feat(admin): add read-only pricing simulator

frontend/src/lib/pricing-simulation.ts

@@ -0,0 +1,90 @@
+export const CREDITS_PER_CNY = 10;
+export const CONSULTATION_DOMAIN_DURATION_MS = 21_000;
+const MICROUSD_PER_USD = 1_000_000;
+
+export type Metric = Readonly<{ runs: number; avg: number | null; p50: number | null; p95: number | null; max: number | null }>;
+export type UsageAggregate = Readonly<{
+  hasData: boolean;
+  metrics: Readonly<{ costMicrousd: Metric; inputTokens: Metric; outputTokens: Metric; durationMs: Metric }>;
+}>;
+export type ModelPrice = Readonly<{
+  modelTier: string;
+  inputCostMicrousdPerMillion: number;
+  outputCostMicrousdPerMillion: number;
+}>;
+export type DistributionBand = Readonly<{ weight: number; monthlyMessages: number }>;
+
+export type FeatureSimulationInput = Readonly<{
+  featureKey: string;
+  creditCost: number | null;
+  model: ModelPrice | null;
+  usage: UsageAggregate | null;
+  usdToCny: number | null;
+}>;
+
+export type FeatureSimulation = Readonly<{
+  featureKey: string;
+  saleCny: number | null;
+  costMicrousd: number | null;
+  costCny: number | null;
+  marginPercent: number | null;
+  source: "ledger" | "model_estimate" | "unavailable";
+}>;
+
+function metricValue(metric: Metric, percentile: "p50" | "p95" | "max"): number | null {
+  return metric[percentile];
+}
+
+export function estimateFeature(input: FeatureSimulationInput, percentile: "p50" | "p95" | "max" = "p50"): FeatureSimulation {
+  const saleCny = input.creditCost === null ? null : input.creditCost / CREDITS_PER_CNY;
+  if (input.creditCost === null || !input.usage?.hasData) {
+    return { featureKey: input.featureKey, saleCny, costMicrousd: null, costCny: null, marginPercent: null, source: "unavailable" };
+  }
+
+  const observedCost = metricValue(input.usage.metrics.costMicrousd, percentile);
+  const modelCost = input.model && input.usage.metrics.inputTokens[percentile] !== null && input.usage.metrics.outputTokens[percentile] !== null
+    ? (input.usage.metrics.inputTokens[percentile]! * input.model.inputCostMicrousdPerMillion
+      + input.usage.metrics.outputTokens[percentile]! * input.model.outputCostMicrousdPerMillion) / 1_000_000
+    : null;
+  const costMicrousd = observedCost ?? modelCost;
+  const costCny = costMicrousd === null || input.usdToCny === null
+    ? null
+    : (costMicrousd / MICROUSD_PER_USD) * input.usdToCny;
+  return {
+    featureKey: input.featureKey,
+    saleCny,
+    costMicrousd,
+    costCny,
+    marginPercent: costCny === null || saleCny === null || saleCny === 0 ? null : ((saleCny - costCny) / saleCny) * 100,
+    source: observedCost !== null ? "ledger" : costMicrousd === null ? "unavailable" : "model_estimate",
+  };
+}
+
+export function weightedAverageMessages(distribution: readonly DistributionBand[]): number | null {
+  const usable = distribution.filter((band) => Number.isFinite(band.weight) && band.weight > 0 && Number.isFinite(band.monthlyMessages));
+  const totalWeight = usable.reduce((sum, band) => sum + band.weight, 0);
+  if (totalWeight <= 0) return null;
+  return usable.reduce((sum, band) => sum + (band.weight / totalWeight) * Math.max(0, band.monthlyMessages), 0);
+}
+
+export function membershipCost(distribution: readonly DistributionBand[], unitCostCny: number | null, billingLimit: number | null) {
+  const averageMessages = weightedAverageMessages(distribution);
+  return {
+    averageMessages,
+    averageCostCny: averageMessages === null || unitCostCny === null ? null : averageMessages * unitCostCny,
+    worstCostCny: billingLimit === null || unitCostCny === null ? null : billingLimit * unitCostCny,
+    unlimitedWorstCase: billingLimit === null,
+  };
+}
+
+export function dailySerialCapacity(durationMs = CONSULTATION_DOMAIN_DURATION_MS): number | null {
+  if (!Number.isFinite(durationMs) || durationMs <= 0) return null;
+  return Math.floor(86_400_000 / durationMs);
+}
+
+export function memberCapacity(distribution: readonly DistributionBand[], unitDurationMs: number): number | null {
+  const averageMessages = weightedAverageMessages(distribution);
+  const dailyCapacity = dailySerialCapacity(unitDurationMs);
+  if (averageMessages === null || dailyCapacity === null || averageMessages <= 0) return null;
+  return Math.floor(dailyCapacity / (averageMessages / 30));
+}