<?php

use FFMpeg\Coordinate\TimeCode;
use FFMpeg\FFMpeg;
use FFMpeg\FFProbe;
use Gregwar\Captcha\CaptchaBuilder;
use mystic\forum\Database;
use mystic\forum\exceptions\DatabaseConnectionException;
use mystic\forum\Messaging;
use mystic\forum\orm\Attachment;
use mystic\forum\orm\Post;
use mystic\forum\orm\Topic;
use mystic\forum\orm\TopicLogMessage;
use mystic\forum\orm\User;
use mystic\forum\orm\UserPermissions;
use mystic\forum\utils\FileUtils;
use mystic\forum\utils\RequestUtils;
use mystic\forum\utils\ValidationUtils;
use Symfony\Component\Mailer\Exception\TransportException;
use Symfony\Component\Mailer\Transport;
use Symfony\Component\Mime\Address;
use Symfony\Component\Mime\Email;
use Symfony\Contracts\Service\Attribute\Required;

header_remove("X-Powered-By");

const MYSTICBB_VERSION = "0.2.0-dev";

if (($_SERVER["HTTP_USER_AGENT"] ?? "") === "") {
    http_response_code(403);
    exit;
}

define("REGISTRATION_ENABLED", isTrue(env("REGISTRATION_ENABLED") ?? ""));

session_name("fsid");
session_start();

const MAX_ATTACHMENT_SIZE = 0x200000;
const MAX_ATTACHMENT_COUNT = 4;
const THUMB_MAX_DIM = 100;
const CAPTCHA_PHRASE_LENGTH = 7;
const CAPTCHA_CHARSET = 'ABCDEFGHKLMNPQRTWXYZ234789abdefghkmnpqr';

$_rq_method = $_SERVER["REQUEST_METHOD"] ?? "GET";
$_action = $_GET["_action"] ?? null;

$GLOBALS["action"] = $_action;

function msg_error(string $err, bool $skipLoginCheck = false): void {
    _view("template_start", ["_title" => __("Error")]);
    _view("template_navigation_start");
    if (!$skipLoginCheck)
        _view("template_navigation", ["user" => RequestUtils::getAuthorizedUser($GLOBALS["db"])]);
    _view("template_navigation_end");
    _view("alert_error", ["message" => $err]);
    _view("template_end", [...getThemeAndLangInfo()]);
}

function msg_info(string $msg, bool $skipLoginCheck = false): void {
    _view("template_start", ["_title" => __("Information")]);
    _view("template_navigation_start");
    if (!$skipLoginCheck)
        _view("template_navigation", ["user" => RequestUtils::getAuthorizedUser($GLOBALS["db"])]);
    _view("template_navigation_end");
    _view("alert_info", ["message" => $msg]);
    _view("template_end", [...getThemeAndLangInfo()]);
}

function generateCaptchaText(): string {
    $phrase = "";
    for ($i = 0; $i < CAPTCHA_PHRASE_LENGTH; ++$i)
        $phrase .= CAPTCHA_CHARSET[random_int(0, strlen(CAPTCHA_CHARSET) - 1)];
    return $phrase;
}

function generatePasswordResetLink(Database &$db, User &$user): ?string {
    $token = $db->generateId(20);

    $user->passwordResetToken = $token;
    $user->passwordResetTokenCreated = new \DateTimeImmutable();

    if (!$db->update($user)) {
        return null;
    }

    return env("PUBLIC_URL") . "?_action=pwreset&token=" . urlencode($user->passwordResetToken) . "&sig=" . urlencode(base64_encode(hash("sha256", env("SECRET") . $user->passwordResetToken . $user->id . $user->passwordHash, true)));
}

function decodePasswordResetLink(Database &$db, string $token, string $signature): ?User {
    $user = new User();
    $user->passwordResetToken = $token;

    if (!$db->fetchWhere($user, "password_reset_token")) {
        return null;
    }

    $then = $user->passwordResetTokenCreated;
    $now = new \DateTimeImmutable();
    if (($now->getTimestamp() - $then->getTimestamp()) >= 3600) {
        return null;
    }

    $expectedSignature = base64_encode(hash("sha256", env("SECRET") . $user->passwordResetToken . $user->id . $user->passwordHash, true));
    if ($expectedSignature !== $signature) {
        return null;
    }

    return $user;
}

function getThemeAndLangInfo(): array {
    $availableThemes = [];
    $currentTheme = $_GET["theme"] ?? $_COOKIE["theme"] ?? env("MYSTIC_FORUM_THEME") ?? "default";
    foreach (scandir($dir = __DIR__ . '/themes/') as $ent) {
        if ($ent[0] === "." || !is_dir($dir . "/" . $ent) || !is_file($theme_file = $dir . "/" . $ent . "/theme.json"))
            continue;
        $theme_info = json_decode(file_get_contents($theme_file));
        $availableThemes[$ent] = $theme_info;
    }

    $availableLangs = [
        "en" => "English",
    ];
    foreach (i18n_get_available_locales() as $loc) {
        if (isset($availableLangs[$loc]))
            continue;
        $metadata = i18n_metadata($loc);
        $availableLangs[$loc] = $metadata["langName"] ?? $loc;
    }

    return [
        "availableThemes" => $availableThemes,
        "currentTheme" => $currentTheme,

        "availableLangs" => $availableLangs,
        "currentLang" => i18n_get_current_locale(),
    ];
}

function _view(string $___NAME, array $___PARAMS = []): void {
    $___PATH = __DIR__ . "/application/views/" . $___NAME . ".php";
    if (!is_file($___PATH)) {
        echo "<!--!ERROR Failed to include {" . htmlentities($___NAME) . "}-->\n";
        echo "<br><p><strong style=\"color:red !important\">Failed to include <em>" . htmlentities($___NAME) . "</em></strong></p><br>\n";
        echo "<!--/ERROR-->\n";
    } else {
        extract($___PARAMS);
        echo "<!--{" . htmlentities($___NAME) . "}-->\n";
        include $___PATH;
        echo "<!--{/" . htmlentities($___NAME) . "}-->\n";
    }
}

function isTrue(string $str): bool {
    $str = strtolower($str);
    return in_array($str, ["yes","true","y","t","on","enabled","1","?1"]);
}

function reArrayFiles(&$file_post) {
    $file_ary = [];
    $file_count = count($file_post['name']);
    $file_keys = array_keys($file_post);

    for ($i=0; $i<$file_count; $i++) {
        if ($file_post["error"][$i] !== UPLOAD_ERR_OK)
            continue;
        foreach ($file_keys as $key) {
            $file_ary[$i][$key] = $file_post[$key][$i];
        }
    }

    return $file_ary;
}

function renderPost(string $contents): string {
    $contents = preg_replace('~\R~u', "\n", $contents);
    $contents = trim($contents);
    $contents = preg_replace('/\n{3,}/', "\n\n", $contents);
    $contents = htmlentities($contents);
    $contents = nl2br($contents, false);
    $lines = explode("\n", $contents);
    $contents = "";
    $lineBuf = [];
    $inQuote = false;
    foreach ($lines as $ln) {
        if (str_starts_with($ln, "&gt; ")) {
            if (!$inQuote) {
                $contents .= implode("\n", $lineBuf);
                $lineBuf = [];
                $inQuote = true;
            }
            $lineBuf []= substr($ln, 5);
        } else {
            if ($inQuote) {
                $contents .= "<blockquote>\n" . implode("\n", $lineBuf) . "</blockquote>\n";
                $lineBuf = [];
                $inQuote = false;
                if (trim($ln) === "<br>")
                    continue;
            }
            $lineBuf []= $ln;
        }
    }
    if ($inQuote) {
        $contents .= "<blockquote>" . implode("\n", $lineBuf) . "</blockquote>";
    } else {
        $contents .= implode("\n", $lineBuf);
    }

    return $contents;
}

function env(string $key): ?string {
    $val = getenv($key);
    if ($val === false)
        return null;
    return $val;
}

require_once __DIR__ . "/vendor/autoload.php";
require_once __DIR__ . "/application/i18n.php";

if ($_SERVER["REQUEST_METHOD"] === "GET" && isset($_GET["lang"])) {
    parse_str($_SERVER["QUERY_STRING"], $query);
    if (empty($query["lang"])) {
        setcookie("lang", "", 100);
    } else {
        setcookie("lang", $query["lang"], time()+60*60*24*30);
    }
    unset($query["lang"]);
    $path = strtok($_SERVER["REQUEST_URI"], "?");
    header("Location: $path?" . http_build_query($query));
    exit;
}

