timmy-tower/artifacts/api-server/src/lib/pricing.ts

import { getBtcPriceUsd, usdToSats } from "./btc-oracle.js";

// ── Env-var helpers ────────────────────────────────────────────────────────────

function envFloat(name: string, fallback: number): number {
  const raw = parseFloat(process.env[name] ?? "");
  return Number.isFinite(raw) && raw > 0 ? raw : fallback;
}

function envInt(name: string, fallback: number): number {
  const raw = parseInt(process.env[name] ?? "", 10);
  return Number.isFinite(raw) && raw > 0 ? raw : fallback;
}

// ── Model rate tables ──────────────────────────────────────────────────────────

export interface ModelRates {
  inputPer1kUsd: number;
  outputPer1kUsd: number;
}

/**
 * Anthropic model rates (USD per 1 000 tokens).
 * Defaults approximate claude-haiku-4-x / claude-sonnet-4-x pricing.
 * Override via env vars.
 */
const HAIKU_RATES: ModelRates = {
  inputPer1kUsd: envFloat("HAIKU_INPUT_COST_PER_1K_TOKENS", 0.0008),
  outputPer1kUsd: envFloat("HAIKU_OUTPUT_COST_PER_1K_TOKENS", 0.004),
};

const SONNET_RATES: ModelRates = {
  inputPer1kUsd: envFloat("SONNET_INPUT_COST_PER_1K_TOKENS", 0.003),
  outputPer1kUsd: envFloat("SONNET_OUTPUT_COST_PER_1K_TOKENS", 0.015),
};

function ratesForModel(modelId: string): ModelRates {
  const id = modelId.toLowerCase();
  if (id.includes("haiku")) return HAIKU_RATES;
  if (id.includes("sonnet")) return SONNET_RATES;
  return SONNET_RATES; // conservative fallback
}

// ── Output token estimates by request length tier ─────────────────────────────

const OUTPUT_EST_SHORT = envInt("OUTPUT_TOKENS_SHORT_EST", 200);
const OUTPUT_EST_MEDIUM = envInt("OUTPUT_TOKENS_MEDIUM_EST", 400);
const OUTPUT_EST_LONG = envInt("OUTPUT_TOKENS_LONG_EST", 800);
const SHORT_MAX_CHARS = envInt("SHORT_MAX_CHARS", 100);
const MEDIUM_MAX_CHARS = envInt("MEDIUM_MAX_CHARS", 300);

// Approximate tokens in the work system prompt (for input token estimation).
const WORK_SYSTEM_PROMPT_TOKENS = envInt("WORK_SYSTEM_PROMPT_TOKENS_EST", 50);

// ── DO infra amortisation ─────────────────────────────────────────────────────

const DO_MONTHLY_COST_USD = envFloat("DO_MONTHLY_COST_USD", 100);
const DO_MONTHLY_REQUESTS = envInt("DO_MONTHLY_REQUEST_VOLUME", 1000);
const DO_INFRA_PER_REQUEST_USD = DO_MONTHLY_COST_USD / DO_MONTHLY_REQUESTS;

// ── Originator margin ──────────────────────────────────────────────────────────

const ORIGINATOR_MARGIN_PCT = envFloat("ORIGINATOR_MARGIN_PCT", 25);

// ── Fixed fees ────────────────────────────────────────────────────────────────

const EVAL_FEE_SATS = envInt("EVAL_FEE_SATS", 10);

const BOOTSTRAP_FEE_SATS = (() => {
  const raw = parseInt(process.env.BOOTSTRAP_FEE_SATS ?? "", 10);
  return Number.isFinite(raw) && raw > 0 ? raw : 10_000;
})();

// ── Public types ──────────────────────────────────────────────────────────────

export interface WorkFeeBreakdown {
  amountSats: number;
  estimatedCostUsd: number;
  marginPct: number;
  btcPriceUsd: number;
}

// ── PricingService ────────────────────────────────────────────────────────────

export class PricingService {
  readonly marginPct = ORIGINATOR_MARGIN_PCT;

  // ── Fixed fees (unchanged from v1) ───────────────────────────────────────

  calculateEvalFeeSats(): number {
    return EVAL_FEE_SATS;
  }

  calculateBootstrapFeeSats(): number {
    return BOOTSTRAP_FEE_SATS;
  }

  // ── Token estimation ─────────────────────────────────────────────────────

  /**
   * Estimate input tokens for a work request.
   * Uses chars/4 rule for the user message plus a fixed system-prompt overhead.
   */
  estimateInputTokens(requestText: string): number {
    return Math.ceil(requestText.length / 4) + WORK_SYSTEM_PROMPT_TOKENS;
  }

