Add support for Resend mailer

This update expands the mailer support by adding the Resend mailer as an alternative to NodeMailer and Cloudflare Mailer. After setting the environment variable 'MAILER_PROVIDER' to 'resend', users can utilize the Resend HTTP API for mailing. Necessary instructions and variable settings regarding the usage of Resend mailer have also been added to README.md and related modules.

README.md

@@ -339,7 +339,7 @@ This will enable the Edge runtime for your application.
 
 ### 2. Using the Cloudflare Mailer
 
-Since the default library `nodemailer` relies on Node.js, we cannot use it in the Edge runtime. Instead, we will use the Cloudflare Mailer.
+Since the default library `nodemailer` relies on Node.js, we cannot use it in the Edge runtime. Instead, we will use the Cloudflare Mailer or the Resend Mailer.
 
 To use the Cloudflare Mailer, you need to do the following. Set the `MAILER_PROVIDER` environment variable to `cloudflare` in the `apps/web/.env` file:
 
@@ -351,6 +351,18 @@ Setup SPF and DKIM records in your DNS settings.
 
 Please follow [the Vercel Email documentation](https://github.com/Sh4yy/vercel-email?tab=readme-ov-file#setup-spf) to set up the SPF and DKIM records.
 
+Alternatively, you can use the Resend Mailer. Set the `MAILER_PROVIDER` environment variable to `resend` in the `apps/web/.env` file:
+
+```
+MAILER_PROVIDER=resend
+```
+
+And provide the Resend API key:
+
+```
+RESEND_API_KEY=your-api-key
+```
+
 ### 3. Installing the Cloudflare CLI
 
 Please follow the instructions on the [Cloudflare documentation](https://github.com/cloudflare/next-on-pages/tree/main/packages/next-on-pages#3-deploy-your-application-to-cloudflare-pages) to install the Cloudflare CLI.

packages/mailers/README.md

@@ -25,6 +25,12 @@ To use Cloudflare, please set the environment variable `MAILER_PROVIDER` to `clo
 MAILER_PROVIDER=cloudflare
 ```
 
+To use [Resend](https:///resend.com)'s HTTP API, please set the environment variable `MAILER_PROVIDER` to `resend`.
+
+```
+MAILER_PROVIDER=resend
+```
+
 ### Send an email
 
 ```tsx
@@ -42,4 +48,14 @@ async function sendEmail() {
 }
 ```
 
+## Cloudflare
+
 If you're using the `cloudflare` provider, please also read the instructions of the package [Vercel Email](https://github.com/Sh4yy/vercel-email) to setup your Workers.
+
+## Resend
+
+If you're using the `resend` provider, please add the following environment variables:
+
+```
+RESEND_API_KEY=your-api-key
+```

packages/mailers/src/impl/resend/index.ts

@@ -0,0 +1,54 @@
+import 'server-only';
+
+import { z } from 'zod';
+
+import { Mailer } from '../../mailer';
+import { MailerSchema } from '../../schema/mailer.schema';
+
+type Config = z.infer<typeof MailerSchema>;
+
+const RESEND_API_KEY = z
+  .string({
+    description: 'The API key for the Resend API',
+    required_error: 'Please provide the API key for the Resend API',
+  })
+  .parse(process.env.RESEND_API_KEY);
+
+/**
+ * A class representing a mailer using the Resend HTTP API.
+ * @implements {Mailer}
+ */
+export class ResendMailer implements Mailer {
+  async sendEmail(config: Config) {
+    const contentObject =
+      'text' in config
+        ? {
+            text: config.text,
+          }
+        : {
+            html: config.html,
+          };
+
+    const res = await fetch('https://api.resend.com/emails', {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        Authorization: `Bearer ${RESEND_API_KEY}`,
+      },
+      body: JSON.stringify({
+        from: config.from,
+        to: [config.to],
+        subject: config.subject,
+        ...contentObject,
+      }),
+    });
+
+    if (res.ok) {
+      const data = await res.json();
+
+      return data;
+    }
+
+    throw new Error('Failed to send email');
+  }
+}

packages/mailers/src/index.ts

@@ -1,7 +1,7 @@
 import { z } from 'zod';
 
 const MAILER_PROVIDER = z
-  .enum(['nodemailer', 'cloudflare'])
+  .enum(['nodemailer', 'cloudflare', 'resend'])
   .default('nodemailer')
   .parse(process.env.MAILER_PROVIDER);
 
@@ -26,6 +26,12 @@ export async function getMailer() {
       return new CloudflareMailer();
     }
 
+    case 'resend': {
+      const { ResendMailer } = await import('./impl/resend');
+
+      return new ResendMailer();
+    }
+
     default:
       throw new Error(`Invalid mailer: ${MAILER_PROVIDER as string}`);
   }