feat: Add email notifications for all notification types

Sends HTML email via Gmail SMTP when notifications are created.
Supports multi-language (en/ko/mn/ru) based on user country.
Runs in background thread to avoid blocking requests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/api/notification.py

@@ -10,6 +10,7 @@ from ..schemas.notification import (
     NotificationCreate, NotificationResponse,
     NotificationListResponse, NotificationMarkRead
 )
+from ..services.email_service import send_notification_email
 from .auth import get_current_user
 
 router = APIRouter(prefix="/notifications", tags=["notifications"])
@@ -29,7 +30,7 @@ def create_notification(
     related_id: Optional[int] = None,
     related_type: Optional[str] = None
 ) -> Notification:
-    """Create a new notification"""
+    """Create a new notification and send email"""
     notification = Notification(
         user_id=user_id,
         notification_type=notification_type,
@@ -42,6 +43,23 @@ def create_notification(
     db.add(notification)
     db.commit()
     db.refresh(notification)
+
+    # Send email notification (background thread, non-blocking)
+    try:
+        user = db.query(User).filter(User.id == user_id).first()
+        if user and user.email:
+            send_notification_email(
+                to_email=user.email,
+                notification_type=notification_type,
+                title=title,
+                message=message,
+                link=link,
+                user_name=user.name,
+                user_country=user.country,
+            )
+    except Exception as e:
+        print(f"[WARN] Email notification failed for user {user_id}: {e}")
+
     return notification
 
 