  /**
   * Estimate output tokens based on request length tier.
   */
  estimateOutputTokens(requestText: string): number {
    const len = requestText.trim().length;
    if (len <= SHORT_MAX_CHARS) return OUTPUT_EST_SHORT;
    if (len <= MEDIUM_MAX_CHARS) return OUTPUT_EST_MEDIUM;
    return OUTPUT_EST_LONG;
  }

  // ── Cost calculation (pure, no oracle) ──────────────────────────────────

  /**
   * Calculate the total USD cost for a set of token counts + model.
   * Includes DO infra amortisation and originator margin.
   */
  calculateWorkFeeUsd(inputTokens: number, outputTokens: number, modelId: string): number {
    const rates = ratesForModel(modelId);
    const tokenCostUsd =
      (inputTokens / 1000) * rates.inputPer1kUsd +
      (outputTokens / 1000) * rates.outputPer1kUsd;
    const rawCostUsd = tokenCostUsd + DO_INFRA_PER_REQUEST_USD;
    return rawCostUsd * (1 + this.marginPct / 100);
  }

  /**
   * Calculate actual token cost (no infra, no margin — raw Anthropic spend).
   * Used for the post-work cost ledger.
   */
  calculateActualCostUsd(inputTokens: number, outputTokens: number, modelId: string): number {
    const rates = ratesForModel(modelId);
    return (
      (inputTokens / 1000) * rates.inputPer1kUsd +
      (outputTokens / 1000) * rates.outputPer1kUsd
    );
  }

  // ── Invoice amount (calls oracle) ────────────────────────────────────────

  /**
   * Fetch BTC price, convert USD cost to sats, and return the full breakdown.
   * This is the main entry point for generating a work invoice amount.
   */
  async calculateWorkFeeSats(
    inputTokens: number,
    outputTokens: number,
    modelId: string,
  ): Promise<WorkFeeBreakdown> {
    const estimatedCostUsd = this.calculateWorkFeeUsd(inputTokens, outputTokens, modelId);
    const btcPriceUsd = await getBtcPriceUsd();
    const amountSats = usdToSats(estimatedCostUsd, btcPriceUsd);
    return { amountSats, estimatedCostUsd, marginPct: this.marginPct, btcPriceUsd };
  }

  /**
   * Combined estimate: input tokens + output tokens + work fee USD for a given request.
   * Single call-site for pre-gate cost estimation — replaces duplicated logic in routes.
   */
  estimateRequestCost(
    requestText: string,
    modelId: string,
  ): { estimatedInputTokens: number; estimatedOutputTokens: number; estimatedCostUsd: number } {
    const estimatedInputTokens = this.estimateInputTokens(requestText);
    const estimatedOutputTokens = this.estimateOutputTokens(requestText);
    const estimatedCostUsd = this.calculateWorkFeeUsd(estimatedInputTokens, estimatedOutputTokens, modelId);
    return { estimatedInputTokens, estimatedOutputTokens, estimatedCostUsd };
  }

  // ── Post-work honest accounting ──────────────────────────────────────────

  /**
   * Full actual charge in USD: raw Anthropic token cost + DO infra amortisation + margin.
   * Pass in the already-computed actualCostUsd (raw token cost, no extras).
   */
  calculateActualChargeUsd(actualCostUsd: number): number {
    const rawCostUsd = actualCostUsd + DO_INFRA_PER_REQUEST_USD;
    return rawCostUsd * (1 + this.marginPct / 100);
  }

  /**
   * Convert the actual charge to satoshis using the BTC price that was locked
   * at invoice-creation time. This keeps pre- and post-work accounting in the
   * same BTC denomination without a second oracle call.
   */
  calculateActualChargeSats(actualCostUsd: number, lockedBtcPriceUsd: number): number {
    const chargeUsd = this.calculateActualChargeUsd(actualCostUsd);
    return usdToSats(chargeUsd, lockedBtcPriceUsd);
  }

  /**
   * Refund amount in sats: what was overpaid by the user.
   * Always >= 0 (clamped — never ask the user to top up due to BTC price swings).
   */
  calculateRefundSats(workAmountSats: number, actualAmountSats: number): number {
    return Math.max(0, workAmountSats - actualAmountSats);
  }
}

export const pricingService = new PricingService();