export function loadBillingConfig() {
  const useBackendCost = process.env.H5_USE_BACKEND_COST !== '0';
  return {
    useBackendCost,
    usdCnyRate: Number(process.env.H5_USD_CNY_RATE ?? 7.2),
    inputCentsPer1k: Number(process.env.H5_BILL_INPUT_CENTS_PER_1K ?? 2),
    outputCentsPer1k: Number(process.env.H5_BILL_OUTPUT_CENTS_PER_1K ?? 6),
    minBillCents: Number(process.env.H5_MIN_BILL_CENTS ?? 1),
  };
}

export function normalizeTokenState(raw) {
  if (!raw || typeof raw !== 'object') {
    return {
      inputTokens: 0,
      outputTokens: 0,
      totalTokens: 0,
      accumulatedInputTokens: 0,
      accumulatedOutputTokens: 0,
      accumulatedTotalTokens: 0,
      accumulatedCost: null,
    };
  }
  return {
    inputTokens: Number(raw.inputTokens ?? raw.input_tokens ?? 0),
    outputTokens: Number(raw.outputTokens ?? raw.output_tokens ?? 0),
    totalTokens: Number(raw.totalTokens ?? raw.total_tokens ?? 0),
    accumulatedInputTokens: Number(
      raw.accumulatedInputTokens ?? raw.accumulated_input_tokens ?? raw.inputTokens ?? 0,
    ),
    accumulatedOutputTokens: Number(
      raw.accumulatedOutputTokens ?? raw.accumulated_output_tokens ?? raw.outputTokens ?? 0,
    ),
    accumulatedTotalTokens: Number(
      raw.accumulatedTotalTokens ?? raw.accumulated_total_tokens ?? raw.totalTokens ?? 0,
    ),
    accumulatedCost:
      raw.accumulatedCost ?? raw.accumulated_cost ?? null,
  };
}

export function computeDeltaCostCents(previous, current, config = loadBillingConfig()) {
  const prevCost =
    previous?.lastAccumulatedCost == null ? null : Number(previous.lastAccumulatedCost);
  const currCost =
    current.accumulatedCost == null ? null : Number(current.accumulatedCost);

  if (config.useBackendCost && prevCost != null && currCost != null && currCost >= prevCost) {
    const deltaUsd = currCost - prevCost;
    return Math.max(config.minBillCents, Math.ceil(deltaUsd * config.usdCnyRate * 100));
  }
  if (config.useBackendCost && prevCost == null && currCost != null && currCost > 0) {
    return Math.max(config.minBillCents, Math.ceil(currCost * config.usdCnyRate * 100));
  }

  const prevIn = Number(previous?.lastInputTokens ?? 0);
  const prevOut = Number(previous?.lastOutputTokens ?? 0);
  const deltaIn = Math.max(0, current.accumulatedInputTokens - prevIn);
  const deltaOut = Math.max(0, current.accumulatedOutputTokens - prevOut);
  if (deltaIn === 0 && deltaOut === 0) return 0;

  const raw =
    (deltaIn / 1000) * config.inputCentsPer1k + (deltaOut / 1000) * config.outputCentsPer1k;
  if (raw <= 0) return 0;
  return Math.max(config.minBillCents, Math.ceil(raw));
}