require "fiona7/verity_search_engine"

module Fiona7
  class FacetBuilder
    def initialize(facet_params, query, klass)
      @query        = query
      @klass        = klass

      @attribute    = facet_params[:attribute]

      @limit        = [facet_params[:limit] || 10, 100].min # default = 10, limit <= 100
      @fake_limit   = 100
      @include_objs = facet_params[:include_objs] || false

      @known_values = Set.new
      @facets       = []
      @next_facets  = []
    end

    def build
      @facets << fetch_more_facets until limit_reached or !more_facets_available

      # adjust totals
      for index in 0.upto(@facets.length-2)
        next_facet_total = @facets[index+1].first[:total] rescue 0
        @facets[index].each do |facet|
          facet[:total] -= next_facet_total
        end
      end

      # flatten
      @facets.flatten!

      # sort
      @facets.sort_by! {|f| f[:total] }.reverse!

      # delete superfluous elements
      @facets.slice!(@limit, @facets.length)

      # add included objs
      if @include_objs
        @facets.each do |facet|
          include_objs_query = @query.dup
          include_objs_query << {field: @attribute, operator: :__in__, value: facet[:value]}
          search = VeritySearchEngine.new(@klass, include_objs_query, 0, @include_objs, @attribute, :desc)
          facet[:results] = search.results.map {|o_id| {id: o_id.to_s}}
          # this gives a true total!
          facet[:total] = search.total
        end
      else
        @facets.each do |facet|
          facet[:results] = []
        end
      end

      @facets
    end

    protected
    def limit_reached
      (@fake_limit -= 1) < 0
    end

    def fetch_more_facets
      @next_facets
    end

    def more_facets_available
      @next_facets = []

      search = build_search
      return false if search.results.empty?

      sample_object = Fiona7::WriteObj.where(obj_id: search.results).first
      return false if sample_object.nil?
      new_values = get_attribute_values(sample_object)

      new_values.each do |new_value|
        next if @known_values.include?(new_value)
        @known_values << new_value

        @next_facets << {
          value: new_value,
          total: search.total
        }
      end

      return !@next_facets.empty?
    end

    def build_search
      facet_query   = @query.dup
      facet_query   << {field: @attribute, operator: :__not_in__, value: serialize_known_values} unless @known_values.empty?
      facet_query   << any_value_present_in_attribute_query
      # search engine likes to return object which do not exist anymore
      # hence we try ten objects
      facet_size    = 10
      facet_offset  = 0
      facet_sort    = @attribute
      facet_order   = :desc

      VeritySearchEngine.new(@klass, facet_query, facet_offset, facet_size, facet_sort, facet_order)
    end

    # TODO: remove this ugly code
    def get_attribute_values(sample_object)
      # TODO: extend this code to handle stringlists and multienums
      type_definition =  Fiona7::TypeRegister.instance.read_mangled(sample_object.obj_class)
      attribute = type_definition.find_attribute(@attribute)

      return nil unless attribute

      if attribute.type == :stringlist
        # TODO: remove deserialization duplication
        deserialized = ::JSON.parse(sample_object[attribute.real_name]) rescue []
        deserialized.kind_of?(Array) ? deserialized : []
      elsif attribute.real_type == :multienum
        sample_object[attribute.real_name] || []
      else
        # TODO: add warning/handling for wrong attributes
        [sample_object[attribute.real_name].to_s]
      end
    end

    def any_value_present_in_attribute_query
      letters = ('a'..'z').map {|l| "*#{l}*" }
      numbers = ('0'..'9').map {|l| "*#{l}*" }
      sanity_patterns = letters + numbers

      {field: @attribute, operator: :__in__, value: sanity_patterns}
    end

    def serialize_known_values
      @known_values.map do |kv|
        kv.blank? ? "dummy123dummy456dummy" : kv.to_s
      end
    end

  end
end