kubectl_manager.rb

# frozen_string_literal: true

require 'open3'
require 'pry'

module Utils
  class GemVerifier
    def check_needed_gems
      require 'tty-prompt'
    rescue LoadError
      system('gem install tty-prompt > /dev/null')
      Gem.clear_paths
      require 'tty-prompt'
    end
  end
end

class PromptApplication
  def prompt
    @prompt ||= TTY::Prompt.new
  end

  def select(message, collection, options)
    prompt.select(message, collection, options.merge(filter: true))
  end
end

class ContextExecutor < PromptApplication
  COMMAND = 'kubectl config get-contexts -o name'
  private_constant :COMMAND

  def context_selection
    lambda do |selection|
      contexts.find { |context| context[:name] == selection }[:fullname]
    end.call(select('Select a context', context_names, per_page: contexts.size))
  end

  private

  def context_names
    contexts.map { |context| context[:name] }
  end

  def contexts
    @contexts ||= raw_contexts.split("\n").map do |context|
                    { name: context[/\/(.*)$/, 1], fullname: context }
                  end
  end

  def raw_contexts
    Open3.capture3(COMMAND).first
  end
end

class PodsExecutor < PromptApplication
  COMMAND = 'kubectl get pods'
  POD_DATA = %i[name ready status restarts age].freeze
  RAILS_CONSOLE = 'RAILS_ENV=production bundle exec rails c'
  private_constant :COMMAND, :POD_DATA, :RAILS_CONSOLE

  def enter_to_pod
    system("kubectl config use-context #{ContextExecutor.new.context_selection} > /dev/null")
    pod = pod_selection
    open_console = prompt.yes?('Open the application console?')

    system("kubectl exec -it #{pod} bash") unless open_console
    system("kubectl exec -it #{pod} -- bash -c '#{RAILS_CONSOLE}'")
  rescue NoMethodError
    puts "error: the server doesn't have a resource type \"pods\""
  end

  private

  def pod_selection
    select('Select a pod', pod_names, per_page: pods.size)
  end

  def pod_names
    pods.filter { |pod| pod[:status] == 'Running' }.map { |pod| pod[:name] }
  end

  def pods
    @pods ||= pods_output.split("\n")[1..-1].map(&:split).map { |line| POD_DATA.zip(line).to_h }
  end

  def pods_output
    Open3.capture3(COMMAND).first
  end
end

Utils::GemVerifier.new.check_needed_gems
PodsExecutor.new.enter_to_pod