Way more progress on forum

12 files changed, 378 insertions, 55 deletions

diff --git a/src/application/mystic/forum/Database.php b/src/application/mystic/forum/Database.php
index 9b9cf55..7c9ac7a 100644
--- a/src/application/mystic/forum/Database.php
+++ b/src/application/mystic/forum/Database.php
@@ -6,10 +6,12 @@ namespace mystic\forum;
 use DateTime;
 use DateTimeImmutable;
 use mystic\forum\attributes\Column;
+use mystic\forum\attributes\DefaultValue;
 use mystic\forum\attributes\NotNull;
 use mystic\forum\attributes\PrimaryKey;
 use mystic\forum\attributes\References;
 use mystic\forum\attributes\Table;
+use mystic\forum\attributes\Unique;
 use mystic\forum\exceptions\DatabaseConnectionException;
 use mystic\forum\orm\Entity;
 use mystic\forum\utils\ArrayUtils;
@@ -25,6 +27,25 @@ class Database {
     private const PRIMARY_KEY = 0b0000_0001;
     private const NOT_NULL    = 0b0000_0010;
     private const REFERENCES  = 0b0000_0100;
+    private const UNIQUE      = 0b0000_1000;
+    private const DEFAULT     = 0b0001_0000;
+
+    protected static function encodeBinary(string $bin): string {
+        return "\\x" . bin2hex($bin);
+    }
+
+    protected static function decodeBinary(string $enc): string {
+        return hex2bin(substr($enc, 2));
+    }
+
+    public static function generateId(int $length = 64): string {
+        static $charset = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
+        static $charsetLength = strlen($charset);
+        $buf = "";
+        for ($i = 0; $i < $length; ++$i)
+            $buf .= $charset[random_int(0, $charsetLength - 1)];
+        return $buf;
+    }
 
     public function __construct(string $connectionString) {
         try {
@@ -136,6 +157,14 @@ class Database {
             $colType = self::getColumnType($rflProp);
             $statement = "$colName $colType";
 
+            if (($colInfo["flags"] & self::DEFAULT) !== 0) {
+                $statement .= " DEFAULT " . $colInfo["defaultValue"];
+            }
+
+            if (($colInfo["flags"] & self::UNIQUE) !== 0) {
+                $statement .= " UNIQUE";
+            }
+
             if (($colInfo["flags"] & self::NOT_NULL) !== 0) {
                 $statement .= " NOT NULL";
             }
@@ -159,15 +188,21 @@ class Database {
             $flags = 0;
             $attrs = $prop->getAttributes();
             $reference = "";
+            $defaultValue = null;
             foreach ($attrs as $attr) {
                 $attrName = $attr->getName();
                 if ($attrName === PrimaryKey::class) {
                     $flags |= self::PRIMARY_KEY;
                 } elseif ($attrName === NotNull::class) {
                     $flags |= self::NOT_NULL;
+                } elseif ($attrName === Unique::class) {
+                    $flags |= self::UNIQUE;
                 } elseif ($attrName === References::class) {
                     $flags |= self::REFERENCES;
                     $reference = $attr->newInstance()->__toString();
+                } elseif ($attrName === DefaultValue::class) {
+                    $flags |= self::DEFAULT;
+                    $defaultValue = $attr->newInstance()->defaultValue;
                 }
             }
 
@@ -175,6 +210,8 @@ class Database {
                 "propertyName" => $prop->getName(),
                 "flags" => $flags,
                 "reference" => $reference,
+                "defaultValue" => $defaultValue,
+                "columnType" => self::getColumnType($prop),
             ]];
         }, $rflEntity->getProperties(ReflectionProperty::IS_PUBLIC)));
     }
@@ -186,8 +223,10 @@ class Database {
         return null;
     }
 
-    private static function stringifyValue(mixed $value): ?string {
-        if (is_null($value))
+    private static function stringifyValue(mixed $value, string $columnType): ?string {
+        if ($columnType === "bytea" && is_string($value))
+            return self::encodeBinary($value);
+        elseif (is_null($value))
             return null;
         elseif (is_bool($value))
             return $value ? "true" : "false";
@@ -201,6 +240,7 @@ class Database {
 
     private static function assignValue(Entity &$entity, array $colProps, ?string $value): void {
         $propName = $colProps["propertyName"];
+        $colType = $colProps["columnType"];
         $prop = new \ReflectionProperty($entity, $propName);
 
