GSA/asis

# frozen_string_literal: true

class TopHits
  DEFAULT_PRE_TAG = '<strong>'
  DEFAULT_POST_TAG = '</strong>'
  TEXT_FIELDS = %w[title description caption].freeze

  CUTOFF_FOR_DECAY = 'now-6w/w'

  # https://github.com/elastic/elasticsearch/pull/19102
  DECAY_SCALE = '28d'
  CUTOFF_WEIGHT = 0.119657286

  def initialize(query, size, from, flickr_groups, flickr_users, mrss_names)
    @query = query
    @size = size
    @from = from
    @flickr_groups = flickr_groups
    @flickr_users = flickr_users
    @mrss_names = mrss_names
  end

  def query_body(search_type: :query_then_fetch)
    Jbuilder.encode do |json|
      json.size 0 if search_type == :count
      filtered_query(json)
      aggs(json)
      suggest(json)
    end
  end

  def aggs(json)
    json.aggs do
      json.album_agg do
        albums(json)
        top_hits(json)
      end
    end
  end

  def top_hits(json)
    json.aggs do
      json.top_image_hits do
        json.top_hits do
          json.size 1
        end
      end
      json.top_score do
        json.max do
          # https://www.elastic.co/guide/en/elasticsearch/reference/2.0/breaking_20_scripting_changes.html#_scripting_syntax
          json.script do
            json.source '_score'
            json.lang 'painless'
          end
        end
      end
    end
  end

  def albums(json)
    json.terms do
      json.field 'album'
      json.order do
        json.top_score 'desc'
      end
      json.size @from + @size + 1
    end
  end

  def suggest(json)
    json.suggest do
      json.text @query
      json.suggestion do
        phrase_suggestion(json)
      end
    end
  end

  def phrase_suggestion(json)
    json.phrase do
      json.analyzer 'bigram_analyzer'
      json.field 'bigram'
      json.size 1
      direct_generator(json)
      suggestion_highlight(json)
    end
  end

  def suggestion_highlight(json)
    json.highlight do
      json.pre_tag pre_tags.first
      json.post_tag post_tags.first
    end
  end

  def direct_generator(json)
    json.direct_generator do
      json.child! do
        json.field 'bigram'
        json.prefix_length 1 # https://www.elastic.co/guide/en/elasticsearch/reference/current/search-suggesters-phrase.html#_direct_generators
      end
    end
  end

  def filtered_query(json)
    json.query do
      json.function_score do
        json.functions do
          popularity_boost(json)
          recency_decay(json)
          older_photos(json)
        end
        json.query do
          # https://www.elastic.co/guide/en/elasticsearch/reference/2.0/breaking_20_query_dsl_changes.html#_literal_filtered_literal_query_and_literal_query_literal_filter_deprecated
          json.bool do
            filtered_query_query(json)
            filtered_query_filter(json)
          end
        end
      end
    end
  end

  def older_photos(json)
    json.child! do
      json.filter do
        json.range do
          json.taken_at do
            json.lt CUTOFF_FOR_DECAY
          end
        end
      end
      # https://www.elastic.co/guide/en/elasticsearch/reference/1.4/query-dsl-function-score-query.html#_boost_factor
      json.weight CUTOFF_WEIGHT
    end
  end

  def recency_decay(json)
    json.child! do
      json.filter do
        json.range do
          json.taken_at do
            json.gte CUTOFF_FOR_DECAY
          end
        end
      end
      json.gauss do
        json.taken_at do
          json.scale DECAY_SCALE
        end
      end
    end
  end

  def popularity_boost(json)
    json.child! do
      json.field_value_factor do
        json.field 'popularity'
        json.modifier 'log2p'
      end
    end
  end

  def filtered_query_filter(json)
    return unless some_profile_specified?

    json.filter do
      json.bool do
        json.set! :should do
          should_flickr(json)
          should_mrss(json)
        end
      end
    end
  end

  def should_mrss(json)
    json.child! { mrss_profiles_filter(json, @mrss_names) } if @mrss_names.present?
  end

  def should_flickr(json)
    json.child! { flickr_profiles_filter(json, @flickr_groups, @flickr_users) } if @flickr_users.present? || @flickr_groups.present?
  end

  def mrss_profiles_filter(json, mrss_names)
    type_and_terms_filter(json, 'mrss_photo', :mrss_names, mrss_names)
  end

  def flickr_profiles_filter(json, flickr_groups, flickr_users)
    json.bool do
      json.must do
        json.child! { json.term { json._type 'flickr_photo' } }
      end
      json.set! :should do
        flickr_profiles_filter_child('owner', flickr_users, json)
        flickr_profiles_filter_child('groups', flickr_groups, json)
      end

      json.minimum_should_match 1
    end
  end

  def flickr_profiles_filter_child(field, terms, json)
    json.child! { json.terms { json.set! field, terms } } if terms.present?
  end

  def filtered_query_query(json)
    json.must do
      json.bool do
        json.set! :should do
          json.child! { match_tags(json) }
          json.child! { simple_query_string(json) }
          match_phrase_collection(json)
        end
      end
    end
  end

  def match_tags(json)
    json.match do
      json.tags do
        json.query @query
        json.analyzer 'tag_analyzer'
      end
    end
  end

  def simple_query_string(json)
    json.simple_query_string do
      json.fields TEXT_FIELDS
      json.query @query
      json.analyzer 'en_analyzer'
      json.default_operator 'AND'
    end
  end

  def pre_tags
    [DEFAULT_PRE_TAG]
  end

  def post_tags
    [DEFAULT_POST_TAG]
  end

  def some_profile_specified?
    @flickr_groups.present? || @flickr_users.present? || @mrss_names.present?
  end

  def match_phrase_collection(json)
    TEXT_FIELDS.each do |field|
      json.child! do
        json.match_phrase do
          json.set! field, @query
        end
      end
    end
  end

  def type_and_terms_filter(json, type, field, terms)
    json.bool do
      json.must do
        json.child! { json.terms { json.set! field, terms } }
        json.child! { json.term { json._type type } }
      end
    end
  end
end