Implementing Sorting, Searching and pagination In ROR app

sort_search_paginate.rb

class PostList
  SEARCH_COLUMNS = [
    'documents.original_document_name',
    'users.name',
    'languages.name',
    'post_statuses.label'
  ].freeze

  ALLOWED_SORT_COLUMNS = {
    'title' => 'title',
    'username' => 'users.name',
    'language_name' => 'languages.name',
    'status_label' => 'post_statuses.label',
    'created_at' => 'posts.created_at'
  }.freeze

  ALLOWED_SORT_DIRECTIONS = %w[asc desc].freeze
  
  attr_reader :search, :sort_column, :sort_direction, :page, :per_page
  
  def initialize(serach, sort_column, sort_direction, page, per_page)
    @serach = serach
    @sort_column = sort_column
    @sort_direction = sort_direction
    @page = page
    @per_page = per_page
  end
  
  def call
    result = all_data

    result = apply_sorting(result)
    result, search_result = apply_searching(result)
    result = apply_pagination(result)
    {
      data: result,
      current_page: result.current_page,
      objects_on_page: result.size,
      total_pages: result.total_pages,
      total_count: all_data.size
      search_count: search_result.size
    }
  end
  
  private
  
  def all_data
    @all_data ||= post_list_query
  end
  
  def post_list_query
    Post.select("title, created_at, documents.original_document_name, users.name AS username, post_statuses.labe AS post_status_label, languages.name AS language_name")
        .joins(:documents, :user, :post_status, :language)
  end
  
  def apply_sorting(result)
    sort_column = sort_column.presence || 'created_at'
    sort_column = ALLOWED_SORT_COLUMNS[sort_column] || ALLOWED_SORT_COLUMNS['created_at']
    sort_direction = sort_direction.presence || 'desc'
    sort_direction = ALLOWED_SORT_DIRECTIONS.include?(sort_direction.downcase) ? sort_direction : 'desc'
    result.order("#{sort_column} #{sort_direction}")
  end
  
  def apply_searching(result)
    return result if search.blank?

    search_pattern = "%#{search}%"
    conditions = SEARCH_COLUMNS.map { |col| "#{col} ILIKE :search" }.join(' OR ')
    result.where(conditions, search: search_pattern)
  end
  
  # Using Kaminari gem
  def apply_pagination(result)
    result.page(page).per(per_page)
  end
end