backend/app/services/email_service.py

@@ -0,0 +1,187 @@
+"""
+Email Notification Service
+Sends email notifications to users for important events (recommendations, shipping, payments, etc.)
+Reuses existing SMTP configuration (Gmail).
+"""
+import smtplib
+import threading
+from email.mime.text import MIMEText
+from email.mime.multipart import MIMEMultipart
+from typing import Optional
+
+from ..config import get_settings
+
+settings = get_settings()
+
+# Notification types that should trigger email
+EMAIL_ENABLED_TYPES = {
+    "vehicle_recommended",
+    "shipping_update",
+    "payment_confirmed",
+    "withdrawal_processed",
+    "inquiry_reply",
+    "dealer_approved",
+    "dealer_rejected",
+    "referral_reward",
+    "share_purchased",
+}
+
+
+def get_user_language(country: Optional[str]) -> str:
+    """Detect language from user's country"""
+    if not country:
+        return "en"
+    c = country.lower().strip()
+    if c in ("korea", "south korea", "kr", "한국"):
+        return "ko"
+    if c in ("mongolia", "mn", "монгол"):
+        return "mn"
+    if c in ("russia", "ru", "россия"):
+        return "ru"
+    return "en"
+
+
+def _build_email_content(
+    notification_type: str,
+    title: str,
+    message: str,
+    link: Optional[str],
+    user_name: Optional[str],
+    language: str,
+) -> tuple[str, str]:
+    """Build email subject and HTML body for a notification.
+    Returns (subject, html_body).
+    """
+    base_url = "https://autonetsellcar.com"
+    full_link = f"{base_url}{link}" if link else base_url
+
+    # Greeting by language
+    greetings = {
+        "en": f"Hi {user_name}," if user_name else "Hello,",
+        "ko": f"{user_name}님, 안녕하세요." if user_name else "안녕하세요,",
+        "mn": f"Сайн байна уу, {user_name}." if user_name else "Сайн байна уу,",
+        "ru": f"Здравствуйте, {user_name}." if user_name else "Здравствуйте,",
+    }
+
+    button_labels = {
+        "en": "View Details",
+        "ko": "자세히 보기",
+        "mn": "Дэлгэрэнгүй үзэх",
+        "ru": "Подробнее",
+    }
+
+    footers = {
+        "en": "You received this email because you have an account on AutonetSellCar.com",
+        "ko": "AutonetSellCar.com 계정이 있어 이 이메일을 받으셨습니다",
+        "mn": "Та AutonetSellCar.com-д бүртгэлтэй тул энэ имэйлийг хүлээн авлаа",
+        "ru": "Вы получили это письмо, так как у вас есть аккаунт на AutonetSellCar.com",
+    }
+
+    greeting = greetings.get(language, greetings["en"])
+    button_label = button_labels.get(language, button_labels["en"])
+    footer = footers.get(language, footers["en"])
+
+    subject = f"AutonetSellCar - {title}"
+
+    html_body = f"""\
+<!DOCTYPE html>
+<html>
+<head><meta charset="utf-8"></head>
+<body style="margin:0;padding:0;background:#f4f4f4;font-family:Arial,sans-serif;">
+<table width="100%" cellpadding="0" cellspacing="0" style="background:#f4f4f4;padding:20px 0;">
+<tr><td align="center">
+<table width="600" cellpadding="0" cellspacing="0" style="background:#ffffff;border-radius:8px;overflow:hidden;box-shadow:0 2px 8px rgba(0,0,0,0.08);">
+  <!-- Header -->
+  <tr>
+    <td style="background:#1a1a2e;padding:24px 32px;">
+      <h1 style="margin:0;color:#ffffff;font-size:20px;font-weight:600;">AutonetSellCar</h1>
+    </td>
+  </tr>
+  <!-- Body -->
+  <tr>
+    <td style="padding:32px;">
+      <p style="margin:0 0 16px;color:#333;font-size:15px;">{greeting}</p>
+      <h2 style="margin:0 0 12px;color:#1a1a2e;font-size:18px;">{title}</h2>
+      <p style="margin:0 0 24px;color:#555;font-size:15px;line-height:1.6;">{message}</p>
+      <a href="{full_link}"
+         style="display:inline-block;background:#2563eb;color:#ffffff;text-decoration:none;padding:12px 28px;border-radius:6px;font-size:14px;font-weight:600;">
+        {button_label}
+      </a>
+    </td>
+  </tr>
+  <!-- Footer -->
+  <tr>
+    <td style="padding:20px 32px;background:#f9fafb;border-top:1px solid #e5e7eb;">
+      <p style="margin:0;color:#9ca3af;font-size:12px;">{footer}</p>
+    </td>
+  </tr>
+</table>
+</td></tr>
+</table>
+</body>
+</html>"""
+
+    return subject, html_body
+
+
+def _send_smtp(to_email: str, subject: str, html_body: str) -> bool:
+    """Send an email via SMTP. Returns True on success."""
+    try:
+        if not settings.SMTP_USER or not settings.SMTP_PASSWORD:
+            print(f"[DEV] Notification email to {to_email}: {subject}")
+            return True
+
+        msg = MIMEMultipart("alternative")
+        msg["From"] = f"{settings.SMTP_FROM_NAME} <{settings.SMTP_FROM_EMAIL or settings.SMTP_USER}>"
+        msg["To"] = to_email
+        msg["Subject"] = subject
+        msg.attach(MIMEText(html_body, "html", "utf-8"))
+
+        with smtplib.SMTP(settings.SMTP_HOST, settings.SMTP_PORT) as server:
+            server.starttls()
+            server.login(settings.SMTP_USER, settings.SMTP_PASSWORD)
+            server.send_message(msg)
+
+        print(f"[INFO] Notification email sent to {to_email}: {subject}")
+        return True
+
+    except Exception as e:
+        print(f"[ERROR] Failed to send notification email to {to_email}: {e}")
+        return False
+
+
+def send_notification_email(
+    to_email: str,
+    notification_type: str,
+    title: str,
+    message: str,
+    link: Optional[str] = None,
+    user_name: Optional[str] = None,
+    user_country: Optional[str] = None,
+) -> None:
+    """Send a notification email in a background thread (non-blocking).
+    Only sends for notification types in EMAIL_ENABLED_TYPES.
+    """
+    if notification_type not in EMAIL_ENABLED_TYPES:
+        return
+
+    if not to_email:
+        return
+
+    language = get_user_language(user_country)
+    subject, html_body = _build_email_content(
+        notification_type=notification_type,
+        title=title,
+        message=message,
+        link=link,
+        user_name=user_name,
+        language=language,
+    )
+
+    # Send in background thread to avoid blocking the request
+    thread = threading.Thread(
+        target=_send_smtp,
+        args=(to_email, subject, html_body),
+        daemon=True,
+    )
+    thread.start()