Add email notifications via Resend

- src/lib/email.ts: HTML templates for 4 email types (Second Brain design)
- Welcome email on user registration (Better Auth databaseHooks)
- Course access email when admin grants enrollment
- Homework submitted email to all admins/curators (first submission only)
- Feedback received email to student with feedback text and lesson link
- Update TECHNICAL.md: Resend domain, from-address, email vars, Stage 3 summary

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

src/app/(student)/courses/[slug]/lessons/[lessonId]/homework-actions.ts

@@ -4,6 +4,7 @@ import { prisma } from "@/lib/prisma";
 import { auth } from "@/lib/auth";
 import { headers } from "next/headers";
 import { revalidatePath } from "next/cache";
+import { sendHomeworkSubmittedEmail } from "@/lib/email";
 
 interface HomeworkFile {
   name: string;
@@ -31,15 +32,37 @@ export async function submitHomework(
     throw new Error("Работа уже проверена");
   }
 
+  let submissionId: string;
   if (existing) {
-    await prisma.homeworkSubmission.update({
+    const updated = await prisma.homeworkSubmission.update({
       where: { id: existing.id },
       data: { text, files: files as object[], submittedAt: new Date() },
     });
+    submissionId = updated.id;
   } else {
-    await prisma.homeworkSubmission.create({
+    const created = await prisma.homeworkSubmission.create({
       data: { homeworkId, userId: session.user.id, text, files: files as object[] },
     });
+    submissionId = created.id;
+
+    // Notify admins/curators on first submission only
+    const [lesson, admins] = await Promise.all([
+      prisma.homework.findUnique({
+        where: { id: homeworkId },
+        include: { lesson: { select: { title: true } } },
+      }),
+      prisma.user.findMany({
+        where: { role: { in: ["admin", "curator"] } },
+        select: { email: true, name: true },
+      }),
+    ]);
+    if (lesson) {
+      await Promise.all(
+        admins.map((a) =>
+          sendHomeworkSubmittedEmail(a.email, a.name, session.user.name, lesson.lesson.title, submissionId)
+        )
+      );
+    }
   }
 
   revalidatePath(`/courses/${slug}/lessons/${lessonId}`);

src/app/admin/courses/[courseId]/actions.ts

@@ -5,6 +5,7 @@ import { headers } from "next/headers";
 import { auth } from "@/lib/auth";
 import { revalidatePath } from "next/cache";
 import { redirect } from "next/navigation";
+import { sendCourseAccessEmail } from "@/lib/email";
 
 async function requireAdmin() {
   const session = await auth.api.getSession({ headers: await headers() });
@@ -70,6 +71,16 @@ export async function grantAccess(
       note: note || null,
     },
   });
+
+  // Send email notification
+  const [user, course] = await Promise.all([
+    prisma.user.findUnique({ where: { id: userId }, select: { email: true, name: true } }),
+    prisma.course.findUnique({ where: { id: courseId }, select: { title: true } }),
+  ]);
+  if (user && course) {
+    await sendCourseAccessEmail(user.email, user.name, course.title);
+  }
+
   revalidatePath(`/admin/courses/${courseId}`);
 }
 

src/app/curator/homework/[submissionId]/actions.ts

@@ -4,6 +4,7 @@ import { prisma } from "@/lib/prisma";
 import { auth } from "@/lib/auth";
 import { headers } from "next/headers";
 import { revalidatePath } from "next/cache";
+import { sendFeedbackReceivedEmail } from "@/lib/email";
 
 export async function submitFeedback(submissionId: string, text: string) {
   const session = await auth.api.getSession({ headers: await headers() });
@@ -15,6 +16,36 @@ export async function submitFeedback(submissionId: string, text: string) {
     data: { submissionId, curatorId: session.user.id, text },
   });
 
+  // Send email to student
+  const submission = await prisma.homeworkSubmission.findUnique({
+    where: { id: submissionId },
+    include: {
+      user: { select: { email: true, name: true } },
+      homework: {
+        include: {
+          lesson: {
+            select: {
+              title: true,
+              module: { select: { course: { select: { slug: true } } } },
+            },
+          },
+        },
+      },
+    },
+  });
+
+  if (submission) {
+    const { lesson } = submission.homework;
+    const lessonUrl = `${process.env.BETTER_AUTH_URL ?? "https://school.second-brain.ru"}/courses/${lesson.module.course.slug}/lessons/${submission.homework.lessonId}`;
+    await sendFeedbackReceivedEmail(
+      submission.user.email,
+      submission.user.name,
+      lesson.title,
+      text,
+      lessonUrl
+    );
+  }
+
   revalidatePath("/curator/homework");
   revalidatePath(`/curator/homework/${submissionId}`);
 }

src/lib/auth.ts

@@ -3,6 +3,7 @@ import { prismaAdapter } from "better-auth/adapters/prisma";
 import { admin } from "better-auth/plugins";
 import { prisma } from "./prisma";
 import bcrypt from "bcryptjs";
+import { sendWelcomeEmail } from "./email";
 
 export const auth = betterAuth({
   database: prismaAdapter(prisma, {
@@ -16,6 +17,15 @@ export const auth = betterAuth({
       verify: ({ hash, password }) => bcrypt.compare(password, hash),
     },
   },
+  databaseHooks: {
+    user: {
+      create: {
+        after: async (user) => {
+          await sendWelcomeEmail(user.email, user.name);
+        },
+      },
+    },
+  },
   plugins: [
     admin({
       defaultRole: "student",

