philomena/lib/philomena_web/controllers/image/related_controller.ex

defmodule PhilomenaWeb.Image.RelatedController do
  use PhilomenaWeb, :controller

  alias PhilomenaWeb.ImageLoader
  alias Philomena.Interactions
  alias Philomena.Images.Image

  plug PhilomenaWeb.CanaryMapPlug, index: :show
  plug :load_and_authorize_resource, model: Image, id_name: "image_id", persisted: true, preload: [:tags, :faves]

  def index(conn, _params) do
    image = conn.assigns.image
    user = conn.assigns.current_user

    tags_to_match =
      image.tags
      |> Enum.reject(& &1.category == "rating")
      |> Enum.sort_by(& &1.images_count)
      |> Enum.take(10)
      |> Enum.map(& &1.id)

    low_count_tags =
      tags_to_match
      |> Enum.take(5)
      |> Enum.map(&%{term: %{tag_ids: &1}})

    high_count_tags =
      tags_to_match
      |> Enum.take(-5)
      |> Enum.map(&%{term: %{tag_ids: &1}})

    favs_to_match =
      image.faves
      |> Enum.take(11)
      |> Enum.map(&%{term: %{favourited_by_user_ids: &1.user_id}})

    query =
      %{
        bool: %{
          must: [
            %{bool: %{should: low_count_tags, boost: 2}},
            %{bool: %{should: high_count_tags, boost: 3, minimum_should_match: "5%"}},
            %{bool: %{should: favs_to_match, boost: 0.2, minimum_should_match: "5%"}}
          ],
          must_not: %{term: %{id: image.id}}
        }
      }

    {images, _tags} =
      ImageLoader.query(
        conn,
        query,
        sorts: [%{_score: :desc}],
        pagination: %{conn.assigns.image_pagination | page_number: 1}
      )

    interactions = Interactions.user_interactions(images, user)

    render(conn, "index.html", title: "##{image.id} - Related Images", layout_class: "wide", images: images, interactions: interactions)
  end
end