snowcell/dist/util.js

Official Snowcell Node.js/TypeScript SDK

const RETRYABLE_METHODS = new Set(['HEAD', 'GET', 'PUT', 'DELETE', 'OPTIONS', 'TRACE']);
const RETRYABLE_STATUS = new Set([429, 503, 504]);
const sleep = (ms) => new Promise((r) => setTimeout(r, ms));
export function calculateBackoff(attempt, opts) {
    const backoff = (opts?.backoffFactor ?? 0.1) * 2 ** (attempt - 1);
    const jitter = backoff * (opts?.jitterRatio ?? 0.1) * (Math.random() < 0.5 ? -1 : 1);
    return Math.min(backoff + jitter, opts?.maxBackoffWait ?? 60);
}
export async function fetchWithRetries(input, init = {}) {
    const method = (init.method ?? 'GET').toUpperCase();
    const maxAttempts = init.retry?.maxAttempts ?? 10;
    if (!RETRYABLE_METHODS.has(method)) {
        return fetch(input, init);
    }
    let lastRes;
    for (let attempt = 1; attempt <= maxAttempts; attempt++) {
        const res = await fetch(input, init);
        if (!RETRYABLE_STATUS.has(res.status))
            return res;
        lastRes = res;
        const ra = res.headers.get('retry-after');
        const waitSec = ra && /^\d+$/.test(ra) ? Number(ra) : calculateBackoff(attempt, init.retry);
        try {
            await res.arrayBuffer(); // drain for keep-alive
        }
        catch { }
        await sleep(waitSec * 1000);
    }
    if (lastRes)
        return lastRes;
    return fetch(input, init);
}
// SSE line parser yielding `data:` payloads
export async function* iterSSE(res) {
    if (!res.body)
        return;
    const reader = res.body.getReader();
    const decoder = new TextDecoder();
    let buffer = '';
    while (true) {
        const { value, done } = await reader.read();
        if (done)
            break;
        buffer += decoder.decode(value, { stream: true });
        let idx;
        while ((idx = buffer.indexOf('\n')) >= 0) {
            const line = buffer.slice(0, idx).trimEnd();
            buffer = buffer.slice(idx + 1);
            if (line.startsWith('data:')) {
                const data = line.slice(5).trim();
                if (data)
                    yield data;
            }
        }
    }
    if (buffer.startsWith('data:')) {
        const data = buffer.slice(5).trim();
        if (data)
            yield data;
    }
}
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