テスト送信すると400エラーが出る

実現したいこと

Fiebase と Stripe を組み合わせてサブスクなどを実装したいです。
Firebase側とStripe側の設定は終わっています。

【目標】
・テスト送信して実際に成功
・Firebaseにusers/userId/に書き込む
・成功メールを送信する

発生している問題・分からないこと

stripe trigger checkout.session.completed

すると以下のエラーが出る。

【問題】
・テスト送信失敗
・Firebaseにusers/userId/に書き込み失敗
・成功メールを未送信

が出ます。

エラーメッセージ

error
12025-11-05 13:42:38  <--  [400] POST https://your-products-id.cloudfunctions.net/stripeWebhook [....]

該当のソースコード

index.js
1// functions/index.js
2import { onRequest, onCall } from "firebase-functions/v2/https";
3import { setGlobalOptions } from "firebase-functions/v2";
4import { logger } from "firebase-functions";
5import admin from "firebase-admin";
6import Stripe from "stripe";
7
8setGlobalOptions({ maxInstances: 10 });
9
10// ======================================================
11// Firebase 初期化
12// ======================================================
13if (!admin.apps.length) {
14  admin.initializeApp();
15}
16const db = admin.firestore();
17
18// ======================================================
19// Stripe 初期化
20// ======================================================
21const stripe = new Stripe(process.env.STRIPE_SECRET_KEY, {
22  apiVersion: "2024-06-20",
23});
24
25// ======================================================
26// Webhook 関数（rawBody 対応）
27// ======================================================
28export const stripeWebhook = onRequest(
29  {
30    secrets: ["STRIPE_SECRET_KEY", "STRIPE_WEBHOOK_SECRET"],
31    region: "us-central1",
32    memory: "256MiB",
33    timeoutSeconds: 60,
34    rawBody: true, // ここが必須
35  },
36  async (req, res) => {
37    const sig = req.headers["stripe-signature"];
38    if (!sig) {
39      logger.warn("No stripe-signature");
40      return res.status(400).send("Missing signature");
41    }
42
43    let event;
44    try {
45      // rawBody は Buffer になっている
46      event = stripe.webhooks.constructEvent(
47        req.rawBody,
48        sig,
49        process.env.STRIPE_WEBHOOK_SECRET
50      );
51    } catch (err) {
52      logger.error("Webhook signature failed", err.message);
53      return res.status(400).send(`Webhook Error: ${err.message}`);
54    }
55
56    logger.info(`✅ Event received: ${event.type}`);
57
58    if (event.type === "checkout.session.completed") {
59      const session = event.data.object;
60      const userId = session.client_reference_id;
61
62      if (!userId) {
63        logger.warn("No client_reference_id", session.id);
64        return res.status(400).send("No userId");
65      }
66
67      // Firestore 書き込み
68      try {
69        await db.collection("users").doc(userId).set(
70          {
71            stripeCustomerId: session.customer,
72            subscription: {
73              active: true,
74              stripeSubscriptionId: session.subscription,
75              plan: session.metadata?.plan || "basic",
76              updatedAt: admin.firestore.FieldValue.serverTimestamp(),
77            },
78          },
79          { merge: true }
80        );
81        logger.info("Subscription activated", { userId });
82      } catch (error) {
83        logger.error("Firestore write failed", error);
84        return res.status(500).send("Firestore error");
85      }
86
87      // 歓迎メール送信
88      const email = session.customer_details?.email;
89      if (email) {
90        await sendWelcomeEmail(email, session.metadata?.plan || "basic");
91      }
92    }
93
94    res.json({ received: true });
95  }
96);
97
98// ======================================================
99// Checkout セッション作成
100// ======================================================
101export const createCheckoutSession = onCall(
102  {
103    secrets: ["STRIPE_SECRET_KEY"],
104    region: "us-central1",
105  },
106  async (request) => {
107    const uid = request.auth?.uid;
108    if (!uid) throw new Error("ログインが必要です。");
109
110    const priceId = request.data.priceId;
111    const customerId = await getOrCreateCustomer(uid, stripe, db);
112
113    const session = await stripe.checkout.sessions.create({
114      mode: "subscription",
115      payment_method_types: ["card"],
116      customer: customerId,
117      line_items: [{ price: priceId, quantity: 1 }],
118      client_reference_id: uid,
119      metadata: { plan: request.data.plan || "basic" },
120      success_url: "https://your-domain.com/success.html",
121      cancel_url: "https://your-domain.com/cancel.html",
122    });
123
124    return { url: session.url };
125  }
126);
127
128// ======================================================
129// カスタマー取得 or 作成
130// ======================================================
131async function getOrCreateCustomer(uid, stripe, db) {
132  const userRef = db.collection("users").doc(uid);
133  const userSnap = await userRef.get();
134
135  if (userSnap.exists && userSnap.data()?.stripeCustomerId) {
136    return userSnap.data().stripeCustomerId;
137  }
138
139  const userRecord = await admin.auth().getUser(uid);
140  const customer = await stripe.customers.create({
141    email: userRecord.email,
142    metadata: { uid },
143  });
144
145  await userRef.set({ stripeCustomerId: customer.id }, { merge: true });
146  return customer.id;
147}
148
149// ======================================================
150// 歓迎メール送信関数
151// ======================================================
152async function sendWelcomeEmail(email, plan) {
153  const nodemailer = await import("nodemailer"); // 関数内 import
154  const transporter = nodemailer.createTransport({
155    service: "gmail",
156    auth: {
157      user: "your-gmail@gmail.com",
158      pass: process.env.GMAIL_APP_PASSWORD,
159    },
160  });
161
162  const mailOptions = {
163    from: "メルカリ売上管理ツール <noreply@your-domain.com>",
164    to: email,
165    subject: "有料プランへようこそ！",
166    html: `
167      <h2>おめでとうございます！</h2>
168      <p><strong>${plan}プラン</strong>が有効になりました！</p>
169      <p>今すぐ自動売上取得がスタートします。</p>
170      <p><a href="https://your-tool.com">ツールにログイン</a></p>
171      <hr>
172      <small>30日間返金保証付き | support@your-domain.com</small>
173    `,
174  };
175
176  await transporter.sendMail(mailOptions);
177  logger.info("Welcome email sent", { email });
178}
179

firebase.json
1{
2  "functions": {
3    "source": "functions"
4  },
5  "emulators": {
6    "functions": {
7      "port": 8358
8    },
9    "firestore": {
10      "port": 8082
11    },
12    "ui": {
13      "enabled": true
14    }
15  }
16}
17

packege.json
1{
2  "name": "functions",
3  "type": "module",
4  "scripts": {
5    "lint": "eslint .",
6    "serve": "firebase emulators:start --only functions",
7    "shell": "firebase functions:shell",
8    "start": "npm run shell",
9    "deploy": "firebase deploy --only functions",
10    "logs": "firebase functions:log"
11  },
12  "engines": {
13    "node": "20"
14  },
15  "main": "index.js",
16  "dependencies": {
17    "express": "^5.1.0",
18    "firebase-admin": "^12.6.0",
19    "firebase-functions": "^5.1.1",
20    "nodemailer": "^7.0.10",
21    "stripe": "^16.12.0"
22  },
23  "devDependencies": {
24    "eslint": "^8.15.0",
25    "eslint-config-google": "^0.14.0"
26  },
27  "private": true
28}
29