$user_locale = env("LOCALE") ?? $_COOKIE["lang"] ?? locale_accept_from_http($_SERVER["HTTP_ACCEPT_LANGUAGE"] ?? "");
$chosen_locale = locale_lookup(i18n_get_available_locales(), $user_locale, true, "en");
i18n_locale($user_locale);

$db = null;
try {
    $db = new Database(Database::getConnectionString("db", getenv("POSTGRES_USER"), getenv("POSTGRES_PASSWORD"), getenv("POSTGRES_DBNAME")));
} catch (DatabaseConnectionException $ex) {
    msg_error(
        __("Failed to connect to database:\n%details%", [
            "details" => $ex->getMessage(),
        ]),
        true
    );
    exit;
}

$GLOBALS["db"] = &$db;

$db->ensureTable(User::class);
$db->ensureTable(Topic::class);
$db->ensureTable(Post::class);
$db->ensureTable(Attachment::class);
$db->ensureTable(TopicLogMessage::class);

$superuser = new User();
$superuser->id = "SUPERUSER";
if (!$db->fetch($superuser)) {
    $superUserPassword = base64_encode(random_bytes(12));

    $suEmail = env("MYSTIC_FORUM_SUPERUSER_EMAIL");
    if ($suEmail === null) {
        http_response_code(500);
        Messaging::error("No superuser email defined. Please set the 'MYSTIC_FORUM_SUPERUSER_EMAIL' environment variable accordingly");
        exit;
    }

    $superuser->name = "superuser";
    $superuser->email = $suEmail;
    $superuser->passwordHash = password_hash($superUserPassword, PASSWORD_DEFAULT);
    $superuser->displayName = "SuperUser";
    $superuser->created = new \DateTimeImmutable();
    $superuser->permissionMask = PHP_INT_MAX;
    $superuser->passwordResetRequired = false;
    $superuser->activated = true;
    $superuser->activationToken = "";

    $db->insert($superuser);

    Messaging::info([
        Messaging::bold("Superuser account created"),
        [
            "Username" => $superuser->name,
            "Password" => $superUserPassword,
        ],
        "Please note that the password can only be shown this time, so please note it down!",
    ]);
    exit;
}

$currentUser = RequestUtils::getAuthorizedUser($db);
$GLOBALS["currentUser"] = &$currentUser;

// initialization finished

if ($_action === "auth") {
    if ($currentUser) {
        header("Location: " . ($_GET["next"] ?? "."));
        exit;
    }

    if (RequestUtils::isRequestMethod("POST")) {
        $formId = "login";
        $username = RequestUtils::getRequiredField("username", $formId);
        $password = RequestUtils::getRequiredField("password", $formId);

        $user = new User();
        $user->name = $username;
        if (!$db->fetchWhere($user, "name") || !password_verify($password, $user->passwordHash)) {
            RequestUtils::triggerFormError(__("Username or password incorrect!"), $formId);
        }
        
        if (!$user->activated) {
            RequestUtils::triggerFormError(__("Please activate your user account first!"), $formId);
        }

        RequestUtils::setAuthorizedUser($user);
        header("Location: " . ($_GET["next"] ?? "."));
    } else {
        _view("template_start", ["_title" => __("Log in")]);
        _view("template_navigation_start");
        _view("template_navigation", ["user" => RequestUtils::getAuthorizedUser($db)]);
        _view("template_navigation_end");
        _view("form_login");
        _view("template_end", [...getThemeAndLangInfo()]);
    }
} elseif ($_action === "register") {
    if ($currentUser) {
        header("Location: " . ($_GET["next"] ?? "."));
        exit;
    }

    if (!REGISTRATION_ENABLED) {
        http_response_code(403);
        msg_error(__("Public registration disabled"));
        exit;
    }

    if (RequestUtils::isRequestMethod("POST")) {
        $formId = "register";
        $doNotFill = $_POST["username"] ?? null;
        if (!empty($doNotFill)) {
            sleep(10);
            http_response_code(204);
            exit;
        }
        $username = RequestUtils::getRequiredField("df82a9bc21", $formId);
        $password = RequestUtils::getRequiredField("password", $formId);
        $passwordRetype = RequestUtils::getRequiredField("password_retype", $formId);
        $email = trim(RequestUtils::getRequiredField("email", $formId));
        $displayName = RequestUtils::getRequiredField("display_name", $formId);
        $captcha = RequestUtils::getRequiredField("captcha", $formId);

        if ($captcha !== ($_SESSION["captchaPhrase"] ?? null)) {
            RequestUtils::triggerFormError(__("Incorrect CAPTCHA text!"), $formId);
        }
        
        // usernames are always lowercase
        $username = strtolower($username);

        if ($password !== $passwordRetype) {
            RequestUtils::triggerFormError(__("Passwords do not match!"), $formId);
        }

        if (strlen($password) < 8) {
            RequestUtils::triggerFormError(__("Password too short! Your password must consist of 8 or more characters"), $formId);
        }

        if (!ValidationUtils::isUsernameValid($username)) {
            RequestUtils::triggerFormError(__("Username has an invalid format"), $formId);
        }
        
        if (filter_var($email, FILTER_VALIDATE_EMAIL) === false) {
            RequestUtils::triggerFormError(__("Invalid email address"), $formId);
        }

        $user = new User();
        $user->name = $username;
        $user->email = $email;

        if ($db->fetchWhere($user, "name")) {
            RequestUtils::triggerFormError(__("This username is already taken!"), $formId);
        }

        if ($db->fetchWhere($user, "email")) {
            RequestUtils::triggerFormError(__("This email address is already in use!"), $formId);
        }

        // re-create user so we don't forget to clear properties set by the above queries

        $user = new User();
        $user->id = $db->generateId();
        $user->displayName = $displayName;
        $user->name = $username;
        $user->email = $email;
        $user->passwordHash = password_hash($password, PASSWORD_DEFAULT);
        $user->permissionMask = UserPermissions::GROUP_USER;
        $user->passwordResetRequired = false;
        $user->activated = false;
        $user->activationToken = $db->generateId(12);
        $user->created = new \DateTimeImmutable();

        Transport::fromDsn(env("MAILER_DSN"))->send(
            (new Email())
                ->from(env("MAILER_FROM"))
                ->to(new Address($email, $displayName))
                ->text(__(
                    "Welcome to %forum_title%, %user_display_name%!\n" .
                    "\n" .
                    "Please activate your account by clicking the link below:\n" .
                    "%activation_link%\n" .
                    "\n" .
                    "Kind regards,\n" .
                    "%forum_copyright%",
                    params: [
                        "forum_title" => (env("MYSTIC_FORUM_TITLE") ?? "Forum"),
                        "user_display_name" => $displayName,
                        "activation_link" => env("PUBLIC_URL") . "?_action=verifyemail&token=" . urlencode($user->activationToken) . "&sig=" . urlencode(base64_encode(hash("sha256", env("SECRET") . $user->activationToken . $user->id, true))),
                        "forum_copyright" => (env("MYSTIC_FORUM_COPYRIGHT") ?? env("MYSTIC_FORUM_TITLE") ?? "Forum")
                    ]
                ))
                ->subject(__("Please activate your account"))
        );

        $db->insert($user);

        msg_info(__("Your account has been created!\nPlease check your emails for an activation link!"));
    } else {
        _view("template_start", ["_title" => __("Register")]);
        _view("template_navigation_start");
        _view("template_navigation", ["user" => RequestUtils::getAuthorizedUser($db)]);
        _view("template_navigation_end");
        _view("form_register");
        _view("template_end", [...getThemeAndLangInfo()]);
    }
} elseif ($_action === "verifyemail") {
    RequestUtils::ensureRequestMethod("GET");
    $token = $_GET["token"] ?? throw new Exception("Missing token");
    $sig = $_GET["sig"] ?? throw new Exception("Missing signature");

