app.js

const express = require("express");
const { google } = require("googleapis");
const { mongoose } = require("mongoose");
const Tokens = require("./models/tokens");
const path = require("path");
const fs = require("fs");
const blob = require("blob-to-buffer");
const Blob = require("blob-util");
const { Readable } = require("stream");
const fileWrite = fs.createWriteStream("./" + "a.png");
fileWrite.on("finish", function () {
  console.log("downloaded", "a.png");
});
const scopes = [
  "https://www.googleapis.com/auth/drive",
  "https://www.googleapis.com/auth/drive.file",
  "https://www.googleapis.com/auth/drive.readonly",
  "https://www.googleapis.com/auth/drive.metadata.readonly",
  "https://www.googleapis.com/auth/drive.appdata",
  "https://www.googleapis.com/auth/drive.metadata",
  "https://www.googleapis.com/auth/drive.photos.readonly",
];

const app = express();

const oauth2Client = new google.auth.OAuth2(
  process.env.CLIENT_ID,
  process.env.CLIENT_SECRET,
  "http://localhost:3000/oauth2callback"
);
google.options({ auth: oauth2Client });

app.get("/test", (req, res, next) => {
  exportPdf("18JI23oqQLWduBy7-fxWS26L2NUCguez1");
  res.json({ mesage: "Hello World!" }); //testing purposes
  // next();
});
//creating path for upload
const filePath = path.join(__dirname, "image.png");

app.get("/upload", async (req, res, next) => {
  /*
    I have retrieved the tokens from the database as i thought that the refresh token would change for every refresh as it was the case for twitter Oauth but you can store as an environment variable as well and is valid for 100 refreshes or 6 months but no limits for service account
    */
  const test = await Tokens.findOne({ user: "chinujod" })
    .then((user) => {
      oauth2Client.setCredentials({
        refresh_token: user.refresh_token,
      });
    })
    .catch((err) => {
      console.log(err);
    });

  //Creating a drive object
  const drive = google.drive({ version: "v3", auth: oauth2Client });
  console.log("drive succesfully created");
  //File data we want to upload
  const fileMetadata = {
    name: "ima.png",
    mimeType: "image/png",
  };
  //media data
  const media = {
    mimeType: "image/png",
    body: fs.createReadStream(filePath),
  };
  //creating a file in drive
  const response = drive.files.create(
    {
      resource: fileMetadata,
      media: media,
      fields: "id",
    },
    (err, file) => {
      if (err) {
        // Handle error
        console.error(err);
      } else {
        console.log("File Id: ", file.data.id);
        console.log(file);
        console.log(file.data);
      }
    }
  );
});

//generating a public url for the file uploaded
app.get("/generateurl", async (req, res, next) => {
  try {
    const fileId = "1T7d5H5vvF9OSK84c3EUYPcWAKKnwEKvJ";
    const drive = google.drive({ version: "v3", auth: oauth2Client });
    const test = await Tokens.findOne({ user: "chinujod" })
      .then((user) => {
        oauth2Client.setCredentials({
          refresh_token: user.refresh_token,
        });
      })
      .catch((err) => {
        console.log(err);
      });
    // console.log(oauth2Client);
    //change file permision
    await drive.permissions.create({
      fileId: fileId,
      requestBody: {
        role: "reader",
        type: "anyone",
      },
    });
    console.log("permission changed");

    const result = await drive.files.get(
      {
        fileId: fileId,
        alt: "media",
        //   fields: "webContentLink",
      },
      { responseType: "stream" }
    );
    const chunks = [];
    const readable = new Readable();
    readable._read = () => {};
    console.log(typeof result.data);
    // console.log(result.data);
    if (result) {
      result.data
        .on("end", () => {
          console.log("Done");
          const bbuff = Buffer.concat(chunks);
          fs.writeFileSync("buff.png", bbuff);
        })
        .on("error", (err) => {
          console.log("Error", err);
        })
        .on("data", (chuunk) => {
          chunks.push(chuunk);
        })
        .pipe(fileWrite);
    }
    // const lite = Blob.binaryStringToArrayBuffer(result.data);
    // console.log("lost");
    // const blob = Blob.base64StringToBlob(result.data);
    // const buff = Blob.blobToArrayBuffer(blob);
    // console.log(lite);
    // const buffer = await Buffer.from(lite);
    // console.log(buffer);
    // fs.writeFileSync("ima", buffer);
  } catch (error) {
    console.log("error");
    console.log(error.message);
    res.json({ error: error.message });
  }
});

/* 
With this endpoint you will get a url to login for oauth and will be redirected to callback 
which will store tokens in the database
*/
app.get("/login", (req, res, next) => {
  const authorizeUrl = oauth2Client.generateAuthUrl({
    access_type: "offline",
    scope: scopes.join(" "),
  });
  console.log(authorizeUrl);
  res.json({
    url: authorizeUrl,
  });
});

app.use("/oauth2callback", async (req, res, next) => {
  const code = req.query.code;
  const r = await oauth2Client.getToken(code); //Will return tokens json
  const tokens = new Tokens({
    user: "chinujod",
    access_token: r.tokens.access_token,
    refresh_token: r.tokens.refresh_token,
    code: code,
  });
  tokens.save();
  console.log("Tokens :" + tokens);
});

mongoose
  .connect(process.env.MONGODB_URL)
  .then(
    app.listen(3000, () => {
      console.log("Imagify is listening on port 3000!");
    })
  )
  .catch((err) => {
    console.log(err);
  });

/**
 * Download a Document file in PDF format
 * @param{string} fileId file ID
 * @return{obj} file status
 * */
async function exportPdf(fileId) {
  const { GoogleAuth } = require("google-auth-library");
  const { google } = require("googleapis");

  // Get credentials and build service
  // TODO (developer) - Use appropriate auth mechanism for your app
  const auth = new GoogleAuth({
    scopes: "https://www.googleapis.com/auth/drive",
  });
  const service = google.drive({ version: "v3", auth });

  try {
    const result = await service.files.export({
      fileId: fileId,
      mimeType: "application/pdf",
    });
    console.log(result);
    return result;
  } catch (err) {
    // TODO(developer) - Handle error
    throw err;
  }
}