AI 产品创造：从需求洞察到付费闭环的工程化路径

用户输入 → API 网关(鉴权/限流) → 生成服务(模型+缓存) → 用量计费 → 交付

// app/api/generate/route.ts
import { NextRequest, NextResponse } from "next/server";
import OpenAI from "openai";
import { Redis } from "@upstash/redis";
import { z } from "zod";

const openai = new OpenAI({ apiKey: process.env.OPENAI_API_KEY });
const redis = Redis.fromEnv();

const Input = z.object({
  product: z.string().min(2).max(500),
  tone: z.enum(["professional", "casual", "luxury"]).default("professional"),
});

const FREE_QUOTA = 10; // 每月免费次数

export async function POST(req: NextRequest) {
  const userId = req.headers.get("x-user-id");
  if (!userId) return NextResponse.json({ error: "未登录" }, { status: 401 });

  const parsed = Input.safeParse(await req.json());
  if (!parsed.success) {
    return NextResponse.json({ error: "参数非法" }, { status: 400 });
  }
  const { product, tone } = parsed.data;

  // 1. 用量检查
  const monthKey = `quota:${userId}:${new Date().toISOString().slice(0, 7)}`;
  const used = (await redis.get<number>(monthKey)) ?? 0;
  if (used >= FREE_QUOTA) {
    return NextResponse.json(
      { error: "免费额度已用完", paywall: true }, { status: 402 });
  }

  // 2. 缓存命中直接返回，节省成本
  const cacheKey = `gen:${tone}:${Buffer.from(product).toString("base64")}`;
  const cached = await redis.get<string>(cacheKey);
  if (cached) {
    return NextResponse.json({ listing: cached, source: "cache" });
  }

  // 3. 调用模型，温度与 max_tokens 严格控制成本
  const resp = await openai.chat.completions.create({
    model: "gpt-4o-mini",
    messages: [
      { role: "system", content:
        `你是跨境电商文案专家。语气：${tone}。` +
        "输出格式：标题一行，五点描述，每点不超过30词。" },
      { role: "user", content: product },
    ],
    temperature: 0.7,
    max_tokens: 400,
  });
  const listing = resp.choices[0].message.content ?? "";

  // 4. 写入缓存与用量
  await redis.setex(cacheKey, 86400, listing);
  await redis.incr(monthKey);
  await redis.expire(monthKey, 60 * 60 * 24 * 32);

  return NextResponse.json({
    listing,
    source: "llm",
    remaining: FREE_QUOTA - used - 1,
  });
}

// app/api/checkout/route.ts
import { NextRequest, NextResponse } from "next/server";
import Stripe from "stripe";

const stripe = new Stripe(process.env.STRIPE_SECRET_KEY!);

export async function POST(req: NextRequest) {
  const { userId } = await req.json();
  const session = await stripe.checkout.sessions.create({
    mode: "payment",
    line_items: [{ price: process.env.STRIPE_PRICE_ID!, quantity: 1 }],
    success_url: `${process.env.APP_URL}/success?uid=${userId}`,
    cancel_url: `${process.env.APP_URL}/pricing`,
    metadata: { userId },
  });
  return NextResponse.json({ url: session.url });
}

// app/api/webhook/route.ts
import { NextRequest, NextResponse } from "next/server";
import Stripe from "stripe";
import { Redis } from "@upstash/redis";

const stripe = new Stripe(process.env.STRIPE_SECRET_KEY!);
const redis = Redis.fromEnv();

export async function POST(req: NextRequest) {
  const sig = req.headers.get("stripe-signature")!;
  const body = await req.text();
  const event = stripe.webhooks.constructEvent(
    body, sig, process.env.STRIPE_WEBHOOK_SECRET!);

  if (event.type === "checkout.session.completed") {
    const userId = (event.data.object as any).metadata.userId;
    const monthKey = `quota:${userId}:${new Date().toISOString().slice(0, 7)}`;
    await redis.set(monthKey, -100); // 负数表示已付费，额度充足
  }
  return NextResponse.json({ received: true });
}

export async function POST(req: NextRequest) {
  const stream = await openai.chat.completions.create({
    model: "gpt-4o-mini",
    messages: [{ role: "user", content: product }],
    stream: true,
  });

  const encoder = new TextEncoder();
  const readable = new ReadableStream({
    async start(controller) {
      for await (const chunk of stream) {
        const text = chunk.choices[0]?.delta?.content ?? "";
        if (text) controller.enqueue(encoder.encode(text));
      }
      controller.close();
    },
  });
  return new Response(readable, {
    headers: { "Content-Type": "text/plain; charset=utf-8" },
  });
}