<?php
/**
 * request_new_otp.php — Resend OTP during the 2-factor login flow
 *
 * Called by: login page AJAX "Resend OTP" button on the OTP input screen.
 * Input:     All data sourced from $_SESSION (written by login_otp.php).
 *            No new user input is accepted — credentials are re-read from session
 *            to avoid re-exposing the password in a second HTTP request.
 *
 * This endpoint regenerates a fresh TOTP and resends the OTP email without
 * requiring the user to re-enter their username and password.  It is only
 * reachable after login_otp.php has successfully validated credentials and
 * written the login session state.
 *
 * Full flow:
 *   1. Reload username, password, and user_id from session.
 *   2. Fetch the full user row (need the password hash to regenerate OTP
 *      and the email address to resend to).
 *   3. Re-verify the stored password against the session-stored hash.
 *      This is a safety re-check — the session could theoretically have been
 *      tampered with between login_otp.php and this call.
 *   4. On password mismatch → clear cookies, return "Incorrect Password".
 *   5. On success:
 *        a. Generate a fresh 6-digit TOTP (new timestamp → new OTP).
 *        b. Generate a new 6-letter reference number.
 *        c. Send the OTP email via system SMTP ($SMTP from config.php).
 *           Note: uses system-level SMTP unconditionally (unlike login_otp.php
 *           which tries the company SMTP first). The if(true) wrapper is a
 *           placeholder left from the original — email always sends.
 *        d. Clear session and repopulate with new OTP state.
 *   6. Return { success: 1, message: "Login Complete!" }.
 *
 * Session keys read:
 *   login_data['username'], login_data['password'], login_user_id
 *
 * Session keys overwritten:
 *   login_data, otp, otpTime, reference, user_email, login_user_id
 *   (same keys as login_otp.php — login_confirm.php reads the same structure)
 *
 * Response JSON:
 *   On success:  { "success": 1, "message": "Login Complete!" }
 *   On failure:  { "message": "Incorrect Password" }
 */

require_once '../../../session.php';
require_once '../../../config.php';
require_once '../../../preset.php';
define('UNAUTHENTICATED_ROUTE', true);
require_once '../../../assets/utils/db_auth.php';

// ── Step 1: Reload credentials from session ───────────────────────────────────
// These were stored by login_otp.php so the user doesn't have to retype them.
$data["username"] = $_SESSION["login_data"]['username'];
$data["password"] = $_SESSION["login_data"]['password'];
$user_id          = (int)$_SESSION["login_user_id"];

// ── Step 2: Fetch user record ─────────────────────────────────────────────────
$sth = $pdo1->prepare("select * from user where user_id = :user_id limit 1;");
$sth->execute([":user_id" => $user_id]);
$temp = $sth->fetch(PDO::FETCH_ASSOC);

$user_email = $temp["email"];

// ── Step 3–4: Re-verify password ─────────────────────────────────────────────
// Safety check — ensures the session hasn't been tampered with between
// login_otp.php and this resend call.
if (password_verify(trim($data["password"]), $temp["password"])) {

    // ── Step 5a: Generate fresh 6-digit TOTP ──────────────────────────────────
    // Same HMAC-SHA1 algorithm as login_otp.php and login_confirm.php.
    // A new $otpTime is captured so the OTP window resets from this moment.
    function generateOTP($sercet_key, $time_step = 180, $length = 6) {

        global $otpTime;

        $otpTime = time(); // new timestamp — extends the 5-minute validity window

        $counter = floor($otpTime / $time_step);
        $data    = pack("NN", 0, $counter);
        $hash    = hash_hmac('sha1', $data, $sercet_key, true);
        $offset  = ord(substr($hash, -1)) & 0x0F;
        $value   = unpack("N", substr($hash, $offset, 4));
        $otp     = ($value[1] & 0x7FFFFFFF) % pow(10, $length);

        return str_pad(strval($otp), $length, '0', STR_PAD_LEFT);
    }

    // ── Step 5b: Generate 6-letter reference number ───────────────────────────
    // Converts a second TOTP (derived from the first OTP as the key) to a
    // base-26 uppercase letter string shown on the OTP input screen.
    function numberToLetters($num) {
        $result = '';
        while ($num > 0) {
            $mod    = ($num - 1) % 26;
            $result = chr(65 + $mod) . $result;
            $num    = intval(($num - $mod) / 26);
        }
        return str_pad($result, 6, 'A', STR_PAD_LEFT);
    }

    $otp              = generateOTP($temp["password"]);
    $reference_number = numberToLetters(generateOTP($otp));

    // ── Step 5c: Send OTP email ───────────────────────────────────────────────
    // Uses the system-level $SMTP config from config.php.
    // The if(true) wrapper is a no-op placeholder from the original code —
    // the email block always executes.
    require "../../../assets/utils/module/mailer.php";

    if (true) {

        $mailer = new mailer(["pdo1" => $pdo1]);

        $mailer->send_email([
            "company_id"   => 0,
            "smtp"         => $SMTP,
            "subject"      => "One Time Password (OTP) For reference number " . $reference_number,
            "message"      => implode("\n", [
                "Dear WMS user,",
                "",
                "You requested a One-Time Password (OTP) to log in to WMS.",
                "",
                "Please use the OTP below to complete your request:",
                "• OTP code: " . $otp,
                "• Reference number: " . $reference_number,
                "",
                "Please note:",
                "• This code will expire in 3 minutes. Please complete your action promptly.",
                "• Do not share this code with anyone to keep your account secure.",
                "• If you did not request this code, please ignore this email.",
            ]),
            "channel_name" => "WMS LOGIN OTP ",
            "to"           => $user_email,
            "key"          => $pinkey,
        ]);
    }

    // ── Step 5d: Reset session with new OTP state ─────────────────────────────
    // Full session is cleared before repopulating to avoid stale state
    // from the previous OTP attempt leaking into this one.
    $_SESSION = [];

    $_SESSION["login_data"]    = $data;
    $_SESSION["otp"]           = $otp;
    $_SESSION["otpTime"]       = $otpTime;     // new timestamp — login_confirm.php uses this
    $_SESSION["reference"]     = $reference_number;
    $_SESSION["user_email"]    = $user_email;
    $_SESSION["login_user_id"] = $user_id;

    // ── Step 6: Respond ───────────────────────────────────────────────────────
    $answer["success"] = 1;
    $answer["message"] = "Login Complete!";
    exit(json_encode($answer));

} else {

    // ── Password mismatch — clear cookies and reject ──────────────────────────
    $answer["message"] = "Incorrect Password";
    setcookie("u",  "", time() - 1, "/");
    setcookie("h1", "", time() - 1, "/");
    setcookie("h2", "", time() - 1, "/");
    exit(json_encode($answer));
}

$answer["success"] = 1;
exit(json_encode($answer));