import { HydrusClient, extractTitleFromTags, type ServerConfig } from './api/hydrusClient'
import { buildLibraryCacheKey, loadLibraryCache, saveLibraryCache } from './libraryCache'
import type { MediaSection, ServerSyncSummary, Track } from './types'

const SYNC_SECTION_LIMIT = 2000
const SYNC_SECTIONS: Array<{ id: Exclude<MediaSection, 'all'>; predicate: string }> = [
  { id: 'audio', predicate: 'system:filetype = audio' },
  { id: 'video', predicate: 'system:filetype = video' },
  { id: 'image', predicate: 'system:filetype = image' },
  { id: 'application', predicate: 'system:filetype = application' },
]

export const LIBRARY_CACHE_SYNC_EVENT = 'api-media-player:library-cache-sync'

type SyncEventDetail = {
  cacheKey: string
  phase: 'started' | 'completed' | 'failed'
  serverIds: string[]
  error?: string
}

export type LibrarySyncServer = ServerConfig

export type LibraryCacheSyncResult = {
  cacheKey: string
  summaries: Record<string, ServerSyncSummary>
  addedCounts: Record<string, number>
  removedCounts: Record<string, number>
}

function dispatchSyncEvent(detail: SyncEventDetail) {
  if (typeof window === 'undefined' || typeof window.dispatchEvent !== 'function' || typeof CustomEvent === 'undefined') return
  window.dispatchEvent(new CustomEvent(LIBRARY_CACHE_SYNC_EVENT, { detail }))
}

function extractNamespaceValue(tags: string[] | null | undefined, ns: string) {
  if (!tags || !Array.isArray(tags)) return null
  const prefix = `${ns.toLowerCase()}:`
  const values = tags
    .filter((tag) => typeof tag === 'string' && tag.toLowerCase().startsWith(prefix))
    .map((tag) => tag.slice(prefix.length).replace(/_/g, ' ').trim())
    .filter(Boolean)

  return values.sort((left, right) => right.length - left.length)[0] || null
}

function buildTrackCacheKey(serverId?: string, fileId?: number) {
  return serverId && fileId != null ? `${serverId}:${fileId}` : ''
}

export async function syncLibraryCache(servers: LibrarySyncServer[], options: { targetServerIds?: string[] } = {}): Promise<LibraryCacheSyncResult> {
  const cacheKey = buildLibraryCacheKey(servers)
  const targetServerIds = new Set(options.targetServerIds && options.targetServerIds.length > 0
    ? options.targetServerIds
    : servers.map((server) => server.id))
  const targetServers = servers.filter((server) => targetServerIds.has(server.id))

  if (!cacheKey || targetServers.length === 0) {
    return {
      cacheKey,
      summaries: {},
      addedCounts: {},
      removedCounts: {},
    }
  }

  dispatchSyncEvent({ cacheKey, phase: 'started', serverIds: targetServers.map((server) => server.id) })

  try {
    const snapshot = await loadLibraryCache(cacheKey)
    const snapshotTracks = snapshot?.tracks ?? []
    const mergedSearchCache = { ...(snapshot?.searchCache ?? {}) }
    const mergedTrackMap: Record<string, Track> = {}
    const snapshotTracksByServer: Record<string, Track[]> = {}
    let localCounter = Date.now()

    for (const track of snapshotTracks) {
      const hydratedTrack: Track = { ...track, id: ++localCounter }
      const key = buildTrackCacheKey(hydratedTrack.serverId, hydratedTrack.fileId)
      if (!key || !hydratedTrack.serverId) continue

      if (!snapshotTracksByServer[hydratedTrack.serverId]) {
        snapshotTracksByServer[hydratedTrack.serverId] = []
      }
      snapshotTracksByServer[hydratedTrack.serverId].push(hydratedTrack)

      if (!targetServerIds.has(hydratedTrack.serverId)) {
        mergedTrackMap[key] = hydratedTrack
      }
    }

