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Add whiteboard sample and MCP server implementation
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‎samples/Whiteboard/Controllers/BackgroundController.cs‎

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// Copyright (c) Microsoft. All rights reserved.
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// Licensed under the MIT license. See LICENSE file in the project root for full license information.
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using Microsoft.AspNetCore.Http;
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using Microsoft.AspNetCore.Mvc;
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using Microsoft.AspNetCore.SignalR;
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using System;
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using System.IO;
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using System.Threading.Tasks;
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namespace Microsoft.Azure.SignalR.Samples.Whiteboard;
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[Route("/background")]
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public class BackgroundController(IHubContext<DrawHub> context, Diagram diagram) : Controller
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{
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private readonly IHubContext<DrawHub> hubContext = context;
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private readonly Diagram diagram = diagram;
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[HttpPost("upload")]
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public async Task<IActionResult> Upload(IFormFile file)
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{
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diagram.BackgroundId = Guid.NewGuid().ToString().Substring(0, 8);
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diagram.Background = new byte[file.Length];
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diagram.BackgroundContentType = file.ContentType;
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using (var stream = new MemoryStream(diagram.Background))
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{
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await file.CopyToAsync(stream);
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}
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await hubContext.Clients.All.SendAsync("BackgroundUpdated", diagram.BackgroundId);
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return Ok();
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}
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[HttpGet("{id}")]
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public IActionResult Download(string id)
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{
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if (diagram.BackgroundId != id) return NotFound();
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return File(diagram.Background, diagram.BackgroundContentType);
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}
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}

‎samples/Whiteboard/Diagram.cs‎

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// Copyright (c) Microsoft. All rights reserved.
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// Licensed under the MIT license. See LICENSE file in the project root for full license information.
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using System.Collections.Concurrent;
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using System.Collections.Generic;
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using System.Threading;
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namespace Microsoft.Azure.SignalR.Samples.Whiteboard;
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public class Point
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{
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public int X { get; set; }
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public int Y { get; set; }
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}
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public abstract class Shape
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{
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public string Color { get; set; }
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public int Width { get; set; }
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}
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public class Polyline : Shape
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{
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public List<Point> Points { get; set; }
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}
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public class Line : Shape
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{
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public Point Start { get; set; }
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public Point End { get; set; }
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}
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public class Circle : Shape
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{
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public Point Center { get; set; }
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public int Radius { get; set; }
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}
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public class Rect : Shape
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{
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public Point TopLeft { get; set; }
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public Point BottomRight { get; set; }
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}
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public class Ellipse : Shape
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{
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public Point TopLeft { get; set; }
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public Point BottomRight { get; set; }
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}
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public class Diagram
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{
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private int totalUsers = 0;
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public byte[] Background { get; set; }
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public string BackgroundContentType { get; set; }
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public string BackgroundId { get; set; }
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public ConcurrentDictionary<string, Shape> Shapes { get; } = new ConcurrentDictionary<string, Shape>();
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public int UserEnter()
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{
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return Interlocked.Increment(ref totalUsers);
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}
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public int UserLeave()
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{
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return Interlocked.Decrement(ref totalUsers);
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}
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}

‎samples/Whiteboard/Hub/DrawHub.cs‎

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// Copyright (c) Microsoft. All rights reserved.
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// Licensed under the MIT license. See LICENSE file in the project root for full license information.
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using Microsoft.AspNetCore.SignalR;
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using System.Collections.Generic;
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using System.Threading.Tasks;
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using System.Linq;
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using System;
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namespace Microsoft.Azure.SignalR.Samples.Whiteboard;
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public class DrawHub(Diagram diagram) : Hub
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{
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private readonly Diagram diagram = diagram;
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private async Task UpdateShape(string id, Shape shape)
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{
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diagram.Shapes[id] = shape;
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await Clients.Others.SendAsync("ShapeUpdated", id, shape.GetType().Name, shape);
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}
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public override Task OnConnectedAsync()
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{
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var t = Task.WhenAll(diagram.Shapes.AsEnumerable().Select(l => Clients.Client(Context.ConnectionId).SendAsync("ShapeUpdated", l.Key, l.Value.GetType().Name, l.Value)));
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if (diagram.Background != null) t = t.ContinueWith(_ => Clients.Client(Context.ConnectionId).SendAsync("BackgroundUpdated", diagram.BackgroundId));
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return t.ContinueWith(_ => Clients.All.SendAsync("UserUpdated", diagram.UserEnter()));
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}
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public override Task OnDisconnectedAsync(Exception exception)
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{
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return Clients.All.SendAsync("UserUpdated", diagram.UserLeave());
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}
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public async Task RemoveShape(string id)
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{
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diagram.Shapes.Remove(id, out _);
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await Clients.Others.SendAsync("ShapeRemoved", id);
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}
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public async Task AddOrUpdatePolyline(string id, Polyline polyline)
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{
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await this.UpdateShape(id, polyline);
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}
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public async Task PatchPolyline(string id, Polyline polyline)
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{
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if (diagram.Shapes[id] is not Polyline p) throw new InvalidOperationException($"Shape {id} does not exist or is not a polyline.");
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if (polyline.Color != null) p.Color = polyline.Color;
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if (polyline.Width != 0) p.Width = polyline.Width;
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p.Points.AddRange(polyline.Points);
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await Clients.Others.SendAsync("ShapePatched", id, polyline);
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}
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public async Task AddOrUpdateLine(string id, Line line)
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{
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await this.UpdateShape(id, line);
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}
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public async Task AddOrUpdateCircle(string id, Circle circle)
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{
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await this.UpdateShape(id, circle);
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}
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public async Task AddOrUpdateRect(string id, Rect rect)
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{
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await this.UpdateShape(id, rect);
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}
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public async Task AddOrUpdateEllipse(string id, Ellipse ellipse)
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{
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await this.UpdateShape(id, ellipse);
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}
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public async Task Clear()
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{
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diagram.Shapes.Clear();
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diagram.Background = null;
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await Clients.Others.SendAsync("Clear");
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}
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public async Task SendMessage(string name, string message)
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{
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await Clients.Others.SendAsync("NewMessage", name, message);
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}
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}

