Ruby helper class for working with terraform

terraform_helper.rb

require 'json'
require 'logger'

# Helper class for interacting with Terraform
class TerraformHelper
  def initialize(s3_bucket)
    @logger = Logger.new(STDOUT)
    @logger.level = Logger::DEBUG
    @logger.formatter = proc do |severity, datetime, _progname, msg|
      format("%-5s [%s] - %s\n", severity, datetime.strftime('%F %T,%L'), msg)
    end

    @s3_bucket = s3_bucket
  end

  # This assumes environments are ../terraform/environments from this script
  def terraform_directory(environment)
    terraform_dir = File.join(File.dirname(__FILE__), '..', 'terraform', 'environments', environment)
    fail "#{terraform_dir} does not exist" unless File.directory?(terraform_dir)
    terraform_dir
  end

  # Configures the s3 backend and runs terraform get
  def init_environment(environment)
    terraform_dir = terraform_directory(environment)

    unless system("rm -rf #{terraform_dir}/.terraform")
      @logger.error("rm -rf #{terraform_dir}/.terraform failed")
      return false
    end

    set_config = "terraform remote config -backend=s3 -backend-config='bucket=#{@s3_bucket}' " \
      "-backend-config='key=#{environment}/terraform.tfstate' " \
      "-backend-config='region=us-west-2'"

    unless system("cd #{terraform_dir} && #{set_config}")
      @logger.error('Failed to set the terraform config')
      return false
    end

    unless system("cd #{terraform_dir} && terraform get > /dev/null 2>&1")
      @logger.error('terraform get failed')
      return false
    end

    return true
  rescue RuntimeError => ex
    @logger.error("failed to initialize the environment: #{ex}")
    return false
  end

  def taint_resource(environment, module_name, resource_name)
    terraform_dir = terraform_directory(environment)

    unless system("cd #{terraform_dir} && terraform taint --module=#{module_name} #{resource_name}")
      @logger.error('terraform taint failed')
      return false
    end

    return true
  rescue RuntimeError => ex
    @logger.error("failed to taint the resource: #{ex}")
    return false
  end

  def apply(environment)
    terraform_dir = terraform_directory(environment)
    plan_file = "#{environment}.plan"

    unless system("cd #{terraform_dir} && terraform plan --module-depth=1 -out #{plan_file}")
      @logger.error('terraform plan failed')
      return false
    end

    unless system("cd #{terraform_dir} && terraform apply #{plan_file}")
      @logger.error('terraform apply failed')
      return false
    end

    return true
  rescue RuntimeError => ex
    @logger.error("failed to apply the plan: #{ex}")
    return false
  end

  def destroy(environment, force = false)
    terraform_dir = terraform_directory(environment)

    force_flag = force ? '-force' : ''

    unless system("cd #{terraform_dir} && terraform destroy #{force_flag}")
      @logger.error('terraform destroy failed')
      return false
    end

    return true
  rescue RuntimeError => ex
    @logger.error("failed to destroy the resource: #{ex}")
    return false
  end

  def write_vars(environment, terraform_vars)
    terraform_dir = terraform_directory(environment)

    File.open("#{terraform_dir}/terraform.tfvars", 'w') do |f|
      f.write(JSON.pretty_generate(terraform_vars) + "\n")
    end
  rescue RuntimeError => ex
    @logger.error("failed to save the terraform vars: #{ex}")
    return false
  end
end