feat: add resend mail transport

packages/email/mailer.ts

@@ -1,6 +1,7 @@
 import { createTransport } from 'nodemailer';
 
 import { MailChannelsTransport } from './transports/mailchannels';
+import { ResendTransport } from './transports/resend';
 
 const getTransport = () => {
   const transport = process.env.NEXT_PRIVATE_SMTP_TRANSPORT ?? 'smtp-auth';
@@ -14,6 +15,14 @@ const getTransport = () => {
     );
   }
 
+  if (transport === 'resend') {
+    return createTransport(
+      ResendTransport.makeTransport({
+        apiKey: process.env.NEXT_PRIVATE_RESEND_API_KEY || '',
+      }),
+    );
+  }
+
   if (transport === 'smtp-api') {
     if (!process.env.NEXT_PRIVATE_SMTP_HOST || !process.env.NEXT_PRIVATE_SMTP_APIKEY) {
       throw new Error(

packages/email/package.json

@@ -19,7 +19,8 @@
   "dependencies": {
     "@react-email/components": "^0.0.7",
     "nodemailer": "^6.9.3",
-    "react-email": "^1.9.4"
+    "react-email": "^1.9.4",
+    "resend": "^1.1.0"
   },
   "devDependencies": {
     "@documenso/tailwind-config": "*",

packages/email/transports/resend.ts

@@ -0,0 +1,145 @@
+import { type SentMessageInfo, type Transport } from 'nodemailer';
+import type Mail from 'nodemailer/lib/mailer';
+import type MailMessage from 'nodemailer/lib/mailer/mail-message';
+import { Resend } from 'resend';
+
+const VERSION = '1.0.0';
+
+type ResendTransportOptions = {
+  apiKey: string;
+};
+
+type ResendResponseError = {
+  statusCode: number;
+  name: string;
+  message: string;
+};
+
+const isResendResponseError = (error: unknown): error is ResendResponseError => {
+  // We could use Zod here, but it's not worth the extra bundle size
+  return (
+    typeof error === 'object' &&
+    error !== null &&
+    'statusCode' in error &&
+    typeof error.statusCode === 'number' &&
+    'name' in error &&
+    typeof error.name === 'string' &&
+    'message' in error &&
+    typeof error.message === 'string'
+  );
+};
+
+/**
+ * Transport for sending email via the Resend SDK.
+ */
+export class ResendTransport implements Transport<SentMessageInfo> {
+  public name = 'ResendMailTransport';
+  public version = VERSION;
+
+  private _client: Resend;
+  private _options: ResendTransportOptions;
+
+  public static makeTransport(options: Partial<ResendTransportOptions>) {
+    return new ResendTransport(options);
+  }
+
+  constructor(options: Partial<ResendTransportOptions>) {
+    const { apiKey = '' } = options;
+
+    this._options = {
+      apiKey,
+    };
+
+    this._client = new Resend(apiKey);
+  }
+
+  public send(mail: MailMessage, callback: (_err: Error | null, _info: SentMessageInfo) => void) {
+    if (!mail.data.to || !mail.data.from) {
+      return callback(new Error('Missing required fields "to" or "from"'), null);
+    }
+
+    this._client
+      .sendEmail({
+        subject: mail.data.subject ?? '',
+        from: this.toResendFromAddress(mail.data.from),
+        to: this.toResendAddresses(mail.data.to),
+        cc: this.toResendAddresses(mail.data.cc),
+        bcc: this.toResendAddresses(mail.data.bcc),
+        html: mail.data.html?.toString() || '',
+        text: mail.data.text?.toString() || '',
+        attachments: this.toResendAttachments(mail.data.attachments),
+      })
+      .then((response) => {
+        if (isResendResponseError(response)) {
+          throw new Error(`[${response.statusCode}]: ${response.name} ${response.message}`);
+        }
+
+        callback(null, response);
+      })
+      .catch((error) => {
+        callback(error, null);
+      });
+  }
+
+  private toResendAddresses(addresses: Mail.Options['to']) {
+    if (!addresses) {
+      return [];
+    }
+
+    if (typeof addresses === 'string') {
+      return [addresses];
+    }
+
+    if (Array.isArray(addresses)) {
+      return addresses.map((address) => {
+        if (typeof address === 'string') {
+          return address;
+        }
+
+        return address.address;
+      });
+    }
+
+    return [addresses.address];
+  }
+
+  private toResendFromAddress(address: Mail.Options['from']) {
+    if (!address) {
+      return '';
+    }
+
+    if (typeof address === 'string') {
+      return address;
+    }
+
+    return `${address.name} <${address.address}>`;
+  }
+
+  private toResendAttachments(attachments: Mail.Options['attachments']) {
+    if (!attachments) {
+      return [];
+    }
+
+    return attachments.map((attachment) => {
+      if (!attachment.filename || !attachment.content) {
+        throw new Error('Attachment is missing filename or content');
+      }
+
+      if (typeof attachment.content === 'string') {
+        return {
+          filename: attachment.filename,
+          content: Buffer.from(attachment.content),
+        };
+      }
+
+      if (attachment.content instanceof Buffer) {
+        return {
+          filename: attachment.filename,
+          content: attachment.content,
+        };
+      }
+
+      throw new Error('Attachment content must be a string or a buffer');
+    });
+  }
+}

packages/email/tsconfig.json

@@ -1,5 +1,10 @@
 {
   "extends": "@documenso/tsconfig/react-library.json",
+  "compilerOptions": {
+    "types": [
+      "@documenso/tsconfig/process-env.d.ts",
+    ]
+  },
   "include": ["**/*.ts", "**/*.tsx", "**/*.d.ts", "**/*.json"],
   "exclude": ["dist", "build", "node_modules"]
 }

packages/tsconfig/process-env.d.ts

@@ -27,7 +27,9 @@ declare namespace NodeJS {
     NEXT_PRIVATE_SIGNING_LOCAL_FILE_CONTENTS?: string;
     NEXT_PRIVATE_SIGNING_LOCAL_FILE_ENCODING?: string;
 
-    NEXT_PRIVATE_SMTP_TRANSPORT?: 'mailchannels' | 'smtp-auth' | 'smtp-api';
+    NEXT_PRIVATE_SMTP_TRANSPORT?: 'mailchannels' | 'resend' | 'smtp-auth' | 'smtp-api';
+
+    NEXT_PRIVATE_RESEND_API_KEY?: string;
 
     NEXT_PRIVATE_MAILCHANNELS_API_KEY?: string;
     NEXT_PRIVATE_MAILCHANNELS_DKIM_DOMAIN?: string;