import { isAbsolute, normalize, sep } from "node:path";

/** Normalised relative path, or throws. Rejects absolute paths, `..`, `.git` and NUL. */
export function checkRelPath(p: string): string {
  if (typeof p !== "string" || p === "" || p.includes("\0") || isAbsolute(p) || p.includes("\\")) throw new Error(`invalid path: ${JSON.stringify(p)}`);
  const n = normalize(p);
  const parts = n.split(sep);
  if (n === "." || parts[0] === ".." || parts.some((x) => x === ".." || x.toLowerCase() === ".git") || n.endsWith(sep)) {
    throw new Error(`invalid path: ${JSON.stringify(p)}`);
  }
  return n;
}