@langchain/langgraph-sdk/dist/client/stream/subscription.js

Client library for interacting with the LangGraph API

//#region src/client/stream/subscription.ts
/**
* Strip dynamic suffixes (after `:`) from a namespace segment.
*
* Mirrors `normalize_namespace_segment` in
* `api/langgraph_api/protocol/namespace.py`. Server-emitted namespaces
* contain runtime-generated suffixes like `"fetcher:abc-uuid"`, while
* user-supplied filters are typically static names (`"fetcher"`).
*/
function normalizeSegment(segment) {
	const idx = segment.indexOf(":");
	return idx === -1 ? segment : segment.slice(0, idx);
}
/**
* Whether `eventNamespace` starts with `prefix`.
*
* Segments are compared literally first; if the prefix segment itself
* contains no `:`, the candidate segment is also compared after its
* dynamic suffix is stripped. This mirrors `is_prefix_match` in
* `api/langgraph_api/protocol/namespace.py` so server-side filtering
* and client-side per-subscription narrowing stay consistent.
*/
function isPrefixMatch(eventNamespace, prefix) {
	if (prefix.length > eventNamespace.length) return false;
	for (let i = 0; i < prefix.length; i += 1) {
		const segment = prefix[i];
		const candidate = eventNamespace[i];
		if (candidate === segment) continue;
		if (segment.includes(":")) return false;
		if (normalizeSegment(candidate) === segment) continue;
		return false;
	}
	return true;
}
function namespaceMatches(eventNamespace, prefixes, depth) {
	if (!prefixes || prefixes.length === 0) return true;
	return prefixes.some((prefix) => {
		if (!isPrefixMatch(eventNamespace, prefix)) return false;
		if (depth === void 0) return true;
		return eventNamespace.length - prefix.length <= depth;
	});
}
/**
* Maps a protocol event method to its subscription channel.
*
* Returns `undefined` for unrecognized methods so that new server-side
* channels (e.g. from extension transformers) don't break existing clients.
*
* @param event - Event whose method should be mapped to a channel.
*/
function inferChannel(event) {
	switch (event.method) {
		case "values": return "values";
		case "checkpoints": return "checkpoints";
		case "updates": return "updates";
		case "messages": return "messages";
		case "tools": return "tools";
		case "custom": {
			const data = event.params.data;
			return data?.name != null ? `custom:${data.name}` : "custom";
		}
		case "lifecycle": return "lifecycle";
		case "input.requested": return "input";
		case "tasks": return "tasks";
		default: return;
	}
}
/**
* Returns whether an event should be delivered for a subscription definition.
*
* @param event - Event being checked for delivery.
* @param definition - Subscription filter definition to evaluate against.
*/
function matchesSubscription(event, definition) {
	const channel = inferChannel(event);
	if (channel === void 0) return false;
	const channels = definition.channels;
	if (!(channels.includes(channel) || channel.startsWith("custom:") && channels.includes("custom"))) return false;
	return namespaceMatches(event.params.namespace, definition.namespaces, definition.depth);
}
//#endregion
export { inferChannel, matchesSubscription };

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