rudeshark.net/packages/backend/src/services/validate-email-for-account.ts

import { validate as validateEmail } from "deep-email-validator";
import { UserProfiles } from "@/models/index.js";
import { fetchMeta } from "@/misc/fetch-meta.js";

export async function validateEmailForAccount(emailAddress: string): Promise<{
	available: boolean;
	reason: null | "used" | "format" | "disposable" | "mx" | "smtp";
}> {
	const meta = await fetchMeta();

	const exist = await UserProfiles.countBy({
		emailVerified: true,
		email: emailAddress,
	});

	const validated = meta.enableActiveEmailValidation
		? await validateEmail({
				email: emailAddress,
				validateRegex: true,
				validateMx: true,
				validateTypo: false, // TLDを見ているみたいだけどclubとか弾かれるので
				validateDisposable: true, // 捨てアドかどうかチェック
				validateSMTP: false, // 日本だと25ポートが殆どのプロバイダーで塞がれていてタイムアウトになるので
		  })
		: { valid: true };

	const available = exist === 0 && validated.valid;

	return {
		available,
		reason: available
			? null
			: exist !== 0
			? "used"
			: validated.reason === "regex"
			? "format"
			: validated.reason === "disposable"
			? "disposable"
			: validated.reason === "mx"
			? "mx"
			: validated.reason === "smtp"
			? "smtp"
			: null,
	};
}