import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js'
import { z } from 'zod'
import open from 'open'
import { getSession, listSessions } from '../state.js'
import { getServerPort } from '../http-server.js'
import { log } from '../logger.js'
import { getSessionClientCount } from '../websocket.js'
const RECENT_OPEN_WINDOW_MS = 15000
const recentSessionOpenAt = new Map<string, number>()
/**
* 启动浏览器预览会话
* 打开 Excalidraw 界面并建立 WebSocket 连接
* 支持多会话：可以指定 sessionId 或自动创建
*/
export function registerStartSession(server: McpServer): void {
server.registerTool(
'start_session',
{
description:
'Start browser preview and open Excalidraw editor interface.\n\n' +
'Multi-session support:\n' +
'- No sessionId: Uses default session (default)\n' +
'- sessionId specified: Open/Create specific session\n' +
'- Multiple sessions can be opened simultaneously for different diagrams\n\n' +
'After calling this tool:\n' +
'1. Browser window opens automatically\n' +
'2. Excalidraw editor loads\n' +
'3. WebSocket realtime connection is established\n\n' +
'Please pass the same sessionId when using tools like add_elements, update_element subsequently.',
inputSchema: z.object({
sessionId: z
.string()
.optional()
.describe(
'Session ID. If not provided, uses default session. Supports opening multiple sessions.',
),
}),
},
async ({ sessionId }) => {
try {
// 获取或创建会话
const session = getSession(sessionId)
const port = getServerPort() || parseInt(process.env.PORT || '3100', 10)
const hostEnv = process.env.HOST || process.env.BIND || 'localhost'
const host = hostEnv === '0.0.0.0' || hostEnv === '::' ? 'localhost' : hostEnv
// URL 中携带 sessionId 参数
const url = `http://${host}:${port}?sessionId=${encodeURIComponent(session.id)}`
const now = Date.now()
const clientCount = getSessionClientCount(session.id)
const lastOpenAt = recentSessionOpenAt.get(session.id) || 0
const openedRecently = now - lastOpenAt < RECENT_OPEN_WINDOW_MS
if (clientCount === 0 && !openedRecently) {
log.info(`Opening browser at ${url}`)
// 打开浏览器
await open(url, { wait: false })
recentSessionOpenAt.set(session.id, now)
} else {
log.info(
`Skip opening browser for session ${session.id}: ` +
`clientCount=${clientCount}, openedRecently=${openedRecently}`,
)
}
// 获取当前所有会话
const allSessions = listSessions()
const sessionList = allSessions
.map((s) => ` - ${s.id} (${s.elementCount} elements)`)
.join('\n')
return {
content: [
{
type: 'text',
text:
`✅ Session started!\n\n` +
`${clientCount > 0 || openedRecently ? 'Browser already active' : 'Browser opened'} at: ${url}\n` +
`Session ID: ${session.id}\n\n` +
`Active Sessions:\n${sessionList}\n\n` +
`You can now use the following tools (remember to pass sessionId):\n` +
`• add_elements - Add elements\n` +
`• create_from_mermaid - Build diagram from Mermaid\n` +
`• update_element - Update elements\n` +
`• delete_element - Delete elements\n` +
`• get_scene - Get current scene\n` +
`• export_diagram - Export diagram`,
},
],
}
} catch (error) {
const message = error instanceof Error ? error.message : String(error)
return {
content: [{ type: 'text', text: `Error opening browser: ${message}` }],
isError: true,
}
}
},
)
// 注册列出会话的工具
server.registerTool(
'list_sessions',
{
description: 'List all currently active Excalidraw sessions.',
inputSchema: z.object({}),
},
async () => {
const sessions = listSessions()
if (sessions.length === 0) {
return {
content: [
{
type: 'text',
text: 'No active sessions. Use start_session to create a new session.',
},
],
}
}
const list = sessions
.map(
(s) =>
`- **${s.id}**: ${s.elementCount} elements (last updated: ${s.lastUpdated.toISOString()})`,
)
.join('\n')
return {
content: [
{
type: 'text',
text: `Active Sessions (${sessions.length}):\n\n${list}`,
},
],
}
},
)
}
