generateConfig.js

const fs = require('fs')
const { resolve } = require('path')
const { inspect } = require('util')
const https = require('https')
const yaml = require('yaml-js')

function getFirestoreApiDefinition() {
	return new Promise((resolve, reject) => {
		let data = ''

		const req = https.get(
			'https://raw.githubusercontent.com/googleapis/googleapis/master/google/firestore/firestore_v1.yaml',
			(res) => {
				res.on('data', (chunk) => (data += chunk))
				res.on('end', () => {
					resolve(yaml.load(data))
				})
			},
		)
	})
}

async function main() {
	const serviceDefinition = await getFirestoreApiDefinition()
	const serviceAccountConfig = require('./gcp-auth.json')

	const payload = {
		aud: `https://${serviceDefinition.name}/${serviceDefinition.apis[0].name}`,
		iss: serviceAccountConfig.client_email,
		sub: serviceAccountConfig.client_email,
	}
	const privateKeyID = serviceAccountConfig.private_key_id
	const algorithm = 'RS256'
	const url = `https://firestore.googleapis.com/v1beta1/projects/${serviceAccountConfig.project_id}/databases/(default)/documents`

	const output = {
		payload,
		privateKeyID,
		algorithm,
		url,
	}

	const file = fs.createWriteStream(resolve(__dirname, './src', 'config.ts'))
	file.write(
		'/*\n\tAuto-generated file, private key stripped from GCP service account keyfile\n*/\n\nconst config = {\n',
	)

	for (const key in output) {
		if (Object.hasOwnProperty.call(output, key)) {
			const value = output[key]

			if (typeof value === 'string') {
				file.write(`\t${key}: "${value}",\n`)
			} else if (typeof value === 'object') {
				file.write(
					`\t${key}: ${inspect(value, false, null).replace(/^/gm, '\t')},\n`,
				)
			}
		}
	}

	file.write('}\n\nexport = config')

	file.end()
}

main()