import { OnInit } from '@angular/core'
import { ActivatedRoute, Router } from '@angular/router'
import { NotificationsService } from 'angular2-notifications'
import { Observable } from 'rxjs/Observable'
import { AuthService } from '../../core/auth'
import { ComponentPagination } from '../rest/component-pagination.model'
import { SortField } from './sort-field.type'
import { Video } from './video.model'

export abstract class AbstractVideoList implements OnInit {
  pagination: ComponentPagination = {
    currentPage: 1,
    itemsPerPage: 25,
    totalItems: null
  }
  sort: SortField = '-createdAt'
  defaultSort: SortField = '-createdAt'
  videos: Video[] = []
  loadOnInit = true

  protected abstract notificationsService: NotificationsService
  protected abstract authService: AuthService
  protected abstract router: Router
  protected abstract route: ActivatedRoute

  protected abstract currentRoute: string

  abstract titlePage: string

  protected otherParams = {}

  private loadedPages: { [ id: number ]: boolean } = {}

  abstract getVideosObservable (): Observable<{ videos: Video[], totalVideos: number}>

  get user () {
    return this.authService.getUser()
  }

  ngOnInit () {
    // Subscribe to route changes
    const routeParams = this.route.snapshot.params
    this.loadRouteParams(routeParams)

    if (this.loadOnInit === true) this.loadMoreVideos('after')
  }

  onNearOfTop () {
    if (this.pagination.currentPage > 1) {
      this.previousPage()
    }
  }

  onNearOfBottom () {
    if (this.hasMoreVideos()) {
      this.nextPage()
    }
  }

  reloadVideos () {
    this.videos = []
    this.loadedPages = {}
    this.loadMoreVideos('before')
  }

  loadMoreVideos (where: 'before' | 'after') {
    if (this.loadedPages[this.pagination.currentPage] === true) return

    const observable = this.getVideosObservable()

    observable.subscribe(
      ({ videos, totalVideos }) => {
        // Paging is too high, return to the first one
        if (this.pagination.currentPage > 1 && totalVideos <= ((this.pagination.currentPage - 1) * this.pagination.itemsPerPage)) {
          this.pagination.currentPage = 1
          this.setNewRouteParams()
          return this.reloadVideos()
        }

        this.loadedPages[this.pagination.currentPage] = true
        this.pagination.totalItems = totalVideos

        if (where === 'before') {
          this.videos = videos.concat(this.videos)
        } else {
          this.videos = this.videos.concat(videos)
        }
      },
      error => this.notificationsService.error('Error', error.message)
    )
  }

  protected hasMoreVideos () {
    // No results
    if (this.pagination.totalItems === 0) return false

    // Not loaded yet
    if (!this.pagination.totalItems) return true

    const maxPage = this.pagination.totalItems / this.pagination.itemsPerPage
    return maxPage > this.pagination.currentPage
  }

  protected previousPage () {
    this.pagination.currentPage--

    this.setNewRouteParams()
    this.loadMoreVideos('before')
  }

  protected nextPage () {
    this.pagination.currentPage++

    this.setNewRouteParams()
    this.loadMoreVideos('after')
  }

  protected buildRouteParams () {
    // There is always a sort and a current page
    const params = {
      sort: this.sort,
      page: this.pagination.currentPage
    }

    return Object.assign(params, this.otherParams)
  }

  protected loadRouteParams (routeParams: { [ key: string ]: any }) {
    this.sort = routeParams['sort'] as SortField || this.defaultSort

    if (routeParams['page'] !== undefined) {
      this.pagination.currentPage = parseInt(routeParams['page'], 10)
    } else {
      this.pagination.currentPage = 1
    }
  }

  protected setNewRouteParams () {
    const routeParams = this.buildRouteParams()
    this.router.navigate([ this.currentRoute, routeParams ])
  }
}