<?php
require_once __DIR__ . '/../helpers.php';
runAuth();

try {
    $data = readJsonBody();
    $tabID = (int) ($data['TabID'] ?? 0);
    $ownerUserID = (int) ($data['OwnerUserID'] ?? 0);
    $targetUserID = (int) ($data['TargetUserID'] ?? 0);

    if ($tabID === 0) apiAbort(['OK' => false, 'ERROR' => 'missing_TabID']);
    if ($ownerUserID === 0) apiAbort(['OK' => false, 'ERROR' => 'missing_OwnerUserID']);
    if ($targetUserID === 0) apiAbort(['OK' => false, 'ERROR' => 'missing_TargetUserID']);

    $qTab = queryOne("
        SELECT t.ID, t.OwnerUserID, t.StatusID, t.BusinessID, b.TabMaxMembers
        FROM Tabs t JOIN Businesses b ON b.ID = t.BusinessID
        WHERE t.ID = ? LIMIT 1
    ", [$tabID]);

    if (!$qTab) apiAbort(['OK' => false, 'ERROR' => 'tab_not_found']);
    if ((int) $qTab['StatusID'] !== 1) apiAbort(['OK' => false, 'ERROR' => 'tab_not_open']);
    if ((int) $qTab['OwnerUserID'] !== $ownerUserID) apiAbort(['OK' => false, 'ERROR' => 'not_owner']);

    // Check member limit
    $qCount = queryOne("SELECT COUNT(*) AS Cnt FROM TabMembers WHERE TabID = ? AND StatusID = 1", [$tabID]);
    if ((int) $qCount['Cnt'] >= (int) ($qTab['TabMaxMembers'] ?? 0)) {
        apiAbort(['OK' => false, 'ERROR' => 'max_members', 'MESSAGE' => 'Tab has reached the maximum number of members.']);
    }

    // Check target not already on any tab
    $qExisting = queryOne("
        SELECT t.ID, b.Name AS BusinessName
        FROM TabMembers tm JOIN Tabs t ON t.ID = tm.TabID JOIN Businesses b ON b.ID = t.BusinessID
        WHERE tm.UserID = ? AND tm.StatusID = 1 AND t.StatusID = 1 LIMIT 1
    ", [$targetUserID]);
    if ($qExisting) apiAbort(['OK' => false, 'ERROR' => 'user_already_on_tab', 'MESSAGE' => 'This user is already on a tab.']);

    // Check target user exists
    $qTarget = queryOne("SELECT FirstName, LastName FROM Users WHERE ID = ? LIMIT 1", [$targetUserID]);
    if (!$qTarget) apiAbort(['OK' => false, 'ERROR' => 'user_not_found']);

    queryTimed("
        INSERT INTO TabMembers (TabID, UserID, RoleID, StatusID, JoinedOn)
        VALUES (?, ?, 2, 1, NOW())
        ON DUPLICATE KEY UPDATE StatusID = 1, LeftOn = NULL, JoinedOn = NOW()
    ", [$tabID, $targetUserID]);

    jsonResponse([
        'OK' => true,
        'MEMBER' => [
            'UserID' => $targetUserID,
            'FirstName' => $qTarget['FirstName'],
            'LastName' => $qTarget['LastName'],
            'RoleID' => 2,
        ],
    ]);

} catch (Exception $e) {
    jsonResponse(['OK' => false, 'ERROR' => 'server_error', 'MESSAGE' => $e->getMessage()]);
}