<?php
namespace TSHW\Paste;

use League\OAuth2\Client\Provider\AbstractProvider;
use League\Plates\Engine;

class App {

    /** @var Engine */
    private $tpl;

    /** @var string */
    private $dataDir;

    /** @var AbstractProvider */
    private $oauthProvider;

    /** @var \GeSHi */
    private $highlighter;

    private $popularLanguages = [
        'php', 'java', 'scala', 'javascript', 'xml', 'text', 'python'
    ];

    private $ignoredLanguages = [
        'text'
    ];

    private $userWhitelist = [
        'Tar-Minyatur',
        'chani'
    ];

    /**
     * App constructor.
     * @param Engine $tpl Template engine (Plates)
     * @param string $dataDir Directory where pastes are stored
     * @param AbstractProvider $oauthProvider
     */
    public function __construct(Engine $tpl, string $dataDir, AbstractProvider $oauthProvider) {
        $this->tpl = $tpl;
        $this->dataDir = rtrim($dataDir, '/') . '/';
        $this->oauthProvider = $oauthProvider;
        $this->highlighter = new \GeSHi();
        $this->highlighter->enable_classes(true);
        $this->highlighter->enable_line_numbers(GESHI_NORMAL_LINE_NUMBERS);
        $this->highlighter->set_line_style('background: #eaeaea; padding-left: 0.4em');
        $this->highlighter->set_header_type(GESHI_HEADER_NONE);
        $this->highlighter->set_overall_class('highlighted_code');
    }

    public function handleRequest() {
        session_start();

        if (array_key_exists('username', $_SESSION)) {
            $this->tpl->addData(['user' => $_SESSION['username']]);
        }

        $this->handleFormActions();

        $url = $_SERVER['REQUEST_URI'];
        if (strpos($url, '?') !== false) {
            $url = substr($url, 0, strpos($url, '?'));
        }
        if (preg_match('_^/([a-z0-9]{8,12})(/raw)?$_', $url, $matches)) {
            $this->showPaste($matches[1], $matches[2] === '/raw');
        } else if ($url === '/p/github-login') {
            $this->handleOauthLogin();
        } else if ($url === '/p/logout') {
            unset($_SESSION['username']);
            $this->redirect('/');
        } else if ($url === '/') {
            $this->enforceOauthLogin();
            $this->showIndex();
        } else {
            $this->showError('Oh damn, this page does not exist. :-(');
        }
    }

    private function redirect(string $path) {
        http_response_code(302);
        $url = sprintf('%s://%s%s', (!empty($_SERVER['HTTPS']) ? 'https' : 'http'), $_SERVER['HTTP_HOST'], $path);
        header('Location: ' . $url);
        die('You will be redirected to ' . $url);
    }

    private function showError(string $message) {
        http_response_code(400);
        die($this->tpl->render('error', ['message' => $message]));
    }

    private function handleFormActions() {
        if (array_key_exists('action', $_POST)) {
            switch ($_POST['action']) {
                case "create":
                    $pasteId = $this->createNewPaste($_POST);
                    $this->redirect('/' . $pasteId);
                    break;
            }
        }
    }

    private function createNewPaste(array $params) {
        if (!array_key_exists('code', $params)) {
            $this->showError('Something went completely wrong. This should not have happened. :-( Please try again.');
        }
        $language = array_key_exists('language', $params) ? $params['language'] : 'text';
        $pasteId = $this->getNewPasteId();
        if (is_null($pasteId)) {
            $this->showError('For some unclear reason I could not generate a new ID for you. :-( Please try again.');
        }
        $content = [
            'language' => $language,
            'created' => date('c'),
            'creator' => $_SESSION['username'],
            'code' => $params['code'],
        ];
        if (file_put_contents($this->dataDir . $pasteId, json_encode($content)) === false) {
            $this->showError('Your paste could not be created. Sorry about that. :-( Please try again.');
        }
        return $pasteId;
    }

    private function getNewPasteId() {
        $attempts = 3;
        $pasteId = null;
        do {
            $attempts -= 1;
            $length = mt_rand(8, 12);
            $hash = sha1(microtime());
            $newId = substr($hash, 0, $length);
            if (!file_exists($this->dataDir . $newId)) {
                $pasteId = $newId;
            }
        } while (is_null($pasteId) && ($attempts > 0));
        return $pasteId;
    }

    private function showPaste(string $pasteId, bool $showRaw = false) {
        $filename = $this->dataDir . $pasteId;
        if (!file_exists($filename)) {
            $this->showError('Oh no...looks like this paste is gone or never existed. :-(');
        }
        $content = json_decode(file_get_contents($filename));
        if (is_null($content)) {
            $this->showError('Oh no...looks like this paste a little more than I can chew right now. :-(');
        }
        if ($showRaw) {
            header("Content-Type: text/plain");
            die($content->code);
        }
        $this->highlighter->set_source($content->code);
        $this->highlighter->set_language($content->language);
        if ($this->highlighter->error() !== false) {
            $this->showError("This is embarrassing. I failed to render the paste you wanted to open. Sorry. :-(");
        }
        echo $this->tpl->render('paste', [
            'pasteId' => $pasteId,
            'source' => $this->highlighter->parse_code(),
            'header' => 'Code (' . $this->highlighter->get_language_name() . ') pasted on ' . date('Y-m-d, H:i', strtotime($content->created)),
            'stylesheet' => $this->highlighter->get_stylesheet()]);
    }

    private function showIndex() {
        $languages = [
            'popular' => [],
            'others' => []
        ];
        foreach (glob(BASE_PATH . '/vendor/geshi/geshi/src/geshi/*.php') as $file) {
            $language = basename($file, '.php');
            if (in_array($language, $this->ignoredLanguages)) continue;
            include $file;
            $languageName = $language_data['LANG_NAME'];
            if (in_array($language, $this->popularLanguages)) {
                $languages['popular'][$language] = $languageName;
            } else {
                $languages['others'][$language] = $languageName;
            }
        }
        asort($languages['popular']);
        asort($languages['others']);
        echo $this->tpl->render('index', ['languages' => $languages]);
    }

    private function handleOauthLogin() {
        if (!isset($_GET['code'])) {
            // If we don't have an authorization code then get one
            $authUrl = $this->oauthProvider->getAuthorizationUrl();
            $_SESSION['oauth2state'] = $this->oauthProvider->getState();
            header('Location: ' . $authUrl);
            die();
        } elseif (empty($_GET['state']) || ($_GET['state'] !== $_SESSION['oauth2state'])) {
            unset($_SESSION['oauth2state']);
            $this->showError('Uh! Something went wrong with the authorization. I aborted this for security reasons, but please feel free to try again!');
        } else {
            // Try to get an access token (using the authorization code grant)
            try {
                $token = $this->oauthProvider->getAccessToken('authorization_code', [
                    'code' => $_GET['code']
                ]);
                // We got an access token, let's now get the user's details
                $user = $this->oauthProvider->getResourceOwner($token);
                if (!in_array($user->getNickname(), $this->userWhitelist)) {
                    $this->showError('Sorry, your username (' . $user->getNickname() . ') is not whitelisted and therefore I cannot allow you to create Pastes. :-(');
                }
                $_SESSION['username'] = $user->getNickname();
                $this->redirect('/');
            } catch (\Exception $e) {
                // Failed to get user details
                $this->showError('Oh no! Something is wrong with your authorization!');
            }
        }
    }

    private function enforceOauthLogin() {
        if (!array_key_exists('username', $_SESSION)) {
            echo $this->tpl->render('login_required');
            die();
        }
    }


}