import express from 'express'
import memoizee from 'memoizee'
import { logger } from '@server/helpers/logger.js'
import { Hooks } from '@server/lib/plugins/hooks.js'
import { getServerActor } from '@server/models/application/application.js'
import { VideoModel } from '@server/models/video/video.js'
import { CategoryOverview, ChannelOverview, TagOverview, VideosOverview } from '@peertube/peertube-models'
import { buildNSFWFilter } from '../../helpers/express-utils.js'
import { MEMOIZE_TTL, OVERVIEWS } from '../../initializers/constants.js'
import { apiRateLimiter, asyncMiddleware, optionalAuthenticate, videosOverviewValidator } from '../../middlewares/index.js'
import { TagModel } from '../../models/video/tag.js'

const overviewsRouter = express.Router()

overviewsRouter.use(apiRateLimiter)

overviewsRouter.get('/videos',
  videosOverviewValidator,
  optionalAuthenticate,
  asyncMiddleware(getVideosOverview)
)

// ---------------------------------------------------------------------------

export { overviewsRouter }

// ---------------------------------------------------------------------------

const buildSamples = memoizee(async function () {
  const [ categories, channels, tags ] = await Promise.all([
    VideoModel.getRandomFieldSamples('category', OVERVIEWS.VIDEOS.SAMPLE_THRESHOLD, OVERVIEWS.VIDEOS.SAMPLES_COUNT),
    VideoModel.getRandomFieldSamples('channelId', OVERVIEWS.VIDEOS.SAMPLE_THRESHOLD, OVERVIEWS.VIDEOS.SAMPLES_COUNT),
    TagModel.getRandomSamples(OVERVIEWS.VIDEOS.SAMPLE_THRESHOLD, OVERVIEWS.VIDEOS.SAMPLES_COUNT)
  ])

  const result = { categories, channels, tags }

  logger.debug('Building samples for overview endpoint.', { result })

  return result
}, { maxAge: MEMOIZE_TTL.OVERVIEWS_SAMPLE })

// This endpoint could be quite long, but we cache it
async function getVideosOverview (req: express.Request, res: express.Response) {
  const attributes = await buildSamples()

  const page = req.query.page || 1
  const index = page - 1

  const categories: CategoryOverview[] = []
  const channels: ChannelOverview[] = []
  const tags: TagOverview[] = []

  await Promise.all([
    getVideosByCategory(attributes.categories, index, res, categories),
    getVideosByChannel(attributes.channels, index, res, channels),
    getVideosByTag(attributes.tags, index, res, tags)
  ])

  const result: VideosOverview = {
    categories,
    channels,
    tags
  }

  return res.json(result)
}

async function getVideosByTag (tagsSample: string[], index: number, res: express.Response, acc: TagOverview[]) {
  if (tagsSample.length <= index) return

  const tag = tagsSample[index]
  const videos = await getVideos(res, { tagsOneOf: [ tag ] })

  if (videos.length === 0) return

  acc.push({
    tag,
    videos
  })
}

async function getVideosByCategory (categoriesSample: number[], index: number, res: express.Response, acc: CategoryOverview[]) {
  if (categoriesSample.length <= index) return

  const category = categoriesSample[index]
  const videos = await getVideos(res, { categoryOneOf: [ category ] })

  if (videos.length === 0) return

  acc.push({
    category: videos[0].category,
    videos
  })
}

async function getVideosByChannel (channelsSample: number[], index: number, res: express.Response, acc: ChannelOverview[]) {
  if (channelsSample.length <= index) return

  const channelId = channelsSample[index]
  const videos = await getVideos(res, { videoChannelId: channelId })

  if (videos.length === 0) return

  acc.push({
    channel: videos[0].channel,
    videos
  })
}

async function getVideos (
  res: express.Response,
  where: { videoChannelId?: number, tagsOneOf?: string[], categoryOneOf?: number[] }
) {
  const serverActor = await getServerActor()

  const query = await Hooks.wrapObject({
    start: 0,
    count: 12,
    sort: '-createdAt',
    displayOnlyForFollower: {
      actorId: serverActor.id,
      orLocalVideos: true
    },
    nsfw: buildNSFWFilter(res),
    user: res.locals.oauth ? res.locals.oauth.token.User : undefined,
    countVideos: false,

    ...where
  }, 'filter:api.overviews.videos.list.params')

  const { data } = await Hooks.wrapPromiseFun(
    VideoModel.listForApi,
    query,
    'filter:api.overviews.videos.list.result'
  )

  return data.map(d => d.toFormattedJSON())
}