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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 | 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x | /**
* @module mcp-client/transport/session
* @description MCP session bootstrap + SSE response parsing helpers.
*
* Extracted from `jsonrpc.ts` so the wire-level request loop stays focused
* on JSON-RPC dispatch + retry, while session lifecycle (initialize +
* notifications/initialized) lives in one auditable place.
*
* @author Hack23 AB
* @license Apache-2.0
*/
import type { JsonRpcResponse } from '../../types/mcp.js';
import { performPost } from '../transport.js';
/**
* Parse an SSE-framed JSON-RPC response. Falls back to plain-JSON parsing
* when no `data:` lines are present.
*/
export function parseSSEResponse(text: string): JsonRpcResponse {
const lines = text.split('\n');
for (const line of lines) {
if (line.startsWith('data: ')) {
return JSON.parse(line.substring(6)) as JsonRpcResponse;
}
}
return JSON.parse(text) as JsonRpcResponse;
}
export interface SessionInitContext {
readonly baseURL: string;
readonly timeout: number;
readonly customHeaders: Readonly<Record<string, string>>;
readonly authToken: string;
sessionId: string | null;
nextJsonRpcId(): number;
}
/**
* Perform the MCP session handshake (initialize + notifications/initialized).
*
* No-op when the context already has a session id or when no auth token is
* configured (anonymous gateway). On success, `ctx.sessionId` is mutated
* with the returned `Mcp-Session-Id` header value (when present).
*/
export async function initializeSession(ctx: SessionInitContext): Promise<void> {
Iif (ctx.sessionId || !ctx.authToken) return;
const controller = new AbortController();
const timeoutId = setTimeout(() => controller.abort(), ctx.timeout);
try {
const headers: Record<string, string> = {
'Content-Type': 'application/json',
Accept: 'application/json, text/event-stream',
...ctx.customHeaders,
};
Eif (ctx.authToken) headers['Authorization'] = ctx.authToken;
const response = await performPost(
ctx.baseURL,
headers,
JSON.stringify({
jsonrpc: '2.0',
id: ctx.nextJsonRpcId(),
method: 'initialize',
params: {
protocolVersion: '2024-11-05',
capabilities: {},
clientInfo: { name: 'riksdagsmonitor-news', version: '1.0.0' },
},
}),
controller.signal,
);
Iif (!response.ok) {
throw new Error(`Session init failed: ${response.status} ${response.statusText}`);
}
const sessionId =
response.headers && typeof response.headers.get === 'function'
? response.headers.get('Mcp-Session-Id')
: null;
Iif (sessionId) {
ctx.sessionId = sessionId;
console.log(` 🔗 MCP session initialized: ${sessionId.substring(0, 8)}...`);
}
await performPost(
ctx.baseURL,
{
...headers,
...(ctx.sessionId ? { 'Mcp-Session-Id': ctx.sessionId } : {}),
},
JSON.stringify({
jsonrpc: '2.0',
method: 'notifications/initialized',
}),
controller.signal,
);
} finally {
clearTimeout(timeoutId);
}
}
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