def prepare_items_for_mass_display(items) 
  items.to_json(
     :except => [:created_at, :current_input_price, :stock, :on_display],
     :include => [      
      :unit ,
      :multi_media_descriptions ,
      :sub_category
  ])
end




def offset_and_limit_invalid?(offset, limit)
  offset < 0 or limit <= 0 or limit > 100
end


# gets single item for detailed display (like comments etc. ) # TODO: change when comments are added
get '/item/:id' do |id_s| 
  item = Item.find(id_s.to_i)
  prepare_items_for_mass_display(item)
end


# gets items regardless of classification ( useful for frontpage )
get '/item/offset/:offset/limit/:limit' do |offset_s, limit_s|
  offset, limit = mass_to_i(offset_s, limit_s)
  return [].to_json if offset_and_limit_invalid?(offset,limit)
  
  items = Item.best_selling(offset,limit)
  prepare_items_for_mass_display(items)
end


# gets items in section ( useful for page showing single section )
get '/item/section/:section_id/offset/:offset/limit/:limit' do |section_id_s, offset_s, limit_s|
  section_id, offset, limit = mass_to_i(section_id_s, offset_s, limit_s)
  input_invalid = offset_and_limit_invalid?(offset,limit) or section_id <= 0
  return [].to_json if input_invalid 
  
  items = Item.best_selling_in_section(section_id, offset, limit)
  prepare_items_for_mass_display(items)
end

# gets items in category ( useful for page showing single category )
get '/item/category/:category_id/offset/:offset/limit/:limit' do |category_id_s, offset_s, limit_s|
  category_id, offset, limit = mass_to_i(category_id_s, offset_s, limit_s)
  input_invalid = offset_and_limit_invalid?(offset,limit) or category_id <= 0
  return [].to_json if input_invalid 

  items = Item.best_selling_in_category(category_id, offset,limit)
  prepare_items_for_mass_display(items)
end

# gets items in sub category ( useful for page showing single sub_category )
get '/item/sub_category/:sub_category_id/offset/:offset/limit/:limit' do |sub_category_id_s, offset_s, limit_s|
  sub_category_id, offset, limit = mass_to_i(sub_category_id_s, offset_s, limit_s)
  input_invalid = offset_and_limit_invalid?(offset,limit) or sub_category_id <= 0
  return [].to_json if input_invalid 

  items = Item.best_selling_in_sub_category(sub_category_id, offset, limit)
  prepare_items_for_mass_display(items)
end