export function normalizeRel(value: unknown = ''): string {
  return String(value).replace(/^\/+/, '').replace(/\/+/g, '/')
}

export function localeCode(value: unknown = ''): string {
  return String(value).trim().toLowerCase()
}

function dirname(rel: unknown): string {
  const normalized = normalizeRel(rel)
  const index = normalized.lastIndexOf('/')
  return index >= 0 ? normalized.slice(0, index) : ''
}

export function relativeAsset(fromRel: unknown, toRel: unknown): string {
  const fromParts = dirname(fromRel).split('/').filter(Boolean)
  const toParts = normalizeRel(toRel).split('/').filter(Boolean)

  while (fromParts.length && toParts.length && fromParts[0] === toParts[0]) {
    fromParts.shift()
    toParts.shift()
  }

  const relative = [...fromParts.map(() => '..'), ...toParts].join('/')
  return relative
    ? relative.startsWith('.')
      ? relative
      : `./${relative}`
    : './'
}