Node.js 8 Cloud Function to write to a Sheets document

.gcloudignore

# This file specifies files that are *not* uploaded to Google Cloud Platform
# using gcloud. It follows the same syntax as .gitignore, with the addition of
# "#!include" directives (which insert the entries of the given .gitignore-style
# file at that point).
#
# For more information, run:
#   $ gcloud topic gcloudignore
#
.gcloudignore
# If you would like to upload your .git directory, .gitignore file or files
# from your .gitignore file, remove the corresponding line
# below:
.git
.gitignore
node_modules
*.csv

.gitignore

*.csv
node_modules/

index.js

// Copyright 2018 Google LLC.
// SPDX-License-Identifier: Apache-2.0
const {google} = require("googleapis");
const {Storage} = require("@google-cloud/storage");

exports.function2sheet = async (req, res) => {
  var file = { name: req.body.name, bucket: req.body.bucket }
  const auth = await google.auth.getClient({
    scopes: ['https://www.googleapis.com/auth/spreadsheets',
             'https://www.googleapis.com/auth/devstorage.read_only']
  });
  const sheetsAPI = google.sheets({version: 'v4', auth});
  const sheetName = file.name.slice(0,-4);
 var getError = false;
    const sheetId = await addEmptySheet(sheetsAPI, sheetName).catch(err => {
        getError = err
    });

    if (getError && getError.indexOf('already exists') == -1) {
        throw (getError)
    } else {
        await clearSheet(sheetsAPI, sheetName)
    }
  const theData = await readCSVContent(sheetsAPI, file, sheetName);
  await populateSheet(sheetsAPI, theData, sheetName); // wrap into "await Promise.all()" if making calls returning multiple promises
  res.status(200).send("done");
};

function readCSVContent(sheetsAPI, file, sheetName) {
  return new Promise((resolve, reject) => {
    const storage = new Storage();
    let fileContents = new Buffer('');
    let rows = [];
    storage.bucket(file.bucket).file(file.name).createReadStream()
    .on('error', function(err) {
      reject('The Storage API returned an error: ' + err);
    })
    .on('data', function(chunk) {
      fileContents = Buffer.concat([fileContents, chunk]);
    })  
    .on('end', function() {
      let content = fileContents.toString('utf8');
      let lines = content.split(/\r\n|\r|\n/);
      lines.forEach(function(line) {
          rows.push ( line.split(',') );
      });
      console.log("CSV content read (" + rows.length + " rows) from " + file.name);
      resolve(rows);
    });
  });
}

function addEmptySheet(sheetsAPI, sheetName) {
  return new Promise((resolve, reject) => {
    const addEmptySheetParams = {
      spreadsheetId: process.env.SPREADSHEET_ID,
      resource: {
        requests: [{
            addSheet: {
              properties: {
                title: sheetName,
                index: 1,
                gridProperties: {
                  rowCount: 2000,
                  columnCount: 26,
                  frozenRowCount: 1
                }
              }
            }
        }]}
    };
    sheetsAPI.spreadsheets.batchUpdate(addEmptySheetParams, function( err, response ) {
      if (err) {
        reject("The Sheets API returned an error: " + err);
      } else {
        const sheetId = response.data.replies[0].addSheet.properties.sheetId;
        console.log("Created empty sheet: " + sheetId);
        resolve(sheetId);
      }
    });
  });
}

function populateSheet(sheetsAPI, theData, sheetName) {
  return new Promise((resolve, reject) => {
    const editRange = sheetName+"!A1:Z";
    const initTrixHeadersRequest = {
      spreadsheetId: process.env.SPREADSHEET_ID,
      range: editRange,
      resource : {
        range: editRange,
        majorDimension: "ROWS",
        values: theData
      },
      valueInputOption: "RAW"
    }
    sheetsAPI.spreadsheets.values.update(initTrixHeadersRequest, function(err, response) {
      if (err) {
        reject ("The Sheets API returned an error: " + err);
      } else {
        console.log(sheetName + " sheet populated with " + theData.length + " rows" );
        resolve();
      }
    });  
  });
}

function clearSheet(sheetsAPI, sheetName) {
    return new Promise((resolve, reject) => {
        const editRange = sheetName + "!A1:Z";
        const initTrixHeadersRequest = {
            spreadsheetId: process.env.SPREADSHEET_ID,
            range: editRange,

        }
        sheetsAPI.spreadsheets.values.clear(initTrixHeadersRequest, function(err, response) {
            if (err) {
                reject("The Sheets API returned an error: " + err);
            } else {
                console.log(sheetName + " cleared");
                resolve();
            }
        });
    });
}

package.json

{
  "name": "sheets",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "start": "functions-framework --target=function2sheet --port   8001"
  },
  "repository": {
    "type": "git",
    "url": "git+https://gist.github.com/3d6f2ed8459bf858276259df25a6d746.git"
  },
  "author": "",
  "license": "ISC",
  "bugs": {
    "url": "https://gist.github.com/3d6f2ed8459bf858276259df25a6d746"
  },
  "homepage": "https://gist.github.com/3d6f2ed8459bf858276259df25a6d746",
  "dependencies": {
    "@google-cloud/functions-framework": "^1.2.1",
    "@google-cloud/storage": "^3.0.4",
    "googleapis": "^41.0.1"
  }
}