         $type = $prop->getType();
@@ -210,38 +250,43 @@ class Database {
         $typeName = $type->getName();
         if (!$type->isBuiltin() && $typeName !== \DateTime::class && $typeName !== \DateTimeImmutable::class)
             throw new \RuntimeException("User-defined types cannot be converted to from a database type.");
-        switch ($typeName) {
-            case \DateTime::class:
-                $typedValue = new \DateTime($value);
-                break;
-            case \DateTimeImmutable::class:
-                $typedValue = new \DateTimeImmutable($value);
-                break;
-            case "true":
-            case "false":
-            case "bool":
-                $typedValue = in_array(strtolower($value), ["true","yes","on","1"]) ? true : (in_array(strtolower($value), ["false","no","off","0"]) ? false : null);
-                break;
-            case "float":
-                $typedValue = floatval($value);
-                break;
-            case "int":
-                $typedValue = intval($value);
-                break;
-            case "string":
-            case "null":
-                $typedValue = strval($value);
-                break;
-            case "object":
-            case "array":
-            case "iterable":
-            case "callable":
-            case "mixed":
-            case "never":
-            case "void":
-            default:
-                throw new \RuntimeException("The type \"$typeName\" cannot be restored from the database");
-        }
+        if ($value !== null)
+            switch ($typeName) {
+                case \DateTime::class:
+                    $typedValue = new \DateTime($value);
+                    break;
+                case \DateTimeImmutable::class:
+                    $typedValue = new \DateTimeImmutable($value);
+                    break;
+                case "true":
+                case "false":
+                case "bool":
+                    $typedValue = in_array(strtolower($value), ["true","t","yes","on","1"]) ? true : (in_array(strtolower($value), ["false","f","no","off","0"]) ? false : null);
+                    break;
+                case "float":
+                    $typedValue = floatval($value);
+                    break;
+                case "int":
+                    $typedValue = intval($value);
+                    break;
+                case "string":
+                case "null":
+                    if ($colType === "bytea") {
+                        $typedValue = self::decodeBinary(strval($value));
+                    } else {
+                        $typedValue = strval($value);
+                    }
+                    break;
+                case "object":
+                case "array":
+                case "iterable":
+                case "callable":
+                case "mixed":
+                case "never":
+                case "void":
+                default:
+                    throw new \RuntimeException("The type \"$typeName\" cannot be restored from the database");
+            }
         $entity->{$propName} = $typedValue;
     }
 
@@ -249,7 +294,7 @@ class Database {
         $values = [];
 
         foreach ($cols as $colInfo) {
-            $values []= self::stringifyValue($entity->{$colInfo["propertyName"]} ?? null);
+            $values []= self::stringifyValue($entity->{$colInfo["propertyName"]} ?? null, $colInfo["columnType"]);
         }
 
         return $values;
@@ -288,6 +333,67 @@ class Database {
         return true;
     }
 
+    public function fetchWhere(Entity &$entity, string $columnName): bool {
+        $entityClassName = get_class($entity);
+        $tableName = self::getTableName($entityClassName);
+        $reflClass = new ReflectionClass($entityClassName);
+        $cols = self::getColumns($reflClass);
+        if (!isset($cols[$columnName]))
+            throw new \RuntimeException("Column $columnName does not exist!");
+        $query = "SELECT * FROM $tableName WHERE $columnName = \$1 LIMIT 1;";
+        $result = \pg_query_params($this->connection, $query, [ $entity->{$cols[$columnName]["propertyName"]} ]);
+        if ($result === false)
+            throw new \RuntimeException("Fetch failed: " . \pg_last_error($this->connection));
+        $row = \pg_fetch_assoc($result);
+        \pg_free_result($result);
+        if ($row === false)
+            return false;
+        foreach ($cols as $colName => $colProps)
+            self::assignValue($entity, $colProps, $row[$colName]);
+        return true;
+    }
+
+    public function fetchAll(string $entityClassName): array {
+        $tableName = self::getTableName($entityClassName);
+        $reflClass = new ReflectionClass($entityClassName);
+        $cols = self::getColumns($reflClass);
+        $query = "SELECT * FROM $tableName;";
+        $result = \pg_query($this->connection, $query);
+        if ($result === false)
+            throw new \RuntimeException("Fetch failed: " . \pg_last_error($this->connection));
+        $items = [];
+        while (($row = \pg_fetch_assoc($result)) !== false) {
+            $entity = new $entityClassName();
+            foreach ($cols as $colName => $colProps)
+                self::assignValue($entity, $colProps, $row[$colName]);
+            $items []= $entity;
+        }
+        \pg_free_result($result);
+        return $items;
+    }
+
+    public function fetchCustom(string $entityClassName, string $customQuery, ?array $customQueryParams = null): array {
+        $tableName = self::getTableName($entityClassName);
+        $reflClass = new ReflectionClass($entityClassName);
+        $cols = self::getColumns($reflClass);
+        $query = "SELECT * FROM $tableName $customQuery;";
+        if ($customQueryParams === null)
+            $result = \pg_query($this->connection, $query);
+        else
+            $result = \pg_query_params($this->connection, $query, $customQueryParams);
+        if ($result === false)
+            throw new \RuntimeException("Fetch failed: " . \pg_last_error($this->connection));
+        $items = [];
+        while (($row = \pg_fetch_assoc($result)) !== false) {
+            $entity = new $entityClassName();
+            foreach ($cols as $colName => $colProps)
+                self::assignValue($entity, $colProps, $row[$colName]);
+            $items []= $entity;
+        }
+        \pg_free_result($result);
+        return $items;
+    }
+
     public function delete(Entity &$entity): bool {
         $entityClassName = get_class($entity);
         $tableName = self::getTableName($entityClassName);
@@ -313,14 +419,20 @@ class Database {
         if ($primaryCol === null)
             throw new \RuntimeException("Updating an entity requires a primary key column to be specified");
 
