import type { AIModel, Usage } from "./types";

/** Estimated cost in USD from verified list prices; null when the model has no verified price. */
export function estimateCost(model: Pick<AIModel, "pricing">, usage: Usage): number | null {
  const p = model.pricing;
  if (!p || p.input == null || p.output == null) return null;
  const cached = usage.cached ?? 0;
  const fresh = Math.max(0, usage.input - cached);
  return (fresh * p.input + cached * (p.cachedInput ?? p.input) + usage.output * p.output) / 1e6;
}

export function blendedPrice(model: Pick<AIModel, "pricing">): number | null {
  const p = model.pricing;
  if (!p || p.input == null || p.output == null) return null;
  return (3 * p.input + p.output) / 4;
}

export function fmtUsd(v: number | null | undefined, digits = 4): string {
  if (v == null) return "—";
  if (v === 0) return "$0";
  if (v < 0.01) return `$${v.toFixed(digits)}`;
  return `$${v.toFixed(2)}`;
}