// The browser tab title, including WHICH record is open.
//
// The router can only name the KIND of page, because it runs before the view
// has fetched anything: every application read "<facility> ShopDB -
// Application", so two tabs on two different machines were indistinguishable,
// and a shared link previewed as the section rather than the thing.
//
// So a detail view names itself once its record arrives:
//
//     setRecordTitle(machine.assetnumber)
//
// THE ORDERING IS THE WHOLE PROBLEM. The router's afterEach awaits the site
// settings before it can build "<facility> ShopDB - <page>", so on a cold load
// it finishes AFTER a view that fetched quickly has already set a good title,
// and would overwrite it with the generic one. Both writers therefore go
// through here, and the generic write is dropped when a record title already
// belongs to the route being landed on. The key is the route's fullPath, so
// navigating away invalidates the previous record's claim.

import { getFacilityName } from '@/utils/siteSettings'

let activeKey = null       // fullPath of the route the tab is currently showing
let recordTitle = null     // record name set by a view for activeKey, if any
let sitePrefix = 'ShopDB'  // '<facility> ShopDB', resolved once and cached

function compose(page) {
  return page && page !== 'Home' ? `${sitePrefix} - ${page}` : sitePrefix
}

async function resolveSitePrefix() {
  try {
    const facility = await getFacilityName()
    if (facility && facility !== 'ShopDB') sitePrefix = `${facility} ShopDB`
  } catch (settingsError) {
    // settings unavailable: plain ShopDB is a fine tab title
  }
  return sitePrefix
}

// Called by the router on every navigation, BEFORE it awaits anything, so a
// view that resolves first is not treated as belonging to the previous route.
export function beginNavigation(key) {
  activeKey = key
  recordTitle = null
}

// Called by the router once it knows the site prefix. Skipped when a view has
// already named the record for this route.
export async function applyGenericTitle(key, page) {
  await resolveSitePrefix()
  if (key !== activeKey) return      // navigated on while we awaited
  // A view that named the record before the facility name arrived composed its
  // title against the placeholder prefix, so rewrite it rather than leaving
  // 'ShopDB - CSF16' without the facility name in front of it.
  document.title = compose(recordTitle !== null ? recordTitle : page)
}

// A tab shows very little, and the browser truncates mid-word wherever it runs
// out. Cut at a word boundary instead, so what survives is readable. Knowledge
// base articles are the case that forces this: their name is a whole sentence
// of description, not a short label.
const MAXLENGTH = 60

function shorten(text) {
  if (text.length <= MAXLENGTH) return text
  const cut = text.slice(0, MAXLENGTH)
  const space = cut.lastIndexOf(' ')
  return `${(space > MAXLENGTH / 2 ? cut.slice(0, space) : cut).trimEnd()}...`
}

// Called by a detail view once its record has loaded. An empty or missing name
// leaves the generic title in place rather than showing a bare id: "Machine"
// beats "Machine 4192" for somebody scanning a row of tabs, and a record that
// failed to load has no name to show anyway.
export function setRecordTitle(name) {
  const text = (name === null || name === undefined) ? '' : String(name).trim()
  if (!text) return
  recordTitle = shorten(text)
  document.title = compose(recordTitle)
}

// Exposed for tests.
export function _state() {
  return { activeKey, recordTitle, sitePrefix }
}

export function _reset() {
  activeKey = null
  recordTitle = null
  sitePrefix = 'ShopDB'
}