/**
 * Sync triggers — register event listeners that flush the mutation queue
 * and/or run a full trip sync based on the connectivity trigger source.
 *
 * Trigger matrix:
 *   window 'online'          → flush mutations + full syncAll (network truly back)
 *   visibilitychange visible → flush mutations only (avoid hammering server on tab switch)
 *   periodic 30s             → flush mutations only
 *   WS reconnect             → flush mutations only (no syncAll — avoids rate-limiter
 *                              on server restart / socket timeout while already online)
 *
 * Call `registerSyncTriggers()` once on app mount.
 * Call `unregisterSyncTriggers()` on unmount / logout.
 */
import { mutationQueue } from './mutationQueue'
import { tripSyncManager } from './tripSyncManager'
import { isEffectivelyOnline, onNetworkModeChange } from './networkMode'
import { setPreReconnectHook, setRefetchCallback, getActiveTrips, reconnectNow } from '../api/websocket'
import { useTripStore } from '../store/tripStore'
import { reloadTourVisits } from '../store/tourVisitStore'
import { useSettingsStore } from '../store/settingsStore'
import { useAuthStore } from '../store/authStore'

const PERIODIC_MS = 30_000

let _intervalId: ReturnType<typeof setInterval> | null = null
let _unsubscribeNetworkMode: (() => void) | null = null
let _wasEffectivelyOnline = isEffectivelyOnline()
let _registered = false

/**
 * User settings are loaded once on the auth transition (App.tsx), with no retry.
 * If that single GET fails — offline at launch, or a server cold-start racing the
 * first request — the store stays on built-in DEFAULT_SETTINGS and the user sees
 * their currency/units/time-format "reset" for the whole session (#1618). Heal it
 * on the same connectivity triggers that re-hydrate trips: retry until it loads.
 */
function ensureSettingsLoaded() {
  if (!useAuthStore.getState().isAuthenticated) return
  if (!isEffectivelyOnline()) return
  if (useSettingsStore.getState().isLoaded) return
  useSettingsStore.getState().loadSettings().catch(console.error)
}

/**
 * Pull the latest server state for every open trip into the Zustand store,
 * and the visits of its city walks, now that the queued marks were sent.
 */
function rehydrateActiveTrips() {
  const store = useTripStore.getState()
  for (const tripId of getActiveTrips()) {
    store.hydrateActiveTrip(tripId).catch(console.error)
    reloadTourVisits(tripId)
  }
}

/**
 * Network came back — flush local writes first, then re-seed Dexie for all
 * cacheable trips and re-hydrate the open trip's store so a collaborator's
 * edits made while we were offline appear without navigating away.
 */
function onOnline() {
  // A real browser reconnect must NOT override a user-forced offline session:
  // syncAll would re-seed Dexie from the server and wipe un-flushed optimistic
  // edits from the cache/UI. Stay put until the user lifts the switch (which
  // routes through onNetworkMode → here with the force flag already cleared).
  if (!isEffectivelyOnline()) return
  ensureSettingsLoaded()
  reconnectNow()
  mutationQueue.flush()
    .catch(console.error)
    .finally(() => {
      tripSyncManager.syncAll().catch(console.error)
      rehydrateActiveTrips()
    })
}

/** Tab became visible — flush only; don't trigger a potentially expensive syncAll. */
function onVisibility() {
  if (!document.hidden && isEffectivelyOnline()) {
    ensureSettingsLoaded()
    reconnectNow()
    mutationQueue.flush().catch(console.error)
  }
}

/** Periodic heartbeat — drain any lingering pending mutations. */
function onPeriodic() {
  if (isEffectivelyOnline()) {
    ensureSettingsLoaded()
    mutationQueue.flush().catch(console.error)
  }
}

/**
 * The force-offline toggle (or a browser online/offline event) changed the
 * effective network mode. Coming back online — whether the network returned or
 * the user lifted the force-offline switch — behaves like a real reconnection:
 * flush queued writes, then re-seed and re-hydrate.
 */
function onNetworkMode() {
  const nowOnline = isEffectivelyOnline()
  if (nowOnline && !_wasEffectivelyOnline) onOnline()
  _wasEffectivelyOnline = nowOnline
}

export function registerSyncTriggers(): void {
  if (_registered) return
  _registered = true

  // WS reconnect: flush mutations only — no syncAll to avoid triggering rate
  // limiters when the socket drops and reconnects while the device is online.
  setPreReconnectHook(() => mutationQueue.flush())
  // After the reconnect flush, pull canonical state for the open trip back into
  // the store (the WS layer awaits the flush hook before invoking this), and
  // the walk visits, so a mark the replay dropped or failed leaves the day plan.
  setRefetchCallback(tripId => {
    useTripStore.getState().hydrateActiveTrip(tripId).catch(console.error)
    reloadTourVisits(tripId)
  })

  window.addEventListener('online', onOnline)
  document.addEventListener('visibilitychange', onVisibility)
  // React to the force-offline toggle (and browser online/offline) so lifting
  // the switch immediately flushes + re-seeds like a real reconnection.
  _wasEffectivelyOnline = isEffectivelyOnline()
  _unsubscribeNetworkMode = onNetworkModeChange(onNetworkMode)
  _intervalId = setInterval(onPeriodic, PERIODIC_MS)
}

export function unregisterSyncTriggers(): void {
  if (!_registered) return
  _registered = false

  setPreReconnectHook(null)
  setRefetchCallback(null)
  window.removeEventListener('online', onOnline)
  document.removeEventListener('visibilitychange', onVisibility)
  if (_unsubscribeNetworkMode) {
    _unsubscribeNetworkMode()
    _unsubscribeNetworkMode = null
  }
  if (_intervalId !== null) {
    clearInterval(_intervalId)
    _intervalId = null
  }
}