import { PathError } from '../errors.ts';

/**
 * Checks a project path against the lexicon's rules: relative, `/`-separated, with no empty, `.`, or `..` segments.
 * Returns it in NFC so that one file has one spelling across operating systems.
 */
export function normalizePath(input: string): string {
  const path = input.normalize('NFC');
  if (path === '') throw new PathError('path is empty', path);
  if (path.includes('\\')) throw new PathError(`path ${path} uses a backslash`, path);
  if (path.startsWith('/')) throw new PathError(`path ${path} is absolute`, path);
  for (const segment of path.split('/')) {
    if (segment === '') throw new PathError(`path ${path} has an empty segment`, path);
    if (segment === '.' || segment === '..') throw new PathError(`path ${path} has a ${segment} segment`, path);
  }
  if (new TextEncoder().encode(path).length > 1024) throw new PathError(`path ${path} is over 1024 bytes`, path);
  return path;
}