Function constrainSourceId

bin/gstack-gbrain-sync.ts:575–607

* Build a gbrain-valid source id (1-32 lowercase alnum + interior hyphens). Sanitizes * `raw`, prefixes with `prefix`, and falls back to a hashed-tail form when total length * would exceed 32 chars. * * Truncation cuts on hyphen boundaries (whole-word units) from the right, never * mid-word. In

(prefix: string, raw: string)

 * "${prefix}-270c0001-<hash>", not "${prefix}-kill-270c0001-<hash>".
 */
function constrainSourceId(prefix: string, raw: string): string {
  const MAX = 32;
  const slug = raw.toLowerCase().replace(/[^a-z0-9]+/g, "-").replace(/^-+|-+$/g, "");
  // Empty slug after sanitize (e.g. raw was all non-alnum like "___") would
  // produce "${prefix}-" which fails gbrain's validator on the trailing
  // hyphen. Fall back to a deterministic hash of the original input so the
  // result is stable across runs of the same repo.
  if (!slug) {
    const hash = createHash("sha1").update(raw || "_empty").digest("hex").slice(0, 6);
    return `${prefix}-${hash}`;
  }
  const full = `${prefix}-${slug}`;
  if (full.length <= MAX) return full;
  const hash = createHash("sha1").update(slug).digest("hex").slice(0, 6);
  // Total budget: prefix + "-" + tail + "-" + hash
  const tailBudget = MAX - prefix.length - 2 - hash.length;
  if (tailBudget < 1) return `${prefix}-${hash}`;
  // Cut on hyphen boundaries instead of mid-word. Walk tokens from the right,
  // accumulating until adding the next token would exceed tailBudget. This
  // preserves readable suffixes (pathhash, repo name) and avoids embarrassing
  // mid-word artifacts like "skill" → "kill".
  const tokens = slug.split("-").filter(Boolean);
  const kept: string[] = [];
  let len = 0;
  for (let i = tokens.length - 1; i >= 0; i--) {
    const add = kept.length === 0 ? tokens[i].length : tokens[i].length + 1;
    if (len + add > tailBudget) break;
    kept.unshift(tokens[i]);
    len += add;
  }
  const tail = kept.join("-");
  return tail ? `${prefix}-${tail}-${hash}` : `${prefix}-${hash}`;
}

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