Function canAddSeat

server/src/db/organization-db.ts:422–484

(
  orgId: string,
  seatType: SeatType
)

 * and counts pending invitations as reserved seats.
 */
export async function canAddSeat(
  orgId: string,
  seatType: SeatType
): Promise<{ allowed: boolean; reason?: string }> {
  const pool = getPool();
  const client = await pool.connect();
  try {
    await client.query('BEGIN');

    // Lock the org row to serialize concurrent seat checks and resolve
    // the tier from the same (locked) read.
    const tier = await readMembershipTierFromClient(client, orgId, { forUpdate: true });
    const limits = getSeatLimits(tier);

    // Count active members (contributor = admin-assigned OR Slack-mapped OR in working group)
    const memberResult = await client.query<{ total: string; contributor: string }>(
      `SELECT
         COUNT(*) as total,
         COUNT(*) FILTER (WHERE
           om.seat_type = 'contributor'
           OR EXISTS (SELECT 1 FROM slack_user_mappings sm WHERE sm.workos_user_id = om.workos_user_id AND sm.mapping_status = 'mapped')
           OR EXISTS (SELECT 1 FROM working_group_memberships wgm WHERE wgm.workos_user_id = om.workos_user_id AND wgm.status = 'active')
         ) as contributor
       FROM organization_memberships om
       WHERE om.workos_organization_id = $1`,
      [orgId]
    );
    const total = parseInt(memberResult.rows[0]?.total ?? '0', 10);
    const contributors = parseInt(memberResult.rows[0]?.contributor ?? '0', 10);

    // Pending invitations also reserve seats
    const pendingResult = await client.query<{ seat_type: string; count: string }>(
      `SELECT seat_type, COUNT(*) as count FROM invitation_seat_types WHERE workos_organization_id = $1 GROUP BY seat_type`,
      [orgId]
    );
    let pendingContributors = 0;
    let pendingCommunity = 0;
    for (const row of pendingResult.rows) {
      if (row.seat_type === 'contributor') pendingContributors = parseInt(row.count, 10);
      if (row.seat_type === 'community_only') pendingCommunity = parseInt(row.count, 10);
    }

    const usage = {
      contributor: contributors + pendingContributors,
      community_only: (total - contributors) + pendingCommunity,
    };

    await client.query('COMMIT');

    const limit = seatType === 'contributor' ? limits.contributor : limits.community;
    const used = seatType === 'contributor' ? usage.contributor : usage.community_only;

    if (limit === -1) return { allowed: true };
    if (limit === 0) return { allowed: false, reason: `Your membership tier does not include ${seatType === 'contributor' ? 'contributor' : 'community'} seats. Upgrade at /membership.` };
    if (used >= limit) return { allowed: false, reason: `All ${limit} ${seatType === 'contributor' ? 'contributor' : 'community'} seats are in use. Upgrade at /membership to add more.` };
    return { allowed: true };
  } catch (error) {
    await client.query('ROLLBACK');