fix(realtime-token): spend the session quota only after a token is minted and stop leaking provider errors

server/supabase/functions/realtime-token/policy.ts

@@ -0,0 +1,82 @@
+// server/supabase/functions/realtime-token/policy.ts
+// Realtime 세션 발급 정책 — 순수 함수만 둔다 (IO·Deno 전역·네트워크 import 없음).
+// 티어별 허용 모델 결정과 OpenAI client_secrets 세션 설정 조립을 담당한다.
+
+import type { PlanQuotaTier } from '../_shared/core-contract.generated.ts'
+
+export type RealtimeTier = PlanQuotaTier
+
+export interface RealtimeTokenRequest {
+  model?: unknown
+  voice?: unknown
+  instructions?: unknown
+}
+
+/** 티어별 허용 Realtime 모델 — free 차단, pro는 mini만, 상위 티어는 풀 모델까지 */
+export const TIER_MODELS: Readonly<Record<RealtimeTier, readonly string[]>> = {
+  free: [],
+  pro: ['gpt-realtime-2.1-mini'],
+  pro_plus: ['gpt-realtime-2.1', 'gpt-realtime-2.1-mini'],
+  team: ['gpt-realtime-2.1', 'gpt-realtime-2.1-mini'],
+  enterprise: ['gpt-realtime-2.1', 'gpt-realtime-2.1-mini'],
+}
+
+export const DEFAULT_MODEL: Readonly<Record<RealtimeTier, string | null>> = {
+  free: null,
+  pro: 'gpt-realtime-2.1-mini',
+  pro_plus: 'gpt-realtime-2.1',
+  team: 'gpt-realtime-2.1',
+  enterprise: 'gpt-realtime-2.1',
+}
+
+export const DEFAULT_VOICE = 'marin'
+export const MAX_INSTRUCTIONS_LENGTH = 2000
+
+export type ModelResolution =
+  | { allowed: true; model: string }
+  | {
+    allowed: false
+    error: 'tier_not_allowed' | 'model_not_allowed'
+    requested: string | null
+    allowedModels: readonly string[]
+  }
+
+/** 요청 모델(없으면 티어 기본값)이 티어에서 허용되는지 판정한다. */
+export function resolveRealtimeModel(tier: RealtimeTier, requested: unknown): ModelResolution {
+  const requestedModel = typeof requested === 'string' ? requested : null
+  const allowedModels = TIER_MODELS[tier] ?? []
+  const model = requestedModel ?? DEFAULT_MODEL[tier] ?? null
+  if (model && allowedModels.includes(model)) {
+    return { allowed: true, model }
+  }
+  return {
+    allowed: false,
+    error: tier === 'free' ? 'tier_not_allowed' : 'model_not_allowed',
+    requested: requestedModel,
+    allowedModels,
+  }
+}
+
+export interface RealtimeSessionConfig {
+  type: 'realtime'
+  model: string
+  instructions?: string
+  audio: { output: { voice: string } }
+}
+
+/** OpenAI client_secrets 요청의 session 객체를 조립한다. */
+export function buildRealtimeSessionConfig(
+  body: RealtimeTokenRequest,
+  model: string,
+): RealtimeSessionConfig {
+  const instructions = typeof body.instructions === 'string'
+    ? body.instructions.slice(0, MAX_INSTRUCTIONS_LENGTH)
+    : undefined
+  const voice = typeof body.voice === 'string' && body.voice ? body.voice : DEFAULT_VOICE
+  return {
+    type: 'realtime',
+    model,
+    ...(instructions ? { instructions } : {}),
+    audio: { output: { voice } },
+  }
+}