require "rails_erd"
require "rails_erd/domain/attribute"
require "rails_erd/domain/entity"
require "rails_erd/domain/relationship"
require "rails_erd/domain/specialization"

module RailsERD
  # The domain describes your Rails domain model. This class is the starting
  # point to get information about your models.
  #
  # === Options
  #
  # The following options are available:
  #
  # warn:: When set to +false+, no warnings are printed to the
  #        command line while processing the domain model. Defaults
  #        to +true+.
  class Domain
    class << self
      # Generates a domain model object based on all loaded subclasses of
      # <tt>ActiveRecord::Base</tt>. Make sure your models are loaded before calling
      # this method.
      #
      # The +options+ hash allows you to override the default options. For a
      # list of available options, see RailsERD.
      def generate(options = {})
        new ActiveRecord::Base.descendants, options
      end

      # Returns the method name to retrieve the foreign key from an
      # association reflection object.
      def foreign_key_method_name # @private :nodoc:
        @foreign_key_method_name ||= ActiveRecord::Reflection::AssociationReflection.method_defined?(:foreign_key) ? :foreign_key : :primary_key_name
      end
    end

    extend Inspectable
    inspection_attributes

    # The options that are used to generate this domain model.
    attr_reader :options

    # Create a new domain model object based on the given array of models.
    # The given models are assumed to be subclasses of <tt>ActiveRecord::Base</tt>.
    def initialize(models = [], options = {})
      @source_models, @options = models, RailsERD.options.merge(options)
    end

    # Returns the domain model name, which is the name of your Rails
    # application or +nil+ outside of Rails.
    def name
      defined? Rails and Rails.application and Rails.application.class.parent.name
    end

    # Returns all entities of your domain model.
    def entities
      @entities ||= Entity.from_models(self, models)
    end

    # Returns all relationships in your domain model.
    def relationships
      @relationships ||= Relationship.from_associations(self, associations)
    end

    # Returns all specializations in your domain model.
    def specializations
      @specializations ||= Specialization.from_models(self, models)
    end

    # Returns a specific entity object for the given Active Record model.
    def entity_by_name(name) # @private :nodoc:
      entity_mapping[name]
    end

    # Returns an array of relationships for the given Active Record model.
    def relationships_by_entity_name(name) # @private :nodoc:
      relationships_mapping[name] or []
    end

    def specializations_by_entity_name(name)
      specializations_mapping[name] or []
    end

    def warn(message) # @private :nodoc:
      puts "Warning: #{message}" if options.warn
    end

    private

    def entity_mapping
      @entity_mapping ||= {}.tap do |mapping|
        entities.each do |entity|
          mapping[entity.name] = entity
        end
      end
    end

    def relationships_mapping
      @relationships_mapping ||= {}.tap do |mapping|
        relationships.each do |relationship|
          (mapping[relationship.source.name] ||= []) << relationship
          (mapping[relationship.destination.name] ||= []) << relationship
        end
      end
    end

    def specializations_mapping
      @specializations_mapping ||= {}.tap do |mapping|
        specializations.each do |specialization|
          (mapping[specialization.generalized.name] ||= []) << specialization
          (mapping[specialization.specialized.name] ||= []) << specialization
        end
      end
    end

    def models
      @models ||= @source_models.reject(&:abstract_class?).select { |model| check_model_validity(model) }
    end

    def associations
      @associations ||= models.collect(&:reflect_on_all_associations).flatten.select { |assoc| check_association_validity(assoc) }
    end

    def check_model_validity(model)
      model.table_exists? or raise "table #{model.table_name} does not exist"
    rescue => e
      warn "Ignoring invalid model #{model.name} (#{e.message})"
    end

    def check_association_validity(association)
      # Raises an ActiveRecord::ActiveRecordError if the association is broken.
      association.check_validity!

      if association.options[:polymorphic]
        entity_name = association.class_name
        entity_by_name(entity_name) or raise "polymorphic interface #{entity_name} does not exist"
      else
        entity_name = association.klass.name # Raises NameError if the associated class cannot be found.
        entity_by_name(entity_name) or raise "model #{entity_name} exists, but is not included in domain"
      end
    rescue => e
      warn "Ignoring invalid association #{association_description(association)} (#{e.message})"
    end

    def association_description(association)
      "#{association.name.inspect} on #{association.active_record}"
    end
  end
end