    $user = new User();
    $user->activationToken = $token;

    if (!$db->fetchWhere($user, "activation_token")) {
        http_response_code(400);
        msg_error(__("Invalid token"));
        exit;
    }

    $expectedSignature = base64_encode(hash("sha256", env("SECRET") . $user->activationToken . $user->id, true));
    
    if ($expectedSignature !== $sig) {
        http_response_code(400);
        msg_error(__("Invalid signature."));
        exit;
    }

    $isActivation = !$user->activated;
    if ($isActivation) {
        $user->activated = true;
        $user->activationToken = "";

        if (!$db->update($user)) {
            http_response_code(400);
            msg_error(__("Failed to update user"));
            exit;
        }

        msg_info("?!HTML::" . __(
            "Your account has been activated!\nPlease click %link%here%/link% to log in!",
            [
                "link" => '<a href="?_action=auth">',
                "/link" => '</a>',
            ]
        ));
    } else {
        $oldEmail = $user->email;
        $newEmail = $user->pendingEmail;

        $user->activationToken = "";
        $user->email = $user->pendingEmail;
        $user->pendingEmail = null;
        $user->pendingEmailCreated = null;

        if (!$db->update($user)) {
            http_response_code(400);
            msg_error(__("Failed to update user"));
            exit;
        }

        $transport = Transport::fromDsn(env("MAILER_DSN"));

        try {
            $transport->send(
                (new Email())
                    ->from(env("MAILER_FROM"))
                    ->to(new Address($oldEmail, $user->displayName))
                    ->text(__(
                        "Hello, %user_display_name%!\n" .
                        "\n" .
                        "Your email address has been successfully changed from %old_email% to %new_email%!\n" .
                        "\n" .
                        "Kind regards,\n" .
                        "%forum_copyright%",
                        params: [
                            "forum_title" => (env("MYSTIC_FORUM_TITLE") ?? "Forum"),
                            "user_display_name" => $user->displayName,
                            "old_email" => $oldEmail,
                            "new_email" => $newEmail,
                            "forum_copyright" => (env("MYSTIC_FORUM_COPYRIGHT") ?? env("MYSTIC_FORUM_TITLE") ?? "Forum")
                        ]
                    ))
                    ->subject(__("Email address changed"))
            );
        } catch (TransportException $_) {
            // fail silently
        }

        try {
            $transport->send(
                (new Email())
                    ->from(env("MAILER_FROM"))
                    ->to(new Address($newEmail, $user->displayName))
                    ->text(__(
                        "Hello, %user_display_name%!\n" .
                        "\n" .
                        "Your email address has been successfully changed from %old_email% to %new_email%!\n" .
                        "\n" .
                        "Kind regards,\n" .
                        "%forum_copyright%",
                        params: [
                            "forum_title" => (env("MYSTIC_FORUM_TITLE") ?? "Forum"),
                            "user_display_name" => $user->displayName,
                            "old_email" => $oldEmail,
                            "new_email" => $newEmail,
                            "forum_copyright" => (env("MYSTIC_FORUM_COPYRIGHT") ?? env("MYSTIC_FORUM_TITLE") ?? "Forum")
                        ]
                    ))
                    ->subject(__("Email address changed"))
            );
        } catch (TransportException $_) {
            // fail silently
        }

        msg_info("?!HTML::" . __(
            "Your email address has been changed successfully!\nPlease click %link%here%/link% to return to your profile!",
            [
                "link" => '<a href="?_action=viewuser&user=' . htmlentities(urlencode($user->id)) . '">',
                "/link" => '</a>',
            ]
        ));
    }
} elseif ($_action === "logout") {
    RequestUtils::unsetAuthorizedUser();
    header("Location: " . ($_GET["next"] ?? "."));
} elseif ($_action === "viewtopic") {
    $formId = "addpost";
    $topicId = $_GET["topic"] ?? throw new Exception("Missing topic id");
    $topic = new Topic();
    $topic->id = $topicId;
    if (!$db->fetch($topic)) {
        http_response_code(404);
        msg_error("No topic exists with this id");
        exit;
    }

    if (RequestUtils::isRequestMethod("POST")) {
        if (!$currentUser) {
            http_response_code(403);
            msg_error("You need to be logged in to add new posts!");
            exit;
        }
        
        if ($topic->isLocked) {
            http_response_code(403);
            msg_error("This topic is locked!");
            exit;
        }

        $attachments = reArrayFiles($_FILES["files"]);

        if (count($attachments) > MAX_ATTACHMENT_COUNT)
            RequestUtils::triggerFormError(__("Too many attachments"), $formId);

        // check all attachments before saving one
        foreach ($attachments as $att) {
            if ($att["size"] > MAX_ATTACHMENT_SIZE) {
                RequestUtils::triggerFormError(__("Individual file size exceeded"), $formId);
            }
        }

        $message = trim(RequestUtils::getRequiredField("message", $formId));

        if (strlen($message) < 1 || strlen($message) > 0x8000) {
            RequestUtils::triggerFormError(__("Message too short or too long!"), $formId);
        }

        $item = new Post();
        $item->id = $db->generateId();
        $item->authorId = $currentUser->id;
        $item->topicId = $topicId;
        $item->content = $message;
        $item->postDate = new DateTimeImmutable();
        $item->deleted = false;
        $item->edited = false;

        $db->insert($item);

        foreach ($attachments as $att) {
            [
                "name" => $name,
                "type" => $type,
                "tmp_name" => $tmpName,
            ] = $att;
            $attachment = new Attachment();
            $attachment->id = $db->generateId();
            $attachment->name = $name;
            $attachment->mimeType = $type;
            $attachment->postId = $item->id;
            $attachment->contents = file_get_contents($tmpName);
            
            $db->insert($attachment);
        }

        header("Location: ?_action=viewtopic&topic=" . urlencode($topicId) . "#form");
    } else {
        /** @var Post[] $posts */
        $posts = $db->fetchCustom(Post::class, 'WHERE topic_id = $1 ORDER BY post_date', [ $topicId ]);
        /** @var TopicLogMessage[] $logMessages */
        $logMessages = $db->fetchCustom(TopicLogMessage::class, 'WHERE topic_id = $1 ORDER BY post_date', [ $topicId ]);
        $userCache = [];

        $topicAuthor = null;
        if ($topic->createdBy !== null) {
            $topicAuthor = new User();
            $topicAuthor->id = $topic->createdBy;
            if (!$db->fetch($topicAuthor)) {
                $topicAuthor = null;
            }
        }

        $allItems = [...$posts, ...$logMessages];
        usort($allItems, fn(Post|TopicLogMessage $a, Post|TopicLogMessage $b): int => $a->postDate <=> $b->postDate);

        _view("template_start", ["_title" => $topic->title]);
        _view("template_navigation_start");
        _view("template_navigation", ["user" => RequestUtils::getAuthorizedUser($db)]);
        _view("template_navigation_end");
        _view("view_topic_start", ["topic" => $topic, "topicAuthor" => $topicAuthor]);

        foreach ($allItems as $item) {
            /** @var ?User $postAuthor */
            $postAuthor = null;
            if ($item->authorId !== null && !isset($userCache[$item->authorId])) {
                $usr = new User();
                $usr->id = $item->authorId;
                if ($db->fetch($usr))
                    $userCache[$item->authorId] = &$usr;
            }
            if (isset($userCache[$item->authorId]))
                $postAuthor = &$userCache[$item->authorId];

            if ($item instanceof Post) {
                $attachments = $db->fetchCustom(Attachment::class, 'WHERE post_id = $1', [ $item->id ]);

                _view("view_post", [
                    "post" => $item,
                    "postAuthor" => $postAuthor,
                    "topicAuthor" => $topicAuthor,
                    "attachments" => $attachments,
                    "topic" => $topic,
                ]);
            } else {
                _view("view_topiclog", [
                    "logMessage" => $item,
                    "postAuthor" => $postAuthor,
                    "topicAuthor" => $topicAuthor,
                    "topic" => $topic,
                ]);
            }
        }

