【実装】Cloudflare Workers + Next.js でエラーをDiscord Webhookに自動通知する仕組みを作った

APIルート catch → notifyError() → Discord Webhook POST
worker.ts catch → notifyError(env, ...) → Discord Webhook POST
                        ↓
              buildDiscordPayload() ← 共通関数

// src/lib/error-notify.ts
export function buildDiscordPayload(
  options: ErrorNotifyOptions,
  appEnv: string
): object {
  const config = SEVERITY_CONFIG[options.severity];
  const envEmoji = ENV_EMOJI[appEnv] ?? "⚪";
  const fields = options.metadata
    ? Object.entries(options.metadata).map(([name, value]) => ({
        name: `🔹 ${name}`,
        value: `\`${value}\``,
        inline: true,
      }))
    : [];

  return {
    embeds: [{
      author: { name: `${config.emoji} ${config.label}` },
      title: options.title,
      description: `\`\`\`\n${options.description}\n\`\`\``,
      color: config.color,
      fields,
      footer: {
        text: `${envEmoji} ${appEnv.toUpperCase()}  •  anoni`,
      },
      timestamp: new Date().toISOString(),
    }],
  };
}

// src/lib/error-notify.ts
export async function notifyError(options: ErrorNotifyOptions): Promise<void> {
  console.error(
    `[${options.severity.toUpperCase()}] ${options.title}:`,
    options.description
  );

  const webhookUrl = process.env.DISCORD_WEBHOOK_URL;
  if (!webhookUrl) return;

  const env = process.env.APP_ENV
    || (process.env.NODE_ENV === "production" ? "prod" : "local");

  await fetch(webhookUrl, {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify(buildDiscordPayload(options, env)),
  }).catch(() => {});
}

// worker.ts
import { buildDiscordPayload, type ErrorNotifyOptions } from "./src/lib/error-notify";

async function notifyError(
  env: CloudflareEnv,
  options: ErrorNotifyOptions
): Promise<void> {
  console.error(...);
  const webhookUrl = env.DISCORD_WEBHOOK_URL;
  if (!webhookUrl) return;
  await fetch(webhookUrl, {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify(buildDiscordPayload(options, env.APP_ENV || "local")),
  }).catch(() => {});
}

} catch (error) {
  void notifyError({
    severity: "critical",
    title: "Stripe Webhook 処理エラー",
    description: `イベント処理に失敗: ${error instanceof Error ? error.message : String(error)}`,
    metadata: { eventType: event.type, eventId: event.id },
  });
  return NextResponse.json({ error: "Webhook processing failed" }, { status: 500 });
}

const notifiedNamespaces = new Set<string>();

if (isOverLimit && !notifiedNamespaces.has(key)) {
  notifiedNamespaces.add(key);
  void notifyError({ ... });
}

function maskIdentifier(identifier: string): string {
  if (identifier.includes("@")) {
    const [local, domain] = identifier.split("@");
    return `${local[0]}***@${domain}`;
  }
  return identifier.length > 4
    ? `${identifier.slice(0, 2)}***${identifier.slice(-2)}`
    : "***";
}

description: `\`\`\`\n${options.description.replaceAll("\`", "ˋ")}\n\`\`\``,

it("DISCORD_WEBHOOK_URL 設定時に fetch を呼ぶ", async () => {
  process.env.DISCORD_WEBHOOK_URL = "https://discord.com/api/webhooks/test";
  await notifyError({ severity: "warning", title: "テスト", description: "テスト" });
  expect(fetchSpy).toHaveBeenCalledOnce();
});