Email templating engine

.python-version

@@ -1 +1 @@
-3.12.9
+3.13.8

app/core/config.py

@@ -23,7 +23,9 @@ class Settings(BaseSettings):
         frozen=True,
     )
     # APP
-    RUN_ENV: Literal["local", "develop", "staging", "production"] = "local"
+    RUN_ENV: Literal["local", "develop", "staging", "production", "test"] = (
+        "local"
+    )
     PROCESS_TYPE: Literal["api", "worker", "beat"]
     API_V1_STR: str = "/api/v1"
     SECRET_KEY: str = secrets.token_urlsafe(32)

app/emails/services/email_templates_service.py

@@ -0,0 +1,52 @@
+from __future__ import annotations
+
+from enum import Enum
+from typing import Any, ClassVar, Literal, TypedDict, Unpack, overload
+
+from jinja2 import Environment, FileSystemLoader
+
+
+class EmailTemplate(Enum):
+    WELCOME = "welcome.j2"
+    OTHER = "_base.j2"
+
+
+class _WelcomeKwargs(TypedDict):
+    name: str
+
+
+class _OtherKwargs(TypedDict):
+    pass
+
+
+class EmailTemplatesService:
+    _instance: ClassVar[EmailTemplatesService | None] = None
+    _environment: ClassVar[Environment]
+
+    def __new__(cls) -> EmailTemplatesService:
+        if cls._instance:
+            return cls._instance
+
+        cls._environment = Environment(
+            loader=FileSystemLoader("app/emails/templates"),
+        )
+
+        cls._instance = super().__new__(cls)
+        return cls._instance
+
+    @overload
+    def render(
+        self,
+        template: Literal[EmailTemplate.WELCOME],
+        **kw: Unpack[_WelcomeKwargs],
+    ) -> str: ...
+    @overload
+    def render(
+        self,
+        template: Literal[EmailTemplate.OTHER],
+        **kw: Unpack[_OtherKwargs],
+    ) -> str: ...
+
+    def render(self, template: EmailTemplate, **kw: Any) -> str:
+        jinja_template = self._environment.get_template(template.value)
+        return jinja_template.render(**kw)

app/emails/services/emails_service.py

@@ -1,54 +1,36 @@
-from enum import Enum
-from string import Template
-
 from app.core.config import settings
 from app.users.schemas.user_schema import UserInDB
+
+from app.emails._global_state import get_client
 from app.emails.clients.base import BaseEmailClient
 from app.emails.schema.email import Email, EmailContext
-from app.emails._global_state import get_client
-
-
-class Paths(Enum):
-    NEW_USER = "app/emails/templates/welcome_email.html"
+from app.emails.services.email_templates_service import (
+    EmailTemplatesService,
+    EmailTemplate,
+)
 
 
 class EmailService:
     def __init__(self, email_client: BaseEmailClient | None = None):
         self.email_client = email_client or get_client()
-
-    def _get_email(
-        self,
-        recipient_email: str,
-        template: str,
-        subject: str,
-        html_message_input: dict | None = None,
-    ) -> Email:
-        with open(template, "r") as file:
-            html_template_string = file.read()
-
-        html_message_input = html_message_input or {}
-        html = Template(html_template_string).substitute(**html_message_input)
-
-        return Email(
-            to_emails=[recipient_email],
-            subject=subject,
-            html=html,
-        )
+        self.template_service = EmailTemplatesService()
 
     def send_new_user_email(
         self,
         user: UserInDB,
     ) -> None:
-        email = self._get_email(
-            user.email,
-            Paths.NEW_USER.value,
-            "Welcome",
-        )
-
-        email.context = EmailContext(
-            max_retries=settings.SEND_WELCOME_EMAIL_MAX_RETRIES,
-            backoff_in_seconds=settings.SEND_WELCOME_EMAIL_RETRY_BACKOFF_VALUE,
-            error_message=f"Sending new user email to user {user.id} failed",
+        email = Email(
+            to_emails=[user.email],
+            subject="Welcome",
+            html=self.template_service.render(
+                EmailTemplate.WELCOME,
+                name=user.email,
+            ),
+            context=EmailContext(
+                max_retries=settings.SEND_WELCOME_EMAIL_MAX_RETRIES,
+                backoff_in_seconds=settings.SEND_WELCOME_EMAIL_RETRY_BACKOFF_VALUE,
+                error_message=f"Sending new user email to user {user.id} failed",
+            ),
         )
 
         self.email_client.send_email(email)
@@ -57,10 +39,13 @@ def send_user_remind_email(
         self,
         user: UserInDB,
     ) -> None:
-        email = self._get_email(
-            user.email,
-            Paths.NEW_USER.value,
-            "Welcome",
+        email = Email(
+            to_emails=[user.email],
+            subject="Welcome",
+            html=self.template_service.render(
+                EmailTemplate.WELCOME,
+                name=user.email,
+            ),
         )
 
         self.email_client.send_email(email)

app/emails/templates/welcome_email.html → app/emails/templates/_base.j2

@@ -3,7 +3,9 @@
   <head>
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-    <title>Email Template</title>
+    <title>
+        {% block title %}{% endblock title %}
+    </title>
     <style>
       @media screen and (max-width: 599px) {
         .mobile-hidden {
@@ -31,6 +33,6 @@
       justify-content: center;
     "
   >
-    <h1>Welcome</h1>
+    {% block body %}{% endblock body %}
   </body>
 </html>

app/emails/templates/welcome.j2

@@ -0,0 +1,9 @@
+{% extends "_base.j2" %}
+
+{% block title %}
+    Welcome
+{% endblock title %}
+
+{% block body %}
+    <h1>Welcome {{ name }}</h1>
+{% endblock body %}