        _view("view_topic_end");

        if ($topic->isLocked) {
            _view("view_topic_locked");
        } elseif ($currentUser) {
            _view("form_addpost");
        } else {
            _view("view_logintoreply");
        }

        _view("template_end", [...getThemeAndLangInfo()]);
    }

} elseif ($_action === "newtopic") {
    if (!$currentUser) {
        http_response_code(403);
        msg_error("You need to be logged in to create new topics!");
        exit;
    }

    if (RequestUtils::isRequestMethod("POST")) {
        $formId = "newtopic";
        $title = trim(RequestUtils::getRequiredField("title", $formId));
        $message = trim(RequestUtils::getRequiredField("message", $formId));

        $attachments = reArrayFiles($_FILES["files"]);

        if (count($attachments) > MAX_ATTACHMENT_COUNT)
            RequestUtils::triggerFormError(__("Too many attachments"), $formId);

        // check all attachments before saving one
        foreach ($attachments as $att) {
            if ($att["size"] > MAX_ATTACHMENT_SIZE) {
                RequestUtils::triggerFormError(__("Individual file size exceeded"), $formId);
            }
        }

        if (strlen($title) < 1 || strlen($title) > 255) {
            RequestUtils::triggerFormError(__("Title too short or too long!"), $formId);
        }

        if (strlen($message) < 1 || strlen($message) > 0x8000) {
            RequestUtils::triggerFormError(__("Message too short or too long!"), $formId);
        }

        $topic = new Topic();
        $topic->createdBy = $currentUser->id;
        $topic->id = $db->generateId();
        $topic->title = $title;
        $topic->creationDate = new DateTimeImmutable();
        $topic->isLocked = false;

        $db->insert($topic);

        $item = new Post();
        $item->id = $db->generateId();
        $item->authorId = $currentUser->id;
        $item->topicId = $topic->id;
        $item->content = $message;
        $item->postDate = $topic->creationDate;
        $item->deleted = false;
        $item->edited = false;

        $db->insert($item);

        foreach ($attachments as $att) {
            [
                "name" => $name,
                "type" => $type,
                "tmp_name" => $tmpName,
            ] = $att;
            $attachment = new Attachment();
            $attachment->id = $db->generateId();
            $attachment->name = $name;
            $attachment->mimeType = $type;
            $attachment->postId = $item->id;
            $attachment->contents = file_get_contents($tmpName);
            
            $db->insert($attachment);
        }

        header("Location: ?_action=viewtopic&topic=" . urlencode($topic->id));
    } else {
        _view("template_start", ["_title" => __("New topic")]);
        _view("template_navigation_start");
        _view("template_navigation", ["user" => RequestUtils::getAuthorizedUser($db)]);
        _view("template_navigation_end");
        _view("form_newtopic");
        _view("template_end", [...getThemeAndLangInfo()]);
    }
} elseif ($_action === "lookupuser") {
    RequestUtils::ensureRequestMethod("GET");
    $userHandle = $_GET["handle"] ?? throw new Exception("Missing handle");

    $user = new User();
    $user->name = $userHandle;

    if (!$db->fetchWhere($user, "name")) {
        http_response_code(404);
        msg_error(__("No user with name @%user_handle%", [ "user_handle" => $userHandle ]));
        exit;
    }

    header("Location: ./?_action=viewuser&user=" . urlencode($user->id));
} elseif ($_action === "viewuser") {
    $userId = $_GET["user"] ?? throw new Exception("Missing user id");
    $user = new User();
    $user->id = $userId;
    if (!$db->fetch($user)) {
        http_response_code(404);
        msg_error(__("No user exists with this id"));
        exit;
    }

    $lastNameChangeTooRecent = false;
    $isOwnProfile = $user->id === $currentUser?->id;
    if ($isOwnProfile && $user->nameLastChanged !== null) {
        $diff = $user->nameLastChanged->diff(new DateTime());
        $diffSeconds = (new DateTime())->setTimestamp(0)->add($diff)->getTimestamp();
        $diffDays = $diffSeconds / 60.0 / 60.0 / 24.0 / 30.0;
        $lastNameChangeTooRecent = $diffDays <= 30;
    }

    if (RequestUtils::isRequestMethod("POST")) {
        $formId = $_POST["form_id"] ?? null;
        if ($formId === null) {
            http_response_code(400);
            msg_error("Missing form_id");
            exit;
        }

        if ($formId === "update_password") {
            if (!$currentUser) {
                http_response_code(403);
                msg_error(__("You must be logged in to update your password"));
                exit;
            }

            if (!$isOwnProfile) {
                RequestUtils::triggerFormError(__("You don't have permission to update this user's password"), $formId);
            }

            RequestUtils::ensureRequestMethod("POST");
            $currentPassword = RequestUtils::getRequiredField("current_password", $formId);
            $newPassword = RequestUtils::getRequiredField("new_password", $formId);
            $retypePassword = RequestUtils::getRequiredField("retype_password", $formId);

            if (!password_verify($currentPassword, $currentUser->passwordHash)) {
                RequestUtils::triggerFormError(__("Current password is incorrect"), $formId);
            }

            if ($newPassword !== $retypePassword) {
                RequestUtils::triggerFormError(__("New passwords don't match"), $formId);
            }

            if (strlen($newPassword) < 8) {
                RequestUtils::triggerFormError(__("Password too short! Your password must consist of 8 or more characters"), $formId);
            }

            $currentUser->passwordHash = password_hash($newPassword, PASSWORD_DEFAULT);
            
            if (!$db->update($currentUser)) {
                RequestUtils::triggerFormError(__("Failed to update password"), $formId);
            }

            header("Location: $_SERVER[REQUEST_URI]");
        } elseif ($formId === "update_profile") {
            if (!$currentUser) {
                http_response_code(403);
                msg_error(__("You must be logged in to update your profile"));
                exit;
            }

            $canEdit = ($currentUser?->id === $user?->id && $user?->hasPermission(UserPermissions::EDIT_OWN_USER))
                    || ($currentUser?->hasPermission(UserPermissions::EDIT_OTHER_USER));

            if (!$canEdit) {
                http_response_code(403);
                msg_error(__("You don't have permission to update this profile"));
                exit;
            }

            $displayName = RequestUtils::getRequiredField("display_name", $formId);
            $pfpAction = RequestUtils::getRequiredField("pfp_action", $formId);

            $userName = $_POST["name"] ?? $user->name;
            $email = $_POST["email"] ?? $user->email;

            $user->displayName = $displayName;

            $userName = strtolower($userName);

            if ($userName !== $user->name) {
                if ($lastNameChangeTooRecent) {
                    RequestUtils::triggerFormError(__("You can only change your username every 30 days!"), $formId);
                } else {
                    if (!ValidationUtils::isUsernameValid($userName))
                        RequestUtils::triggerFormError(__("Invalid username!"), $formId);
                    if (!ValidationUtils::isUsernameAvailable($db, $userName))
                        RequestUtils::triggerFormError(__("This username is already taken!"), $formId);
                    $user->name = $userName;
                    $user->nameLastChanged = new DateTimeImmutable();
                }
            }

            if ($email !== $user->email) {
                if ($user->pendingEmailCreated !== null) {
                    RequestUtils::triggerFormError(__("Please verify your email first!"), $formId);
                } else {
                    $queryUser = new User();
                    $queryUser->email = $email;
                    $queryUser->pendingEmail = $email;
                    if ($db->fetchWhere($queryUser, "email") || $db->fetchWhere($queryUser, "pending_email")) {
                        RequestUtils::triggerFormError(__("This email address is already in use!"), $formId);
                    }
                    $user->pendingEmail = $email;
                    $user->pendingEmailCreated = new DateTimeImmutable();
                    $user->activationToken = $db->generateId(12);