src/lib/email.ts

@@ -0,0 +1,107 @@
+import { Resend } from "resend";
+
+const resend = new Resend(process.env.RESEND_API_KEY);
+const FROM = process.env.EMAIL_FROM ?? "noreply@mailsend.second-brain.ru";
+const BASE_URL = process.env.BETTER_AUTH_URL ?? "https://school.second-brain.ru";
+
+function base(content: string) {
+  return `<!DOCTYPE html>
+<html lang="ru">
+<head>
+  <meta charset="UTF-8" />
+  <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
+  <style>
+    body { margin: 0; padding: 0; background: #F5F5F0; font-family: 'Courier New', monospace; color: #323232; }
+    .wrap { max-width: 560px; margin: 40px auto; background: #F5F5F0; border: 2px solid #AAAAAA; box-shadow: 4px 4px 0 0 #AAAAAA; }
+    .header { padding: 24px 32px; border-bottom: 2px solid #AAAAAA; }
+    .header p { margin: 0; font-size: 14px; font-weight: 700; letter-spacing: 0.1em; text-transform: uppercase; }
+    .body { padding: 32px; }
+    .body p { margin: 0 0 16px; font-size: 14px; line-height: 1.6; }
+    .btn { display: inline-block; padding: 10px 24px; background: #E8F0D8; border: 2px solid #323232; box-shadow: 3px 3px 0 0 #323232; font-size: 13px; font-weight: 700; text-decoration: none; color: #323232; letter-spacing: 0.05em; text-transform: uppercase; }
+    .footer { padding: 16px 32px; border-top: 2px solid #AAAAAA; }
+    .footer p { margin: 0; font-size: 11px; color: #AAAAAA; }
+    .tag { display: inline-block; padding: 2px 8px; border: 1px solid #AAAAAA; font-size: 11px; color: #666; text-transform: uppercase; letter-spacing: 0.08em; }
+  </style>
+</head>
+<body>
+  <div class="wrap">
+    <div class="header"><p>Second Brain · Образовательная платформа</p></div>
+    <div class="body">${content}</div>
+    <div class="footer"><p>Это автоматическое письмо, не отвечайте на него.</p></div>
+  </div>
+</body>
+</html>`;
+}
+
+// ── Email senders ─────────────────────────────────────────────────────────────
+
+export async function sendCourseAccessEmail(to: string, name: string, courseTitle: string) {
+  await resend.emails.send({
+    from: FROM,
+    to,
+    subject: `Вам открыт доступ к курсу «${courseTitle}»`,
+    html: base(`
+      <p>Привет, ${name}!</p>
+      <p>Вам открыт доступ к курсу <strong>«${courseTitle}»</strong>.</p>
+      <p style="margin-bottom: 24px;">Перейдите на платформу чтобы начать обучение:</p>
+      <a href="${BASE_URL}/dashboard" class="btn">Перейти к курсам →</a>
+    `),
+  }).catch((e) => console.error("[email] sendCourseAccessEmail:", e));
+}
+
+export async function sendHomeworkSubmittedEmail(
+  to: string,
+  curatorName: string,
+  studentName: string,
+  lessonTitle: string,
+  submissionId: string
+) {
+  await resend.emails.send({
+    from: FROM,
+    to,
+    subject: `Новая работа на проверку — ${lessonTitle}`,
+    html: base(`
+      <p>Привет, ${curatorName}!</p>
+      <p>Студент <strong>${studentName}</strong> сдал работу по уроку <strong>«${lessonTitle}»</strong>.</p>
+      <p style="margin-bottom: 24px;">Откройте работу чтобы проверить и оставить фидбек:</p>
+      <a href="${BASE_URL}/curator/homework/${submissionId}" class="btn">Проверить работу →</a>
+    `),
+  }).catch((e) => console.error("[email] sendHomeworkSubmittedEmail:", e));
+}
+
+export async function sendFeedbackReceivedEmail(
+  to: string,
+  studentName: string,
+  lessonTitle: string,
+  feedbackText: string,
+  lessonUrl: string
+) {
+  await resend.emails.send({
+    from: FROM,
+    to,
+    subject: `Получен фидбек по уроку «${lessonTitle}»`,
+    html: base(`
+      <p>Привет, ${studentName}!</p>
+      <p>Куратор проверил вашу работу по уроку <strong>«${lessonTitle}»</strong> и оставил обратную связь:</p>
+      <div style="border-left: 3px solid #323232; padding: 12px 16px; margin: 16px 0; background: #E8F0D8; font-size: 13px; line-height: 1.6;">
+        ${feedbackText.replace(/\n/g, "<br/>")}
+      </div>
+      <p style="margin-bottom: 24px;">Вернитесь к уроку чтобы увидеть полный фидбек:</p>
+      <a href="${lessonUrl}" class="btn">Открыть урок →</a>
+    `),
+  }).catch((e) => console.error("[email] sendFeedbackReceivedEmail:", e));
+}
+
+export async function sendWelcomeEmail(to: string, name: string) {
+  await resend.emails.send({
+    from: FROM,
+    to,
+    subject: "Добро пожаловать в Second Brain",
+    html: base(`
+      <p>Привет, ${name}!</p>
+      <p>Ваш аккаунт на образовательной платформе <strong>Second Brain</strong> подтверждён.</p>
+      <p style="margin-bottom: 24px;">После того как администратор откроет вам доступ к курсу, вы получите письмо и сможете начать обучение.</p>
+      <a href="${BASE_URL}/dashboard" class="btn">Перейти на платформу →</a>
+    `),
+  }).catch((e) => console.error("[email] sendWelcomeEmail:", e));
+}