import type { RegisterServerOptions } from '@peertube/peertube-types'
import { getProsodyDomain } from '../prosody/config/domain'
import { listProsodyRooms } from '../prosody/api/list-rooms'
import { getChannelInfosById } from '../database/channel'
import * as path from 'path'
import * as fs from 'fs'

let singleton: RoomChannel | undefined

/**
 * Class used to request and store some informations about relation between rooms and channels.
 */
class RoomChannel {
  protected readonly options: RegisterServerOptions
  protected readonly prosodyDomain: string
  protected readonly dataFilePath: string
  protected readonly logger: {
    debug: (s: string) => void
    info: (s: string) => void
    warn: (s: string) => void
    error: (s: string) => void
  }

  protected room2Channel: Map<string, number> = new Map<string, number>()
  protected channel2Rooms: Map<number, Map<string, true>> = new Map<number, Map<string, true>>()
  protected needSync: boolean = false

  protected syncTimeout: ReturnType<typeof setTimeout> | undefined
  protected isWriting: boolean = false

  constructor (params: {
    options: RegisterServerOptions
    prosodyDomain: string
    dataFilePath: string
  }) {
    this.options = params.options
    this.prosodyDomain = params.prosodyDomain
    this.dataFilePath = params.dataFilePath

    const logger = params.options.peertubeHelpers.logger
    this.logger = {
      debug: (s) => logger.debug('[RoomChannel] ' + s),
      info: (s) => logger.info('[RoomChannel] ' + s),
      warn: (s) => logger.warn('[RoomChannel] ' + s),
      error: (s) => logger.error('[RoomChannel] ' + s)
    }
  }

  /**
   * Instanciate the singleton
   */
  public static async initSingleton (options: RegisterServerOptions): Promise<RoomChannel> {
    const prosodyDomain = await getProsodyDomain(options)
    const dataFilePath = path.resolve(
      options.peertubeHelpers.plugin.getDataDirectoryPath(),
      'room-channel',
      prosodyDomain + '.json'
    )

    singleton = new RoomChannel({
      options,
      prosodyDomain,
      dataFilePath
    })

    return singleton
  }

  /**
   * frees the singleton
   */
  public static async destroySingleton (): Promise<void> {
    if (!singleton) { return }
    singleton.cancelScheduledSync()
    await singleton.sync()
    singleton.cancelScheduledSync() // in case sync rescheduled... we will lose data, but they could be rebuild later
    singleton = undefined
  }

  /**
   * Gets the singleton, or raise an exception if it is too soon.
   * @returns the singleton
   */
  public static singleton (): RoomChannel {
    if (!singleton) {
      throw new Error('RoomChannel singleton is not initialized yet')
    }
    return singleton
  }

  /**
   * Reads data from the room-channel data file.
   * @return Returns true if the data where found and valid. If there is no data (or no valid data), returns false.
   */
  public async readData (): Promise<boolean> {
    // Reading the data file (see https://livingston.frama.io/peertube-plugin-livechat/fr/technical/data/)

    let content: string
    try {
      content = (await fs.promises.readFile(this.dataFilePath)).toString()
    } catch (err) {
      this.logger.info('Failed reading room-channel data file (' + this.dataFilePath + '), assuming it does not exists')
      return false
    }
    content ??= '{}'

    let data: any
    try {
      data = JSON.parse(content)
    } catch (err) {
      this.logger.error('Unable to parse the content of the room-channel data file, will start with an empty database.')
      return false
    }

    // This part must be done atomicly:
    return this._readData(data)
  }

  /**
   * _readData is the atomic part of readData:
   * once the date are read from disk, object data must be emptied and filled atomicly.
   */
  protected _readData (data: any): boolean {
    this.room2Channel.clear()
    this.channel2Rooms.clear()
    this.needSync = true

    if (typeof data !== 'object') {
      this.logger.error('Invalid room-channel data file content')
      return false
    }

    for (const k in data) {
      if (!/^\d+$/.test(k)) {
        this.logger.error('Invalid channel ID type, should be a number, dropping')
        continue
      }
      const channelId = parseInt(k)
      const rooms = data[k]
      if (!Array.isArray(rooms)) {
        this.logger.error('Invalid room list for Channel ' + channelId.toString() + ', dropping')
        continue
      }

