index.js

const { createPatch } = require('diff')
const Ajv = require('ajv')
const schema = require('./schema.json')
const YAML = require('yaml')

// setup json schema validation
const ajv = new Ajv()
const validate = ajv.compile(schema)

module.exports = function (plan) {
  const valid = validate(plan)

  if (!valid) {
    throw new Error('invalid Terraform Plan JSON data')
  }

  const patches = []

  for (const resource of plan?.resource_changes || []) {
    // skip early
    if (resource.change.actions.includes('no-op')) continue

    // convert to yaml for better visibility
    const before = YAML.stringify(resource.change.before || '')
    const after = YAML.stringify(resource.change.after || '')

    const patch = createPatch(resource.address, before, after)

    patches.push(patch)
  }

  const counter = {
    create: 0,
    update: 0,
    delete: 0
  }

  // const summary = [...plan.resource_changes, ...plan.resource_drift].reduce((counter, { change: { actions } }) => {
  const summary = (plan?.resource_changes || []).reduce((counter, { change: { actions } }) => {
    for (const action of actions) {
      switch (action) {
        case 'create':
        case 'delete-create':
          counter.create += 1
          break

        case 'update':
          counter.update += 1
          break

        case 'delete':
        case 'create-delete':
          counter.delete += 1
          break
      }
    }
    return counter
  }, counter)

  return { summary, patches }
}