Some kind of stages stub to be able to use serverless-next.js in order to deploy to multiple envs

serverless.js

// serverless/stages/serverless.js

const { Component } = require('@serverless/core');

const required = (name) => {
  throw new Error(`An argument "${name}" is required.`);
};

const processRef = (value, data) => {
  for (const key in data) {
    value = value.replace(new RegExp(`%\\{${key}}`, 'g'), data[key]);
  }
  return value;
};

const resolveInputRefs = (input, data) => {
  if (Array.isArray(input)) {
    return input.map(i => resolveInputRefs(i, data));
  }
  if (typeof input === 'object') {
    const result = {};
    for (const key in input) {
      if (input.hasOwnProperty(key)) {
        result[key] = resolveInputRefs(input[key], data);
      }
    }
    return result;
  }
  if (typeof input === 'string') {
    return processRef(input, data);
  }
  return input;
};

class StagesComponent extends Component {
  async default({
    target: {
      component: targetComponent = required('target.component'),
      input: targetInput = {},
    } = required('target'),
    branchEnv = required('branchEnv'),
    stages: {
      default: defaultStage = required('stages.default'),
      ...stages
    } = required('branches'),
    envs = required('envs'),
  } = {}) {
    this.context.log('Processing inputs');
    const stage = stages[process.env[branchEnv]] || defaultStage;
    const data = envs[stage];
    const resolvedInput = resolveInputRefs(targetInput, data);

    this.context.log('Loading target component');
    const target = await this.load(targetComponent, targetInput);

    this.context.log('Executing target component');
    return target(resolvedInput);
  }
}

module.exports = StagesComponent;

serverless.yml

name: website

website:
  component: './serverless/stages'
  inputs:
    target:
      component: 'serverless-next.js'
      input:
        domain:
        - www
        - '%{domain}' # Note '%' instead of '$'
    branchEnv: GITHUB_REF # Branch name is taken from "GITHUB_REF" variable - this example works in Github Actions
    stages: # Usually in CI/CD you have to map branch name to environment, you can do it here
      default: 'dev' # Default "stage"
      'refs/heads/develop': 'dev'
      'refs/heads/staging': 'staging'
      'refs/heads/master': 'prod'
    envs:
      dev:
        domain: dev.example.com
      staging:
        domain: staging.example.com
      prod:
        domain: example.com