Antigravity エージェントを商品にして売る90日設計図 — 関門と撤退ラインを先に決める

// lib/run-with-guards.ts — 呼び出し先（SDK・API）は call として注入する
type AgentCall = (
  input: string,
  signal: AbortSignal,
) => Promise<{ text: string; tokensIn: number; tokensOut: number }>;
 
function isRetryable(e: unknown): boolean {
  if (e instanceof DOMException && e.name === 'AbortError') return true;
  const status = (e as { status?: number })?.status;
  return status === 429 || (status !== undefined && status >= 500);
}
 
export async function runWithGuards(
  call: AgentCall,
  input: string,
  opts: { timeoutMs?: number; maxAttempts?: number } = {},
) {
  const timeoutMs = opts.timeoutMs ?? 60_000;
  const maxAttempts = opts.maxAttempts ?? 3;
  let lastError: unknown;
 
  for (let attempt = 1; attempt <= maxAttempts; attempt++) {
    const ctrl = new AbortController();
    const timer = setTimeout(() => ctrl.abort(), timeoutMs);
    try {
      return await call(input, ctrl.signal);
    } catch (e) {
      lastError = e;
      if (!isRetryable(e) || attempt === maxAttempts) break;
      // 指数バックオフ + ジッター（同時リトライの集中を避ける）
      const wait = 2 ** attempt * 500 + Math.random() * 250;
      await new Promise((r) => setTimeout(r, wait));
    } finally {
      clearTimeout(timer);
    }
  }
  throw lastError;
}

CREATE TABLE IF NOT EXISTS usage (
  user_id TEXT NOT NULL,
  day     TEXT NOT NULL,
  runs    INTEGER NOT NULL,
  PRIMARY KEY (user_id, day)
);

// 上限内なら +1 して true、上限に達していれば false を返す
export async function consumeQuota(
  db: D1Database,
  userId: string,
  dailyLimit: number,
): Promise<boolean> {
  const day = new Date().toISOString().slice(0, 10);
  const row = await db
    .prepare(
      `INSERT INTO usage (user_id, day, runs) VALUES (?1, ?2, 1)
       ON CONFLICT(user_id, day) DO UPDATE SET runs = runs + 1
       WHERE runs < ?3
       RETURNING runs`,
    )
    .bind(userId, day, dailyLimit)
    .first<{ runs: number }>();
  return row !== null;
}

const MODEL_LIGHT = process.env.MODEL_LIGHT!; // 安価・高速なモデルの ID
const MODEL_HEAVY = process.env.MODEL_HEAVY!; // 品質重視のモデルの ID
 
export function pickModel(input: string, needsReasoning: boolean) {
  if (needsReasoning || input.length > 5000) return MODEL_HEAVY;
  return MODEL_LIGHT;
}

// app/api/checkout/route.ts
import Stripe from 'stripe';
 
const stripe = new Stripe(process.env.STRIPE_SECRET_KEY!);
 
const PLANS = {
  oneshot:  { mode: 'payment',      amount: 480,  name: '1回利用' },
  monthly:  { mode: 'subscription', amount: 980,  name: '月額 Pro' },
  lifetime: { mode: 'payment',      amount: 4800, name: '買い切り' },
} as const;
 
export async function createCheckout(
  plan: keyof typeof PLANS,
  userId: string,
  agentId: string,
  origin: string,
) {
  const p = PLANS[plan];
  return stripe.checkout.sessions.create({
    mode: p.mode,
    line_items: [
      {
        quantity: 1,
        price_data: {
          currency: 'jpy', // JPY は最小単位が円なので 480 は 480 円
          unit_amount: p.amount,
          product_data: { name: p.name },
          ...(p.mode === 'subscription'
            ? { recurring: { interval: 'month' as const } }
            : {}),
        },
      },
    ],
    client_reference_id: userId,
    metadata: { plan, agent_id: agentId }, // キー名は Webhook 側と一字一句そろえる
    success_url: `${origin}/agent/${agentId}?checkout=success`,
    cancel_url: `${origin}/agent/${agentId}`,
  });
}

// app/api/stripe/webhook/route.ts
import Stripe from 'stripe';
 
const stripe = new Stripe(process.env.STRIPE_SECRET_KEY!);
 
export async function POST(req: Request) {
  const body = await req.text(); // 署名検証には生の本文が必要
  const sig = req.headers.get('stripe-signature');
  if (!sig) return new Response('missing signature', { status: 400 });
 
  let event: Stripe.Event;
  try {
    // Workers / Edge 環境では constructEventAsync を使う
    event = await stripe.webhooks.constructEventAsync(
      body,
      sig,
      process.env.STRIPE_WEBHOOK_SECRET!,
    );
  } catch {
    return new Response('invalid signature', { status: 400 });
  }
 
  if (event.type === 'checkout.session.completed') {
    const s = event.data.object as Stripe.Checkout.Session;
    const userId = s.client_reference_id;
    const plan = s.metadata?.plan;
    const agentId = s.metadata?.agent_id;
 
    if (!userId || !plan || !agentId) {
      console.error('webhook metadata missing', event.id);
      return new Response('missing metadata', { status: 400 }); // 再配信させて気づく
    }
    if (s.payment_status !== 'paid') {
      return new Response('not paid yet', { status: 200 }); // 非同期決済は別イベントで付与
    }
 
    // event.id を主キーにした処理済みテーブルへ INSERT し、重複なら何もしない
    await grantOnce({ eventId: event.id, userId, agentId, plan });
  }
  return new Response('ok', { status: 200 });
}