app.js

const express = require('express')
const axios = require('axios')
const app = express()
const videoDetailsURL = `https://yt.lemnoslife.com/noKey/videos?part=contentDetails&fields=items/contentDetails/duration`
const playlistItemsURL = `https://yt.lemnoslife.com/noKey/playlistItems?part=contentDetails&maxResults=50&fields=items/contentDetails/videoId,nextPageToken`

app.use(express.urlencoded({ extended: true }))
app.use(express.static('views'))

//Generates URL for required videos.
function generateVideosURL (id) {
  return `${videoDetailsURL}&id=${id}`
}

// Requests for videoIDS and nextPageToken(s)
async function getVideoIdsForPageToken (url) {
  try {
    console.log(url)
    const { data } = await axios.get(url)
    const nextPageToken = data.nextPageToken
    const videoIds = data.items.map(video => {
      return video.contentDetails.videoId
    })
    return { videoIds, nextPageToken }
  } catch (e) {
    if (e.response) {
      const { code, message } = e.response.data.error
      console.log('Errow while fetching videos list.')
      throw new Error(`StatusCode ${code}. Reason: ${message}`)
    } else {
      throw new Error(e.message)
    }
  }
}

// Returns details for videos in the playlist.
async function getDetailsForVideoIds (id) {
  try {
    const { data } = await axios.get(generateVideosURL(id))
    return data.items
  } catch (e) {
    console.log('Error while fetching video details. ')
    throw new Error(e.message)
  }
}

// Formats all the returned duration info into seconds.
function returnedToSeconds (input) {
  try {
    const daysHrsMinsSecs = /^P(?:(\d+)D)?T(?:(\d+)H)?(?:(\d+)M)?(?:(\d+)S)?$/
    let days = 0
    let hours = 0
    let minutes = 0
    let seconds = 0
    let totalSeconds = 0
    if (daysHrsMinsSecs.test(input)) {
      let toMatch = daysHrsMinsSecs.exec(input)
      if (toMatch[1]) days = Number(toMatch[1])
      if (toMatch[2]) hours = Number(toMatch[2])
      if (toMatch[3]) minutes = Number(toMatch[3])
      if (toMatch[4]) seconds = Number(toMatch[4])
      totalSeconds = days * 86400 + hours * 3600 + minutes * 60 + seconds
    } else {
      console.log(returnedToSeconds)
    }
    return totalSeconds
  } catch (e) {
    console.error(e)
    if (e.message.includes('Invalid date')) {
      return 'Invalid date in returned data.'
    }
  }
}


async function getPlaylistTotalDuration (extractedPlaylistIDId, newPageToken) {
  try {
    // Step 1: Create the required query URL based on the newPageToken parameter
    let url = newPageToken
      ? `${playlistItemsURL}&playlistId=${extractedPlaylistIDId}&pageToken=${newPageToken}`
      : `${playlistItemsURL}&playlistId=${extractedPlaylistIDId}`

    // Step 2: Start a local duration counter
    let totalDuration = 0
    let numberOfVideos = 0
    let firstVideoIds

    // Step 3: Get the video details based on the URL created in Step 1
    const { videoIds, nextPageToken } = await getVideoIdsForPageToken(url)
    const returnedVideoIds = []
    returnedVideoIds.push(getDetailsForVideoIds(videoIds))
    const videoGroups = await Promise.all(returnedVideoIds)
    for (const group of videoGroups) {
      for (const video of group) {
        // Step 4: Get the durations in seconds and add it to the local duration counter created in Step 2
        totalDuration += returnedToSeconds(video.contentDetails.duration)
      }
    }

    numberOfVideos = videoGroups[0].length
    firstVideoIds = videoIds[0]

    // Step 5: Check if the return of Step 3 has a nextPageToken, if so do a recursive call to self with the new token
    if (nextPageToken) {
      firstVideoIds
      let returnedTotalDuration = await getPlaylistTotalDuration(
        extractedPlaylistIDId,
        nextPageToken
      )
      totalDuration += returnedTotalDuration.totalDuration
      let returnedNoOfVideos = returnedTotalDuration.numberOfVideos
      numberOfVideos += returnedNoOfVideos
      firstVideoIds = videoIds[0]
    }
    return { totalDuration, numberOfVideos, firstVideoIds }
  } catch (e) {
    console.log('Error while navigating between video pages.')
    throw new Error(e)
  }
}

app.post('/search', async (req, res) => {
  async function checkID (playlistID) {
    let checkRes
    await axios
      .get(
        `https://yt.lemnoslife.com/noKey/playlistItems?part=status&maxResults=1&playlistId=${playlistID}`
      )
      .then(res => {
        checkRes = true
      })
      .catch(error => {
        if (error.response) {
          console.log(error.response.status)
          checkRes = false
        }
      })
    return checkRes
  }

  ;(async () => {
    extractedPlaylistIDId = null
    const playlisturl = req.body.playlistID
    if (await checkID(playlisturl)) {
      let resp = await getPlaylistTotalDuration(playlisturl)
      console.log(
        'Someone just fetched a playlist of ' +
          resp.totalDuration +
          ' seconds with ' +
          resp.numberOfVideos +
          ' videos with the first video id ' +
          resp.firstVideoIds
      )
      res.send(resp)
    } else {
      res.send('API_Error')
    }
  })()
})

app.get('/', function (req, res) {
  res.render('index')
})

// Port Route.
app.listen(process.env.PORT || 3000, () => {
  console.log(`Playlist data is now running baby!)`)
})