require "erb"
require "stringio"
require "capistrano/plugin"

module Capistrano
  module Systemd
    module MultiService
      class SystemService < ::Capistrano::Plugin
        attr_reader :app

        def initialize(app)
          @app = app
          super()
        end

        def nsp
          @app.to_sym
        end

        def prefix
          "systemd_#{@app}"
        end

        def define_tasks
          eval_rakefile File.expand_path("../../../tasks/systemd/multiservice/system_service.rake", __FILE__)
        end

        def register_hooks
          after   "deploy:check",          "systemd:#{nsp}:validate"
          after   "systemd:#{nsp}:setup",  "systemd:#{nsp}:daemon-reload"
          after   "systemd:#{nsp}:setup",  "systemd:#{nsp}:enable"
          before  "systemd:#{nsp}:remove", "systemd:#{nsp}:disable"
          after   "systemd:#{nsp}:remove", "systemd:#{nsp}:daemon-reload"
        end

        def set_defaults
          set_if_empty :"#{prefix}_role", ->{ :app }

          set_if_empty :"#{prefix}_units_src", ->{ Dir["config/systemd/#{@app}{,@}.*.erb"].sort }

          set_if_empty :"#{prefix}_units_dir", ->{ default_units_dir }

          set_if_empty :"#{prefix}_units_dest", ->{
            fetch(:"#{prefix}_units_src").map{|src|
              "%s/%s_%s-%s" % [ fetch(:"#{prefix}_units_dir"), fetch(:application),  fetch(:stage), File.basename(src, ".erb") ]
            }
          }

          set_if_empty :"#{prefix}_instances", ->{
            if fetch(:"#{prefix}_units_dest").map{|dst| File.basename(dst) }.find{|f| f =~ /@\.service\z/ }
              1.times.to_a
            else
              nil
            end
          }

          set_if_empty :"#{prefix}_service", ->{
            service = fetch(:"#{prefix}_units_dest").map{|dst| File.basename(dst) }.find{|f| f =~ /\.service\z/ && f !~ /@\.service\z/ }
            service || fetch(:"#{prefix}_instance_services")
          }

          set_if_empty :"#{prefix}_instance_services", ->{
            if fetch(:"#{prefix}_instances")
              fetch(:"#{prefix}_instances").map{|i|
                service_template = fetch(:"#{prefix}_units_dest").map{|dst| File.basename(dst) }.find{|f| f =~ /@\.service\z/ }
                service_template && service_template.sub(/@\.service\z/, "@#{i}.service")
              }
            else
              []
            end
          }
        end

        def default_units_dir
          "/etc/systemd/system"
        end

        def setup
          fetch(:"#{prefix}_units_src").zip(fetch(:"#{prefix}_units_dest")).each do |src, dest|
            buf = StringIO.new(ERB.new(File.read(src), nil, 2).result(binding))
            setup_service buf, src, dest
          end
        end

        def remove
          backend.sudo :rm, '-f', '--', fetch(:"#{prefix}_units_dest")
        end

        def validate
          fetch(:"#{prefix}_units_dest").each do |dest|
            unless backend.test("[ -f #{dest} ]")
              backend.error "#{dest} not found"
              exit 1
            end
          end
        end

        def daemon_reload
          systemctl :"daemon-reload"
        end

        %i[start stop reload restart reload-or-restart enable disable].each do |act|
          define_method act.to_s.tr('-','_') do
            systemctl act, fetch(:"#{prefix}_service")
          end
        end

        def systemctl(*args)
          args.unshift :sudo, :systemctl
          backend.execute(*args)
        end

        private

        def setup_service(buf, src, dest)
          remote_tmp  = "#{fetch(:tmp_dir)}/#{File.basename(src, ".erb")}"
          backend.upload! buf, remote_tmp
          backend.sudo :install, '-m 644 -o root -g root -D', remote_tmp, dest
          backend.execute :rm, remote_tmp
        end
      end
    end
  end
end