/**
 * Trip sync manager — seeds Dexie with trip data for offline use.
 *
 * Cache scope: trips where end_date >= today OR end_date is null/empty.
 * Eviction: trips where end_date < today - 7 days.
 * File blobs: all non-photo files (MIME type != image/*) for cached trips.
 *
 * syncAll() is manual-only — triggered via Settings → Offline tab.
 * No automatic sync on login, dashboard load, or WS reconnect.
 */
import { tripsApi, tagsApi, categoriesApi } from '../api/client'
import {
  offlineDb,
  upsertTrip,
  upsertDays,
  upsertPlaces,
  upsertPackingItems,
  upsertTodoItems,
  upsertBudgetItems,
  upsertReservations,
  upsertTripFiles,
  upsertAccommodations,
  upsertTripMembers,
  upsertTags,
  upsertCategories,
  upsertSyncMeta,
  clearTripData,
  clearBlobCache,
  clearAll,
} from '../db/offlineDb'
import { prefetchTilesForTrip } from './tilePrefetcher'
import { useSettingsStore } from '../store/settingsStore'
import type { Trip, Day, Place, PackingItem, TodoItem, BudgetItem, Reservation, TripFile, Accommodation, TripMember } from '../types'

// ── Types ─────────────────────────────────────────────────────────────────────

interface TripBundle {
  trip: Trip
  days: Day[]
  places: Place[]
  packingItems: PackingItem[]
  todoItems: TodoItem[]
  budgetItems: BudgetItem[]
  reservations: Reservation[]
  files: TripFile[]
  accommodations: Accommodation[]
  members: TripMember[]
}

// ── Helpers ───────────────────────────────────────────────────────────────────

function todayStr(): string {
  return new Date().toISOString().slice(0, 10)
}

function shouldCache(trip: Trip): boolean {
  if (!trip.end_date) return true            // no end date → cache forever
  return trip.end_date >= todayStr()          // ongoing or future
}

function isStale(trip: Trip): boolean {
  if (!trip.end_date) return false
  const cutoff = new Date()
  cutoff.setDate(cutoff.getDate() - 7)
  return trip.end_date < cutoff.toISOString().slice(0, 10)
}

function isPhoto(file: TripFile): boolean {
  return file.mime_type.startsWith('image/')
}

function isQuotaError(err: unknown): boolean {
  if (!(err instanceof Error)) return false
  if (err.name === 'QuotaExceededError') return true
  // Dexie wraps IDB errors: AbortError with inner QuotaExceededError
  const inner = (err as { inner?: unknown }).inner
  return inner instanceof Error && inner.name === 'QuotaExceededError'
}

// ── Core logic ────────────────────────────────────────────────────────────────

/** Fetch bundle + write all entities for one trip into Dexie. */
async function syncTrip(tripId: number): Promise<void> {
  const bundle = await tripsApi.bundle(tripId) as TripBundle

  await upsertTrip(bundle.trip)
  await upsertDays(bundle.days)
  await upsertPlaces(bundle.places)
  await upsertPackingItems(bundle.packingItems)
  await upsertTodoItems(bundle.todoItems)
  await upsertBudgetItems(bundle.budgetItems)
  await upsertReservations(bundle.reservations)
  await upsertTripFiles(bundle.files)
  await upsertAccommodations(bundle.accommodations || [])
  await upsertTripMembers(tripId, bundle.members || [])
  await upsertSyncMeta({
    tripId,
    lastSyncedAt: Date.now(),
    status: 'idle',
    tilesBbox: null,
    filesCachedCount: 0,
  })
}

/** Cache non-photo file blobs for a trip. Fire-and-forget safe. */
async function cacheFilesForTrip(files: TripFile[]): Promise<void> {
  const nonPhotos = files.filter(f => f.url && !isPhoto(f))
  let cached = 0

  for (const file of nonPhotos) {
    // Skip if already cached
    const existing = await offlineDb.blobCache.get(file.url!)
    if (existing) { cached++; continue }

    try {
      const resp = await fetch(file.url!, { credentials: 'include' })
      if (!resp.ok) continue
      const blob = await resp.blob()
      await offlineDb.blobCache.put({ url: file.url!, blob, mime: file.mime_type, cachedAt: Date.now() })
      cached++
    } catch {
      // Network failure — skip this file, will retry next sync
    }
  }

