module UniverseCompiler
  module Universe

    module Entities

      def empty?
        entities.empty?
      end

      def add(entity)
        raise UniverseCompiler::Error, 'An entity cannot be null !' if entity.nil?
        raise UniverseCompiler::Error, 'An entity must have a name !' unless entity.respond_to? :name
        raise UniverseCompiler::Error, 'An entity must have a name !' if entity.name.nil? or entity.name.empty?
        unless UniverseCompiler::Entity::TypeManagement.valid_for_type? entity
          entity.extend UniverseCompiler::Entity::TypeManagement
        end
        raise UniverseCompiler::Error, "An entity named '#{entity.name}' already exists with the type '#{entity.type}' !" if by_uniq_key.keys.include? [entity.type, entity.name]
        raise UniverseCompiler::Error, 'Invalid type specified' if entity.type.nil?
        raise UniverseCompiler::Error, 'Type cannot contain spaces' if entity.type =~ /\s/
        # Normally here the entity is valid
        # We add it to the universe and index it
        entities << entity
        if entity.respond_to? :'universe='
          entity.universe = self
        end
        index entity
        entity
      end

      def <<(entity)
        add entity
        self
      end

      def delete(entity)
        # Remove references to entity
        entities.each do |e|
          e.class.fields_constraints.each do |field_name, constraints|
            if constraints.keys.include? :has_one
              e[field_name] = nil if e[field_name] == entity
            end
            if constraints.keys.include? :has_many
              e[field_name].delete entity if e[field_name].include? entity
            end
          end
        end
        # Then delete the entity
        entities.delete entity
        reindex_all entities
      end

      def replace(entity, by)
        raise UniverseCompiler::Error, "Wrong type, cannot replace '#{entity.as_path}' by '#{by.as_path}' !" unless entity.type == by.type
        raise UniverseCompiler::Error, "Cannot replace '#{entity.as_path}' with '#{by.as_path}' which is alreadyin the universe!" if entity.universe == by.universe

        # Change references to entity
        entities.each do |e|
          e.class.fields_constraints.each do |field_name, constraints|
            if constraints.keys.include? :has_one
              e[field_name] = by if e[field_name] == entity
            end
            if constraints.keys.include? :has_many
              if e[field_name].map! do |entity_list_item|
                (entity == entity_list_item) ? by : entity_list_item
              end
              end
            end
          end
        end
        # Then replace the entity
        entities[entities.index(entity)] = by
        reindex_all entities
      end

      def clear
        entities.clear
        clear_indices
      end

      private

      attr_reader :entities

    end

  end
end