<?php
/*
=========================================================
EXAM-GATE ENTERPRISE
---------------------------------------------------------
File:
config/core.php

Version:
3.0.0

Description:
Enterprise Core System Library (Foundation)

Compatible:
JSON Edition

Author:
Zamex Link Limited
=========================================================
*/

require_once __DIR__ . "/settings.php";

if (session_status() === PHP_SESSION_NONE) {
    session_name(SESSION_NAME);
    session_start();
}

if (APP_DEBUG) {
    ini_set("display_errors",1);
    ini_set("display_startup_errors",1);
    error_reporting(E_ALL);
} else {
    ini_set("display_errors",0);
    error_reporting(0);
}

require_once __DIR__ . "/json.php";

foreach ([DATA_PATH,EXAMS_PATH,ANSWERS_PATH,BACKUP_PATH,TEMP_PATH,LOG_PATH] as $dir){
    ensure_directory($dir);
}

function sanitize($v){ return htmlspecialchars(trim((string)$v),ENT_QUOTES,"UTF-8"); }
function sanitizeInput($v){ return sanitize($v); }

function redirect($url){
    header("Location: ".$url);
    exit;
}

function isLoggedIn(): bool{
    return !empty($_SESSION["logged_in"]) && $_SESSION["logged_in"]===true;
}

function requireLogin(){
    if(!isLoggedIn()){
        redirect("login.php");
    }
}

function currentDate(){ return date("Y-m-d"); }
function currentTime(){ return date("H:i:s"); }
function currentDateTime(){ return date("Y-m-d H:i:s"); }

function generate_exam_id(){
    return "EXAM-".date("Y")."-".str_pad((string)random_int(1,999999),6,"0",STR_PAD_LEFT);
}

function generate_password($length=8){
    $chars="ABCDEFGHJKLMNPQRSTUVWXYZ23456789";
    $out="";
    for($i=0;$i<$length;$i++){
        $out.=$chars[random_int(0,strlen($chars)-1)];
    }
    return $out;
}

function generate_ref(){
    return "REF-".date("YmdHis")."-".random_int(1000,9999);
}

function system_log($action,$exam_id=null,$extra=[]){
    $log=read_json(SYSTEM_LOG);
    $log[]=array_merge([
        "datetime"=>currentDateTime(),
        "action"=>$action,
        "exam_id"=>$exam_id,
        "ip"=>$_SERVER["REMOTE_ADDR"]??"",
        "browser"=>$_SERVER["HTTP_USER_AGENT"]??""
    ],$extra);
    write_json(SYSTEM_LOG,$log);
}

function writeLog($action,$exam_id=null,$extra=[]){
    system_log($action,$exam_id,$extra);
}

/*
=========================================================
LOGGING FUNCTIONS
=========================================================
*/

function writeLog($action, $exam_id = null, $extra = [])
{
    system_log($action, $exam_id, $extra);
}

function writeAuditLog($action, $details = [])
{
    $log = read_json(AUDIT_LOG);

    $log[] = [
        "date"       => currentDate(),
        "time"       => currentTime(),
        "datetime"   => currentDateTime(),
        "action"     => $action,
        "details"    => $details,
        "ip_address" => $_SERVER["REMOTE_ADDR"] ?? "",
        "browser"    => $_SERVER["HTTP_USER_AGENT"] ?? ""
    ];

    write_json(AUDIT_LOG, $log);
}

function writeErrorLog($message, $details = [])
{
    $log = read_json(ERROR_LOG);

    $log[] = [
        "date"       => currentDate(),
        "time"       => currentTime(),
        "datetime"   => currentDateTime(),
        "message"    => $message,
        "details"    => $details
    ];

    write_json(ERROR_LOG, $log);
}

/*
=========================================================
EXAM ID GENERATORS
=========================================================
*/

function generate_question_id()
{
    return "Q" . str_pad((string) random_int(1, 999999), 6, "0", STR_PAD_LEFT);
}

function generate_answer_id()
{
    return "ANS-" . date("YmdHis") . "-" . random_int(1000, 9999);
}

function generate_session_token()
{
    return bin2hex(random_bytes(32));
}

/*
=========================================================
FILE HELPERS
=========================================================
*/

function fileExistsSafe($file)
{
    return is_file($file);
}

function loadExam($examFile)
{
    return read_json($examFile);
}

function saveExam($examFile, array $examData)
{
    return write_json($examFile, $examData);
}

