
+<?php
+
+require 'data/classes/core/Autoloader.php';
+
+$autoloader = new Autoloader('data/cache');