fix: useState hook error in catalog + add certificate download in learning page

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/web/src/app/(dashboard)/dashboard/catalog/[id]/page.tsx

@@ -34,6 +34,7 @@ export default function PublicCoursePage() {
   const [loading, setLoading] = useState(true);
   const [enrolling, setEnrolling] = useState(false);
   const [enrolled, setEnrolled] = useState(false);
+  const [expandedChapters, setExpandedChapters] = useState<string[]>([]);
 
   useEffect(() => {
     if (!id) return;
@@ -221,12 +222,19 @@ export default function PublicCoursePage() {
           <h2 className="text-xl font-semibold mb-4">Содержание курса</h2>
           <div className="space-y-2">
             {course.chapters.map((chapter: any) => {
-              const [expanded, setExpanded] = useState(false);
+              const expanded = expandedChapters.includes(chapter.id);
+              const toggleExpanded = () => {
+                setExpandedChapters(prev =>
+                  prev.includes(chapter.id)
+                    ? prev.filter(id => id !== chapter.id)
+                    : [...prev, chapter.id]
+                );
+              };
               return (
                 <div key={chapter.id} className="border rounded-lg overflow-hidden">
                   <button
                     className="flex items-center justify-between w-full p-4 hover:bg-muted/50 transition-colors"
-                    onClick={() => setExpanded(!expanded)}
+                    onClick={toggleExpanded}
                   >
                     <div className="flex items-center gap-3">
                       <BookOpen className="h-4 w-4 text-primary" />

apps/web/src/app/(dashboard)/dashboard/learning/page.tsx

@@ -2,7 +2,8 @@
 
 import { useEffect, useState } from 'react';
 import Link from 'next/link';
-import { GraduationCap, BookOpen, Loader2, Trophy } from 'lucide-react';
+import { GraduationCap, BookOpen, Loader2, Trophy, Download } from 'lucide-react';
+import { Button } from '@/components/ui/button';
 import { Card, CardContent } from '@/components/ui/card';
 import { Progress } from '@/components/ui/progress';
 import { api } from '@/lib/api';
@@ -28,6 +29,13 @@ export default function LearningPage() {
   const [enrollments, setEnrollments] = useState<EnrollmentData[]>([]);
   const [loading, setLoading] = useState(true);
 
+  const handleDownloadCertificate = async (courseId: string) => {
+    try {
+      const { certificateUrl } = await api.getCertificate(courseId);
+      window.open(certificateUrl, '_blank');
+    } catch { /* silent */ }
+  };
+
   useEffect(() => {
     if (authLoading || !user) { setLoading(false); return; }
     (async () => {
@@ -97,6 +105,17 @@ export default function LearningPage() {
                       </div>
                       <Progress value={enrollment.progress} className="h-1.5" />
                     </div>
+                    {enrollment.completedAt && (
+                      <Button
+                        size="sm"
+                        variant="outline"
+                        className="w-full mt-3"
+                        onClick={(e) => { e.preventDefault(); handleDownloadCertificate(enrollment.course.id); }}
+                      >
+                        <Download className="mr-2 h-3.5 w-3.5" />
+                        Скачать сертификат
+                      </Button>
+                    )}
                   </CardContent>
                 </Card>
               </Link>

apps/web/src/components/dashboard/course-chat.tsx

@@ -0,0 +1,88 @@
+'use client';
+
+import { useState, useEffect, useRef } from 'react';
+import { Send, MessageCircle } from 'lucide-react';
+import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card';
+import { Button } from '@/components/ui/button';
+import { cn } from '@/lib/utils';
+
+interface Message {
+  id: string;
+  content: string;
+  createdAt: string;
+  user: { id: string; name: string | null; avatarUrl: string | null };
+}
+
+interface CourseChatProps {
+  groupId: string;
+  userId: string;
+  onSendMessage: (content: string) => Promise<void>;
+  messages: Message[];
+}
+
+export function CourseChat({ groupId, userId, onSendMessage, messages }: CourseChatProps) {
+  const [newMessage, setNewMessage] = useState('');
+  const [sending, setSending] = useState(false);
+  const messagesEndRef = useRef<HTMLDivElement>(null);
+
+  useEffect(() => {
+    messagesEndRef.current?.scrollIntoView({ behavior: 'smooth' });
+  }, [messages]);
+
+  const handleSend = async () => {
+    if (!newMessage.trim() || sending) return;
+    setSending(true);
+    try {
+      await onSendMessage(newMessage);
+      setNewMessage('');
+    } finally {
+      setSending(false);
+    }
+  };
+
+  return (
+    <Card className="flex flex-col h-[500px]">
+      <CardHeader className="pb-3">
+        <CardTitle className="flex items-center gap-2 text-base">
+          <MessageCircle className="h-4 w-4" />
+          Чат курса
+        </CardTitle>
+      </CardHeader>
+      <CardContent className="flex-1 flex flex-col min-h-0 p-4">
+        <div className="flex-1 overflow-auto space-y-3 mb-3">
+          {messages.map((msg) => {
+            const isOwn = msg.user.id === userId;
+            return (
+              <div key={msg.id} className={cn('flex gap-2', isOwn && 'flex-row-reverse')}>
+                <div className="h-8 w-8 shrink-0 rounded-full bg-primary/10 flex items-center justify-center text-xs font-bold text-primary">
+                  {msg.user.name?.[0] || 'U'}
+                </div>
+                <div className={cn('flex flex-col gap-1 max-w-[70%]', isOwn && 'items-end')}>
+                  <span className="text-xs text-muted-foreground">{msg.user.name || 'Аноним'}</span>
+                  <div className={cn('rounded-lg px-3 py-2 text-sm', isOwn ? 'bg-primary text-primary-foreground' : 'bg-muted')}>
+                    {msg.content}
+                  </div>
+                </div>
+              </div>
+            );
+          })}
+          <div ref={messagesEndRef} />
+        </div>
+        <div className="flex gap-2">
+          <input
+            type="text"
+            value={newMessage}
+            onChange={(e) => setNewMessage(e.target.value)}
+            onKeyDown={(e) => e.key === 'Enter' && !e.shiftKey && handleSend()}
+            placeholder="Написать сообщение..."
+            className="flex-1 px-3 py-2 text-sm border rounded-lg focus:outline-none focus:ring-2 focus:ring-primary"
+            disabled={sending}
+          />
+          <Button size="sm" onClick={handleSend} disabled={sending || !newMessage.trim()}>
+            <Send className="h-4 w-4" />
+          </Button>
+        </div>
+      </CardContent>
+    </Card>
+  );
+}