/*
This workflow provides an HTTP API to retrieve data in 
JSON format about the number of cases, recoveries and 
deaths by region related to the 2019-nCoV Wuhan coronavirus.
The source data is aggregated and published to Github by 
the The Center for Systems Science and Engineering (CSSE) 
at John Hopkins University.
 
To use this API, make an HTTP request to:

https://coronavirus.m.pipedream.net

The data includes:

1. Summary stats (counts of cases, recoveries and deaths)
   - Global
   - China
   - Non-China

2. Raw data (counts by region as published in the Google Sheet)

Data is cached using $checkpoint to improve performance. The 
cache is updated if it's more than 5 minutes old.

Data source: https://github.com/CSSEGISandData/COVID-19/tree/master/csse_covid_19_data/csse_covid_19_daily_reports

NOTE: The previous version of this API used data published to
Google Sheets. That data is no longer maintained. The source
code for that API is at https://pipedream.com/@pravin/backup-http-api-for-latest-wuhan-coronavirus-data-2019-ncov-p_QPCd3j/edit
*/

// filter out requests for favicon assets
if (steps.trigger.event.url.indexOf('favicon.ico') !== -1) {
  $end('Terminating workfow for favicon request')
}

if (typeof this.$checkpoint === 'undefined') {
  // initialize this.$checkpoint
  this.$checkpoint = {}
  this.$checkpoint.data = {}
  this.$checkpoint.ts = 0
  this.$checkpoint.lastModified = ''
  this.$checkpoint.range = ''
  this.$checkpoint.spreadsheetId = ''
  this.$checkpoint.lastPublished = 0
}

const { Octokit }  = require("@octokit/rest");
const _ = require('lodash')
const moment = require('moment')
const axios = require('axios')
const parse = require('csv-parse/lib/sync')
const stripBom = require('strip-bom');

this.dataExpiry = 5 * 60 * 1000

// If the cache is expired or if there is a request to force an
// update, then we should update the cache
if (((new Date().getTime() - this.$checkpoint.ts) > (this.dataExpiry)) || 
    (event.query.action === 'refresh' && event.query.token === 
    process.env.CSSE_NCOV_REFRESH_TOKEN)) {
  this.updateCache = true
} else {
  this.updateCache = false
}

// Update the cache or return the data from this.$checkpoint
// based on the value of this.updateCache
if (this.updateCache === true) {

  let maxDate = 0

  // initialize octokit
  const octokit = new Octokit({
    userAgent: steps.trigger.context.workflow_id,
    baseUrl: 'https://api.github.com',
  })

  // get the files in the target repo folder
  this.rawData = (await octokit.repos.getContents({
    owner: params.owner,
    repo: params.repo,
    path: params.path,
  })).data
  
  // get the file with the most recent data
  for ( let i = 0; i < this.rawData.length; i++ ) {
    let fileData = this.rawData[i].name.split(".")
    if (fileData[1] === 'csv') {
      if (moment(fileData[0], "MM-DD-YYYY").format('x') > moment(maxDate, "MM-DD-YYYY").format('x') || maxDate === 0) {
        maxDate = fileData[0]
      }
    }
  }

  // export the date associated with the most recent data
  this.maxDate = maxDate

  // get the most recent data
  const dataSourceUrl = `https://raw.githubusercontent.com/${params.owner}/${params.repo}/master/${params.path}/${maxDate}.csv`
  const data = (await axios.get(dataSourceUrl)).data

  // strip the byte order mark
  const cleansedData = stripBom(data)

  // parse the CSV data to an array
  const parsedData = parse(cleansedData, {
    columns: true,
    skip_empty_lines: true
  })

  this.mostRecentData = 0
  parsedData.forEach( update => {
    if ( moment(update['Last Update']).format('x') > moment(this.mostRecentData).format('x') || this.mostRecentData === 0) {
      this.mostRecentData = update['Last Update']
    }
  })

  // get commits to identify when the file was last updated
  this.commits = await octokit.repos.listCommits({
    owner: params.owner,
    repo: params.repo,
    path: `${params.path}/${maxDate}.csv`,
  });

  // save data to $checkpoint
  this.$checkpoint.dataSource = dataSourceUrl
  this.$checkpoint.data = parsedData
  this.$checkpoint.ts = new Date().getTime()
  this.$checkpoint.lastModified = this.commits.data[0].commit.committer.date
  this.$checkpoint.lastPublished = this.maxDate
} else {
  console.log('Return cached data')
}

return this.$checkpoint

// if the cache was updated in steps.get_data, then
// recalculate the summary stats and checkpoint them.
// Otherwise, return the summary cached in this.$checkpoint
if (steps.get_data.updateCache === true) {
  console.log('updating cached stats')

  // initialize the stats object
  const stats = {
    global: { confirmed: 0, recovered: 0, deaths: 0 },
    china: { confirmed: 0, recovered: 0, deaths: 0 },
    nonChina: { confirmed: 0, recovered: 0, deaths: 0 },
  }

  function incrementTotals(statsObj, regionObj) {
    statsObj.confirmed += parseInt(regionObj.Confirmed)
    statsObj.recovered += parseInt(regionObj.Recovered)
    statsObj.deaths += parseInt(regionObj.Deaths)
    return statsObj
  }

  steps.get_data.$return_value.data.forEach(function(region){
    // increment global totals
    stats.global = incrementTotals(stats.global, region)
    if (region['Country/Region'] === 'China') {
      // calculate totals for china
      stats.china = incrementTotals(stats.china, region)
    } else {
      // calculate totals for non-china regions 
      stats.nonChina = incrementTotals(stats.nonChina, region)
    }
  })

  this.$checkpoint = stats
} else {
  console.log('using cached stats')
}

return this.$checkpoint

try {
  const v8 = require('v8');
  this.heapSpaceStats = v8.getHeapSpaceStatistics()
  this.heapStats = v8.getHeapStatistics()
} catch (err) {
  this.err = err
}

// construct the response body and respond to the client
// request using $respond()

const moment = require('moment')

const body = {}
const lastUpdatedTimestamp = steps.get_data.$return_value.ts
const expiresTimestamp = steps.get_data.dataExpiry 
                         + steps.get_data.$return_value.ts

body.summaryStats = steps.summarize_data.$return_value
body.cache = {
  lastUpdated: moment(lastUpdatedTimestamp).fromNow(),
  expires: moment(expiresTimestamp).fromNow(),
  lastUpdatedTimestamp,
  expiresTimestamp
}
body.dataSource = {
  url: steps.get_data.$return_value.dataSource,
  lastGithubCommit: steps.get_data.$return_value.lastModified,
  mostRecentData: steps.get_data.mostRecentData,
  publishedBy: `John Hopkins University Center for Systems Science and Engineering`,
  ref: `https://github.com/CSSEGISandData/COVID-19`
}
body.apiSourceCode = `https://pipedream.com/@/${steps.trigger.context.workflow_id}`
body.rawData = steps.get_data.$return_value.data

$respond({
  status: 200,
  headers: {
    'content-type': 'application/json'
  },
  body: JSON.stringify(body)
})