// native imports
import { EventEmitter as Emitter } from 'events'
import path from 'path'
// third party imports
import { watch } from 'chokidar'
import debounce from 'debounce-fn'
// UCI imports
import readIgnoreLists from '@uci-utils/read-lines'
import logger from '@uci-utils/logger'

let log = {}

const READY_TIMEOUT = 10000 //default 

class Watcher extends Emitter {
  constructor(opts = {}) {
    super()
    log = logger({ package: '@uci-utils/watcher', class: 'Watcher', file: 'src/watcher.js' })
    opts.unlinkDir = 'unlinkDir' in opts ? opts.unlinkDir : true  // delete file even on by default
    this.opts = opts
    this.timeout = process.env.READY_TIMEOUT || opts.readyTimeout || READY_TIMEOUT
    this._ignored = opts.ignored ? (Array.isArray(opts.ignored) ? opts.ignored : opts.ignored.split(',')) : []
    this.handler = opts.handler || _handler
    this._ready = false
    this._watching = false
    // .goutputstream files arise during atomic writes, ignore them by default
    this.ignore_goutputstream = opts.ignore_goutputstream === false ? false : true 
    return this
  }

  get watching() {
    return this._watching
  }

  get ready() {
    return this._ready
  }

  registerHandler(func, opts) {
    opts = Object.assign({}, this.opts, opts)
    if (!this._watcher) return 'failed: watcher not initialized'
    if (typeof func === 'function') this.handler = func
    else if (func) opts = func
    opts = Object.assign({}, this.opts, opts)
    let handler
    if (opts.debounce)
      handler = debounce((type, file) => {
        log.debug(`waited : ${opts.debounce}ms before calling handler`)
        log.info('debounced handler, only last event is emitted')
        this.handler.call(this, type, file)
      }, { wait: opts.debounce })
    else
      handler = (type, file) => { this.handler.call(this, type, file) }

    this._watcher.removeAllListeners()

    if (opts.delDir) this._watcher.on('unlinkDir', handler.bind(this, 'dir-deleted'))
    if (opts.addDir) this._watcher.on('addDir', handler.bind(this, 'dir-added'))

    // these are watched by default, one can take action or not in the handler  
    this._watcher
      .on('add', handler.bind(this, 'added'))
      .on('change', handler.bind(this, 'modified'))
      .on('unlink', handler.bind(this, 'removed'))

    // reset the error event since it got scrubbed 
    this._watcher.on('error', error => {
      const msg = 'chokidar watcher error'
      log.error({ error: error, msg: msg })
      this.emit('error', msg, error)
    })
  }

  async start(opts = {}) {
    if (this._watching) {
      log.warn(`watching aleady running for ${opts.source || this.opts.source}`)
      return false
    }
    if (!this._watcher) opts = await this._init(opts)
    if (this._ready) {
      this.emit('ready', true, opts)
      log.trace({ watching: this._watcher.getWatched(), msg: 'initial files watched' })
      log.info(`now watching ${opts.source || this.opts.source}`)
      if (this.registerHandler(opts)) {
        log.fatal('watcher was not initialized so could not register handler')
        return new Error('watcher was not initialized so could not register handler')
      }
      this._watching = true
      this.emit('watching', true, opts)
    } else {
      const msg = 'watcher is not ready to start, check options and try again'
      log.fatal(msg)
      this.emit('error', msg)
      return new Error('not ready to start check configuration options')
    }
  }

  stop() {
    if (this._watching) {
      this._watching = false
      this._watcher.close()
      this.emit('watching', false)
    }
    else log.warn('not watching, nothing to stop')
  }

  remove() {
    if (this._watcher) {
      this.stop()
      this._watcher.removeAllListeners()
      delete (this._watcher)
    } else log.warn('no watcher started nothing to remove')
    this._ready = false
    this.emit('ready', false)
  }

  async restart(opts, force) {
    if (typeof opts === 'boolean') { force = opts, opts = {} }
    this.stop()
    await this.start(opts)
  }

  getWatcher() {
    return this._watcher
  }

  // private methods
  // set up chokidar
  async _init(opts = {}) {
    if (!opts.overwrite) {
      await this._fetchIgnoreLists(this.opts.excludeFrom)
      await this._fetchIgnoreLists(this.opts.ignoreList)
    }
    await this._fetchIgnoreLists(opts.excludeFrom, opts.overwrite)
    await this._fetchIgnoreLists(opts.ignoreList, opts.overwrite)
    if (!opts.ignored) opts.ignored = []
    opts.ignored = Array.isArray(opts.ignored) ? opts.ignored : opts.ignored.split(',')
    opts.ignored = opts.overwrite ? opts.ignored : [...this._ignored, ...opts.ignored]
    if (this.ignore_goutputstream) opts.ignored.push('**/.goutputstream*')
    opts = Object.assign({}, this.opts, opts) // now that ignore arrays are dealt with merge options
    return new Promise(async (resolve, reject) => {
      log.debug({ options: opts, msg: 'initializing watch with options' })
      if (opts.source) {
        // create chokidar watcher
        this._watcher = watch(opts.source, opts)
        this._watcher.once('error', error => {
          log.error({ error: error, msg: 'Watcher error' })
          reject({ error: error, msg: 'Watcher error' })
        })
        this._watcher.once('ready', () => {
          clearTimeout(readyTimeout)
          log.info('initial scan sucessful, ready to start')
          this._ready = true
          resolve(opts)
        })
        log.debug(`initial scanning, timeout in ${this.timeout}ms`)
        let readyTimeout = setTimeout(() => {
          log.fatal({ options: opts, timeout: this.timeout, msg: 'Timeout: unable to complete initial scan' })
          reject('timeout during initial scan, maybe increase ready timeout')
        }, this.timeout)
      }
      else {
        log.fatal('MUST provide a source directory(s) option to watch')
        reject('watching - no source provided')
      }
    })
  }

  async _fetchIgnoreLists(lists, overwrite) {
    if (typeof lists === 'string') lists = [lists]
    if (!Array.isArray(lists)) return  // no lists
    let ignored = await readIgnoreLists(lists)
    this._ignored = overwrite ? ignored : [...this._ignored, ...ignored]
  }



} //end class

// default handler
function _handler(type, f) {
  log.debug(`file ${f} was ${type}`)
  const fname = path.basename(f)
  if (fname.toLowerCase() === 'package.json' && path.dirname(f) === this.opts.source.replace(/\/$/, ''))
    if (type !== 'modified') {
      const msg = `a package.json in root of ${this.opts.source} was added or removed`
      log.warning(msg)
      this.emit('warning', f, msg)
      return
    } else {
      this.emit('install', f)
    }
  // user might want to run debounce on the listener for this event
  log.debug({ file: f, type: type, msg: 'file system changed, emitting' })
  this.emit('changed', f, type)
} // end handler

export default Watcher
export { Watcher }