<?php
/**
 * invited_onboarding.php — Complete account setup for an invited user.
 *
 * Called by: invited_onboarding.php page AJAX after the user fills in
 *            their name, username, and password.
 *
 * The invited user was created with license='user', status='pending', and
 * default_company = the inviting company. This endpoint activates the account
 * so they can log in using the inviting company's SMTP for OTP delivery.
 *
 * Full flow:
 *   1. Session guard — rejects if 'invited_user_id' is missing.
 *   2. CSRF check.
 *   3. Validate and sanitise input fields (before acquiring DB locks).
 *   4. Username format check.
 *   5. Password match and strength check.
 *   6. Hash password.
 *   7. BEGIN TRANSACTION — SELECT FOR UPDATE to atomically re-validate token
 *      (expiry + status='pending' + license='user').
 *   8. UPDATE user: name, surname, username, password, status='active',
 *      verify_token=NULL, verify_expires_at=NULL. Catches SQLSTATE 23000
 *      (duplicate username). Checks rowCount()=1.
 *   9. UPDATE company_map_user: invite_token=NULL, invite_expires_at=NULL.
 *   10. COMMIT. Return { success: 1 }.
 */

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

header('Content-Type: application/json; charset=utf-8');

$answer = ['success' => 0, 'message' => ''];

// ── Step 1: Session guard ─────────────────────────────────────────────────────
if (empty($_SESSION['invited_user_id']) || empty($_SESSION['invited_token'])) {
    $answer['message'] = 'Invalid session. Please use your invitation link.';
    http_response_code(403);
    exit(json_encode($answer));
}

$user_id = (int)$_SESSION['invited_user_id'];
$token   = $_SESSION['invited_token'];

// ── Step 2: CSRF check ────────────────────────────────────────────────────────
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $csrf = $_SERVER['HTTP_X_CSRF_TOKEN'] ?? '';
    if (empty($csrf) || !hash_equals((string)($_SESSION['csrf_token'] ?? ''), $csrf)) {
        http_response_code(403);
        $answer['message'] = 'Invalid request.';
        exit(json_encode($answer));
    }
}

$data = json_decode($_POST['json'] ?? '{}', true) ?: [];

try {

    // ── Step 4: Sanitise and validate input ───────────────────────────────────
    // Done before the transaction so validation errors don't acquire DB locks.
    $name     = trim($data['name']                ?? '');
    $surname  = trim($data['surname']             ?? '');
    $username = strtolower(trim($data['username'] ?? ''));
    $password = $data['password']                 ?? '';
    $confirm  = $data['confirm_password']         ?? '';

    if (!$name || !$surname || !$username || !$password || !$confirm) {
        throw new Exception('All fields are required.');
    }

    // ── Step 5: Username format, length, and reserved names ──────────────────
    if (!preg_match('/^[a-z0-9_]{3,32}$/', $username)) {
        throw new Exception('Username must be 3–32 characters and may only contain lowercase letters, numbers and underscores.');
    }

    $reserved = ['admin', 'owner', 'support', 'root', 'system', 'superuser', 'administrator'];
    if (in_array($username, $reserved, true)) {
        throw new Exception('That username is reserved. Please choose another.');
    }

    // ── Step 6: Password match and strength ───────────────────────────────────
    if ($password !== $confirm) {
        throw new Exception('Passwords do not match.');
    }

    $pm     = new PasswordManager($pdo1, $include_url);
    $result = $pm->checkStrength($password, [$name, $surname, $username]);
    if ($result['score'] < PasswordManager::MIN_SCORE) {
        $msg = $result['warning'] ?: ($result['suggestions'][0] ?? 'Please choose a stronger password.');
        throw new Exception('Password is too weak. ' . $msg);
    }

    $hashed = password_hash($password, PASSWORD_BCRYPT);

    // ── Steps 3 + 7–9: Atomic token re-validation and activation ─────────────
    // SELECT FOR UPDATE locks the row so a concurrent resendInvite or removeUser
    // cannot mutate the token between our check and the UPDATE.
    $pdo1->beginTransaction();

    $sth = $pdo1->prepare(
        "SELECT user_id FROM user
         WHERE user_id          = :uid
           AND verify_token     = :token
           AND status           = 'pending'
           AND license          = 'user'
           AND verify_expires_at > NOW()
         LIMIT 1
         FOR UPDATE"
    );
    $sth->execute([':uid' => $user_id, ':token' => $token]);
    if (!$sth->fetchColumn()) {
        $pdo1->rollBack();
        $answer['message'] = 'Invitation has expired or already been used. Please request a new invitation.';
        http_response_code(403);
        exit(json_encode($answer));
    }

    // ── Step 7–8: Activate account ────────────────────────────────────────────
    $stmt = $pdo1->prepare(
        "UPDATE user
         SET name              = :name,
             surname           = :surname,
             username          = :username,
             password          = :password,
             status            = 'active',
             verify_token      = NULL,
             verify_expires_at = NULL
         WHERE user_id = :uid"
    );

    try {
        $stmt->execute([
            ':name'     => $name,
            ':surname'  => $surname,
            ':username' => $username,
            ':password' => $hashed,
            ':uid'      => $user_id,
        ]);
    } catch (PDOException $e) {
        $pdo1->rollBack();
        // SQLSTATE 23000 = unique constraint violation (duplicate username)
        if ($e->getCode() === '23000') {
            throw new Exception('Username is already taken. Please choose another.');
        }
        throw $e;
    }

    if ($stmt->rowCount() !== 1) {
        $pdo1->rollBack();
        $answer['message'] = 'Invitation is no longer valid.';
        http_response_code(403);
        exit(json_encode($answer));
    }

    // ── Step 9: Clear invite token from company_map_user ─────────────────────
    $pdo1->prepare(
        "UPDATE company_map_user
         SET invite_token = NULL, invite_expires_at = NULL
         WHERE user_id = :uid"
    )->execute([':uid' => $user_id]);

    $pdo1->commit();

    // ── Step 10: Clear session invite keys ────────────────────────────────────
    unset($_SESSION['invited_user_id'], $_SESSION['invited_token']);

    $answer['success'] = 1;
    $answer['message'] = 'Account setup complete.';

} catch (Exception $e) {
    if ($pdo1->inTransaction()) $pdo1->rollBack();
    $answer['message'] = $e->getMessage();
    http_response_code(400);
}

exit(json_encode($answer));