const Path = require('path')
const EventEmitter = require('events')
const Watcher = require('./libs/watcher/watcher')
const Logger = require('./Logger')
const LibraryScanner = require('./scanner/LibraryScanner')
const Task = require('./objects/Task')
const TaskManager = require('./managers/TaskManager')

const { filePathToPOSIX, isSameOrSubPath, getFileMTimeMs } = require('./utils/fileUtils')

/**
 * @typedef PendingFileUpdate
 * @property {string} path
 * @property {string} relPath
 * @property {string} folderId
 * @property {string} type
 */
class FolderWatcher extends EventEmitter {
  constructor() {
    super()

    /** @type {{id:string, name:string, folders:import('./objects/Folder')[], paths:string[], watcher:Watcher[]}[]} */
    this.libraryWatchers = []
    /** @type {PendingFileUpdate[]} */
    this.pendingFileUpdates = []
    this.pendingDelay = 4000
    /** @type {NodeJS.Timeout} */
    this.pendingTimeout = null
    /** @type {Task} */
    this.pendingTask = null

    this.filesBeingAdded = new Set()

    /** @type {string[]} */
    this.ignoreDirs = []
    /** @type {string[]} */
    this.pendingDirsToRemoveFromIgnore = []
    /** @type {NodeJS.Timeout} */
    this.removeFromIgnoreTimer = null

    this.disabled = false
  }

  get pendingFilePaths() {
    return this.pendingFileUpdates.map(f => f.path)
  }

  buildLibraryWatcher(library) {
    if (this.libraryWatchers.find(w => w.id === library.id)) {
      Logger.warn('[Watcher] Already watching library', library.name)
      return
    }
    Logger.info(`[Watcher] Initializing watcher for "${library.name}".`)

    const folderPaths = library.folderPaths
    folderPaths.forEach((fp) => {
      Logger.debug(`[Watcher] Init watcher for library folder path "${fp}"`)
    })
    const watcher = new Watcher(folderPaths, {
      ignored: /(^|[\/\\])\../, // ignore dotfiles
      renameDetection: true,
      renameTimeout: 2000,
      recursive: true,
      ignoreInitial: true,
      persistent: true
    })
    watcher
      .on('add', (path) => {
        this.onFileAdded(library.id, filePathToPOSIX(path))
      }).on('change', (path) => {
        // This is triggered from metadata changes, not what we want
      }).on('unlink', path => {
        this.onFileRemoved(library.id, filePathToPOSIX(path))
      }).on('rename', (path, pathNext) => {
        this.onFileRename(library.id, filePathToPOSIX(path), filePathToPOSIX(pathNext))
      }).on('error', (error) => {
        Logger.error(`[Watcher] ${error}`)
      }).on('ready', () => {
        Logger.info(`[Watcher] "${library.name}" Ready`)
      }).on('close', () => {
        Logger.debug(`[Watcher] "${library.name}" Closed`)
      })

    this.libraryWatchers.push({
      id: library.id,
      name: library.name,
      folders: library.folders,
      paths: library.folderPaths,
      watcher
    })
  }

  initWatcher(libraries) {
    libraries.forEach((lib) => {
      if (!lib.settings.disableWatcher) {
        this.buildLibraryWatcher(lib)
      }
    })
  }

  addLibrary(library) {
    if (this.disabled || library.settings.disableWatcher) return
    this.buildLibraryWatcher(library)
  }

  updateLibrary(library) {
    if (this.disabled || library.settings.disableWatcher) return
    var libwatcher = this.libraryWatchers.find(lib => lib.id === library.id)
    if (libwatcher) {
      libwatcher.name = library.name

