import { Observable, of } from 'rxjs'
import { map, switchMap } from 'rxjs/operators'
import { Injectable } from '@angular/core'
import { ServerService, UserService } from '@app/core'
import { Video, VideoService } from '@app/shared/shared-main'
import { AdvancedSearch, SearchService } from '@app/shared/shared-search'
import { HTMLServerConfig } from '@shared/models'
import { RecommendationInfo } from './recommendation-info.model'
import { RecommendationService } from './recommendations.service'

/**
 * Provides "recommendations" by providing the most recently uploaded videos.
 */
@Injectable()
export class RecentVideosRecommendationService implements RecommendationService {
  readonly pageSize = 5

  private config: HTMLServerConfig

  constructor (
    private videos: VideoService,
    private searchService: SearchService,
    private userService: UserService,
    private serverService: ServerService
  ) {
    this.config = this.serverService.getHTMLConfig()
  }

  getRecommendations (recommendation: RecommendationInfo): Observable<Video[]> {

    return this.fetchPage(1, recommendation)
      .pipe(
        map(videos => {
          const otherVideos = videos.filter(v => v.uuid !== recommendation.uuid)
          return otherVideos.slice(0, this.pageSize)
        })
      )
  }

  private fetchPage (page: number, recommendation: RecommendationInfo): Observable<Video[]> {
    const pagination = { currentPage: page, itemsPerPage: this.pageSize + 1 }
    const defaultSubscription = this.videos.getVideos({ videoPagination: pagination, sort: '-createdAt' })
                                    .pipe(map(v => v.data))

    const tags = recommendation.tags
    const searchIndexConfig = this.config.search.searchIndex
    if (
      !tags || tags.length === 0 ||
      (searchIndexConfig.enabled === true && searchIndexConfig.disableLocalSearch === true)
    ) {
      return defaultSubscription
    }

    return this.userService.getAnonymousOrLoggedUser()
      .pipe(
        map(user => {
          return {
            search: '',
            componentPagination: pagination,
            advancedSearch: new AdvancedSearch({
              tagsOneOf: recommendation.tags.join(','),
              sort: '-publishedAt',
              searchTarget: 'local',
              nsfw: user.nsfwPolicy
                ? this.videos.nsfwPolicyToParam(user.nsfwPolicy)
                : undefined,
              excludeAlreadyWatched: user.id
                ? true
                : undefined
            })
          }
        }),
        switchMap(params => this.searchService.searchVideos(params)),
        map(v => v.data),
        switchMap(videos => {
          if (videos.length <= 1) return defaultSubscription

          return of(videos)
        })
      )
  }
}