/**
 * Cost tracking.
 *
 * MiniMax doesn't expose an OpenRouter-style `/generation` endpoint for
 * authoritative cost lookup, so we compute cost locally from token
 * counts using the user-configured price per 1M tokens. Pricing is
 * intentionally user-overridable so the same package works as MiniMax
 * revises their rates.
 */
import type { CostSummary, Usage } from "./types.js";

export function computeCost(
  usage: Usage,
  priceInputPer1M: number,
  priceOutputPer1M: number,
): CostSummary {
  const inputUsd = (usage.inputTokens / 1_000_000) * priceInputPer1M;
  const outputUsd = (usage.outputTokens / 1_000_000) * priceOutputPer1M;
  return {
    inputUsd,
    outputUsd,
    totalUsd: round4(inputUsd + outputUsd),
  };
}

export function aggregateUsage(usages: Usage[]): Usage {
  const out: Usage = { inputTokens: 0, outputTokens: 0 };
  for (const u of usages) {
    out.inputTokens += u.inputTokens;
    out.outputTokens += u.outputTokens;
    if (u.cachedInputTokens) out.cachedInputTokens = (out.cachedInputTokens ?? 0) + u.cachedInputTokens;
  }
  out.totalTokens = out.inputTokens + out.outputTokens;
  return out;
}

export function aggregateCost(summaries: CostSummary[]): CostSummary {
  return summaries.reduce(
    (acc, s) => ({
      inputUsd: acc.inputUsd + s.inputUsd,
      outputUsd: acc.outputUsd + s.outputUsd,
      totalUsd: round4(acc.totalUsd + s.totalUsd),
    }),
    { inputUsd: 0, outputUsd: 0, totalUsd: 0 },
  );
}

function round4(n: number): number {
  return Math.round(n * 10_000) / 10_000;
}