import globalWindow from 'global/window.js'

export const VIEW_QUERY_PARAM_NAME = 'view'

// The app is served behind a HashRouter (see src/index.tsx), which owns
// everything after "#" for its own path-based routing (e.g.
// "#online/my-room"). These helpers append/read a query string on that
// same hash, after any router path, so persisted UI state (e.g. the
// current view) round-trips through a reload without going through
// react-router's history/location - which requires a <Router> ancestor
// that isn't present in every test/render context this is used from.
const splitHash = () => {
  const hash = globalWindow.location.hash.replace(/^#/, '')
  const queryIndex = hash.indexOf('?')

  return queryIndex === -1
    ? { path: hash, query: '' }
    : { path: hash.slice(0, queryIndex), query: hash.slice(queryIndex + 1) }
}

export type HashHistoryMode = 'push' | 'replace'

const writeHashQueryParams = (
  params: URLSearchParams,
  mode: HashHistoryMode = 'replace'
): void => {
  const { path } = splitHash()
  const queryString = params.toString()
  const newHash = `${path}${queryString ? `?${queryString}` : ''}`
  const { origin, pathname, search } = globalWindow.location
  const url = `${origin}${pathname}${search}#${newHash}`

  if (mode === 'push') {
    globalWindow.history.pushState({}, '', url)
  } else {
    globalWindow.history.replaceState({}, '', url)
  }
}

export const getHashQueryParams = (): URLSearchParams =>
  new URLSearchParams(splitHash().query)

export const setHashQueryParam = (
  key: string,
  value: string,
  mode: HashHistoryMode = 'replace'
): void => {
  const params = getHashQueryParams()

  params.set(key, value)
  writeHashQueryParams(params, mode)
}

export const removeHashQueryParam = (
  key: string,
  mode: HashHistoryMode = 'replace'
): void => {
  const params = getHashQueryParams()

  params.delete(key)
  writeHashQueryParams(params, mode)
}

// react-router's <Redirect to={path}> replaces the whole hash with `path`,
// dropping whatever query params (view/tab) were already on it - this
// carries them over onto a new redirect target (e.g. going online/offline,
// switching rooms) so navigating doesn't lose your place.
export const withCurrentHashQuery = (path: string): string => {
  const queryString = getHashQueryParams().toString()

  return queryString ? `${path}?${queryString}` : path
}