‎samples/Whiteboard/MCPServer/index.js‎

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import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
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import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';
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import { z } from 'zod';
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import { HubConnectionBuilder } from '@microsoft/signalr';
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import dotenv from 'dotenv';
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dotenv.config();
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const logger = new class {
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log = (level, message) => level > 1 && console.error(`[${level}] ${message}`);
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};
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const connection = new HubConnectionBuilder().withUrl(`${process.env['WHITEBOARD_ENDPOINT'] || 'http://localhost:5000'}/draw`).withAutomaticReconnect().configureLogging(logger).build();
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const server = new McpServer({
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name: 'Whiteboard',
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version: '1.0.0'
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});
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let color = z.string().describe('color of the shape, valid values are: black, grey, darkred, red, orange, yellow, green, deepskyblue, indigo, purple');
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let width = z.number().describe('width of the shape, valid values are: 1, 2, 4, 8');
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let point = z.object({
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x: z.number().describe('x coordinate of the point, 0 denotes the left edge of the whiteboard'),
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y: z.number().describe('y coordinate of the point, 0 denotes the top edge of the whiteboard')
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});
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let id = z.string().describe('unique identifier of the shape, if it does not exist, it will be created, if it exists, it will be updated');
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server.tool('send_message', 'post a message on whiteboard', { name: z.string(), message: z.string() }, async ({ name, message }) => {
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await connection.send('sendMessage', name, message);
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return { content: [{ type: 'text', text: 'Message sent' }] }
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});
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server.tool(
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'add_or_update_polyline', 'add or update a polyline on whiteboard',
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{
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id, polyline: z.object({
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color, width,
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points: z.array(point).describe('array of points that define the polyline')
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})
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},
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async ({ id, polyline }) => {
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await connection.send('addOrUpdatePolyline', id, polyline);
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return { content: [{ type: 'text', text: 'Polyline added or updated' }] };
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});
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server.tool(
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'add_or_update_line', 'add or update a line on whiteboard',
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{
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id, line: z.object({
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color, width,
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start: point.describe('start point of the line'),
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end: point.describe('end point of the line')
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})
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},
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async ({ id, line }) => {
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await connection.send('addOrUpdateLine', id, line);
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return { content: [{ type: 'text', text: 'Line added or updated' }] };
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});
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server.tool(
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'add_or_update_circle', 'add or update a circle on whiteboard',
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{
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id, circle: z.object({
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color, width,
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center: point.describe('center point of the circle'),
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radius: z.number().describe('radius of the circle')
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})
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},
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async ({ id, circle }) => {
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await connection.send('addOrUpdateCircle', id, circle);
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return { content: [{ type: 'text', text: 'Circle added or updated' }] };
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});
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server.tool(
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'add_or_update_rect', 'add or update a rectangle on whiteboard',
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{
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id, rect: z.object({
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color, width,
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topLeft: point.describe('top left corner of the rectangle'),
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bottomRight: point.describe('bottom right of the rectangle')
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})
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},
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async ({ id, rect }) => {
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await connection.send('addOrUpdateRect', id, rect);
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return { content: [{ type: 'text', text: 'Rectangle added or updated' }] };
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});
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server.tool(
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'add_or_update_ellipse', 'add or update an ellipse on whiteboard',
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{
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id, ellipse: z.object({
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color, width,
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topLeft: point.describe('top left corner of the bounding rectangle of the ellipse'),
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bottomRight: point.describe('bottom right of the bounding rectangle of the ellipse')
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})
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},
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async ({ id, ellipse }) => {
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await connection.send('addOrUpdateEllipse', id, ellipse);
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return { content: [{ type: 'text', text: 'Ellipse added or updated' }] };
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});
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server.tool(
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'remove_shape', 'remove a shape from whiteboard',
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{ id },
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async ({ id }) => {
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await connection.send('removeShape', id);
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return { content: [{ type: 'text', text: 'Shape removed' }] };
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});
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server.tool(
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'clear', 'clear the whiteboard',
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{},
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async () => {
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await connection.send('clear');
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return { content: [{ type: 'text', text: 'Whiteboard cleared' }] };
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});
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const transport = new StdioServerTransport();
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await server.connect(transport);
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const sleep = ms => new Promise(resolve => setTimeout(resolve, ms));
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for (;;) {
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try {
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await connection.start();
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break;
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} catch (e) {
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console.error('Failed to start SignalR connection: ' + e.message);
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await sleep(5000);
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}
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}

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