      const c2r = new Map<string, true>()
      this.channel2Rooms.set(channelId, c2r)

      for (const jid of rooms) {
        if (typeof jid !== 'string') {
          this.logger.error('Invalid room jid for Channel ' + channelId.toString() + ', dropping')
          continue
        }
        c2r.set(jid, true)
        this.room2Channel.set(jid, channelId)
      }
    }

    return true
  }

  /**
   * Rebuilt the data from scratch.
   * Can be used for the initial migration.
   * Can also be scheduled daily, or on an admin action (not sure it will be done, at the time of the writing).
   */
  public async rebuildData (): Promise<void> {
    const data: any = {}

    const rooms = await listProsodyRooms(this.options)
    for (const room of rooms) {
      let channelId: string | number | undefined

      const matches = room.localpart.match(/^channel\.(\d+)$/)
      if (matches?.[1]) {
        channelId = parseInt(matches[1])
        if (isNaN(channelId)) {
          this.logger.error(`Invalid room JID '${room.localpart}'`)
          continue
        }
        // Checking that channel still exists
        const channelInfos = await getChannelInfosById(this.options, channelId)
        if (!channelInfos) {
          this.logger.debug(
            `Ignoring room ${room.localpart}, because channel ${channelId} seems to not exist anymore`
          )
          continue
        }
      } else {
        const uuid = room.localpart
        const video = await this.options.peertubeHelpers.videos.loadByIdOrUUID(uuid)
        if (!video) {
          this.logger.debug(
            `Ignoring room ${room.localpart}, because video ${uuid} seems to not exist anymore`
          )
          continue
        }
        channelId = video.channelId
      }

      if (!channelId) {
        this.logger.error(`Did not find channelId for ${room.localpart}`)
        continue
      }
      channelId = channelId.toString()
      if (!(channelId in data)) {
        this.logger.debug(`Room ${room.localpart} is associated to channel ${channelId}`)
        data[channelId] = []
      }
      data[channelId].push(room.localpart)
    }

    // This part must be done atomicly:
    this._readData(data)

    await this.sync() // FIXME: or maybe scheduleSync ?
  }

  /**
   * Syncs data to disk.
   */
  public async sync (): Promise<void> {
    if (!this.needSync) { return }

    if (this.isWriting) {
      this.logger.info('Already writing, scheduling a new sync')
      this.scheduleSync()
      return
    }
    this.logger.info('Syncing...')
    this.isWriting = true
    try {
      const data = this._serializeData() // must be atomic
      this.needSync = false // Note: must be done atomicly with the read

      await fs.promises.mkdir(path.dirname(this.dataFilePath), { recursive: true })
      await fs.promises.writeFile(this.dataFilePath, JSON.stringify(data))
      this.logger.info('Syncing done.')
    } catch (err) {
      this.logger.error(err as string)
      this.logger.error('Syncing failed.')
      this.needSync = true
    } finally {
      this.isWriting = false
    }
  }

  /**
   * Schedules a sync.
   * Each times data are modified, we can schedule a sync, but we don't have to wait the file writing to be done.
   */
  public scheduleSync (): void {
    if (!this.needSync) { return }
    if (this.syncTimeout) {
      // Already scheduled... nothing to do
      this.logger.debug('There is already a sync scheduled, skipping.')
      return
    }
    this.logger.info('Scheduling a new sync...')
    this.syncTimeout = setTimeout(() => {
      this.syncTimeout = undefined
      this.logger.info('Running scheduled sync')
      this.sync().then(() => {}, (err) => {
        this.logger.error(err)
        // We will not re-schedule the sync, to avoid flooding error log if there is an issue with the server
      })
    }, 100)
  }

  public cancelScheduledSync (): void {
    if (this.syncTimeout) {
      clearTimeout(this.syncTimeout)
    }
  }

  /**
   * Sets a relation between room and channel id
   * @param channelId The channel ID
   * @param roomJID The room JID. Can be the local part only, or the full JID.
   *                In the second case, the domain will be checked.
   */
  public link (channelId: number | string, roomJIDParam: string): void {
    channelId = parseInt(channelId.toString())
    if (isNaN(channelId)) {
      this.logger.error('Invalid channelId, we wont link')
      return
    }

    const roomJID = this._canonicJID(roomJIDParam)
    if (!roomJID) {
      this.logger.error('Invalid room JID, we wont link')
      return
    }

