processManifest.js

const _ = require("lodash");
const dotenv = require("dotenv");
const fs = require("fs");
const path = require("path");
const { promisify } = require("util");

module.exports = async function processManifest(manifestData) {
  const stageName = Object.keys(manifestData);
  const { outputs } = manifestData[stageName];

  const getOutputValue = (key) => {
    console.log(`loading output value for [${key}]`);
    const output = _.find(outputs, (x) => x.OutputKey === key);
    if (!output) {
      throw new Error(`No output found for ${key}`);
    }
    return output.OutputValue;
  };

  const dotEnvFile = path.resolve(".env");
  await updateDotEnv(dotEnvFile, {
    API_URL: getOutputValue("AppsynctwitterGraphQlApiUrl"),
  });
};

/* Utils, typically this would be a package includes from NPM */
async function updateDotEnv(filePath, env) {
  // Merge with existing values
  try {
    const existing = dotenv.parse(
      await promisify(fs.readFile)(filePath, "utf-8")
    );
    env = Object.assign(existing, env);
  } catch (err) {
    if (err.code !== "ENOENT") {
      throw err;
    }
  }

  const contents = Object.keys(env)
    .map((key) => format(key, env[key]))
    .join("\n");
  await promisify(fs.writeFile)(filePath, contents);

  return env;
}

function escapeNewlines(str) {
  return str.replace(/\n/g, "\\n");
}

function format(key, value) {
  return `${key}=${escapeNewlines(value)}`;
}