# Copyright (c) 2021 Contrast Security, Inc. See https://www.contrastsecurity.com/enduser-terms-0317a for more details.
# frozen_string_literal: true

require 'contrast/utils/env_configuration_item'
require 'contrast/configuration'

module Contrast
  module Components
    # This component encapsulates reference to the configuration file.
    # At the time of writing, the configuration file is a yaml file reflecting
    # the 'common agent configuration' specification.
    # 'Config' and 'configuration' are to be interpreted as referring
    # specifically to these files and specifications, they are not generic
    # terms for other avenues of user configuration.
    #
    # This component is responsible for...
    #  - encapsulating file access & concomitant error conditions
    #  - implementing validity checks with respect to the specification
    #  - memoizing/streamline field accesses
    #
    # Config fails fast.  if it's not valid, the agent should break, and
    # it should break LOUDLY.  Better to waste half an hour of the sysadmin's
    # time than to silently fail to deliver functionality.
    module Config
      CONTRAST_ENV_MARKER = 'CONTRAST__'

      class Interface # :nodoc:
        def initialize
          build
        end

        def build log: true
          @_valid = nil
          @config = Contrast::Configuration.new
          env_overrides
          validate(log: log)
        end
        alias_method :rebuild, :build

        # @return [Contrast::Config::RootConfiguration]
        def root
          @config.root
        end

        def valid?
          @_valid = validate(log: false) if @_valid.nil?
        end

        def invalid?
          !valid?
        end

        def loggable
          @config.loggable
        end

        private

        SESSION_VARIABLES = 'Invalid configuration. '\
                            "Setting both application.session_id and application.session_metadata is not allowed.\n"
        def validate log: false
          # The config has information about how to construct the logger.
          # If the config is invalid, and you want to know about it, then
          # you have a circular dependency if you try to log it,
          # hence `log: false`.
          if !session_id.empty? && !session_metadata.empty?
            if log
              cs__class.log_error(SESSION_VARIABLES)
            else
              puts SESSION_VARIABLES
            end
            return false
          end

          true
        end

        def env_overrides
          # For env variables resembling CONTRAST__WHATEVER__NESTED_VALUE
          # override raw.whatever.nested_value
          ENV.each do |env_key, env_value|
            next unless env_key.to_s.start_with?(CONTRAST_ENV_MARKER)

            config_item = Contrast::Utils::EnvConfigurationItem.new(env_key, env_value)
            @config.assign_value_to_path_array(config_item.dot_path_array, config_item.value)
          end
        end

        # Typically, this would be accessed through
        # Contrast::Components::AppContext, but we're too early in the
        # initialization of the Agent to use that mechanism, so we look it up
        # directly for ourselves
        #
        # @return [String,nil] the value of the session id set in the
        #   configuration, or nil if unset
        def session_id
          @config.application.session_id
        end

        # Typically, this would be accessed through
        # Contrast::Components::AppContext, but we're too early in the
        # initialization of the Agent to use that mechanism, so we look it up
        # directly for ourselves
        #
        # @return [String,nil] the value of the session metadata set in the
        #   configuration, or nil if unset
        def session_metadata
          @config.application.session_metadata
        end
      end
    end
  end
end