    // First, if the room was linked to another channel, we must unlink.
    const previousChannelId = this.room2Channel.get(roomJID)
    if (previousChannelId) {
      if (this.room2Channel.delete(roomJID)) {
        this.needSync = true
      }
      const previousRooms = this.channel2Rooms.get(previousChannelId)
      if (previousRooms) {
        if (previousRooms.delete(roomJID)) {
          this.needSync = true
        }
      }
    }

    if (this.room2Channel.get(roomJID) !== channelId) {
      this.room2Channel.set(roomJID, channelId)
      this.needSync = true
    }
    let rooms = this.channel2Rooms.get(channelId)
    if (!rooms) {
      rooms = new Map<string, true>()
      this.channel2Rooms.set(channelId, rooms)
      this.needSync = true
    }
    if (!rooms.has(roomJID)) {
      rooms.set(roomJID, true)
      this.needSync = true
    }

    this.scheduleSync()
  }

  /**
   * Removes all relations for this room
   * @param roomJID the room JID
   */
  public removeRoom (roomJIDParam: string): void {
    const roomJID = this._canonicJID(roomJIDParam)
    if (!roomJID) {
      this.logger.error('Invalid room JID, we wont link')
      return
    }

    const channelId = this.room2Channel.get(roomJID)
    if (channelId) {
      const rooms = this.channel2Rooms.get(channelId)
      if (rooms) {
        if (rooms.delete(roomJID)) {
          this.needSync = true
        }
      }
    }

    if (this.room2Channel.delete(roomJID)) {
      this.needSync = true
    }

    this.scheduleSync()
  }

  /**
   * Removes all relations for this channel
   * @param channelId the channel id
   */
  public removeChannel (channelId: number | string): void {
    channelId = parseInt(channelId.toString())
    if (isNaN(channelId)) {
      this.logger.error('Invalid channelId, we wont remove')
      return
    }

    const rooms = this.channel2Rooms.get(channelId)
    if (rooms) {
      for (const jid of rooms.keys()) {
        // checking the consistency... only removing if the channel is the current one
        if (this.room2Channel.get(jid) === channelId) {
          this.room2Channel.delete(jid)
          this.needSync = true
        }
      }
    }

    if (this.channel2Rooms.delete(channelId)) {
      this.needSync = true
    }

    this.scheduleSync()
  }

  /**
   * Get the channel ID for a given room.
   * Returns null if not found.
   * @param roomJIDParam room JID (local part, or full JID)
   */
  public getRoomChannelId (roomJIDParam: string): number | null {
    const roomJID = this._canonicJID(roomJIDParam)
    if (!roomJID) {
      this.logger.error('Invalid room JID: ' + roomJIDParam)
      return null
    }

    return this.room2Channel.get(roomJID) ?? null
  }

  /**
   * Returns room local JID parts for all room linked to given channel.
   * @param channelId channel id
   * @returns list of room JIDs local parts
   */
  public getChannelRoomJIDs (channelId: number | string): string[] {
    channelId = parseInt(channelId.toString())
    if (isNaN(channelId)) {
      this.logger.error('Invalid channelId, we wont link')
      return []
    }

    const rooms = this.channel2Rooms.get(channelId)
    if (!rooms) {
      return []
    }
    return Array.from(rooms.keys())
  }

  protected _canonicJID (roomJID: string): string | null {
    const splits = roomJID.split('@')
    if (splits.length < 2) {
      return roomJID
    }
    if (splits.length > 2) {
      this.logger.error('The room JID contains multiple @, not valid')
      return null
    }
    if (splits[1] !== this.prosodyDomain) {
      this.logger.error('The room JID is not on the correct domain')
      return null
    }

    return splits[0]
  }

  protected _serializeData (): any {
    const data: any = {}
    this.channel2Rooms.forEach((rooms, channelId) => {
      const a: string[] = []
      rooms.forEach((_val, roomJID) => {
        a.push(roomJID)
      })
      data[channelId.toString()] = a
    })
    return data
  }
}

export {
  RoomChannel
}

// TODO: schedule rebuild every X hours/days