revert: Don't use AMQP for emails

src/app/[lang]/dashboard/verify/GetStartedSaaS.tsx

@@ -51,6 +51,7 @@ export function GetStartedSaaS({
 			data: {
 				to_email: email,
 			},
+			retries: 1,
 		})
 			.then((r) => {
 				setResult(r);

src/app/api/v0/check_email/backends.ts

@@ -0,0 +1,168 @@
+import { v4 } from "uuid";
+import axios, { AxiosError } from "axios";
+import { supabaseAdmin } from "@/supabase/supabaseAdmin";
+import { CheckEmailInput, CheckEmailOutput } from "@reacherhq/api";
+import { Tables } from "@/supabase/database.types";
+import { convertPgError } from "@/util/helpers";
+
+// Vercel functions time out after 60s.
+const VERCEL_TIMEOUT = 90_000; // ms
+
+interface ReacherBackend {
+	url: string;
+	name: string;
+}
+
+const RCH_BACKENDS = [
+	{
+		url: "http://backend1.reacher.dev",
+		name: "backend1-ovh",
+	},
+	{
+		url: "http://backend3.reacher.dev",
+		name: "backend3-do",
+	},
+];
+
+/**
+ * Forwards the Next.JS request to Reacher's backends, try them all in the
+ * order given by `RCH_BACKENDS`.
+ */
+export async function tryAllBackends(
+	emailInput: CheckEmailInput,
+	user: Tables<"users">
+): Promise<Response> {
+	try {
+		// The final result to return.
+		let result: CheckEmailOutput;
+
+		let t: NodeJS.Timeout | undefined;
+
+		async function makeBackendCalls(): Promise<Response> {
+			// Create a unique UUID for each verification. The purpose of this
+			// verificationId is that we insert one row in the `calls` table per
+			// backend call. However, if we try the backends sequentially, we don't
+			// want to charge the user 2 credits for 1 email verification.
+			const verificationId = v4();
+
+			// Note that we don't loop the last element of reacherBackends. That
+			// one gets treated specially, as we'll always return its response.
+			for (let i = 0; i < RCH_BACKENDS.length - 1; i++) {
+				try {
+					result = await makeSingleBackendCall(
+						verificationId,
+						RCH_BACKENDS[i],
+						emailInput,
+						user
+					);
+
+					if (result.is_reachable !== "unknown") {
+						return Response.json(result);
+					}
+				} catch {
+					// Continue loop
+				}
+			}
+
+			// If we arrive here, it means all previous backend calls errored or
+			// returned "unknown". We make the last backend call, and always return
+			// its response.
+			result = await makeSingleBackendCall(
+				verificationId,
+				RCH_BACKENDS[RCH_BACKENDS.length - 1],
+				emailInput,
+				user
+			);
+
+			return Response.json(result);
+		}
+
+		const res = await Promise.race([
+			makeBackendCalls(),
+			new Promise<Response>((resolve) => {
+				t = setTimeout(() => {
+					return resolve(
+						Response.json(
+							{
+								error: `The email ${emailInput.to_email} can't be verified within 90s. This is because the email provider imposes obstacles to prevent real-time email verification, such as greylisting. Please try again later.`,
+							},
+							{ status: 504 }
+						)
+					);
+				}, VERCEL_TIMEOUT);
+			}),
+		]);
+
+		if (t) {
+			clearTimeout(t);
+		}
+
+		return res;
+	} catch (err) {
+		const statusCode = (err as AxiosError).response?.status;
+		if (!statusCode) {
+			throw err;
+		}
+
+		return Response.json(
+			{
+				error: (err as AxiosError).response?.data,
+			},
+			{
+				status: statusCode,
+			}
+		);
+	}
+}
+
+/**
+ * Make a single call to the backend, and log some metadata to the DB.
+ */
+async function makeSingleBackendCall(
+	verificationId: string,
+	reacherBackend: ReacherBackend,
+	emailInput: CheckEmailInput,
+	user: Tables<"users">
+): Promise<CheckEmailOutput> {
+	const t0 = performance.now();
+	// Send an API request to Reacher backend, which handles email
+	// verifications, see https://github.com/reacherhq/backend.
+	const result = await axios.post<CheckEmailOutput>(
+		`${reacherBackend.url}/v0/check_email`,
+		emailInput,
+		{
+			headers: {
+				"x-reacher-secret": process.env.RCH_HEADER_SECRET || "",
+			},
+		}
+	);
+	const t1 = performance.now();
+	console.log(`[🐢] Call ${reacherBackend.name}: +${Math.round(t1 - t0)}ms`);
+
+	// Get the domain of the email, i.e. the part after '@'.
+
+	const parts = emailInput.to_email.split("@");
+	const domain = parts && parts[1];
+
+	// If successful, also log an API call entry in the database.
+	const { error } = await supabaseAdmin.from("calls").insert({
+		endpoint: "/v0/check_email",
+		user_id: user.id,
+		backend: reacherBackend.name,
+		backend_ip: result.request?.socket?.remoteAddress as string,
+		domain,
+		verification_id: verificationId,
+		duration:
+			(result?.data.debug?.duration.secs || 0) * 1000 +
+			Math.round((result.data.debug?.duration.nanos || 0) * 1e-6), // in ms
+		is_reachable: result.data.is_reachable,
+		verif_method: result.data.debug?.smtp?.verif_method?.type,
+		result: result.data,
+	});
+	if (error) {
+		throw convertPgError(error);
+	}
+	console.log(`[🐢] Log DB entry: +${Math.round(performance.now() - t1)}ms`);
+
+	return result.data;
+}