-        $filteredCols = array_filter(ArrayUtils::asPairs($cols), function($pair) {
+        $filteredCols = array_values(array_filter(ArrayUtils::asPairs($cols), function($pair) {
             return ($pair[1]["flags"] & self::PRIMARY_KEY) === 0;
-        });
-        $colDef = implode(", ", array_map(function(array $pair): string {
-            return implode("=", [ $pair[0], '$' . $pair[1] ]);
-        }, $filteredCols));
+        }));
+        // echo "<pre>";
+        // var_dump($filteredCols);
+        // exit;
+        $qCols = [];
+        for ($i = 0; $i < count($filteredCols); ++$i) {
+            $qCols []= implode("=", [ $filteredCols[$i][0], '$' . ($i + 2) ]);
+        }
+        $colDef = implode(", ", $qCols);
         $query = "UPDATE $tableName SET $colDef WHERE $primaryCol = \$1;";
-        $result = \pg_query_params($this->connection, $query, array_map(fn($c) => $entity->{$c["propertyName"]}, $filteredCols));
+        //$theCols = ArrayUtils::assocFromPairs($filteredCols);
+        $result = \pg_query_params($this->connection, $query, self::getColumnValues($entity, $cols));
         if ($result === false)
             throw new \RuntimeException("Update failed: " . \pg_last_error($this->connection));
         $num_affected_rows = \pg_affected_rows($result);
diff --git a/src/application/mystic/forum/Messaging.php b/src/application/mystic/forum/Messaging.php
index 2f5c80d..3530d5e 100644
--- a/src/application/mystic/forum/Messaging.php
+++ b/src/application/mystic/forum/Messaging.php
@@ -11,7 +11,7 @@ final class Messaging {
     const ENT_FLAGS = \ENT_COMPAT | \ENT_HTML401 | \ENT_SUBSTITUTE;
 
     protected static function message(array $items, string $headerText, string $headerColor, string $headerTextColor): void {
-        echo "<HTML><BODY>\n";
+        //echo "<HTML><BODY>\n";
         echo "<TABLE cellspacing=2 cellpadding=0 bgcolor=gray><TR><TD>\n";
 
         echo "<TABLE width=\"100%\" cellspacing=0 cellpadding=4 bgcolor=\"".htmlentities($headerColor, self::ENT_FLAGS)."\"><TR><TD align=center>\n";
@@ -20,7 +20,7 @@ final class Messaging {
         
         echo "</TD></TR><TR><TD>\n";
 
