previewCloseTrade

// Full close
const p = await client.previewCloseTrade({ pairId: 0, idx: 0 });

// Half the position
const half = await client.previewCloseTrade({ pairId: 0, idx: 0, closePercent: 50 });

console.log(half.exitPx);      // after spread — closing takes the other side of the book
console.log(half.rollover);    // settled in proportion to the share being closed
console.log(half.received);    // collateral released + net PnL

interface PreviewCloseTradeResult {
  pairId: string;
  pairFrom: string;
  pairTo: string;
  idx: number;
  isLong: boolean;
  closePercent: string;
  midPx: string;
  exitPx: string;             // expected execution price, after dynamic spread
  priceImpactP: string;       // differs from the open-side figure: closing takes the other side
  sizeClosing: string;        // in base-asset units
  collateralClosing: string;  // collateral being released, in USDC
  leverage: string;
  grossPnl: string;           // PnL at the exit price, before rollover
  spreadCost: string;         // PnL at exit minus PnL at mid — usually negative
  rollover: string;           // settled by this close; positive means the trader pays
  funding: string;            // always "0" — funding is excluded throughout the SDK
  oracleFee: string;          // flat deposit the wallet must hold; refunded on execution
  netPnl: string;             // grossPnl after rollover
  netPnlPercent: string;      // as a percentage of the collateral being closed
  received: string;           // collateral released + net PnL
  isFullClose: boolean;
  warnings: Array<{ code: string; message: string }>;
}