require 'og/entity'

# Add cloning functionality to entities.
#--
# WARNING, gmosx: I haven't tested this extensively,
# this is a donated patch.
#++

module EntityMixin

  def og_clone(*args)
    Og::Entity.clone(self,*args)
  end  

end

class Entity

  class << self

    # Entity copying support. Eventually this should all
    # be eval'd in at enchanting stage for the minor
    # speed increase.
    # TODO: Convert to enchantments on objects
    
    # Accepts source object, destination and ignore.
    # Source and destination are self explanatory; ignore
    # is a list of properties not to copy (i.e.
    # :create_time,:update_time).
    # By default sets the class variables directly on the
    # remote model instance, if you set use_setter_method to
    # true, uses create_time= style copying tactics,
    
    def copy_properties(source, destination, ignore = [], use_setter_method = false)
      property_copier(source, destination, ignore, use_setter_method, false)
    end
    
    # Copies relations of one record to another. Only copies
    # has_one, refers_to, belongs_to relationships as 
    # has_many requires modifying of other objects and
    # cannot be copied (by design). If you think you need to copy
    # these relations, what you need is a joins_many relationship
    # which can be copied.
    
    def copy_inferior_relations(source, destination, ignore = [])
      real_ignore = Array.new
      
      # Map relation symbols to foreign keys.
      
      ignore.each do |symbol|
         source.class.relations.reject{|r| [Og::JoinsMany, Og::ManyToMany, Og::HasMany].include?(r.class)}.each do |relation|
           if relation.name == symbol.to_s
             real_ignore << relation.foreign_key.to_sym
             break
           end
         end
      end      
      
      # Use instance variable property copier method.
      
      property_copier(source, destination, real_ignore, false, true)
    end
    
    def copy_equal_relations(source, destination, ignore = [])
      source.class.relations.reject{|r| not [Og::JoinsMany, Og::ManyToMany].include?(r.class)}.each do |relation|
        next if relation.name == nil or ignore.include?(relation.name)
        source.send(relation.name).each do |related|
          destination.send(relation.name).send(:<<, related)
        end
      end
    end
    
    # Copies all relations *except* HasMany which is impossible
    # to copy. Use a JoinsMany relation instead if you need a
    # copyable HasMany (which is irrational).
        
    def copy_relations(source, destination, ignore = [])
      copy_inferior_relations(source, destination, ignore)
      copy_equal_relations(source, destination, ignore)
    end
    
    # Clones an object in every possible way (cannot copy
    # HasMany but can copy all others - BelongsTo, etc).
    # Provide a source object as first arguments, the rest
    # (if any) are passed along to the initialize constructor
    # when calling new to make the copied object.
    
    def clone(source,*args)
      destination = source.class.new(*args)
      copy_properties(source, destination, [], false)
      # Must save here to copy join tables.      
      destination.save!
      copy_relations(source, destination, [])
      destination.save!
      destination
    end

    # Does the work of clone_properties and copy_inferior_relations. 
    # Syntax is the same with one extra field to tell the 
    # routine what it is copying.
    
    def property_copier(source,destination,ignore,use_setter_method,relations)
      primary_key_symbol = source.class.primary_key.symbol
      source.class.properties.to_a.each do |symbol, property|
        next if primary_key_symbol == symbol or ignore.include?(symbol) or
         (relations and not property.relation) or (not relations and property.relation)
         
        variable = "@#{symbol}"
        if use_setter_method
          destination.send("#{symbol}=".to_sym,source.instance_variable_get(variable))
        else      
          destination.instance_variable_set(variable, source.instance_variable_get(variable))        
        end
      end
    end    
  
  end
  
end