/*
=========================================================
REQUEST HELPERS
=========================================================
*/

function post($key, $default = "")
{
    return isset($_POST[$key])
        ? sanitize($_POST[$key])
        : $default;
}

function get($key, $default = "")
{
    return isset($_GET[$key])
        ? sanitize($_GET[$key])
        : $default;
}

/*
=========================================================
CLIENT INFORMATION
=========================================================
*/

function getIPAddress()
{
    return $_SERVER["REMOTE_ADDR"] ?? "";
}

function getBrowser()
{
    return $_SERVER["HTTP_USER_AGENT"] ?? "";
}

function getDeviceType()
{
    $agent = strtolower($_SERVER["HTTP_USER_AGENT"] ?? "");

    if (strpos($agent, "mobile") !== false)
    {
        return "Phone";
    }

    if (strpos($agent, "tablet") !== false)
    {
        return "Tablet";
    }

    return "Computer";
}

function getDeviceModel()
{
    return DEFAULT_DEVICE_MODEL;
}

/*
=========================================================
END OF PART 2
=========================================================
*/
/*
=========================================================
VALIDATION ENGINE
=========================================================
*/

function isEmpty($value)
{
    return trim($value) === "";
}

function isValidEmail($email)
{
    return filter_var($email, FILTER_VALIDATE_EMAIL) !== false;
}

function isValidExamID($examID)
{
    return preg_match(
        '/^EXAM-\d{4}-\d{6}$/',
        trim($examID)
    ) === 1;
}

function isValidQuestionID($questionID)
{
    return preg_match(
        '/^Q\d{6}$/',
        trim($questionID)
    ) === 1;
}

function isValidPassword($password)
{
    return strlen(trim($password)) >= 6;
}

function isPositiveInteger($number)
{
    return filter_var(
        $number,
        FILTER_VALIDATE_INT
    ) !== false
    &&
    $number > 0;
}

/*
=========================================================
STRING UTILITIES
=========================================================
*/

function toUpper($text)
{
    return strtoupper(trim($text));
}

function toLower($text)
{
    return strtolower(trim($text));
}

function titleCase($text)
{
    return ucwords(strtolower(trim($text)));
}

function randomString($length = 10)
{
    $characters =
        "ABCDEFGHJKLMNPQRSTUVWXYZ23456789";

    $string = "";

    for($i = 0; $i < $length; $i++)
    {
        $string .=
            $characters[
                random_int(
                    0,
                    strlen($characters)-1
                )
            ];
    }

    return $string;
}

/*
=========================================================
DATE UTILITIES
=========================================================
*/

function today()
{
    return date("Y-m-d");
}

function now()
{
    return date("Y-m-d H:i:s");
}

function currentTimestamp()
{
    return time();
}

/*
=========================================================
END OF PART 3
=========================================================
*/
/*
=========================================================
EXAM ENGINE
=========================================================
*/

function examExists(string $examID): bool
{
    return is_dir(EXAMS_PATH . "/" . $examID);
}

function getExamFolder(string $examID): string
{
    return EXAMS_PATH . "/" . $examID;
}

function getExamFile(string $examID): string
{
    return getExamFolder($examID) . "/exam.json";
}

function loadExamByID(string $examID): array
{
    $file = getExamFile($examID);

    if (!file_exists($file))
    {
        return [];
    }

    return read_json($file);
}

function saveExamByID(string $examID, array $examData): bool
{
    $folder = getExamFolder($examID);

    ensure_directory($folder);

