comfyui-mcp/dist/experimental/ui-message-stream-parser.js

Local-first, agent-native control plane for ComfyUI — MCP server + autonomous sidebar agent that drives your live graph in natural language on ANY LLM: Claude/ChatGPT/Gemini on your subscription (no API key), free local models via Ollama (fully offline),

// ---------------------------------------------------------------------------
// AI SDK UI Message Stream Protocol — consumer-side parser.
//
// `POST /api/chat` returns a Server-Sent Events stream whose every `data:`
// frame is a JSON-encoded `UIMessageChunk` (the AI SDK v6 UI message stream
// protocol — see `node_modules/ai/dist/index.d.ts` for the full union). The
// terminator frame is the literal `data: [DONE]`.
//
// This module provides a single pure function that turns an arbitrary slice of
// the raw text body (i.e. however much arrived in the latest `reader.read()`)
// into:
//   - a list of decoded chunk objects, and
//   - a `remainder` string (an unterminated partial event) the caller must
//     prepend to the NEXT slice before re-invoking.
//
// Keeping the parser pure (no state, no DOM, no fetch) makes it cheap to test
// against canned byte streams in vitest. The exact same logic is *also*
// inlined into the browser-side panel (web/extensions/...) because that file
// is dropped directly into ComfyUI's `web/extensions/` directory with no
// bundler; the two implementations are kept byte-equivalent.
// ---------------------------------------------------------------------------
/**
 * Parse a slice of an AI SDK UI message stream. Stateless — the caller owns
 * the remainder buffer.
 *
 * Frame grammar: events are separated by `\n\n`; each event is one or more
 * `data: <payload>` lines. The terminator is the literal `[DONE]`. We
 * tolerate `\r\n\n` and stray blank lines.
 */
export function parseUiMessageStream(buffer) {
    const chunks = [];
    let done = false;
    // Normalize line endings so the split below works regardless of transport.
    const normalized = buffer.replace(/\r\n/g, "\n");
    // Split on the blank-line frame boundary. The trailing element is whatever
    // is *after* the last `\n\n` — i.e. an unterminated frame in progress.
    const parts = normalized.split("\n\n");
    const remainder = parts.pop() ?? "";
    for (const frame of parts) {
        // A frame can contain multiple `data:` lines (SSE spec joins them with
        // `\n`). In practice AI SDK emits a single line per frame, but we honor
        // the spec to keep the parser interoperable.
        const dataLines = [];
        for (const line of frame.split("\n")) {
            if (!line.startsWith("data:"))
                continue;
            // Strip `data:` then a single optional leading space (per SSE spec).
            let payload = line.slice(5);
            if (payload.startsWith(" "))
                payload = payload.slice(1);
            dataLines.push(payload);
        }
        if (dataLines.length === 0)
            continue;
        const payload = dataLines.join("\n");
        if (payload === "[DONE]") {
            done = true;
            continue;
        }
        try {
            const parsed = JSON.parse(payload);
            if (parsed && typeof parsed === "object" && typeof parsed.type === "string") {
                chunks.push(parsed);
            }
        }
        catch {
            // Malformed frame — skip silently. The AI SDK never emits invalid
            // JSON; this is just defensive for non-conforming proxies.
        }
    }
    return { chunks, remainder, done };
}
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