const STORAGE_PREFIX = 'ghabilee:event-create-draft'
const CURRENT_VERSION = 1

interface StoredEventDraft<T> {
  version: number
  savedAt: string
  step: number
  data: T
}

const storageKey = (userId: string) => `${STORAGE_PREFIX}:${userId}`

export function loadEventDraft<T>(userId: string): StoredEventDraft<T> | null {
  if (typeof window === 'undefined') return null

  try {
    const raw = localStorage.getItem(storageKey(userId))

    if (!raw) return null

    const parsed = JSON.parse(raw) as Partial<StoredEventDraft<T>>

    if (parsed.version !== CURRENT_VERSION || !parsed.data || typeof parsed.data !== 'object') {
      localStorage.removeItem(storageKey(userId))

      return null
    }

    return {
      version: CURRENT_VERSION,
      savedAt: typeof parsed.savedAt === 'string' ? parsed.savedAt : new Date().toISOString(),
      step: typeof parsed.step === 'number' && parsed.step >= 1 && parsed.step <= 4 ? parsed.step : 1,
      data: parsed.data,
    }
  } catch {
    localStorage.removeItem(storageKey(userId))

    return null
  }
}

export function saveEventDraft(userId: string, data: StoredEventDraft<unknown>['data'], step: number): void {
  if (typeof window === 'undefined') return

  const draft: StoredEventDraft<unknown> = {
    version: CURRENT_VERSION,
    savedAt: new Date().toISOString(),
    step: Math.min(Math.max(step, 1), 4),
    data,
  }

  try {
    localStorage.setItem(storageKey(userId), JSON.stringify(draft))
  } catch {
    // Storage may be unavailable or full; the in-memory wizard remains usable.
  }
}

export function clearEventDraft(userId: string): void {
  if (typeof window === 'undefined') return

  localStorage.removeItem(storageKey(userId))
}