#!/usr/bin/env node

const fs = require("fs")
const readline = require("readline")
const { google } = require("googleapis")
const util = require("util")
const exec = util.promisify(require("child_process").exec)

// If modifying these scopes, delete token.json.
const SCOPES = ["https://www.googleapis.com/auth/calendar.events"]
// The file token.json stores the user's access and refresh tokens, and is
// created automatically when the authorization flow completes for the first
// time.
const TOKEN_PATH = "token.json"

// Load client secrets from a local file.
fs.readFile("credentials.json", (err, content) => {
  if (err) return console.log("Error loading client secret file:", err)
  // Authorize a client with credentials, then call the Google Calendar API.
  //authorize(JSON.parse(content), listEvents);
  authorize(JSON.parse(content), patchCalendar)
})

/**
 * Create an OAuth2 client with the given credentials, and then execute the
 * given callback function.
 * @param {Object} credentials The authorization client creden:Qtials.
 * @param {function} callback The callback to call with the authorized client.
 */
const authorize = (credentials, callback) => {
  const { client_secret, client_id, redirect_uris } = credentials.installed
  const oAuth2Client = new google.auth.OAuth2(
    client_id,
    client_secret,
    redirect_uris[0]
  )

  // Check if we have previously stored a token.
  fs.readFile(TOKEN_PATH, (err, token) => {
    if (err) return getAccessToken(oAuth2Client, callback)
    oAuth2Client.setCredentials(JSON.parse(token))
    callback(oAuth2Client)
  })
}

/**
 * Get and store new token after prompting for user authorization, and then
 * execute the given callback with the authorized OAuth2 client.
 * @param {google.auth.OAuth2} oAuth2Client The OAuth2 client to get token for.
 * @param {getEventsCallback} callback The callback for the authorized client.
 */
const getAccessToken = (oAuth2Client, callback) => {
  const authUrl = oAuth2Client.generateAuthUrl({
    access_type: "offline",
    scope: SCOPES,
  })
  console.log("Authorize this app by visiting this url:", authUrl)
  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
  })
  rl.question("Enter the code from that page here: ", code => {
    rl.close()
    oAuth2Client.getToken(code, (err, token) => {
      if (err) return console.error("Error retrieving access token", err)
      oAuth2Client.setCredentials(token)
      // Store the token to disk for later program executions
      fs.writeFile(TOKEN_PATH, JSON.stringify(token), err => {
        if (err) return console.error(err)
        console.log("Token stored to", TOKEN_PATH)
      })
      callback(oAuth2Client)
    })
  })
}

const slideCount = async () => {
  const cmd = "grep '##' src/presentation.md | wc -l"
  const { stdout } = await exec(cmd)
  return stdout
}

const patchCalendar = async auth => {
  const preExistingSlides = 84
  const targetSlides = 120
  const eventId = "0g1fr1etmld3i9p54v3oti2lep"
  const calendar = google.calendar({ version: "v3", auth })

  const event = await calendar.events.get({
    calendarId: "primary",
    eventId,
  })

  const resource = event.data
  const slides = await slideCount()
  const adjustedSlides = slides - preExistingSlides
  resource.summary = `Coach: ${adjustedSlides}/${targetSlides} slides`

  await calendar.events.patch({
    calendarId: "primary",
    eventId,
    resource,
  })

  console.log(`SLIDES: ${adjustedSlides}/${targetSlides}`)
}