module RCM
  class ConfigManager
    PACKAGES = 'packages'.freeze
    FILES = 'files'.freeze
    SERVICES = 'services'.freeze
    LOGGING = 'logging'.freeze

    @wanted = nil
    @logger = nil
    @env = ''

    VALID_LOG_LEVELS = %w[fatal error info debug].freeze

    def initialize()
      @env = ENV.fetch('ENVIRONMENT', '')
      @wanted = {
        PACKAGES => {},
        FILES => {},
        SERVICES => {}
      }

      config_file = @env.empty? ? 'config.yaml' : "config_#{@env}.yaml"

      raise "#{config_file} not found." unless ::File.readable?(config_file)

      config = YAML.load_file(config_file)
      config.each do |yaml_objects|
        yaml_objects.each do |collection, resource_definition|
          case collection
          when LOGGING
            configure_logging(resource_definition)

          when PACKAGES
            parse_packages(resource_definition)

          when FILES
            parse_files(resource_definition)

          when SERVICES
            parse_services(resource_definition)
          end # of case
        end # of iterating over yaml_objects
      end # of iterating over config
    end

    def logger
      @logger
    end

    def packages
      @wanted[PACKAGES]
    end

    def files
      @wanted[FILES]
    end

    def services
      @wanted[SERVICES]
    end

    def configure_logging(markup)
      file = markup[0]['file']
      device = ''
      level = markup[0]['level']

      if (VALID_LOG_LEVELS & [level]).empty?
        raise "Invalid log level '#{level}'. Valid log levels are: #{VALID_LOG_LEVELS.join(', ')}"
      end

      case file
      when 'STDOUT'
        device = STDOUT

      when 'STDERR'
        device = STDERR

      else
        # treat whatever is written as file
        device = ::File.open(file, 'a+')
      end

      @logger = ::Logger.new(device)
      @logger.level = level
      @logger.progname = 'rcm'
      @logger
    end

    def parse_packages(markup)
      @logger.info("Environment = #{@env}")

      markup.each do |d|
        # ensure package version exists, if mentioned.
        version = d.fetch('version', '')
        desired_state = d.fetch('desired_state', ::RCM::Package::INSTALLED)

        valid_package_states = [::RCM::Package::INSTALLED, ::RCM::Package::REMOVED]

        if (valid_package_states & [desired_state]).empty?
          raise "Unknown desired_state: #{desired_state}. Valid states: #{valid_package_states.join(', ')}"
        end

        unless version.empty?
          # Convenience... check if the version mentioned in config is correct.
          pkg_mgr = ::RCM::Apt.new(@logger)
          available_versions = pkg_mgr.get_versions(d['name'])
          if (available_versions & [version]).empty?
            raise "\n\n#{d['name']} = #{version} is not available.\nAvailable versions: #{available_versions.join(', ')}"
          end
        end
        p = RCM::Package.new(d['name'], version, desired_state)
        @wanted[PACKAGES][d['name']] = p
      end
    end

    def parse_files(markup)
      valid_file_states = [::RCM::File::PRESENT, ::RCM::File::ABSENT]
      markup.each do |d|
        raise "\n\nFile state can only be one of #{valid_file_states.join(', ')}" if (valid_file_states | [d['desired_state']]).empty?
        raise "\n\n'#{d['local_file']}' is not readable.\n\n" if d['desired_state'] == ::RCM::File::PRESENT && !::File.readable?(d['local_file'])
        f = RCM::File.new(d['path'], d['owner'], d['group'], d['mode'], d['local_file'], d['desired_state'])
        @wanted[FILES][d['path']] = f
      end
    end

    def parse_services(markup)
      pkgs = @wanted[PACKAGES]
      files = @wanted[FILES]
      file_dependencies = {}
      package_dependencies = {}
      markup.each do |d|
        dependencies = d.fetch('dependencies', {})
        dependencies.each do |values|
          values.each do |dep_type, dep|
            case dep_type
            when PACKAGES
              dep.each do |pkg_definition|
                pkg_name = pkg_definition['name']
                raise "\n\nPlease ensure #{pkg_name} is managed by this program before adding it as a dependency.\n\n" unless pkgs.key?(pkg_name)
                p = pkgs[pkg_name]
                package_dependencies[pkg_name] = p
              end
            when FILES
              dep.each do |file_defnition|
                path = file_defnition['path']
                raise "\n\nPlease ensure #{path} is managed by this program before adding it as a dependency.\n\n" unless files.key?(path)

                f = files[path]
                file_dependencies[path] = f
              end
            end
          end
        end
        s = RCM::Service.new(d['name'], file_dependencies, package_dependencies)
        @wanted[SERVICES][d['name']] = s
      end
    end

  end # of class ConfigManager
end # module