    $file = getExamFile($examID);

    return write_json($file, $examData);
}

function deleteExamByID(string $examID): bool
{
    $folder = getExamFolder($examID);

    if (!is_dir($folder))
    {
        return false;
    }

    deleteDirectory($folder);

    return true;
}

/*
=========================================================
QUESTION ENGINE
=========================================================
*/

function getQuestionFolder(string $examID): string
{
    return getExamFolder($examID) . "/QUESTIONS-" . $examID;
}

function questionExists(string $examID, string $questionID): bool
{
    return file_exists(
        getQuestionFolder($examID) .
        "/" .
        $questionID .
        ".json"
    );
}

function getQuestionFile(string $examID, string $questionID): string
{
    return getQuestionFolder($examID)
        . "/"
        . $questionID
        . ".json";
}

function loadQuestion(string $examID, string $questionID): array
{
    $file = getQuestionFile($examID, $questionID);

    if (!file_exists($file))
    {
        return [];
    }

    return read_json($file);
}

function saveQuestion(
    string $examID,
    string $questionID,
    array $question
): bool
{
    ensure_directory(getQuestionFolder($examID));

    return write_json(
        getQuestionFile($examID, $questionID),
        $question
    );
}

/*
=========================================================
ANSWER ENGINE
=========================================================
*/

function getAnswerFolder(string $examID): string
{
    return ANSWERS_PATH . "/ANSWER-" . $examID;
}

function getAnswerFile(
    string $examID,
    string $studentID
): string
{
    return getAnswerFolder($examID)
        . "/"
        . $studentID
        . ".json";
}

function loadStudentAnswers(
    string $examID,
    string $studentID
): array
{
    $file = getAnswerFile($examID, $studentID);

    if (!file_exists($file))
    {
        return [];
    }

    return read_json($file);
}

function saveStudentAnswers(
    string $examID,
    string $studentID,
    array $answers
): bool
{
    ensure_directory(getAnswerFolder($examID));

    return write_json(
        getAnswerFile($examID, $studentID),
        $answers
    );
}

/*
=========================================================
END OF PART 4
=========================================================
*/
/*
=========================================================
DIRECTORY ENGINE
---------------------------------------------------------
Enterprise Directory Management
=========================================================
*/

/*
---------------------------------------------------------
CREATE DIRECTORY
---------------------------------------------------------
*/

function ensure_directory(string $directory): bool
{
    if (is_dir($directory))
    {
        return true;
    }

    return mkdir($directory, 0777, true);
}

/*
---------------------------------------------------------
DELETE DIRECTORY
---------------------------------------------------------
*/

function deleteDirectory(string $directory): bool
{
    if (!is_dir($directory))
    {
        return false;
    }

    $items = scandir($directory);

    foreach ($items as $item)
    {
        if ($item == "." || $item == "..")
        {
            continue;
        }

        $path = $directory . DIRECTORY_SEPARATOR . $item;

        if (is_dir($path))
        {
            deleteDirectory($path);
        }
        else
        {
            unlink($path);
        }
    }

    return rmdir($directory);
}

/*
---------------------------------------------------------
EMPTY DIRECTORY
---------------------------------------------------------
*/

function emptyDirectory(string $directory): bool
{
    if (!is_dir($directory))
    {
        return false;
    }

    $items = scandir($directory);

    foreach ($items as $item)
    {
        if ($item == "." || $item == "..")
        {
            continue;
        }

        $path = $directory . DIRECTORY_SEPARATOR . $item;

        if (is_dir($path))
        {
            deleteDirectory($path);
        }
        else
        {
            unlink($path);
        }
    }

    return true;
}

/*
---------------------------------------------------------
COPY DIRECTORY
---------------------------------------------------------
*/

function copyDirectory(string $source, string $destination): bool
{
    if (!is_dir($source))
    {
        return false;
    }

    ensure_directory($destination);

    $items = scandir($source);

    foreach ($items as $item)
    {
        if ($item == "." || $item == "..")
        {
            continue;
        }

