# frozen_string_literal: true

class Serega
  #
  # Constructs plan - list of serialized attributes.
  # We will traverse this plan to construct serialized response.
  #
  class SeregaPlan
    #
    # SeregaPlan class methods
    #
    module ClassMethods
      #
      # Constructs plan of attributes that should be serialized.
      #
      # @param opts Serialization parameters
      # @option opts [Hash] :only The only attributes to serialize
      # @option opts [Hash] :except Attributes to hide
      # @option opts [Hash] :with Attributes (usually marked `hide: true`) to serialize additionally
      #
      # @return [SeregaPlan] Serialization plan
      #
      def call(opts)
        max_cache_size = serializer_class.config.max_cached_plans_per_serializer_count
        return new(opts) if max_cache_size.zero?

        cached_plan_for(opts, max_cache_size)
      end

      private

      def cached_plan_for(opts, max_cache_size)
        @cache ||= {}
        cache_key = construct_cache_key(opts)

        plan = @cache[cache_key] ||= new(opts)
        @cache.shift if @cache.length > max_cache_size
        plan
      end

      def construct_cache_key(opts, cache_key = nil)
        return nil if opts.empty?

        cache_key ||= +""

        opts.each do |key, nested_opts|
          cache_key.insert(-1, SeregaUtils::SymbolName.call(key))
          cache_key.insert(-1, "-")
          construct_cache_key(nested_opts, cache_key)
        end

        cache_key
      end
    end

    #
    # SeregaPlan instance methods
    #
    module InstanceMethods
      # Parent plan point
      # @return [SeregaPlanPoint, nil]
      attr_reader :parent_plan_point

      # Sets new parent plan point
      # @return [SeregaPlanPoint] new parent plan point
      attr_writer :parent_plan_point

      # Serialization points
      # @return [Array<SeregaPlanPoint>] points to serialize
      attr_reader :points

      #
      # Instantiate new serialization plan.
      #
      # @param modifiers Serialization parameters
      # @option modifiers [Hash] :only The only attributes to serialize
      # @option modifiers [Hash] :except Attributes to hide
      # @option modifiers [Hash] :with Hidden attributes to serialize additionally
      #
      # @return [SeregaPlan] Serialization plan
      #
      def initialize(modifiers)
        @points = attributes_points(modifiers)
      end

      #
      # Serializer class of current plan
      #
      def serializer_class
        self.class.serializer_class
      end

      private

      def attributes_points(modifiers)
        only = modifiers[:only] || FROZEN_EMPTY_HASH
        except = modifiers[:except] || FROZEN_EMPTY_HASH
        with = modifiers[:with] || FROZEN_EMPTY_HASH
        points = []

        serializer_class.attributes.each_value do |attribute|
          next unless attribute.visible?(only: only, except: except, with: with)

          child_fields =
            if attribute.relation?
              name = attribute.name
              {only: only[name], with: with[name], except: except[name]}
            end

          point = serializer_class::SeregaPlanPoint.new(attribute, child_fields)
          point.plan = self
          points << point.freeze
        end

        points.freeze
      end
    end

    extend ClassMethods
    include InstanceMethods
    extend SeregaHelpers::SerializerClassHelper
  end
end