feat: [BE] 인메모리 방식으로 중앙 서버 로직 구현

- socket register api 구현
- room join 이벤트 api 구현
- room leave 이벤트 api 구현

backEnd/center/src/connections/connections.controller.ts

@@ -1,13 +1,28 @@
 import { Controller, Post, Body } from '@nestjs/common';
 import { ConnectionsService } from './connections.service';
+import { SignalingConnectionDto } from './dto/signaling-connections.dto';
+import { RegisterSignalingSocket } from './dto/register-signaling-socket.dto';
+import { ReturnConnectionsDto } from './dto/return-connections.dto copy';
 
 @Controller('connections')
 export class ConnectionsController {
   constructor(private readonly connectionsService: ConnectionsService) {}
 
-  @Post()
-  create() {
-    const url = this.connectionsService.create();
-    return { url: url };
+  @Post('signaling')
+  register(@Body() data: RegisterSignalingSocket) {
+    return this.connectionsService.registerSockets(data);
+  }
+
+  @Post('signaling/join')
+  create(@Body() data: SignalingConnectionDto) {
+    const response: ReturnConnectionsDto =
+      this.connectionsService.createConnection(data);
+    return response;
+  }
+
+  @Post('signaling/leave')
+  leave(@Body() data: SignalingConnectionDto) {
+    this.connectionsService.leaveRoom(data);
+    return 'leave Success';
   }
 }

backEnd/center/src/connections/connections.service.ts

@@ -1,8 +1,60 @@
 import { Injectable } from '@nestjs/common';
+import { ReturnConnectionsDto } from './dto/return-connections.dto copy';
+import { SignalingConnectionDto } from './dto/signaling-connections.dto';
+import { RegisterSignalingSocket } from './dto/register-signaling-socket.dto';
 
 @Injectable()
 export class ConnectionsService {
-  create() {
-    return 'url';
+  private roomToSocket = new Map<string, string>();
+  private socketToConnections = new Map<string, number>();
+
+  registerSockets(data: RegisterSignalingSocket) {
+    const url = data.url;
+    console.log(url);
+    const isSocket = this.socketToConnections.has(url);
+
+    if (isSocket) {
+      return 'Already Registered';
+    }
+
+    this.socketToConnections.set(url, 0);
+    return 'Register Success';
+  }
+
+  createConnection(data: SignalingConnectionDto): ReturnConnectionsDto {
+    const { roomName } = data;
+
+    const isRoom = this.roomToSocket.has(roomName);
+
+    if (isRoom) {
+      const socket = this.roomToSocket.get(roomName);
+      const connections = this.socketToConnections.get(socket);
+      this.socketToConnections.set(socket, connections + 1);
+      const result: ReturnConnectionsDto = { url: socket };
+      return result;
+    }
+
+    let socket = null;
+    let connections = Number.MAX_SAFE_INTEGER;
+    this.socketToConnections.forEach((value, key) => {
+      if (value < connections) {
+        connections = value;
+        socket = key;
+      }
+    });
+
+    this.roomToSocket.set(roomName, socket);
+    this.socketToConnections.set(socket, connections + 1);
+    const result: ReturnConnectionsDto = { url: socket };
+
+    return result;
+  }
+
+  leaveRoom(data: SignalingConnectionDto): void {
+    const { roomName } = data;
+    const socket = this.roomToSocket.get(roomName);
+    const connections = this.socketToConnections.get(socket);
+    this.socketToConnections.set(socket, connections - 1);
+    return;
   }
 }

backEnd/center/src/connections/dto/register-signaling-socket.dto.ts

@@ -0,0 +1,3 @@
+export class RegisterSignalingSocket {
+  url: string;
+}

backEnd/center/src/connections/dto/return-connections.dto copy.ts

@@ -0,0 +1,3 @@
+export class ReturnConnectionsDto {
+  url: string;
+}

backEnd/center/src/connections/dto/signaling-connections.dto.ts

@@ -0,0 +1,3 @@
+export class SignalingConnectionDto {
+  roomName: string;
+}