```ruby
class ProductCategory < Category
  # FIXME: do not allow category with products or inputs to be destroyed
  has_many :products
  has_many :inputs

  attr_accessible :name, :parent, :environment

  scope :unique, :select => 'DISTINCT ON (path) categories.*'
  scope :by_enterprise, lambda { |enterprise| {
    :joins => :products,
    :conditions => ['products.profile_id = ?', enterprise.id]
  }}
  scope :unique_by_level, lambda { |level| {
    :select => "DISTINCT ON (filtered_category) split_part(path, '/', #{level}) AS filtered_category, categories.*"
  }}

  def all_products
    Product.find(:all, :conditions => { :product_category_id => (all_children << self).map(&:id) })
  end

  def self.menu_categories(top_category, env)
    top_category ? top_category.children : top_level_for(env).select{|c|c.kind_of?(ProductCategory)}
  end

end
```

Add scope to search product categories by environment
user
```ruby
class ProductCategory < Category
  # FIXME: do not allow category with products or inputs to be destroyed
  has_many :products
  has_many :inputs

  attr_accessible :name, :parent, :environment

  scope :unique, :select => 'DISTINCT ON (path) categories.*'
  scope :by_enterprise, lambda { |enterprise| {
    :joins => :products,
    :conditions => ['products.profile_id = ?', enterprise.id]
  }}
  scope :by_environment, lambda { |environment| {
    :conditions => ['environment_id = ?', environment.id]
  }}
  scope :unique_by_level, lambda { |level| {
    :select => "DISTINCT ON (filtered_category) split_part(path, '/', #{level}) AS filtered_category, categories.*"
  }}

  def all_products
    Product.find(:all, :conditions => { :product_category_id => (all_children << self).map(&:id) })
  end

  def self.menu_categories(top_category, env)
    top_category ? top_category.children : top_level_for(env).select{|c|c.kind_of?(ProductCategory)}
  end

end
```
assistant