require 'glue/validation'

module Glue 

# Extend the Validation methods defined in glue/validation.rb 
# with extra db related options.

module Validation

  # Encapsulates a list of validation errors.
  
  class Errors
    setting :invalid_relation, :default => "Undefined"
    setting :not_unique, :default => 'The value is already used'
  end

  module ClassMethods 
    
    # Validates that the given field(s) contain unique values.
    # Ensures that if a record is found with a matching value,
    # that it is the same record, allowing updates.
    #
    # The Og libraries are required for this method to 
    # work. You can override this method if you want to
    # use another OR mapping library.
    #
    # === Example
    #
    # validate_unique :param, :msg => 'Value is already in use'
    #--
    # TODO: :unique should implicitly generate 
    # validate_unique.
    #++

    def validate_unique *params
      c = parse_config(params, :on => :save)

      params.each do |field|
        c[:msg] ||= "#{self.name} with this #{field} already exists"
  
        define_validation(:unique, field, c[:on]) do |obj|
          # What to do if value is nil?  Right now it is an empty string,
          # which can need to be unique.
          value = obj.send(field) || ''
          others = [*obj.class.send("find_by_#{field}".to_sym, value)]
  
          unless others[0].nil?
            obj.errors.add(field, c[:msg]) if others.size > 1 or others[0].oid != obj.oid
          end
        end
      end
    end

    # Validate that a property relation is not nil.
    # This works for all relations.
    #
    # You should not put a validation in both related
    # classes, because it can cause infinite looping.
    #
    # The Og libraries are required for this method to
    # work. You can override this method if you want to
    # use another OR mapping library.
    #
    # === Example
    #
    # class Uncle
    #   has_many :secrets, Secret
    #   validate_related :secrets
    # end
    #
    # class Secret
    #   belongs_to :uncle, Uncle
    # end
    
    def validate_related *params
      c = parse_config(params,
        :msg => Glue::Validation::Errors.invalid_relation, 
        :on => :save 
      )

      params.each do |field|
        define_validation(:related, field, c[:on]) do |obj|
          value = obj.send(field)
          if value.members.length == 0
            obj.errors.add(field, c[:msg])
          else
            valid = value.members.inject do |memo, rel_obj| 
              (rel_obj.nil? or rel_obj.valid?) and memo
            end
            obj.errors.add(field, c[:msg]) unless valid
          end
        end
      end
    end

    alias validate_associated validate_related

  end 

end

end