const STORAGE_PREFIX = 'challenge_draft_'

const isBrowser = () => typeof window !== 'undefined' && typeof window.localStorage !== 'undefined'

export function saveDraft(taskId: string, result: string) {
  if (!isBrowser()) return
  window.localStorage.setItem(`${STORAGE_PREFIX}${taskId}`, result)
}

export function loadDraft(taskId: string): string | null {
  if (!isBrowser()) return null
  return window.localStorage.getItem(`${STORAGE_PREFIX}${taskId}`)
}

export function clearDraft(taskId: string) {
  if (!isBrowser()) return
  window.localStorage.removeItem(`${STORAGE_PREFIX}${taskId}`)
}

export function listDrafts() {
  if (!isBrowser()) return [] as string[]

  const keys = [] as string[]
  for (let i = 0; i < window.localStorage.length; i += 1) {
    const key = window.localStorage.key(i)
    if (key?.startsWith(STORAGE_PREFIX)) {
      keys.push(key.replace(STORAGE_PREFIX, ''))
    }
  }
  return keys
}