                    try {
                        Transport::fromDsn(env("MAILER_DSN"))->send(
                            (new Email())
                                ->from(env("MAILER_FROM"))
                                ->to(new Address($email, $displayName))
                                ->text(__(
                                    "Hello, %user_display_name%!\n" .
                                    "\n" .
                                    "Please verify your new email address by clicking the link below:\n" .
                                    "%verify_link%\n" .
                                    "\n" .
                                    "Kind regards,\n" .
                                    "%forum_copyright%",
                                    params: [
                                        "forum_title" => (env("MYSTIC_FORUM_TITLE") ?? "Forum"),
                                        "user_display_name" => $displayName,
                                        "verify_link" => env("PUBLIC_URL") . "?_action=verifyemail&token=" . urlencode($user->activationToken) . "&sig=" . urlencode(base64_encode(hash("sha256", env("SECRET") . $user->activationToken . $user->id, true))),
                                        "forum_copyright" => (env("MYSTIC_FORUM_COPYRIGHT") ?? env("MYSTIC_FORUM_TITLE") ?? "Forum")
                                    ]
                                ))
                                ->subject(__("Please verify your email address"))
                        );
                    } catch (TransportException $_) {
                        RequestUtils::triggerFormError(__("Failed to send verification email"), $formId);
                    }
                }
            }

            switch ($pfpAction) {
                case "keep":
                    // Do nothing
                    break;
                case "remove":
                    $user->profilePicture = null;
                    break;
                case "replace": {
                    if (!isset($_FILES["pfp"]) || $_FILES["pfp"]["error"] !== UPLOAD_ERR_OK) {
                        RequestUtils::triggerFormError(__("Please upload an image to change your profile picture"), $formId);
                    }
                    $im = @imagecreatefromjpeg($_FILES["pfp"]["tmp_name"]);
                    if ($im === false)
                        $im = @imagecreatefrompng($_FILES["pfp"]["tmp_name"]);
                    if ($im === false)
                        RequestUtils::triggerFormError(__("Please upload a valid PNG or JPEG file"), $formId);
                    /** @var \GdImage $im */
                    $thumb = imagecreatetruecolor(64, 64);
                    imagecopyresampled($thumb, $im, 0, 0, 0, 0, 64, 64, imagesx($im), imagesy($im));
                    imagedestroy($im);
                    $stream = fopen("php://memory", "w+");
                    imagejpeg($thumb, $stream, 50);
                    rewind($stream);
                    imagedestroy($thumb);
                    $user->profilePicture = stream_get_contents($stream);
                    fclose($stream);
                } break;
                default:
                    RequestUtils::triggerFormError("Invalid value for pfp_action", $formId);
                    break;
            }

            if (!$db->update($user))
                RequestUtils::triggerFormError(__("Failed to save changes", context: "Update profile"), $formId);

            header("Location: $_SERVER[REQUEST_URI]");
        } else {
            msg_error("Invalid formId");
        }
    } else {
        $posts = $db->fetchCustom(Post::class, 'WHERE author_id = $1 ORDER BY post_date DESC', [ $userId ]);
        $topics = [];
        $attachments = [];
        foreach ($posts as $item) {
            if (!isset($topics[$item->topicId])) {
                $topic = new Topic();
                $topic->id = $item->topicId;
                if ($db->fetch($topic))
                    $topics[$item->topicId] = $topic;
            }
            $attachs = $db->fetchCustom(Attachment::class, 'WHERE post_id = $1', [ $item->id ]);
            $attachments[$item->id] = $attachs;
        }
        _view("template_start", ["_title" => $user->displayName]);
        _view("template_navigation_start");
        _view("template_navigation", [
            "user" => $currentUser,
            "isViewingOwnProfile" => $isOwnProfile,
        ]);
        _view("template_navigation_end");
        _view("view_user", [
            "user" => $user,
            "posts" => $posts,
            "topics" => $topics,
            "attachments" => $attachments,
            "lastNameChangeTooRecent" => $lastNameChangeTooRecent,
        ]);
        _view("template_end", [...getThemeAndLangInfo()]);
    }
} elseif ($_action === "attachment") {
    if (!$currentUser) {
        http_response_code(403);
        msg_error(__("You must be logged in to view attachments"));
        exit;
    }

    $attId = $_GET["attachment"] ?? throw new Exception("Missing attachment id");
    $attachment = new Attachment();
    $attachment->id = $attId;
    if (!$db->fetch($attachment)) {
        http_response_code(404);
        msg_error(__("No attachment exists with this id"));
        exit;
    }

    $name = preg_replace('/[\r\n\t\/]/', '_', $attachment->name);
    
    $extension = pathinfo($attachment->name, PATHINFO_EXTENSION);

    $mime = FileUtils::getMimeTypeForExtension($extension);
    switch ($mime) {
        case "text/html":
        case "text/css":
        case "text/javascript":
        case "text/xml":
        case "application/css":
        case "application/javascript":
        case "application/xml":
            $mime = "text/plain";
            break;
    }
    header("Content-Type: " . $mime);
    header("Content-Length: " . strlen($attachment->contents));
    header("Cache-Control: no-cache");
    header("Content-Disposition: inline; filename=\"" . $name . "\"");
    echo $attachment->contents;
} elseif ($_action === "profilepicture") {
    $userId = $_GET["user"] ?? throw new Exception("Missing user id");
    $user = new User();
    $user->id = $userId;
    if (!$db->fetch($user)) {
        http_response_code(404);
        msg_error(__("No user exists with this id"));
        exit;
    }
    
    $ifNoneMatch = $_SERVER["HTTP_IF_NONE_MATCH"] ?? null;
    if ($ifNoneMatch !== null)
        $ifNoneMatch = trim($ifNoneMatch, '"');
    
    if ($user->profilePicture === null) {
        $fallback = __DIR__ . "/application/assets/user-fallback.jpg";
        $etag = md5("\0");
        header("Content-Type: image/jpeg");
        header("Content-Length: " . filesize($fallback));
        header("Cache-Control: no-cache");
        header("ETag: \"" . $etag . "\"");
        if ($ifNoneMatch === $etag)
            http_response_code(304);
        else
            readfile($fallback);
    } else {
        $etag = md5($user->profilePicture);
        header("Content-Type: image/jpeg");
        header("Content-Length: " . strlen($user->profilePicture));
        header("Cache-Control: no-cache");
        header("ETag: \"" . $etag . "\"");
        if ($ifNoneMatch === $etag)
            http_response_code(304);
        else
            echo $user->profilePicture;
    }
} elseif ($_action === "thumb") {

    $attId = $_GET["attachment"] ?? throw new Exception("Missing attachment id");
    $attachment = new Attachment();
    $attachment->id = $attId;
    if (!$db->fetch($attachment)) {
        http_response_code(404);
        msg_error(__("No attachment exists with this id"));
        exit;
    }

    $isImage = str_starts_with($attachment->mimeType, "image/");
    $isVideo = str_starts_with($attachment->mimeType, "video/");

    if (!$isImage && !$isVideo) {
        http_response_code(400);
        msg_error(__("Attachment is neither an image nor a video"));
        exit;
    }

    $contentHash = hash("sha256", $attachment->contents);
    
    $cacheId = bin2hex($attachment->id);
    $cacheDir = sys_get_temp_dir() . "/mystic/forum/0/cache/thumbs/" . substr($cacheId, 0, 2) . "/" . substr($cacheId, 0, 8) . "/";
    if (!is_dir($cacheDir))
        mkdir($cacheDir, recursive: true);

    $cacheFileData = $cacheDir . $cacheId . ".data";
    $cacheFileInfo = $cacheDir . $cacheId . ".info";

    if (is_file($cacheFileData) && is_file($cacheFileInfo)) {
        $info = json_decode(file_get_contents($cacheFileInfo));
        if ($info->contentHash === $contentHash) {
            header("Content-Type: image/jpeg");
            header("Cache-Control: max-age=86400");
            //header("X-Debug-Content: $cacheFileData");
            readfile($cacheFileData);
            exit;
        }
    }

    if ($isVideo) {
        $suffix = (microtime(true) * 1000) . "-" . random_int(0, 99999);
        $tempVid = sys_get_temp_dir() . "/video_" . $suffix;
        file_put_contents($tempVid, $attachment->contents);
        $tempImg = sys_get_temp_dir() . "/image_" . $suffix . ".jpg";

        try {
            $ffprobe = FFProbe::create();
            /** @var string $duration */
            $duration = $ffprobe
                ->format($tempVid)
                ->get("duration", "0");

            $screenshotFramePoint = TimeCode::fromSeconds(floatval($duration) / 2.0);
            
