configure_firebase.js

const { exec } = require('child_process');
const { writeFileSync } = require('fs');
const environment = process.env.ENVIRONMENT || 'development';

// test environment configuration
const configuration = {
  development: {
    common: {
      base_url: 'http://localhost:5001/api/v1',
    },
    facebook: {
      client_id: '123456',
      client_secret: '999999999999',
    },
    google: {
      client_id: '123456',
      client_secret: '999999999999',
    },
  },
  production: {
    common: {
      base_url: 'https://my-useful-api.com/api/v1',
    },
    facebook: {
      client_id: 'dfaDFKJkihag082nja0f8h',
      client_secret: 'SUPER_SECRET',
    },
    google: {
      client_id: 'DF#*DKNFLNJ232DF',
      client_secret: 'ALSO_SUPER_SECRET',
      service_account: {
        type: 'service_account',
        project_id: 'sample',
        private_key_id: '12f21d3233a25127b9080987c5',
        private_key:
          '-----BEGIN PRIVATE KEY-----\nMASDLFJALdmjdnfSODHJFAfnahfa;lmkdl;kjasdJDOJD\n-----END PRIVATE KEY-----\n',
      },
    },
  },
};

const environmentVariableObject = configuration[environment] || {};
const services = Object.keys(environmentVariableObject);
console.log(`Configuring environment for ${environment}`);

if (!services || services.length === 0) {
  console.warn(
    `Warning: no configuration for current environment: ${environment}`
  );
  process.exit(0);
}

// firebase emulators use .runtimeconfig.json within the functions source
if (environment === 'development') {
  writeFileSync(
    './.runtimeconfig.json',
    JSON.stringify(environmentVariableObject, null, 2)
  );
  process.exit(0);
}

// change object to dot notation paths with values
const [paths, values] = pathify(environmentVariableObject);

// now set these values using the firebase functions config
paths.forEach((variablePath, idx) => {
  const value = values[idx];
  if (value === null) {
    return;
  }
  exec(
    `firebase functions:config:set ${variablePath}="${value}"`,
    (err, stdout, stderr) => {
      if (err) {
        console.log(`error: ${err.message}`);
      }
      if (stderr) {
        console.log(`stderr: ${stderr}`);
        return;
      }
      console.log(`stdout: ${stdout} - ${variablePath}="${value}"`);
    }
  );
});

/* ---- UTILITY FUNCTIONS --- */

// https://stackoverflow.com/a/51663539/5472574
// recursive function to change an object into a
// tuple - first element is an array of dot notation "paths"
// second element is an array of the values for
// terminal properties(null for non - terminal)
function pathify(o, res = [], path = [], values = []) {
  for (const dir in o) {
    const s = path.join('.');
    const isObject = typeof o[dir] === 'object';
    // console.log(s, path, dir, path.concat(dir), res);
    if (s) {
      res.push(`${s}.${dir}`);
    } else {
      res.push(dir);
    }

    if (isObject) {
      // non-terminal matches to a null value
      values.push(null);
      pathify(o[dir], res, path.concat(dir), values);
    } else {
      //   terminal matches to the terminal properties value
      values.push(o[dir]);
    }
  }
  return [res, values];
}

export ENVIRONMENT=production && node configure_firebase.js

results in

console.log(functions.config().google.service_account.type) // service_account"
console.log(functions.config().common.base_url)// https://my-useful-api.com/api/v1