-        echo "<TABLE cellspacing=0 cellpadding=4 bgcolor=WHITE><TR><TD align=left><FONT size=2 face=Arial color=BLACK>\n";
+        echo "<TABLE width=\"100%\" cellspacing=0 cellpadding=4 bgcolor=WHITE><TR><TD align=left><FONT size=2 face=Arial color=BLACK>\n";
         
         foreach ($items as $item) {
             if (is_scalar($item)) {
@@ -65,7 +65,7 @@ final class Messaging {
         echo "</FONT></TD></TR></TABLE>\n";
 
         echo "</TD></TR></TABLE>\n";
-        echo "</BODY></HTML>\n";
+        //echo "</BODY></HTML>\n";
     }
 
     public static function bold(string $contents): array {
diff --git a/src/application/mystic/forum/attributes/DefaultValue.php b/src/application/mystic/forum/attributes/DefaultValue.php
new file mode 100644
index 0000000..e3dd1a5
--- /dev/null
+++ b/src/application/mystic/forum/attributes/DefaultValue.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace mystic\forum\attributes;
+
+#[\Attribute(\Attribute::TARGET_PROPERTY)]
+class DefaultValue {
+    public function __construct(
+        public readonly string $defaultValue,
+    ) {}
+}
diff --git a/src/application/mystic/forum/attributes/References.php b/src/application/mystic/forum/attributes/References.php
index 9e33927..8271ebb 100644
--- a/src/application/mystic/forum/attributes/References.php
+++ b/src/application/mystic/forum/attributes/References.php
@@ -4,15 +4,25 @@ namespace mystic\forum\attributes;
 
 #[\Attribute(\Attribute::TARGET_PROPERTY)]
 class References {
+    public const NO_ACTION = 0;
+    public const CASCADE = 1;
+    public const SET_NULL = 2;
+    public const SET_DEFAULT = 3;
+
     public function __construct(
         public readonly string $foreignTableName,
         public readonly ?string $foreignColumnName = null,
-        public readonly bool $cascadeOnDelete = false,
+        public readonly int $onDelete = self::NO_ACTION,
     ) {}
 
     public function __toString(): string {
         return $this->foreignTableName
             . ($this->foreignColumnName !== null ? " ({$this->foreignColumnName})" : "")
-            . ($this->cascadeOnDelete ? " ON DELETE CASCADE" : "");
+            . ([
+                    self::NO_ACTION => "",
+                    self::CASCADE => " ON DELETE CASCADE",
+                    self::SET_NULL => " ON DELETE SET NULL",
+                    self::SET_DEFAULT => " ON DELETE SET DEFAULT",
+               ][$this->onDelete] ?? "");
     }
 }
diff --git a/src/application/mystic/forum/attributes/Unique.php b/src/application/mystic/forum/attributes/Unique.php
new file mode 100644
index 0000000..7c32255
--- /dev/null
+++ b/src/application/mystic/forum/attributes/Unique.php
@@ -0,0 +1,6 @@
+<?php
+
+namespace mystic\forum\attributes;
+
+#[\Attribute(\Attribute::TARGET_PROPERTY)]
+class Unique {}
diff --git a/src/application/mystic/forum/orm/Attachment.php b/src/application/mystic/forum/orm/Attachment.php
new file mode 100644
index 0000000..64e357c
--- /dev/null
+++ b/src/application/mystic/forum/orm/Attachment.php
@@ -0,0 +1,18 @@
+<?php
+declare(strict_types=1);
+
+namespace mystic\forum\orm;
+
+use mystic\forum\attributes\Column;
+use mystic\forum\attributes\PrimaryKey;
+use mystic\forum\attributes\References;
+use mystic\forum\attributes\Table;
+
+#[Table("public.attachments")]
+class Attachment extends Entity {
+    #[PrimaryKey] public string $id;
+    #[References("public.posts", onDelete: References::CASCADE)] public string $postId;
+    public string $name;
+    public string $mimeType;
+    #[Column(columnType: "bytea")] public string $contents;
+}
diff --git a/src/application/mystic/forum/orm/Post.php b/src/application/mystic/forum/orm/Post.php
index 2c9a38c..becbb9d 100644
--- a/src/application/mystic/forum/orm/Post.php
+++ b/src/application/mystic/forum/orm/Post.php
@@ -3,6 +3,7 @@ declare(strict_types=1);
 
 namespace mystic\forum\orm;
 
+use mystic\forum\attributes\DefaultValue;
 use mystic\forum\attributes\PrimaryKey;
 use mystic\forum\attributes\References;
 use mystic\forum\attributes\Table;
@@ -11,7 +12,8 @@ use mystic\forum\attributes\Table;
 class Post extends Entity {
     #[PrimaryKey] public string $id;
     public string $content;
-    #[References("public.users")] public string $authorId;
+    #[References("public.users", onDelete: References::SET_NULL)] public ?string $authorId;
     public \DateTimeImmutable $postDate;
-    #[References("public.topics", cascadeOnDelete: true)] public string $topicId;
+    #[References("public.topics", onDelete: References::CASCADE)] public string $topicId;
+    #[DefaultValue("false")] public bool $deleted;
 }
diff --git a/src/application/mystic/forum/orm/Topic.php b/src/application/mystic/forum/orm/Topic.php
index 202fc50..421f5ec 100644
--- a/src/application/mystic/forum/orm/Topic.php
+++ b/src/application/mystic/forum/orm/Topic.php
@@ -4,12 +4,13 @@ declare(strict_types=1);
 namespace mystic\forum\orm;
 
 use mystic\forum\attributes\PrimaryKey;
+use mystic\forum\attributes\References;
 use mystic\forum\attributes\Table;
 