  // Update filesCachedCount in syncMeta
  const tripId = files[0]?.trip_id
  if (tripId) {
    const meta = await offlineDb.syncMeta.get(tripId)
    if (meta) await upsertSyncMeta({ ...meta, filesCachedCount: cached })
  }
}

// ── Public API ────────────────────────────────────────────────────────────────

const SYNC_TIMEOUT_MS = 90_000
const SYNC_STALE_MS = 120_000

let _syncing = false
let _interrupted = false
let _syncStartedAt = 0

export const tripSyncManager = {
  /**
   * Sync all cache-eligible trips.
   * Evicts stale trips. Caches file blobs in the background.
   * No-ops when offline or already syncing (unless stale flag).
   */
  async syncAll(): Promise<void> {
    // Treat a _syncing flag that's been set for >2 minutes as stale (e.g. page unload mid-sync)
    if (_syncing && Date.now() - _syncStartedAt < SYNC_STALE_MS) return
    if (!navigator.onLine) return
    _syncing = true
    _syncStartedAt = Date.now()
    _interrupted = false

    const timeout = new Promise<never>((_, reject) =>
      setTimeout(() => reject(new Error('syncAll timeout')), SYNC_TIMEOUT_MS)
    )

    try {
      await Promise.race([this._doSync(), timeout])
    } catch (err) {
      if (err instanceof Error && err.message === 'syncAll timeout') {
        console.warn('[tripSync] syncAll timed out after 90 s — interrupting')
        _interrupted = true
      }
    } finally {
      _syncing = false
    }
  },

  async _doSync(): Promise<void> {
    const { trips } = await tripsApi.list() as { trips: Trip[] }

    // Evict stale trips first
    const stale = trips.filter(isStale)
    await Promise.all(stale.map(t => clearTripData(t.id).catch(console.error)))

    // Sync eligible trips — stop early if interrupted (e.g. user navigated to a trip page)
    const toSync = trips.filter(shouldCache)
    for (const trip of toSync) {
      if (_interrupted) return
      try {
        await syncTrip(trip.id)
      } catch (err) {
        if (isQuotaError(err)) {
          console.warn(`[tripSync] quota exceeded for trip ${trip.id}, clearing trip data and retrying`)
          try {
            await clearTripData(trip.id)
            await syncTrip(trip.id)
          } catch (retryErr) {
            if (isQuotaError(retryErr)) {
              console.warn('[tripSync] quota still exceeded — clearing blob cache and retrying')
              await clearBlobCache()
              try {
                await syncTrip(trip.id)
              } catch {
                console.warn('[tripSync] quota still exceeded after blob eviction — clearing all IDB data')
                await clearAll()
                return
              }
            } else {
              console.error(`[tripSync] failed for trip ${trip.id} after eviction:`, retryErr)
            }
          }
        } else {
          console.error(`[tripSync] failed for trip ${trip.id}:`, err)
        }
      }
    }

    if (_interrupted) return

    // Cache global user data (tags + categories) — fire-and-forget
    tagsApi.list().then(d => upsertTags(d.tags)).catch(() => {})
    categoriesApi.list().then(d => upsertCategories(d.categories)).catch(() => {})

    // Cache file blobs + map tiles for all synced trips in parallel (fire-and-forget)
    const tileUrl = useSettingsStore.getState().settings.map_tile_url || undefined
    const prefetchWork = toSync
      .filter(() => !_interrupted)
      .map(async trip => {
        const [files, places] = await Promise.all([
          offlineDb.tripFiles.where('trip_id').equals(trip.id).toArray(),
          offlineDb.places.where('trip_id').equals(trip.id).toArray(),
        ])
        cacheFilesForTrip(files).catch(console.error)
        prefetchTilesForTrip(trip.id, places, tileUrl).catch(console.error)
      })
    await Promise.allSettled(prefetchWork)
  },

  /**
   * Signal syncAll to stop after the current in-flight bundle request.
   * Call when the user navigates to a trip page so loadTrip gets priority.
   */
  interrupt(): void {
    _interrupted = true
  },

  /** Reset syncing flag — useful in tests. */
  _resetSyncing(): void {
    _syncing = false
    _interrupted = false
    _syncStartedAt = 0
  },
}