            $ffmpeg = FFMpeg::create();
            $video = $ffmpeg->open($tempVid);
            $screenshot = $video
                ->frame($screenshotFramePoint)
                ->save($tempImg);
            $im = imagecreatefromjpeg($tempImg);
        } finally {
            if (is_file($tempVid)) unlink($tempVid);
            if (is_file($tempImg)) unlink($tempImg);
        }
    } elseif ($isImage) {
        $im = imagecreatefromstring($attachment->contents);
    }
    
    $w = imagesx($im);
    $h = imagesy($im);
    $r = $w / floatval($h);

    if ($w > $h) {
        $nw = THUMB_MAX_DIM;
        $nh = floor($nw / $r);
    } else {
        $nh = THUMB_MAX_DIM;
        $nw = floor($r * $nh);
    }

    $thumb = imagecreatetruecolor($nw, $nh);
    imagecopyresampled($thumb, $im, 0, 0, 0, 0, $nw, $nh, $w, $h);
    imagedestroy($im);
    
    header("Content-Type: image/jpeg");
    header("Cache-Control: max-age=86400");
    imagejpeg($thumb, $cacheFileData, 40);
    imagedestroy($thumb);
    file_put_contents($cacheFileInfo, json_encode([
        "format" => 1,
        "contentHash" => $contentHash,
        "created" => time(),
    ], JSON_UNESCAPED_SLASHES));
    readfile($cacheFileData);
} elseif ($_action === "deletepost") {
    RequestUtils::ensureRequestMethod("POST");

    if (!$currentUser) {
        http_response_code(403);
        msg_error("You need to be logged in to delete posts!");
        exit;
    }
    $formId = "deletepost";
    $postId = RequestUtils::getRequiredField("post", $formId);

    $item = new Post();
    $item->id = $postId;

    if (!$db->fetch($item) || $item->deleted) {
        http_response_code(404);
        msg_error("No post exists with this id");
        exit;
    }

    $topicAuthor = new User();
    $topicAuthor->id = $item->authorId;

    if (!$db->fetch($topicAuthor))
        $topicAuthor = null;

    $topic = new Topic();
    $topic->id = $item->topicId;

    if (!$db->fetch($topic))
        $topic = null;

    $canEdit = ($currentUser->id === $topicAuthor?->id && $topicAuthor?->hasPermission(UserPermissions::DELETE_OWN_POST))
              || ($currentUser->hasPermission(UserPermissions::DELETE_OTHER_POST));

    if (!$canEdit) {
        http_response_code(403);
        msg_error("You don't have permission to delete this post");
        exit;
    }

    $attachments = $db->fetchCustom(Attachment::class, 'WHERE post_id = $1', [ $item->id ]);

    $confirm = $_POST["confirm"] ?? null;
    if ($confirm !== null) {
        $expectedConfirm = base64_encode(hash("sha256", "confirm" . $item->id, true));
        if ($confirm !== $expectedConfirm) {
            http_response_code(400);
            msg_error("Invalid confirmation");
            exit;
        }

        $item->deleted = true;
        $item->content = "";

        if (!$db->update($item)) {
            http_response_code(500);
            msg_error("Failed to delete post");
            exit;
        }
        
        foreach ($attachments as $attachment) {
            if (!$db->delete($attachment)) {
                http_response_code(500);
                msg_error("Failed to delete attachment");
                exit;
            }
        }

        header("Location: ?_action=viewtopic&topic=" . urlencode($item->topicId));
    } else {
        _view("template_start", ["_title" => __("Delete post")]);
        _view("template_navigation_start");
        _view("template_navigation", ["user" => RequestUtils::getAuthorizedUser($db)]);
        _view("template_navigation_end");
        _view("form_delete_post_confirm", [
            "post" => $item,
            "postAuthor" => $topicAuthor,
            "topicAuthor" => null,
            "attachments" => $attachments,
            "topic" => $topic,
        ]);
        _view("template_end", [...getThemeAndLangInfo()]);
    }
} elseif ($_action === "updatepost") {
    RequestUtils::ensureRequestMethod("POST");

    if (!$currentUser) {
        http_response_code(403);
        msg_error(__("You need to be logged in to update posts!"));
        exit;
    }

    $formId = "updatepost";
    $postId = RequestUtils::getRequiredField("post", $formId);
    $message = RequestUtils::getRequiredField("message", $formId);

    $item = new Post();
    $item->id = $postId;

    if (!$db->fetch($item) || $item->deleted) {
        http_response_code(404);
        msg_error(__("No post exists with this id"));
        exit;
    }

    $topicAuthor = new User();
    $topicAuthor->id = $item->authorId;

    if (!$db->fetch($topicAuthor))
        $topicAuthor = null;

    $canEdit = ($currentUser->id === $topicAuthor?->id && $topicAuthor?->hasPermission(UserPermissions::EDIT_OWN_POST))
              || ($currentUser->hasPermission(UserPermissions::EDIT_OTHER_POST));

    $topic = new Topic();
    $topic->id = $item->topicId;

    if (!$db->fetch($topic))
        $topic = null;

    if ($topic->isLocked) {
        http_response_code(403);
        msg_error(__("This topic has been locked"));
        exit;
    }

    if (!$canEdit) {
        http_response_code(403);
        msg_error(__("You don't have permission to edit this post"));
        exit;
    }

    $confirm = $_POST["confirm"] ?? null;

    $item->content = $message;
    $item->edited = true;

    if (!$db->update($item)) {
        http_response_code(500);
        msg_error(__("Failed to update post"));
        exit;
    }

    header("Location: ?_action=viewtopic&topic=" . urlencode($item->topicId) . "#post-" . urlencode($postId));
} elseif ($_action === "deletetopic") {
    RequestUtils::ensureRequestMethod("POST");

    if (!$currentUser) {
        http_response_code(403);
        msg_error(__("You need to be logged in to delete topics!"));
        exit;
    }

    $formId = "deletetopic";
    $topicId = RequestUtils::getRequiredField("topic", $formId);

    $topic = new Topic();
    $topic->id = $topicId;

    if (!$db->fetch($topic)) {
        http_response_code(404);
        msg_error(__("No topic exists with this id"));
        exit;
    }

    $topicAuthor = new User();
    $topicAuthor->id = $topic->createdBy;

    if (!$db->fetch($topicAuthor))
        $topicAuthor = null;

    $canEdit = ($currentUser->id === $topicAuthor?->id && $topicAuthor?->hasPermission(UserPermissions::DELETE_OWN_TOPIC))
              || ($currentUser->hasPermission(UserPermissions::DELETE_OTHER_TOPIC));

    if (!$canEdit) {
        http_response_code(403);
        msg_error(__("You don't have permission to delete this topic"));
        exit;
    }

    $confirm = $_POST["confirm"] ?? null;
    if ($confirm !== null) {
        $expectedConfirm = base64_encode(hash("sha256", "confirm" . $topic->id, true));
        if ($confirm !== $expectedConfirm) {
            http_response_code(400);
            msg_error(__("Invalid confirmation"));
            exit;
        }

        if (!$db->delete($topic)) {
            http_response_code(500);
            msg_error(__("Failed to delete topic"));
            exit;
        }

        header("Location: .");
    } else {
        _view("template_start", ["_title" => "Delete topic"]);
        _view("template_navigation_start");
        _view("template_navigation", ["user" => RequestUtils::getAuthorizedUser($db)]);
        _view("template_navigation_end");
        _view("form_delete_topic_confirm", [
            "topic" => $topic,
            "topicAuthor" => $topicAuthor,
        ]);
        _view("template_end", [...getThemeAndLangInfo()]);
    }
} elseif ($_action === "updatetopic") {
    RequestUtils::ensureRequestMethod("POST");

    if (!$currentUser) {
        http_response_code(403);
        msg_error(__("You need to be logged in to update topics!"));
        exit;
    }

    $formId = "updatetopic";
    $topicId = RequestUtils::getRequiredField("topic", $formId);
    $title = RequestUtils::getRequiredField("title", $formId);

    $topic = new Topic();
    $topic->id = $topicId;

    if (!$db->fetch($topic)) {
        http_response_code(404);
        msg_error(__("No topic exists with this id"));
        exit;
    }

