// The order of the pages in the rail is the account's: kept here for instant use and saved
// with the UI prefs, so it follows the login. Pages the saved order doesn't name (added since)
// go after the ones it does, in their built-in order.
import { useEffect, useState } from 'react'

const KEY = 'hamlab.rail'

// Pages that were renamed, so an order saved before it still puts the page where it was put:
// Top became Processes, Space became Usage, Cron became Jobs. A page that was removed
// outright (Dashboard) is not here — orderBy drops ids that match no page.
const RENAMED: Record<string, string> = { top: 'procs', space: 'usage', cron: 'jobs' }

export function getRailOrder(): string[] {
  let raw: unknown
  try { raw = JSON.parse(localStorage.getItem(KEY) ?? '[]') } catch { return [] }
  if (!Array.isArray(raw)) return []
  const seen = new Set<string>()
  const out: string[] = []
  for (const x of raw) {
    if (typeof x !== 'string') continue
    const id = RENAMED[x] ?? x
    if (seen.has(id)) continue // a merged page keeps the earlier of the two slots
    seen.add(id)
    out.push(id)
  }
  return out
}

export function setRailOrder(ids: string[], save = true) {
  localStorage.setItem(KEY, JSON.stringify(ids))
  window.dispatchEvent(new Event('hamlab:rail'))
  if (save) import('./accents').then((m) => m.savePrefs())
}

export function resetRailOrder() { localStorage.removeItem(KEY); window.dispatchEvent(new Event('hamlab:rail')); import('./accents').then((m) => m.savePrefs()) }

export function useRailOrder(): string[] {
  const [order, setOrder] = useState(getRailOrder)
  useEffect(() => {
    const h = () => setOrder(getRailOrder())
    window.addEventListener('hamlab:rail', h)
    return () => window.removeEventListener('hamlab:rail', h)
  }, [])
  return order
}

export function orderBy<T extends { id: string }>(items: T[], order: string[]): T[] {
  const by = new Map(items.map((g) => [g.id, g]))
  const named = order.map((id) => by.get(id)).filter((g): g is T => !!g)
  const seen = new Set(named.map((g) => g.id))
  return [...named, ...items.filter((g) => !seen.has(g.id))]
}