      // If any folder paths were added or removed then re-init watcher
      var pathsToAdd = library.folderPaths.filter(path => !libwatcher.paths.includes(path))
      var pathsRemoved = libwatcher.paths.filter(path => !library.folderPaths.includes(path))
      if (pathsToAdd.length || pathsRemoved.length) {
        Logger.info(`[Watcher] Re-Initializing watcher for "${library.name}".`)

        libwatcher.watcher.close()
        this.libraryWatchers = this.libraryWatchers.filter(lw => lw.id !== libwatcher.id)
        this.buildLibraryWatcher(library)
      }
    }
  }

  removeLibrary(library) {
    if (this.disabled) return
    var libwatcher = this.libraryWatchers.find(lib => lib.id === library.id)
    if (libwatcher) {
      Logger.info(`[Watcher] Removed watcher for "${library.name}"`)
      libwatcher.watcher.close()
      this.libraryWatchers = this.libraryWatchers.filter(lib => lib.id !== library.id)
    } else {
      Logger.error(`[Watcher] Library watcher not found for "${library.name}"`)
    }
  }

  close() {
    return this.libraryWatchers.map(lib => lib.watcher.close())
  }

  /**
   * Watcher detected file added
   * 
   * @param {string} libraryId 
   * @param {string} path 
   */
  onFileAdded(libraryId, path) {
    if (this.checkShouldIgnorePath(path)) {
      return
    }
    Logger.debug('[Watcher] File Added', path)
    this.addFileUpdate(libraryId, path, 'added')

    if (!this.filesBeingAdded.has(path)) {
      this.filesBeingAdded.add(path)
      this.waitForFileToAdd(path)
    }
  }

  /**
   * Watcher detected file removed
   * 
   * @param {string} libraryId 
   * @param {string} path 
   */
  onFileRemoved(libraryId, path) {
    if (this.checkShouldIgnorePath(path)) {
      return
    }
    Logger.debug('[Watcher] File Removed', path)
    this.addFileUpdate(libraryId, path, 'deleted')
  }

  /**
   * Watcher detected file renamed
   * 
   * @param {string} libraryId 
   * @param {string} path 
   */
  onFileRename(libraryId, pathFrom, pathTo) {
    if (this.checkShouldIgnorePath(pathTo)) {
      return
    }
    Logger.debug(`[Watcher] Rename ${pathFrom} => ${pathTo}`)
    this.addFileUpdate(libraryId, pathTo, 'renamed')
  }

  /**
   * Get mtimeMs from an added file every second until it is no longer changing
   * Times out after 180s
   * 
   * @param {string} path 
   * @param {number} [lastMTimeMs=0] 
   * @param {number} [loop=0] 
   */
  async waitForFileToAdd(path, lastMTimeMs = 0, loop = 0) {
    // Safety to catch infinite loop (180s)
    if (loop >= 180) {
      Logger.warn(`[Watcher] Waiting to add file at "${path}" timeout (loop ${loop}) - proceeding`)
      return this.filesBeingAdded.delete(path)
    }

    const mtimeMs = await getFileMTimeMs(path)
    if (mtimeMs === lastMTimeMs) {
      if (lastMTimeMs) Logger.debug(`[Watcher] File finished adding at "${path}"`)
      return this.filesBeingAdded.delete(path)
    }
    if (lastMTimeMs % 5 === 0) {
      Logger.debug(`[Watcher] Waiting to add file at "${path}". mtimeMs=${mtimeMs} lastMTimeMs=${lastMTimeMs} (loop ${loop})`)
    }
    // Wait 1 second
    await new Promise((resolve) => setTimeout(resolve, 1000))
    this.waitForFileToAdd(path, mtimeMs, ++loop)
  }

  /**
   * Queue file update
   * 
   * @param {string} libraryId 
   * @param {string} path 
   * @param {string} type 
   */
  addFileUpdate(libraryId, path, type) {
    if (this.pendingFilePaths.includes(path)) return

    // Get file library
    const libwatcher = this.libraryWatchers.find(lw => lw.id === libraryId)
    if (!libwatcher) {
      Logger.error(`[Watcher] Invalid library id from watcher ${libraryId}`)
      return
    }

    // Get file folder
    const folder = libwatcher.folders.find(fold => isSameOrSubPath(fold.fullPath, path))
    if (!folder) {
      Logger.error(`[Watcher] New file folder not found in library "${libwatcher.name}" with path "${path}"`)
      return
    }

    const folderFullPath = filePathToPOSIX(folder.fullPath)

    const relPath = path.replace(folderFullPath, '')

    if (Path.extname(relPath).toLowerCase() === '.part') {
      Logger.debug(`[Watcher] Ignoring .part file "${relPath}"`)
      return
    }