        $src = $source . DIRECTORY_SEPARATOR . $item;
        $dst = $destination . DIRECTORY_SEPARATOR . $item;

        if (is_dir($src))
        {
            copyDirectory($src, $dst);
        }
        else
        {
            copy($src, $dst);
        }
    }

    return true;
}

/*
---------------------------------------------------------
LIST FILES
---------------------------------------------------------
*/

function listFiles(string $directory): array
{
    if (!is_dir($directory))
    {
        return [];
    }

    return array_values(
        array_filter(
            scandir($directory),
            function($file)
            {
                return $file != "." && $file != "..";
            }
        )
    );
}

/*
---------------------------------------------------------
LIST SUBDIRECTORIES
---------------------------------------------------------
*/

function listDirectories(string $directory): array
{
    if (!is_dir($directory))
    {
        return [];
    }

    $folders = [];

    foreach (scandir($directory) as $item)
    {
        if ($item == "." || $item == "..")
        {
            continue;
        }

        if (is_dir($directory . DIRECTORY_SEPARATOR . $item))
        {
            $folders[] = $item;
        }
    }

    return $folders;
}

/*
=========================================================
END OF DIRECTORY ENGINE
=========================================================
*/
/*
=========================================================
EXAM-GATE ENTERPRISE
---------------------------------------------------------
File:
config/core.php

Version:
3.0.0

Description:
Core Library - Security Engine

Compatible:
JSON Edition

Author:
Zamex Link Limited
=========================================================
*/

/*
=========================================================
SECURITY ENGINE
=========================================================
*/

/*
---------------------------------------------------------
ESCAPE HTML
---------------------------------------------------------
*/

function e($value)
{
    return htmlspecialchars(
        (string)$value,
        ENT_QUOTES,
        "UTF-8"
    );
}

/*
---------------------------------------------------------
CSRF TOKEN
---------------------------------------------------------
*/

function generateCSRFToken()
{
    if (empty($_SESSION["csrf_token"]))
    {
        $_SESSION["csrf_token"] = bin2hex(random_bytes(32));
    }

    return $_SESSION["csrf_token"];
}

function getCSRFToken()
{
    return generateCSRFToken();
}

function verifyCSRFToken($token)
{
    if (!isset($_SESSION["csrf_token"]))
    {
        return false;
    }

    return hash_equals(
        $_SESSION["csrf_token"],
        $token
    );
}

/*
---------------------------------------------------------
REQUEST TYPE
---------------------------------------------------------
*/

function isPost()
{
    return $_SERVER["REQUEST_METHOD"] === "POST";
}

function isGet()
{
    return $_SERVER["REQUEST_METHOD"] === "GET";
}

/*
---------------------------------------------------------
AJAX REQUEST
---------------------------------------------------------
*/

function isAjax()
{
    return
        isset($_SERVER["HTTP_X_REQUESTED_WITH"])
        &&
        strtolower(
            $_SERVER["HTTP_X_REQUESTED_WITH"]
        ) === "xmlhttprequest";
}

/*
---------------------------------------------------------
CLIENT IP
---------------------------------------------------------
*/

function clientIP()
{
    if (!empty($_SERVER["HTTP_CLIENT_IP"]))
    {
        return $_SERVER["HTTP_CLIENT_IP"];
    }

    if (!empty($_SERVER["HTTP_X_FORWARDED_FOR"]))
    {
        return trim(
            explode(
                ",",
                $_SERVER["HTTP_X_FORWARDED_FOR"]
            )[0]
        );
    }

    return $_SERVER["REMOTE_ADDR"] ?? "";
}

/*
---------------------------------------------------------
BROWSER INFORMATION
---------------------------------------------------------
*/

function browserInfo()
{
    return $_SERVER["HTTP_USER_AGENT"] ?? "";
}

/*
---------------------------------------------------------
DEVICE INFORMATION
---------------------------------------------------------
*/

function deviceInformation()
{
    return [
        "device_type"  => getDeviceType(),
        "device_model" => getDeviceModel(),
        "browser"      => browserInfo(),
        "ip_address"   => clientIP()
    ];
}