    for (const searchKey of Object.keys(mergedSearchCache)) {
      if (Array.from(targetServerIds).some((serverId) => searchKey.startsWith(`${serverId}|`))) {
        delete mergedSearchCache[searchKey]
      }
    }

    const summaries: Record<string, ServerSyncSummary> = {}
    const addedCounts: Record<string, number> = {}
    const removedCounts: Record<string, number> = {}

    for (const server of targetServers) {
      const previousTracks = snapshotTracksByServer[server.id] ?? []
      const previousServerTrackKeys = new Set(previousTracks.map((track) => buildTrackCacheKey(track.serverId, track.fileId)).filter(Boolean))
      const currentServerTrackKeys = new Set<string>()
      const counts: ServerSyncSummary['counts'] = {}

      try {
        const client = new HydrusClient(server)

        for (const section of SYNC_SECTIONS) {
          const searchTags = [section.predicate]
          const ids = await client.searchFiles(searchTags, SYNC_SECTION_LIMIT)
          counts[section.id] = ids.length
          mergedSearchCache[`${server.id}|${section.id}|tracks|${JSON.stringify(searchTags)}`] = ids

          if (ids.length === 0) continue

          const [tagMap, mediaInfoMap] = await Promise.all([
            client.getFilesTags(ids, 8),
            client.getFilesMediaInfo(ids, 6),
          ])

          for (const fileId of ids) {
            const tags = tagMap[fileId] || []
            const key = buildTrackCacheKey(server.id, fileId)
            if (!key) continue

            currentServerTrackKeys.add(key)
            mergedTrackMap[key] = {
              id: ++localCounter,
              fileId,
              serverId: server.id,
              serverName: server.name || server.host,
              title: extractTitleFromTags(tags) || '',
              artist: extractNamespaceValue(tags, 'artist') || undefined,
              album: extractNamespaceValue(tags, 'album') || undefined,
              tags: tags.length ? tags : undefined,
              url: client.getFileUrl(fileId),
              thumbnail: client.getThumbnailUrl(fileId),
              hasThumbnail: mediaInfoMap[fileId]?.hasThumbnail,
              mimeType: mediaInfoMap[fileId]?.mimeType,
              isVideo: mediaInfoMap[fileId]?.isVideo ?? (section.id === 'video' ? true : undefined),
              mediaKind: section.id,
            }
          }
        }

        const total = Object.values(counts).reduce((sum, value) => sum + (value || 0), 0)
        addedCounts[server.id] = Array.from(currentServerTrackKeys).filter((key) => !previousServerTrackKeys.has(key)).length
        removedCounts[server.id] = Array.from(previousServerTrackKeys).filter((key) => !currentServerTrackKeys.has(key)).length
        summaries[server.id] = {
          updatedAt: Date.now(),
          total,
          counts,
        }
      } catch (error: any) {
        for (const track of previousTracks) {
          const key = buildTrackCacheKey(track.serverId, track.fileId)
          if (!key) continue
          mergedTrackMap[key] = track
        }

        addedCounts[server.id] = 0
        removedCounts[server.id] = 0
        summaries[server.id] = {
          updatedAt: Date.now(),
          total: previousTracks.length,
          counts: {},
          message: `Sync failed: ${error?.message ?? String(error)}`,
        }
      }
    }

    await saveLibraryCache(cacheKey, Object.values(mergedTrackMap), mergedSearchCache)
    dispatchSyncEvent({ cacheKey, phase: 'completed', serverIds: targetServers.map((server) => server.id) })

    return {
      cacheKey,
      summaries,
      addedCounts,
      removedCounts,
    }
  } catch (error: any) {
    const message = error?.message ?? String(error)
    dispatchSyncEvent({ cacheKey, phase: 'failed', serverIds: targetServers.map((server) => server.id), error: message })
    throw error
  }
}