    // Ignore files/folders starting with "."
    const hasDotPath = relPath.split('/').find(p => p.startsWith('.'))
    if (hasDotPath) {
      Logger.debug(`[Watcher] Ignoring dot path "${relPath}" | Piece "${hasDotPath}"`)
      return
    }

    Logger.debug(`[Watcher] Modified file in library "${libwatcher.name}" and folder "${folder.id}" with relPath "${relPath}"`)

    if (!this.pendingTask) {
      const taskData = {
        libraryId,
        libraryName: libwatcher.name
      }
      this.pendingTask = TaskManager.createAndAddTask('watcher-scan', `Scanning file changes in "${libwatcher.name}"`, null, true, taskData)
    }
    this.pendingFileUpdates.push({
      path,
      relPath,
      folderId: folder.id,
      libraryId,
      type
    })

    this.handlePendingFileUpdatesTimeout()
  }

  /**
   * Wait X seconds before notifying scanner that files changed
   * reset timer if files are still copying
   */
  handlePendingFileUpdatesTimeout() {
    clearTimeout(this.pendingTimeout)
    this.pendingTimeout = setTimeout(() => {
      // Check that files are not still being added
      if (this.pendingFileUpdates.some(pfu => this.filesBeingAdded.has(pfu.path))) {
        Logger.debug(`[Watcher] Still waiting for pending files "${[...this.filesBeingAdded].join(', ')}"`)
        return this.handlePendingFileUpdatesTimeout()
      }

      LibraryScanner.scanFilesChanged(this.pendingFileUpdates, this.pendingTask)
      this.pendingTask = null
      this.pendingFileUpdates = []
      this.filesBeingAdded.clear()
    }, this.pendingDelay)
  }

  checkShouldIgnorePath(path) {
    return !!this.ignoreDirs.find(dirpath => {
      return isSameOrSubPath(dirpath, path)
    })
  }

  /**
   * Convert to POSIX and remove trailing slash
   * @param {string} path 
   * @returns {string}
   */
  cleanDirPath(path) {
    path = filePathToPOSIX(path)
    if (path.endsWith('/')) path = path.slice(0, -1)
    return path
  }

  /**
   * Ignore this directory if files are picked up by watcher
   * @param {string} path 
   */
  addIgnoreDir(path) {
    path = this.cleanDirPath(path)
    this.pendingDirsToRemoveFromIgnore = this.pendingDirsToRemoveFromIgnore.filter(p => p !== path)
    if (this.ignoreDirs.includes(path)) {
      // Already ignoring dir
      return
    }
    Logger.debug(`[Watcher] addIgnoreDir: Ignoring directory "${path}"`)
    this.ignoreDirs.push(path)
  }

  /**
   * When downloading a podcast episode we dont want the scanner triggering for that podcast
   * when the episode finishes the watcher may have a delayed response so a timeout is added
   * to prevent the watcher from picking up the episode
   * 
   * @param {string} path 
   */
  removeIgnoreDir(path) {
    path = this.cleanDirPath(path)
    if (!this.ignoreDirs.includes(path)) {
      Logger.debug(`[Watcher] removeIgnoreDir: Path is not being ignored "${path}"`)
      return
    }

    // Add a 5 second delay before removing the ignore from this dir
    if (!this.pendingDirsToRemoveFromIgnore.includes(path)) {
      this.pendingDirsToRemoveFromIgnore.push(path)
    }

    clearTimeout(this.removeFromIgnoreTimer)
    this.removeFromIgnoreTimer = setTimeout(() => {
      if (this.pendingDirsToRemoveFromIgnore.includes(path)) {
        this.pendingDirsToRemoveFromIgnore = this.pendingDirsToRemoveFromIgnore.filter(p => p !== path)
        Logger.debug(`[Watcher] removeIgnoreDir: No longer ignoring directory "${path}"`)
        this.ignoreDirs = this.ignoreDirs.filter(p => p !== path)
      }
    }, 5000)
  }
}
module.exports = FolderWatcher