GoogleDrive.js

const url = 'https://www.googleapis.com/drive/v3'
const uploadUrl = 'https://www.googleapis.com/upload/drive/v3'

const boundaryString = 'this_can_be_anything_lol' // can be anything unique, needed for multipart upload https://developers.google.com/drive/v3/web/multipart-upload

export default class GoogleDrive {
    constructor() {
        this.apiToken = null;
    }


    setApiToken(token) {
        this.apiToken = token
    }

    parseAndHandleErrors(response) {
        if (response.ok) {
            return response.json()
        }
        return response.json()
            .then((error) => {
                throw new Error(JSON.stringify(error))
            })
    }

    configureGetOptions() {
        const headers = new Headers()
        headers.append('Authorization', `Bearer ${this.apiToken}`)
        return {
            method: 'GET',
            headers,
        }
    }

    configurePostOptions(bodyLength, isUpdate = false) {
        const headers = new Headers()
        headers.append('Authorization', `Bearer ${this.apiToken}`)
        headers.append('Content-Type', `multipart/related; boundary=${boundaryString}`)
        headers.append('Content-Length', bodyLength)
        return {
            method: isUpdate ? 'PATCH' : 'POST',
            headers,
        }
    }

    createMultipartBody(body, metaData = {name:'data.json',description:'data',mimeType: 'application/json'}, isUpdate = false) {
        // https://developers.google.com/drive/v3/web/multipart-upload defines the structure
        
        // if it already exists, specifying parents again throws an error
        if (!isUpdate) metaData.parents = ['appDataFolder']

        // request body
        const multipartBody = `\r\n--${boundaryString}\r\nContent-Type: application/json; charset=UTF-8\r\n\r\n`
            + `${JSON.stringify(metaData)}\r\n`
            + `--${boundaryString}\r\nContent-Type: application/json\r\n\r\n`
            + `${JSON.stringify(body)}\r\n`
            + `--${boundaryString}--`

        return multipartBody
    }

    // uploads a file with its contents and its meta data (name, description, type, location)
    uploadFile(content, existingFileId) {
        const body = this.createMultipartBody(content, !!existingFileId)
        const options = this.configurePostOptions(body.length, !!existingFileId)
        return fetch(`${uploadUrl}/files${existingFileId ? `/${existingFileId}` : ''}?uploadType=multipart`, {
            ...options,
            body,
        })
            .then(this.parseAndHandleErrors)
    }

    // Looks for files with the specified file name in your app Data folder only (appDataFolder is a magic keyword)
    queryParams() {
        return encodeURIComponent("name = 'data.json' and 'appDataFolder' in parents")
    }

    // returns the files meta data only. the id can then be used to download the file
    getFile() {
        const qParams = this.queryParams()
        const options = this.configureGetOptions()
        return fetch(`${url}/files?q=${qParams}&spaces=appDataFolder`, options)
            .then(this.parseAndHandleErrors)
            .then((body) => {
                if (body && body.files && body.files.length > 0) return body.files[0]
                return null
            })
    }

    getFiles() {
        const options = this.configureGetOptions()
        return fetch(`${url}/files?spaces=appDataFolder`, options)
            .then(this.parseAndHandleErrors)
            .then((body) => {
                if (body && body.files) return body.files;
                return null;
            })
    }

    // download the file contents given the id
    downloadFile(existingFileId) {
        const options = this.configureGetOptions()
        if (!existingFileId) throw new Error('Didn\'t provide a valid file id.')
        return fetch(`${url}/files/${existingFileId}?alt=media`, options)
            .then(this.parseAndHandleErrors)
    }
}