Resend: new ESP [WIP] - implement backend

anymail/backends/resend.py

@@ -0,0 +1,151 @@
+import mimetypes
+
+from ..message import AnymailRecipientStatus
+from ..utils import CaseInsensitiveCasePreservingDict, get_anymail_setting
+from .base_requests import AnymailRequestsBackend, RequestsPayload
+
+
+class EmailBackend(AnymailRequestsBackend):
+    """
+    Resend (resend.com) API Email Backend
+    """
+
+    esp_name = "Resend"
+
+    def __init__(self, **kwargs):
+        """Init options from Django settings"""
+        esp_name = self.esp_name
+        self.api_key = get_anymail_setting(
+            "api_key", esp_name=esp_name, kwargs=kwargs, allow_bare=True
+        )
+        api_url = get_anymail_setting(
+            "api_url",
+            esp_name=esp_name,
+            kwargs=kwargs,
+            default="https://api.resend.com/",
+        )
+        if not api_url.endswith("/"):
+            api_url += "/"
+        super().__init__(api_url, **kwargs)
+
+    def build_message_payload(self, message, defaults):
+        return ResendPayload(message, defaults, self)
+
+    def parse_recipient_status(self, response, payload, message):
+        # Resend provides single message id, no other information.
+        # Assume "queued".
+        parsed_response = self.deserialize_json_response(response, payload, message)
+        message_id = parsed_response["id"]
+        recipient_status = CaseInsensitiveCasePreservingDict(
+            {
+                recip.addr_spec: AnymailRecipientStatus(
+                    message_id=message_id, status="queued"
+                )
+                for recip in payload.recipients
+            }
+        )
+        return dict(recipient_status)
+
+
+class ResendPayload(RequestsPayload):
+    def __init__(self, message, defaults, backend, *args, **kwargs):
+        self.recipients = []  # for parse_recipient_status
+        headers = kwargs.pop("headers", {})
+        headers["Authorization"] = "Bearer %s" % backend.api_key
+        headers["Content-Type"] = "application/json"
+        headers["Accept"] = "application/json"
+        super().__init__(message, defaults, backend, headers=headers, *args, **kwargs)
+
+    def get_api_endpoint(self):
+        return "emails"
+
+    def serialize_data(self):
+        return self.serialize_json(self.data)
+
+    #
+    # Payload construction
+    #
+
+    def init_payload(self):
+        self.data = {}  # becomes json
+
+    def set_from_email(self, email):
+        self.data["from"] = email.address
+
+    def set_recipients(self, recipient_type, emails):
+        assert recipient_type in ["to", "cc", "bcc"]
+        if emails:
+            field = recipient_type
+            self.data[field] = [email.address for email in emails]
+            self.recipients += emails
+
+    def set_subject(self, subject):
+        self.data["subject"] = subject
+
+    def set_reply_to(self, emails):
+        if emails:
+            self.data["reply_to"] = [email.address for email in emails]
+
+    def set_extra_headers(self, headers):
+        self.data["headers"] = headers
+
+    def set_text_body(self, body):
+        self.data["text"] = body
+
+    def set_html_body(self, body):
+        if "html" in self.data:
+            # second html body could show up through multiple alternatives,
+            # or html body + alternative
+            self.unsupported_feature("multiple html parts")
+        self.data["html"] = body
+
+    @staticmethod
+    def make_attachment(attachment):
+        """Returns Resend attachment dict for attachment"""
+        filename = attachment.name or ""
+        if not filename:
+            # Provide default name with reasonable extension.
+            # (Resend guesses content type from the filename extension;
+            # there doesn't seem to be any other way to specify it.)
+            ext = mimetypes.guess_extension(attachment.content_type)
+            if ext is not None:
+                filename = f"attachment{ext}"
+        att = {"content": attachment.b64content, "filename": filename}
+        # attachment.inline / attachment.cid not supported
+        return att
+
+    def set_attachments(self, attachments):
+        if attachments:
+            if any(att.content_id for att in attachments):
+                self.unsupported_feature("inline content-id")
+            self.data["attachments"] = [
+                self.make_attachment(attachment) for attachment in attachments
+            ]
+
+    def set_metadata(self, metadata):
+        # TODO: optionally use custom header
+        self.data["tags"] = [
+            {"name": key, "value": str(value)} for key, value in metadata.items()
+        ]
+
+    # Resend doesn't support delayed sending
+    # def set_send_at(self, send_at):
+
+    def set_tags(self, tags):
+        # TODO: optionally use tag or custom header
+        super().set_tags(tags)
+
+    # Resend doesn't support changing click/open tracking per message
+    # def set_track_clicks(self, track_clicks):
+    # def set_track_opens(self, track_opens):
+
+    # Resend doesn't support server-rendered templates.
+    # (Their template feature is rendered client-side,
+    # using React in node.js.)
+    # def set_template_id(self, template_id):
+    # def set_merge_data(self, merge_data):
+    # def set_merge_global_data(self, merge_global_data):
+    # def set_merge_metadata(self, merge_metadata):
+
+    def set_esp_extra(self, extra):
+        self.data.update(extra)