gem 'mongoid-tags'

class Document
  include Mongoid::Document
  include Mongoid::Tags
end

# Documents tagged foo || bar
Document.tagged('foo bar')

# Documents tagged foo && bar
Document.tagged('+foo bar')

# Documents tagged foo, but !bar
Document.tagged('foo -bar')

# Documents tagged foo and bar or baz
Document.tagged('(+foo +bar) baz')

# Documents tagged foo and bar, or foo and baz
Document.tagged('(+foo +bar)(+foo +baz)')

# Chaining calls
Document.where(published: true).tagged('foo').desc(:created_at)