 #[Table("public.topics")]
 class Topic extends Entity {
-    #[PrimaryKey]
-    public string $id;
+    #[PrimaryKey] public string $id;
     public string $title;
     public \DateTimeImmutable $creationDate;
+    #[References("public.users", onDelete: References::SET_NULL)] public ?string $createdBy;
 }
diff --git a/src/application/mystic/forum/orm/User.php b/src/application/mystic/forum/orm/User.php
index 3b531b4..1db1d04 100644
--- a/src/application/mystic/forum/orm/User.php
+++ b/src/application/mystic/forum/orm/User.php
@@ -5,13 +5,27 @@ namespace mystic\forum\orm;
 
 use mystic\forum\attributes\PrimaryKey;
 use mystic\forum\attributes\Table;
+use mystic\forum\attributes\Unique;
 
 #[Table("public.users")]
 class User extends Entity {
+    public const SUPERUSER_ID = "SUPERUSER";
+    
     #[PrimaryKey]
     public string $id;
-    public string $name;
+    #[Unique] public string $name;
     public string $displayName;
+    #[Unique] public string $email;
     public \DateTimeImmutable $created;
     public string $passwordHash;
+    public int $permissionMask;
+    public bool $passwordResetRequired;
+    public string $activationToken;
+    public bool $activated;
+
+    public function hasPermission(int $perm): bool {
+        if ($this->id === self::SUPERUSER_ID)
+            return true;
+        return ($this->permissionMask & $perm) === $perm;
+    }
 }
diff --git a/src/application/mystic/forum/orm/UserPermissions.php b/src/application/mystic/forum/orm/UserPermissions.php
new file mode 100644
index 0000000..cd2fdf4
--- /dev/null
+++ b/src/application/mystic/forum/orm/UserPermissions.php
@@ -0,0 +1,59 @@
+<?php
+declare(strict_types=1);
+
+namespace mystic\forum\orm;
+
+use mystic\forum\utils\StaticClass;
+
+final class UserPermissions {
+    use StaticClass;
+
+    public const CREATE_OWN_POST = 0x01;
+    public const EDIT_OWN_POST = 0x02;
+    public const DELETE_OWN_POST = 0x04;
+
+    public const CREATE_OWN_TOPIC = 0x08;
+    public const EDIT_OWN_TOPIC = 0x10;
+    public const DELETE_OWN_TOPIC = 0x20;
+
+    public const CREATE_OWN_ATTACHMENT = 0x40;
+    public const EDIT_OWN_ATTACHMENT = 0x80;
+    public const DELETE_OWN_ATTACHMENT = 0x100;
+
+    // public const CREATE_OWN_USER = n/a;
+    public const EDIT_OWN_USER = 0x200;
+    public const DELETE_OWN_USER = 0x400;
+    
+    // public const CREATE_OTHER_POST = n/a;
+    public const EDIT_OTHER_POST = 0x800;
+    public const DELETE_OTHER_POST = 0x1000;
+
+    public const CREATE_OTHER_USER = 0x2000;
+    public const EDIT_OTHER_USER = 0x4000;
+    public const DELETE_OTHER_USER = 0x8000;
+
+    public const DELETE_OTHER_TOPIC = 0x10000;
+
+    ////////
+
+    public const GROUP_USER = self::CREATE_OWN_POST
+                            | self::EDIT_OWN_POST
+                            | self::DELETE_OWN_POST
+                            | self::CREATE_OWN_TOPIC
+                            | self::DELETE_OWN_TOPIC
+                            | self::CREATE_OWN_ATTACHMENT
+                            | self::EDIT_OWN_ATTACHMENT
+                            | self::DELETE_OWN_ATTACHMENT
+                            | self::EDIT_OWN_USER
+                            | self::DELETE_OWN_USER;
+    
+    public const GROUP_MOD = self::GROUP_USER
+                           | self::EDIT_OTHER_POST
+                           | self::DELETE_OTHER_USER
+                           | self::DELETE_OTHER_TOPIC;
+
+    public const GROUP_ADMIN = self::GROUP_MOD
+                             | self::CREATE_OTHER_USER
+                             | self::EDIT_OTHER_USER
+                             | self::DELETE_OTHER_USER;
+}
diff --git a/src/application/mystic/forum/utils/RequestUtils.php b/src/application/mystic/forum/utils/RequestUtils.php
index 2f40013..f6ce3a3 100644
--- a/src/application/mystic/forum/utils/RequestUtils.php
+++ b/src/application/mystic/forum/utils/RequestUtils.php
@@ -3,17 +3,86 @@ declare(strict_types=1);
 
