feat: support resend templates

README.md

@@ -63,6 +63,48 @@ Resend.Emails.send(client, %{
 
 View additional documentation at <https://hexdocs.pm/resend>.
 
+## Templates
+
+Resend supports [templates](https://resend.com/docs/dashboard/templates/introduction) for sending transactional emails. You can use templates with both the direct API and the Swoosh adapter.
+
+### Using Templates with the Direct API
+
+```ex
+Resend.Emails.send(%{
+  from: "Acme <[email protected]>",
+  to: "[email protected]",
+  template: %{
+    id: "order-confirmation",
+    variables: %{
+      PRODUCT: "Vintage Macintosh",
+      PRICE: 499
+    }
+  }
+})
+```
+
+### Using Templates with Swoosh
+
+To use templates with the Swoosh adapter, use `put_provider_option/3` to add the template information:
+
+```ex
+import Swoosh.Email
+
+new()
+|> from({"Acme", "[email protected]"})
+|> to("[email protected]")
+|> put_provider_option(:template, %{
+  id: "order-confirmation",
+  variables: %{
+    PRODUCT: "Vintage Macintosh",
+    PRICE: 499
+  }
+})
+|> MyApp.Mailer.deliver()
+```
+
+When using templates, you don't need to set the `html_body` or `text_body` as the template will provide the content.
+
 ## Swoosh Adapter
 
 This library includes a Swoosh adapter to make using Resend with a new Phoenix project as easy as

lib/resend/emails.ex

@@ -20,14 +20,29 @@ defmodule Resend.Emails do
     * `:html` - The HTML-formatted body of the email
     * `:text` - The text-formatted body of the email
     * `:attachments` - List of attachments to include in the email
+    * `:template` - Template to use for the email, a map with `:id` and `:variables` keys
 
-  You must include one or both of the `:html` and `:text` options.
+  You must include one or both of the `:html` and `:text` options, or use a `:template`.
+
+  ## Template Example
+
+      Resend.Emails.send(%{
+        from: "Acme <[email protected]>",
+        to: "[email protected]",
+        template: %{
+          id: "order-confirmation",
+          variables: %{
+            PRODUCT: "Vintage Macintosh",
+            PRICE: 499
+          }
+        }
+      })
 
   """
   @spec send(map()) :: Resend.Client.response(Email.t())
   @spec send(Resend.Client.t(), map()) :: Resend.Client.response(Email.t())
   def send(client \\ Resend.client(), opts) do
-    Resend.Client.post(client, Email, "/emails", %{
+    payload = %{
       subject: opts[:subject],
       to: opts[:to],
       from: opts[:from],
@@ -38,7 +53,16 @@ defmodule Resend.Emails do
       html: opts[:html],
       text: opts[:text],
       attachments: opts[:attachments]
-    })
+    }
+
+    payload =
+      if opts[:template] do
+        Map.put(payload, :template, opts[:template])
+      else
+        payload
+      end
+
+    Resend.Client.post(client, Email, "/emails", payload)
   end
 
   @doc """

lib/resend/emails/email.ex

@@ -20,6 +20,7 @@ defmodule Resend.Emails.Email do
           text: String.t() | nil,
           html: String.t() | nil,
           attachments: list(Attachment.t()) | nil,
+          template: map() | nil,
           last_event: String.t() | nil,
           created_at: DateTime.t() | nil
         }
@@ -37,6 +38,7 @@ defmodule Resend.Emails.Email do
     :text,
     :html,
     :attachments,
+    :template,
     :last_event,
     :created_at
   ]
@@ -55,6 +57,7 @@ defmodule Resend.Emails.Email do
       text: map["text"],
       html: map["html"],
       attachments: map["attachments"],
+      template: map["template"],
       last_event: map["last_event"],
       created_at: Util.parse_iso8601(map["created_at"])
     }