/*
=========================================================
SESSION ENGINE
=========================================================
*/

function loginUser($username)
{
    $_SESSION["logged_in"] = true;

    $_SESSION["username"] = $username;

    $_SESSION["login_time"] = time();

    $_SESSION["session_token"] =
        generate_session_token();
}

function logoutUser()
{
    $_SESSION = [];

    if (session_status() === PHP_SESSION_ACTIVE)
    {
        session_destroy();
    }
}

function currentUser()
{
    return $_SESSION["username"] ?? "";
}

/*
=========================================================
END OF PART 6
=========================================================
*/
/*
=========================================================
EXAM-GATE ENTERPRISE
---------------------------------------------------------
File:
config/core.php

Version:
3.0.0

Description:
Core Library - Response Engine & Framework Initialization

Compatible:
JSON Edition

Author:
Zamex Link Limited
=========================================================
*/

/*
=========================================================
RESPONSE ENGINE
=========================================================
*/

function jsonResponse(array $data, int $statusCode = 200)
{
    http_response_code($statusCode);

    header("Content-Type: application/json; charset=UTF-8");

    echo json_encode(
        $data,
        JSON_PRETTY_PRINT |
        JSON_UNESCAPED_UNICODE
    );

    exit;
}

function successResponse($message, array $extra = [])
{
    jsonResponse(array_merge([
        "success" => true,
        "message" => $message
    ], $extra));
}

function errorResponse($message, int $statusCode = 400)
{
    jsonResponse([
        "success" => false,
        "message" => $message
    ], $statusCode);
}

/*
=========================================================
FRAMEWORK INFORMATION
=========================================================
*/

function appName()
{
    return APP_NAME;
}

function appVersion()
{
    return APP_VERSION;
}

function systemTimezone()
{
    return date_default_timezone_get();
}

/*
=========================================================
SYSTEM HEALTH CHECK
=========================================================
*/

function systemHealth(): array
{
    return [

        "application" => APP_NAME,

        "version" => APP_VERSION,

        "php_version" => PHP_VERSION,

        "timezone" => date_default_timezone_get(),

        "json_extension" => extension_loaded("json"),

        "session_status" => session_status(),

        "data_directory" => is_dir(DATA_PATH),

        "exam_directory" => is_dir(EXAMS_PATH),

        "answer_directory" => is_dir(ANSWERS_PATH),

        "backup_directory" => is_dir(BACKUP_PATH),

        "log_directory" => is_dir(LOG_PATH)

    ];
}

/*
=========================================================
ERROR HANDLER
=========================================================
*/

set_error_handler(function(
    $severity,
    $message,
    $file,
    $line
)
{
    writeErrorLog(
        $message,
        [
            "file" => $file,
            "line" => $line,
            "severity" => $severity
        ]
    );

    return false;
});

/*
=========================================================
SHUTDOWN HANDLER
=========================================================
*/

register_shutdown_function(function()
{
    $error = error_get_last();

    if(
        $error &&
        in_array(
            $error["type"],
            [
                E_ERROR,
                E_PARSE,
                E_CORE_ERROR,
                E_COMPILE_ERROR
            ]
        )
    )
    {
        writeErrorLog(
            $error["message"],
            [
                "file" => $error["file"],
                "line" => $error["line"]
            ]
        );
    }
});

/*
=========================================================
FRAMEWORK INITIALIZATION
=========================================================
*/

ensure_directory(DATA_PATH);
ensure_directory(EXAMS_PATH);
ensure_directory(ANSWERS_PATH);
ensure_directory(BACKUP_PATH);
ensure_directory(TEMP_PATH);
ensure_directory(LOG_PATH);

if (!file_exists(SYSTEM_LOG))
{
    write_json(SYSTEM_LOG, []);
}

if (defined("AUDIT_LOG") && !file_exists(AUDIT_LOG))
{
    write_json(AUDIT_LOG, []);
}

if (defined("ERROR_LOG") && !file_exists(ERROR_LOG))
{
    write_json(ERROR_LOG, []);
}

/*
=========================================================
END OF FILE
=========================================================
*/