class ArticleApiIndexService
  DEFAULT_PER_PAGE = 30
  MAX_PER_PAGE = 1000

  def initialize(params)
    @page = params[:page]
    @tag = params[:tag]
    @username = params[:username]
    @state = params[:state]
    @top = params[:top]
    @collection_id = params[:collection_id]
    @per_page = params[:per_page]
  end

  def get
    if tag.present?
      tag_articles
    elsif username.present?
      username_articles
    elsif state.present?
      state_articles(state)
    elsif top.present?
      top_articles
    elsif collection_id.present?
      collection_articles(collection_id)
    else
      base_articles
    end
  end

  private

  attr_reader :tag, :username, :page, :state, :top, :collection_id, :per_page

  def username_articles
    num = if @state == "all"
            MAX_PER_PAGE
          else
            DEFAULT_PER_PAGE
          end

    if (user = User.find_by(username: username))
      user.articles.published.
        includes(:organization).
        order("published_at DESC").
        page(page).
        per(per_page || num)
    elsif (organization = Organization.find_by(slug: username))
      organization.articles.published.
        includes(:user).
        order("published_at DESC").
        page(page).
        per(per_page || num)
    else
      Article.none
    end
  end

  def tag_articles
    articles = Article.published.cached_tagged_with(tag).includes(:user, :organization)

    articles = if Tag.find_by(name: tag)&.requires_approval
                 articles.where(approved: true).order("featured_number DESC")
               elsif top.present?
                 articles.where("published_at > ?", top.to_i.days.ago).
                   order("public_reactions_count DESC")
               else
                 articles.order("hotness_score DESC")
               end

    articles.page(page).per(per_page || DEFAULT_PER_PAGE)
  end

  def top_articles
    Article.published.includes(:user, :organization).
      where("published_at > ?", top.to_i.days.ago).
      order("public_reactions_count DESC").
      page(page).per(per_page || DEFAULT_PER_PAGE)
  end

  def state_articles(state)
    articles = Article.published.includes(:user, :organization)

    articles = if state == "fresh"
                 articles.where(
                   "public_reactions_count < ? AND featured_number > ? AND score > ?", 2, 7.hours.ago.to_i, -2
                 )
               elsif state == "rising"
                 articles.where(
                   "public_reactions_count > ? AND public_reactions_count < ? AND featured_number > ?",
                   19, 33, 3.days.ago.to_i
                 )
               else
                 Article.none
               end

    articles.page(page).per(per_page || DEFAULT_PER_PAGE)
  end

  def collection_articles(collection_id)
    Article.published.
      where(collection_id: collection_id).
      includes(:user, :organization).
      order("published_at").
      page(page).
      per(per_page || DEFAULT_PER_PAGE)
  end

  def base_articles
    Article.published.
      where(featured: true).
      includes(:user, :organization).
      order("hotness_score DESC").
      page(page).
      per(per_page || DEFAULT_PER_PAGE)
  end
end