    $topicAuthor = new User();
    $topicAuthor->id = $topic->createdBy;

    if (!$db->fetch($topicAuthor))
        $topicAuthor = null;

    if ($topic->isLocked) {
        http_response_code(403);
        msg_error(__("This topic has been locked"));
        exit;
    }

    $canEdit = ($currentUser->id === $topicAuthor?->id && $topicAuthor?->hasPermission(UserPermissions::EDIT_OWN_TOPIC))
            || ($currentUser->hasPermission(UserPermissions::EDIT_OTHER_TOPIC));

    if (!$canEdit) {
        http_response_code(403);
        msg_error(__("You don't have permission to update this topic"));
        exit;
    }

    $prevTitle = $topic->title;
    $topic->title = $title;

    $log = new TopicLogMessage();
    $log->id = $db->generateId();
    $log->topicId = $topic->id;
    $log->authorId = $currentUser->id;
    $log->params = [
        "old_value" => $prevTitle,
        "new_value" => $title,
    ];
    $log->type = TopicLogMessage::TITLE_CHANGED;
    $log->postDate = new \DateTimeImmutable();

    $db->insert($log);

    if (!$db->update($topic)) {
        http_response_code(500);
        msg_error(__("Failed to update topic"));
        exit;
    }

    header("Location: ./?_action=viewtopic&topic=" . urlencode($topicId));
} elseif ($_action === "locktopic") {
    RequestUtils::ensureRequestMethod("POST");
    $topicId = $_POST["topic"] ?? null;
    if ($topicId === null) {
        http_response_code(400);
        msg_error(__("Missing topic id"));
        exit;
    }
    RequestUtils::setFormErrorDestination($dest = "Location: ./?_action=viewtopic&topic=" . urlencode($topicId));

    if (!$currentUser) {
        http_response_code(403);
        msg_error(__("You need to be logged in to lock topics!"));
        exit;
    }

    $formId = "locktopic";
    $locked = RequestUtils::getRequiredField("locked", $formId);
    if ($locked === "true") {
        $locked = true;
    } elseif ($locked === "false") {
        $locked = false;
    } else RequestUtils::triggerFormError("Invalid value", $formId);

    $topic = new Topic();
    $topic->id = $topicId;

    if (!$db->fetch($topic)) {
        http_response_code(404);
        msg_error(__("No topic exists with this id"));
        exit;
    }

    $topicAuthor = new User();
    $topicAuthor->id = $topic->createdBy;

    if (!$db->fetch($topicAuthor))
        $topicAuthor = null;

    $canEdit = ($currentUser->id === $topicAuthor?->id && $topicAuthor?->hasPermission(UserPermissions::EDIT_OWN_TOPIC))
            || ($currentUser->hasPermission(UserPermissions::EDIT_OTHER_TOPIC));

    if (!$canEdit) {
        http_response_code(403);
        msg_error(__("You don't have permission to lock or unlock this topic"));
        exit;
    }

    $topic->isLocked = $locked;

    $log = new TopicLogMessage();
    $log->id = $db->generateId();
    $log->topicId = $topic->id;
    $log->authorId = $currentUser->id;
    $log->params = [];
    $log->type = $locked ? TopicLogMessage::LOCKED : TopicLogMessage::UNLOCKED;
    $log->postDate = new \DateTimeImmutable();

    $db->insert($log);

    if (!$db->update($topic)) {
        http_response_code(500);
        msg_error(__("Failed to lock or unlock topic"));
        exit;
    }

    header($dest);
} elseif ($_action === "search") {
    $query = $_GET["query"] ?? null;
    if ($query !== null) {
        $start_time = microtime(true);
        /** @var Post[] $posts */
        $posts = $db->execCustomQuery(<<<SQL
            SELECT posts.* FROM topics, posts
            WHERE
                NOT posts.deleted
                AND to_tsvector('english', topics.title || ' ' || posts.content) @@ websearch_to_tsquery('english', $1)
            ORDER BY posts.post_date DESC
            ;
        SQL, [ $query ], Post::class);

        $topicLookup = [];
        $attachmentLookup = [];
        $userLookup = [];
        foreach ($posts as $item) {
            if (!isset($topicLookup[$item->topicId])) {
                $topic = new Topic;
                $topic->id = $item->topicId;
                if ($db->fetch($topic))
                    $topicLookup[$topic->id] = &$topic;
            }
            if (!isset($attachmentLookup[$item->id])) {
                $attachmentLookup[$item->id] = $db->fetchCustom(Attachment::class, 'WHERE post_id = $1', [ $item->id ]);
            }
            if (!isset($userLookup[$item->authorId])) {
                $user = new User;
                $user->id = $item->authorId;
                if ($db->fetch($user))
                    $userLookup[$item->authorId] = &$user;
            }
        }
        $end_time = microtime(true);
        $search_duration = $end_time - $start_time;
        
        _view("template_start", ["_title" => __("Search results for “%query%”", [ "query" => $query ])]);
        _view("template_navigation_start");
        _view("template_navigation", ["user" => RequestUtils::getAuthorizedUser($db)]);
        _view("template_navigation_end");
        _view("form_search", [ "query" => $query ]);
        _view("view_search_results", [
            "posts" => &$posts,
            "topics" => &$topicLookup,
            "users" => &$userLookup,
            "attachments" => &$attachmentLookup,
            "search_duration" => $search_duration,
        ]);
        _view("template_end", [...getThemeAndLangInfo()]);
    } else {
        _view("template_start", ["_title" => __("Search")]);
        _view("template_navigation_start");
        _view("template_navigation", ["user" => RequestUtils::getAuthorizedUser($db)]);
        _view("template_navigation_end");
        _view("form_search");
        _view("template_end", [...getThemeAndLangInfo()]);
    }
} elseif ($_action === "captcha") {
    $phrase = generateCaptchaText();
    $builder = new CaptchaBuilder($phrase);
    $builder->build(192, 48);
    $_SESSION["captchaPhrase"] = $phrase;
    header("Content-Type: image/jpeg");
    header("Pragma: no-cache");
    header("Cache-Control: no-cache");
    $builder->save(null, 40);
} elseif ($_action === "ji18n") {
    header("Content-Type: application/javascript; charset=UTF-8");
    echo 'var I18N_MESSAGES = ' . json_encode(i18n_get_message_store(i18n_get_current_locale()), JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES) . ";\n";
} elseif ($_action === "debug/list-themes") {
    header("Content-Type: text/plain");
    foreach (scandir($dir = __DIR__ . '/themes/') as $ent) {
        if ($ent[0] === "." || !is_dir($dir . "/" . $ent) || !is_file($theme_file = $dir . "/" . $ent . "/theme.json"))
            continue;
        $theme_info = json_decode(file_get_contents($theme_file));
        echo $ent . "\t" . $theme_info->name . "\n";
    }
} elseif ($_action === "settheme") {
    RequestUtils::ensureRequestMethod("POST");
    $theme = $_POST["theme"] ?? exit(msg_error("Missing required field 'theme'") ?? 1);
    $next = $_POST["next"] ?? ".";
    setcookie("theme", $theme, time()+60*60*24*30);
    header("Location: $next");
} elseif ($_action === "setlang") {
    RequestUtils::ensureRequestMethod("POST");
    $lang = $_POST["lang"] ?? exit(msg_error("Missing required field 'lang'") ?? 1);
    $next = $_POST["next"] ?? ".";
    setcookie("lang", $lang, time()+60*60*24*30);
    header("Location: $next");
} elseif ($_action === "pwreset") {
    if ($currentUser) {
        header("Location: .");
        exit;
    }

    if (RequestUtils::isRequestMethod("POST")) {
        $token = $_GET["token"] ?? null;
        $signature = $_GET["sig"] ?? null;

        if ($token !== null && $signature !== null) {
            RequestUtils::setFormErrorDestination("?_action=pwreset&token=" . urlencode($token) . "&sig=" . urlencode($signature));
            $formId = "pwnew";
            $newPassword = RequestUtils::getRequiredField("new_password", $formId);
            $retypePassword = RequestUtils::getRequiredField("retype_password", $formId);
            $resetUser = decodePasswordResetLink($db, $token, $signature);

            if ($resetUser === null) {
                http_response_code(400);
                msg_error(__("The password reset link is either invalid or it expired"), true);
                exit;
            }

            if ($newPassword !== $retypePassword) {
                RequestUtils::triggerFormError(__("New passwords don't match"), $formId);
            }

            if (strlen($newPassword) < 8) {
                RequestUtils::triggerFormError(__("Password too short! Your password must consist of 8 or more characters"), $formId);
            }