 namespace mystic\forum\utils;
 
+use mystic\forum\Database;
 use mystic\forum\Messaging;
+use mystic\forum\orm\User;
 
 final class RequestUtils {
     use StaticClass;
 
+    public static function getRequestMethod(): string {
+        return strtoupper($_SERVER["REQUEST_METHOD"] ?? "GET");
+    }
+
+    public static function isRequestMethod(string $method): bool {
+        $rMethod = self::getRequestMethod();
+        return strcasecmp($rMethod, $method) === 0;
+    }
+
     public static function ensureRequestMethod(string $method): void {
-        $rMethod = $_SERVER["REQUEST_METHOD"];
-        if (strcasecmp($rMethod, $method) !== 0) {
-            http_response_code(500);
-            Messaging::error("Invalid request method $rMethod");
+        if (!self::isRequestMethod($method)) {
+            http_response_code(415);
+            Messaging::error("Invalid request method " . self::getRequestMethod());
+            exit;
+        }
+    }
+
+    public static function getRequiredField(string $field): string {
+        $fieldValue = $_POST[$field] ?? null;
+        if ($fieldValue === null) {
+            http_response_code(400);
+            Messaging::error("Missing required field $field");
             exit;
         }
+        return $fieldValue;
+    }
+
+    public static function storeForm(): void {
+        $_SESSION["lastForm"] = $_POST ?? [];
+        $_SESSION["lastForm_uri"] = $_SERVER["REQUEST_URI"];
+    }
+
+    public static function triggerFormError(string $message, ?string $next = null): never {
+        $next ??= $_SERVER["REQUEST_URI"];
+        $_SESSION["formError"] = $message;
+        // store last form submission
+        self::storeForm();
+        header("Location: $next");
+        exit;
+    }
+
+    public static function getAndClearFormError(): ?string {
+        $err = $_SESSION["formError"] ?? null;
+        unset($_SESSION["formError"]);
+        return $err;
+    }
+
+    public static function getLastForm(string &$lastFormUri): ?array {
+        $lastFormUri = $_SESSION["lastForm_uri"] ?? "";
+        return $_SESSION["lastForm"] ?? null;
+    }
+
+    public static function clearLastForm(): void {
+        unset($_SESSION["lastForm"]);
+        unset($_SESSION["lastForm_uri"]);
+    }
+
+    public static function getAuthorizedUser(Database &$db): ?User {
+        $userId = $_SESSION["authedUser"] ?? null;
+        if ($userId === null)
+            return null;
+        $user = new User();
+        $user->id = $userId;
+        if (!$db->fetch($user))
+            return null;
+        return $user;
+    }
+
+    public static function setAuthorizedUser(User &$user): void {
+        $_SESSION["authedUser"] = $user->id;
+    }
+
+    public static function unsetAuthorizedUser(): void {
+        unset($_SESSION["authedUser"]);
     }
 }
diff --git a/src/application/mystic/forum/utils/ValidationUtils.php b/src/application/mystic/forum/utils/ValidationUtils.php
new file mode 100644
index 0000000..df97914
--- /dev/null
+++ b/src/application/mystic/forum/utils/ValidationUtils.php
@@ -0,0 +1,22 @@
+<?php
+declare(strict_types=1);
+
+namespace mystic\forum\utils;
+
+use mystic\forum\Database;
+use mystic\forum\orm\User;
+
+final class ValidationUtils {
+    use StaticClass;
+
+    public static function isUsernameValid(string $name): bool {
+        return !!preg_match('/^[a-z0-9]([._](?![._])|[a-z0-9]){2,30}[a-z0-9]$/', $name);
+    }
+
+    public static function isUsernameAvailable(Database &$db, string $name): bool {
+        $user = new User();
+        $user->name = $name;
+        return !$db->fetchWhere($user, "name");
+    }
+}
+