// Profit calculation. Single source of truth for every surface.
// Open Question 1: the workbook computes profit as income - fixed (no running cost).
// The app currently includes running cost. Default matches the workbook; flip the
// flag here to include running cost everywhere in the app at once.
export type ProfitInput = {
  income: number;
  fixed: number;
  running: number;
};
export type ProfitOptions = { includeRunningCost?: boolean };

export function computeProfit(p: ProfitInput, opts: ProfitOptions = {}): number {
  const { income, fixed, running } = p;
  // Q1: default false = match workbook formula `= SUM(income - fixed)`
  const include = opts.includeRunningCost ?? false;
  return include ? income - fixed - running : income - fixed;
}