lib/resend/swoosh/adapter.ex

@@ -28,13 +28,36 @@ defmodule Resend.Swoosh.Adapter do
   ```
 
   And just like that, you should be all set to send emails with Resend!
+
+  ## Using Templates
+
+  To use Resend templates with Swoosh, add the template information using `put_provider_option/3`:
+
+  ```ex
+  import Swoosh.Email
+
+  new()
+  |> from({"Acme", "[email protected]"})
+  |> to("[email protected]")
+  |> put_provider_option(:template, %{
+    id: "order-confirmation",
+    variables: %{
+      PRODUCT: "Vintage Macintosh",
+      PRICE: 499
+    }
+  })
+  |> MyApp.Mailer.deliver()
+  ```
+
+  When using templates, you don't need to set the `html_body` or `text_body` as the template
+  will provide the content.
   """
 
   @behaviour Swoosh.Adapter
 
   @impl true
   def deliver(%Swoosh.Email{} = email, config) do
-    Resend.Emails.send(Resend.client(config), %{
+    payload = %{
       subject: email.subject,
       from: format_sender(email.from),
       to: format_recipients(email.to),
@@ -45,7 +68,16 @@ defmodule Resend.Swoosh.Adapter do
       html: email.html_body,
       text: email.text_body,
       attachments: format_attachments(email.attachments)
-    })
+    }
+
+    payload =
+      if template = email.provider_options[:template] do
+        Map.put(payload, :template, template)
+      else
+        payload
+      end
+
+    Resend.Emails.send(Resend.client(config), payload)
   end
 
   @impl true

test/resend/emails_test.exs

@@ -56,6 +56,97 @@ defmodule Resend.EmailsTest do
       end
     end
 
+    test "Sends an email with a template", context do
+      to = context.to
+      from = context.from
+      template_id = "order-confirmation"
+      variables = %{PRODUCT: "Vintage Macintosh", PRICE: 499}
+
+      opts = [
+        to: to,
+        from: from,
+        template: %{
+          id: template_id,
+          variables: variables
+        }
+      ]
+
+      Tesla.Mock.mock(fn request ->
+        assert request.method == :post
+        assert request.url == "https://api.resend.com/emails"
+
+        body = Jason.decode!(request.body)
+
+        # Assert template fields are present
+        assert body["template"]["id"] == template_id
+        assert body["template"]["variables"]["PRODUCT"] == "Vintage Macintosh"
+        assert body["template"]["variables"]["PRICE"] == 499
+
+        %Tesla.Env{status: 200, body: %{"id" => context.sent_email_id}}
+      end)
+
+      assert {:ok, %Resend.Emails.Email{}} = Resend.Emails.send(Map.new(opts))
+    end
+
+    test "Sends email with template via Swoosh adapter", context do
+      # Create Swoosh email with template in provider_options
+      email =
+        Swoosh.Email.new()
+        |> Swoosh.Email.to(context.to)
+        |> Swoosh.Email.from(context.from)
+        |> Swoosh.Email.put_provider_option(:template, %{
+          id: "welcome-email",
+          variables: %{
+            NAME: "John Doe",
+            COMPANY: "Acme Corp"
+          }
+        })
+
+      # Mock the API call and assert template is sent
+      Tesla.Mock.mock(fn request ->
+        assert request.method == :post
+        assert request.url == "https://api.resend.com/emails"
+
+        body = Jason.decode!(request.body)
+
+        # Assert template fields are present
+        assert body["template"]["id"] == "welcome-email"
+        assert body["template"]["variables"]["NAME"] == "John Doe"
+        assert body["template"]["variables"]["COMPANY"] == "Acme Corp"
+
+        %Tesla.Env{status: 200, body: %{"id" => context.sent_email_id}}
+      end)
+
+      # Deliver via Swoosh adapter
+      config = [api_key: context.api_key]
+      assert {:ok, _} = Resend.Swoosh.Adapter.deliver(email, config)
+    end
+
+    test "Sends email without template when not present in Swoosh email", context do
+      # Create regular Swoosh email without template
+      email =
+        Swoosh.Email.new()
+        |> Swoosh.Email.to(context.to)
+        |> Swoosh.Email.from(context.from)
+        |> Swoosh.Email.subject("Regular Email")
+        |> Swoosh.Email.text_body("This is a regular email")
+
+      # Mock the API call
+      Tesla.Mock.mock(fn request ->
+        body = Jason.decode!(request.body)
+
+        # Assert template field is not present
+        refute Map.has_key?(body, "template")
+        assert body["text"] == "This is a regular email"
+
+        %Tesla.Env{status: 200, body: %{"id" => context.sent_email_id}}
+      end)
+
+      # Deliver via Swoosh adapter
+      config = [api_key: context.api_key]
+      assert {:ok, _} = Resend.Swoosh.Adapter.deliver(email, config)
+    end
+
     test "Attachment struct accepts content_id field" do
       attachment = %Resend.Emails.Attachment{
         filename: "logo.jpg",