// 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 } },
  }
}