            $resetUser->passwordHash = password_hash($newPassword, PASSWORD_DEFAULT);
            $resetUser->passwordResetToken = null;
            $resetUser->passwordResetTokenCreated = null;
            
            if (!$db->update($resetUser)) {
                RequestUtils::triggerFormError(__("Failed to update password"), $formId);
            }

            Transport::fromDsn(env("MAILER_DSN"))->send(
                (new Email())
                    ->from(env("MAILER_FROM"))
                    ->to(new Address($resetUser->email, $resetUser->displayName))
                    ->text(__(
                        "Hello, %user_display_name%!\n" .
                        "\n" .
                        "We are sending this email to let you know your passwort has been reset successfully!\n" .
                        "\n" .
                        "Kind regards,\n" .
                        "%forum_copyright%",
                        params: [
                            "forum_title" => (env("MYSTIC_FORUM_TITLE") ?? "Forum"),
                            "user_display_name" => $resetUser->displayName,
                            "forum_copyright" => (env("MYSTIC_FORUM_COPYRIGHT") ?? env("MYSTIC_FORUM_TITLE") ?? "Forum")
                        ]
                    ))
                    ->subject(__("Password reset successfully!"))
            );

            msg_info(__("Password reset successfully!"), true);
        } else {
            $formId = "pwreset";
            $email = RequestUtils::getRequiredField("email", $formId);

            $user = new User();
            $user->email = $email;

            if ($db->fetchWhere($user, "email")) {
                try {
                    Transport::fromDsn(env("MAILER_DSN"))->send(
                        (new Email())
                            ->from(env("MAILER_FROM"))
                            ->to(new Address($user->email, $user->displayName))
                            ->text(__(
                                "Hello, %user_display_name%!\n" .
                                "\n" .
                                "A password reset has been requested successfully! Please click the link below to set a new password:\n" .
                                "%reset_link%\n" .
                                "\n" .
                                "If this wasn't you, you can safely ignore this email. The link will only be valid for one hour.\n" .
                                "\n" .
                                "Kind regards,\n" .
                                "%forum_copyright%",
                                params: [
                                    "forum_title" => (env("MYSTIC_FORUM_TITLE") ?? "Forum"),
                                    "user_display_name" => $user->displayName,
                                    "reset_link" => generatePasswordResetLink($db, $user),
                                    "forum_copyright" => (env("MYSTIC_FORUM_COPYRIGHT") ?? env("MYSTIC_FORUM_TITLE") ?? "Forum")
                                ]
                            ))
                            ->subject(__("Forgot your password? No problem!"))
                );
                } catch (TransportException $_) {
                    // fail silently
                }
            } else {
                // don't make the delay difference too obvious
                usleep(random_int(900, 4500) * 1000);

                // ideally, at some point we would just want to queue up the email
                // and send it asynchronously, but this'll have to do for now
            }

            msg_info(__("If an account exists with the given email address, we will have sent a password reset link to that email address."), true);
        }
    } else {
        $token = $_GET["token"] ?? null;
        $signature = $_GET["sig"] ?? null;

        if ($token !== null && $signature !== null) {
            $resetUser = decodePasswordResetLink($db, $token, $signature);
            if ($resetUser === null) {
                http_response_code(400);
                msg_error(__("The password reset link is either invalid or it expired"), true);
                exit;
            }

            _view("template_start", [ "_title" => __("Reset password") ]);
            _view("template_navigation_start");
            _view("template_navigation_end");
            _view("form_new_password", [
                "token" => $token,
                "signature" => $signature,
            ]);
            _view("template_end", [...getThemeAndLangInfo()]);
        } else {
            _view("template_start", [ "_title" => __("Reset password") ]);
            _view("template_navigation_start");
            _view("template_navigation", ["user" => null]);
            _view("template_navigation_end");
            _view("form_password_reset");
            _view("template_end", [...getThemeAndLangInfo()]);
        }
    }
} elseif ($_action === "ctheme") {
    // options
    $enableLogging = true;
    $etag_strip_gzip_suffix = true;

    $cssFatal = function(string $msg): never {
        if (!headers_sent())
            http_response_code(500);
        echo "/*!FATAL $msg */\n";
        exit;
    };
    $cssError = function(string &$buffer, string $msg) use($enableLogging): void {
        if ($enableLogging)
            $buffer .= "/*!ERROR $msg */\n";
    };
    $cssWarning = function(string &$buffer, string $msg) use ($enableLogging): void {
        if ($enableLogging)
            $buffer .= "/*!WARN $msg */\n";
    };

    $buffer = "";

    header("Content-Type: text/css; charset=UTF-8");
    header("Cache-Control: no-cache");
    // Disable Apache's gzip filter, as it interferes with our ETag
    // (Apache adds '-gzip' as a ETag suffix)
    if (!$etag_strip_gzip_suffix)
        apache_setenv('no-gzip', '1');

    $themeName = $_GET["theme"] ?? $_COOKIE["theme"] ?? env("MYSTIC_FORUM_THEME") ?? "default";
    if (!preg_match('/^[a-z0-9_-]+$/i', $themeName)) {
        $cssWarning($buffer, "Invalid theme '" . str_replace('*/', '*\\/', $themeName) . "'");
        $cssWarning($buffer, "Loading default theme");
        $themeName = "default";
    }
    $themePath = __DIR__ . '/themes/' . $themeName . '/theme.json';
    $themeDefaultPath = __DIR__ . '/themes/default/theme.json';
    if (!is_file($themePath) && is_file($themeDefaultPath)) {
        $cssWarning($buffer, "Invalid theme '" . str_replace('*/', '*\\/', $themeName) . "'");
        $cssWarning($buffer, "Loading default theme");
        $themePath = $themeDefaultPath;
    } elseif (!is_file($themePath) && !is_file($themeDefaultPath)) {
        $cssFatal("Failed to load default theme");
    }
    $themeDir = dirname($themePath);
    $theme = json_decode(file_get_contents($themePath));
    if ($theme->{'$format'} !== 1)
        $cssFatal("Invalid theme format");
    foreach ($theme->files as $file) {
        if (is_array($file)) {
            if ($enableLogging) $buffer .= "/*!INLINE start */\n";
            $buffer .= implode("\n", $file);
            if ($enableLogging) $buffer .= "/*!INLINE end */\n";
        } elseif (is_file($filePath = $themeDir . "/" . $file)) {
            if ($enableLogging) $buffer .= "/*!INCLUDE " . basename($file) . " */\n";
            $buffer .= file_get_contents($filePath);
            if ($enableLogging) $buffer .= "/*!INCLUDE end */\n";
        } else
            $cssError($buffer, "Could not include file $file");
    }
    $etag = md5($buffer);

    $ifNoneMatch = $_SERVER["HTTP_IF_NONE_MATCH"] ?? null;
    if ($ifNoneMatch !== null) {
        $ifNoneMatch = trim($ifNoneMatch, '"');
        if ($etag_strip_gzip_suffix)
            $ifNoneMatch = preg_replace('/-gzip$/', '', $ifNoneMatch);
    }

    header("ETag: \"$etag\"");
    if ($ifNoneMatch === $etag)
        http_response_code(304);
    else
        echo $buffer;

} elseif ($_action === null) {
    _view("template_start");
    _view("template_navigation_start");
    _view("template_navigation", ["user" => RequestUtils::getAuthorizedUser($db)]);
    _view("template_navigation_end");
    _view("view_topics", ["topics" => $db->fetchCustom(Topic::class, "ORDER BY creation_date DESC")]);
    _view("template_end", [...getThemeAndLangInfo()]);
} else {
    http_response_code(404);
    msg_error(__("Invalid or unknown action $_action"));
}