module L4dServer
  class SystemdManager
    SYSTEMD_USER_DIR = File.expand_path("~/.config/systemd/user").freeze

    def self.start(server)
      new(server).start
    end

    def self.stop(server)
      new(server).stop
    end

    def self.restart(server)
      new(server).restart
    end

    def self.status(server)
      new(server).status
    end

    def self.cleanup(server)
      new(server).cleanup
    end

    def initialize(server)
      @server = server
    end

    def start
      execute("systemctl --user start #{unit_name}")
    end

    def stop
      execute("systemctl --user stop #{unit_name}")
    end

    def restart
      execute("systemctl --user restart #{unit_name}")
    end

    def status
      output = `systemctl --user is-active #{unit_name} 2>&1`
      output.strip
    rescue StandardError => e
      Rails.logger.error("Failed to get status: #{e.message}")
      "unknown"
    end

    def cleanup
      begin
        stop
        execute("systemctl --user disable #{unit_name}")
        execute("systemctl --user daemon-reload")
        File.delete(unit_file_path) if File.exist?(unit_file_path)
      rescue StandardError => e
        Rails.logger.error("Failed to cleanup systemd unit: #{e.message}")
      end
    end

    def create_unit_file
      FileUtils.mkdir_p(SYSTEMD_USER_DIR) unless Dir.exist?(SYSTEMD_USER_DIR)
      File.write(unit_file_path, render_unit)
      @server.update(unit_file_path: unit_file_path)
      execute("systemctl --user daemon-reload")
    end

    def enable_and_start
      execute("systemctl --user enable #{unit_name}")
      start
    end

    private

    def unit_name
      "left4dead2-#{@server.id}.service"
    end

    def unit_file_path
      File.join(SYSTEMD_USER_DIR, unit_name)
    end

    def render_unit
      template = @server.server_template
      overlays_str = template.template_overlays.ordered.map { |to| "/opt/l4d2/overlays/#{to.overlay.name}" }.join(":")

      startup_args = template.startup_params.map { |param| "#{param.param_key} #{param.param_value}" }.join(" ")

      ExecStart = "/opt/l4d2/servers/#{@server.id}/merged/srcds_run -norestart -pidfile /opt/l4d2/servers/#{@server.id}/pid -game left4dead2 -ip 0.0.0.0 -port #{@server.port} +hostname \"#{@server.name}\" +map c1m1_hotel #{startup_args}".strip

      <<~UNIT
        [Unit]
        Description=L4D2 Server #{@server.name}
        After=network-online.target
        Wants=network-online.target

        [Service]
        Type=simple
        User=steam
        ExecStart=/opt/l4d2/bin/start-server #{@server.id}
        ExecStop=/opt/l4d2/bin/stop-server #{@server.id}
        Restart=on-failure
        RestartSec=10
        Nice=-10

        [Install]
        WantedBy=default.target
      UNIT
    end

    def execute(command)
      output = `#{command} 2>&1`
      raise "Command failed: #{command}\n#{output}" unless $?.success?
      output
    rescue StandardError => e
      Rails.logger.error("Systemd command failed: #{e.message}")
      raise
    end
  end
end