feat: add channel support

backend/src/main/java/com/openisle/controller/ChannelController.java

@@ -0,0 +1,35 @@
+package com.openisle.controller;
+
+import com.openisle.dto.ChannelDto;
+import com.openisle.model.User;
+import com.openisle.repository.UserRepository;
+import com.openisle.service.ChannelService;
+import lombok.RequiredArgsConstructor;
+import org.springframework.security.core.Authentication;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.List;
+
+@RestController
+@RequestMapping("/api/channels")
+@RequiredArgsConstructor
+public class ChannelController {
+    private final ChannelService channelService;
+    private final UserRepository userRepository;
+
+    private Long getCurrentUserId(Authentication auth) {
+        User user = userRepository.findByUsername(auth.getName())
+                .orElseThrow(() -> new IllegalArgumentException("User not found"));
+        return user.getId();
+    }
+
+    @GetMapping
+    public List<ChannelDto> listChannels(Authentication auth) {
+        return channelService.listChannels(getCurrentUserId(auth));
+    }
+
+    @PostMapping("/{channelId}/join")
+    public ChannelDto joinChannel(@PathVariable Long channelId, Authentication auth) {
+        return channelService.joinChannel(channelId, getCurrentUserId(auth));
+    }
+}

backend/src/main/java/com/openisle/controller/MessageController.java

@@ -59,6 +59,14 @@ public class MessageController {
         return ResponseEntity.ok(toDto(message));
     }
 
+    @PostMapping("/conversations/{conversationId}/messages")
+    public ResponseEntity<MessageDto> sendMessageToConversation(@PathVariable Long conversationId,
+                                                                @RequestBody ChannelMessageRequest req,
+                                                                Authentication auth) {
+        Message message = messageService.sendMessageToConversation(getCurrentUserId(auth), conversationId, req.getContent());
+        return ResponseEntity.ok(toDto(message));
+    }
+
     @PostMapping("/conversations/{conversationId}/read")
     public ResponseEntity<Void> markAsRead(@PathVariable Long conversationId, Authentication auth) {
         messageService.markConversationAsRead(conversationId, getCurrentUserId(auth));
@@ -114,4 +122,16 @@ public class MessageController {
             this.content = content;
         }
     }
+
+    static class ChannelMessageRequest {
+        private String content;
+
+        public String getContent() {
+            return content;
+        }
+
+        public void setContent(String content) {
+            this.content = content;
+        }
+    }
 }