/** Device-local presentation state; the YAML document remains the only query config. */
const stores = new Map<string, { selected?: string; listeners: Set<() => void> }>()
const KEY_PREFIX = 'reams.base.view.'
let subscriberCount = 0

export function savedBaseView(id: string): string | undefined {
  try { return localStorage.getItem(`${KEY_PREFIX}${id}`) || undefined }
  catch { return undefined }
}

export function hasSavedBaseSelection(id: string): boolean {
  try { return localStorage.getItem(`${KEY_PREFIX}${id}`) !== null }
  catch { return false }
}

function onStorage(event: StorageEvent): void {
  if (event.storageArea !== localStorage || event.key !== null && !event.key.startsWith(KEY_PREFIX)) return
  const ids = event.key === null ? [...stores.keys()] : [event.key.slice(KEY_PREFIX.length)]
  for (const id of ids) {
    const current = stores.get(id)
    if (!current) continue
    const next = savedBaseView(id)
    if (current.selected === next) continue
    current.selected = next
    for (const listener of [...current.listeners]) listener()
  }
}

function store(id: string) {
  let current = stores.get(id)
  if (!current) {
    current = { selected: savedBaseView(id), listeners: new Set() }
    stores.set(id, current)
  }
  return current
}

export function selectedBaseView(id: string): string | undefined { return stores.get(id)?.selected ?? savedBaseView(id) }

export function subscribeBaseSelection(id: string, listener: () => void): () => void {
  const current = store(id)
  current.listeners.add(listener)
  if (subscriberCount++ === 0) window.addEventListener('storage', onStorage)
  let active = true
  return () => {
    if (!active) return
    active = false
    current.listeners.delete(listener)
    if (!current.listeners.size && stores.get(id) === current) stores.delete(id)
    if (--subscriberCount === 0) window.removeEventListener('storage', onStorage)
  }
}

export function selectBaseView(id: string, name: string | undefined): void {
  const current = store(id)
   if (current.selected === name) {
     if (!current.listeners.size) stores.delete(id)
     return
   }
  current.selected = name
  const key = `${KEY_PREFIX}${id}`
  try {
    // Empty string means the user deliberately chose the first view; unlike
    // removing the key, it must override older workspace layout snapshots.
    localStorage.setItem(key, name ?? '')
  } catch { /* Selection still works in this tab when device storage is unavailable. */ }
  for (const listener of [...current.listeners]) listener()
  if (!current.listeners.size) stores.delete(id)
}