module DataMapper
  module Associations
    module ManyToOne #:nodoc:
      # Relationship class with implementation specific
      # to n side of 1 to n association
      class Relationship < Associations::Relationship
        OPTIONS = superclass::OPTIONS.dup << :required << :key << :unique

        # @api semipublic
        alias_method :source_repository_name, :child_repository_name

        # @api semipublic
        alias_method :source_model, :child_model

        # @api semipublic
        alias_method :target_repository_name, :parent_repository_name

        # @api semipublic
        alias_method :target_model, :parent_model

        # @api semipublic
        alias_method :target_key, :parent_key

        # @api semipublic
        def required?
          @required
        end

        # @api semipublic
        def key?
          @key
        end

        # @api semipublic
        def unique?
          !!@unique
        end

        # @deprecated
        def nullable?
          raise "#{self.class}#nullable? is deprecated, use #{self.class}#required? instead (#{caller.first})"
        end

        # Returns a set of keys that identify source model
        #
        # @return   [DataMapper::PropertySet]  a set of properties that identify source model
        # @api private
        def child_key
          return @child_key if defined?(@child_key)

          model           = source_model
          repository_name = source_repository_name || target_repository_name
          properties      = model.properties(repository_name)

          source_key = target_key.zip(@child_properties || []).map do |target_property, property_name|
            property_name ||= "#{name}_#{target_property.name}".to_sym

            properties[property_name] || begin
              # create the property within the correct repository
              DataMapper.repository(repository_name) do
                model.property(property_name, target_property.to_child_key, source_key_options(target_property))
              end
            end
          end

          @child_key = properties.class.new(source_key).freeze
        end

        # @api semipublic
        alias_method :source_key, :child_key

        # Initialize the foreign key property this "many to one"
        # relationship uses to persist itself
        #
        # @return [self]
        #
        # @api public
        def finalize
          child_key
          self
        end

        # Returns a hash of conditions that scopes query that fetches
        # target object
        #
        # @return [Hash]
        #   Hash of conditions that scopes query
        #
        # @api private
        def source_scope(source)
          if source.kind_of?(Resource)
            Query.target_conditions(source, source_key, target_key)
          else
            super
          end
        end

        # Returns a Resource for this relationship with a given source
        #
        # @param [Resource] source
        #   A Resource to scope the collection with
        # @param [Query] other_query (optional)
        #   A Query to further scope the collection with
        #
        # @return [Resource]
        #   The resource scoped to the relationship, source and query
        #
        # @api private
        def resource_for(source, other_query = nil)
          query = query_for(source, other_query)

          # If the target key is equal to the model key, we can use the
          # Model#get so the IdentityMap is used
          if target_key == target_model.key
            target = target_model.get(*source_key.get!(source))
            if query.conditions.matches?(target)
              target
            else
              nil
            end
          else
            target_model.first(query)
          end
        end

        # Loads and returns association target (ex.: author) for given source resource
        # (ex.: article)
        #
        # @param  source  [DataMapper::Resource]
        #   source object (ex.: instance of article)
        # @param  other_query  [DataMapper::Query]
        #   Query options
        #
        # @api semipublic
        def get(source, query = nil)
          lazy_load(source)

          if query
            collection = get_collection(source)
            collection.first(query) if collection
          else
            get!(source)
          end
        end

        def get_collection(source)
          target = get!(source)
          target.collection_for_self if target
        end

        # Sets value of association target (ex.: author) for given source resource
        # (ex.: article)
        #
        # @param source [DataMapper::Resource]
        #   source object (ex.: instance of article)
        #
        # @param target [DataMapper::Resource]
        #   target object (ex.: instance of author)
        #
        # @api semipublic
        def set(source, target)
          target = typecast(target)
          source_key.set(source, target_key.get(target))
          set!(source, target)
        end

        # @api semipublic
        def default_for(source)
          typecast(super)
        end

        # Loads association target and sets resulting value on
        # given source resource
        #
        # @param [Resource] source
        #   the source resource for the association
        #
        # @return [undefined]
        #
        # @api private
        def lazy_load(source)
          source_key_different = source_key_different?(source)

          if (loaded?(source) && !source_key_different) || !valid_source?(source)
            return
          end

          # SEL: load all related resources in the source collection
          if source.saved? && (collection = source.collection).size > 1
            eager_load(collection)
          end

          if !loaded?(source) || (source_key_dirty?(source) && source.saved?)
            set!(source, resource_for(source))
          elsif loaded?(source) && source_key_different
            source_key.set(source, target_key.get!(get!(source)))
          end
        end

        private

        # Initializes the relationship, always using max cardinality of 1.
        #
        # @api semipublic
        def initialize(name, source_model, target_model, options = {})
          if options.key?(:nullable)
            raise ":nullable is deprecated, use :required instead (#{caller[2]})"
          end

          @required      = options.fetch(:required, true)
          @key           = options.fetch(:key,      false)
          @unique        = options.fetch(:unique,   false)
          @unique_index  = options.fetch(:unique_index, @unique)
          target_model ||= DataMapper::Inflector.camelize(name)
          options        = { :min => @required ? 1 : 0, :max => 1 }.update(options)
          super
        end

        # Sets the association targets in the resource
        #
        # @param [Resource] source
        #   the source to set
        # @param [Array(Resource)] targets
        #   the target resource for the association
        # @param [Query, Hash] query
        #   not used
        #
        # @return [undefined]
        #
        # @api private
        def eager_load_targets(source, targets, query)
          set(source, targets.first)
        end

        # @api private
        def typecast(target)
          if target.kind_of?(Hash)
            target_model.new(target)
          else
            target
          end
        end

        # Returns the inverse relationship class
        #
        # @api private
        def inverse_class
          OneToMany::Relationship
        end

        # Returns the inverse relationship name
        #
        # @api private
        def inverse_name
          name = super
          return name if name

          name = DataMapper::Inflector.demodulize(source_model.name)
          name = DataMapper::Inflector.underscore(name)
          name = DataMapper::Inflector.pluralize(name)
          name.to_sym
        end

        # @api private
        def source_key_options(target_property)
          DataMapper::Ext::Hash.only(target_property.options, :length, :precision, :scale).update(
            :index        => name,
            :required     => required?,
            :key          => key?,
            :unique       => @unique,
            :unique_index => @unique_index
          )
        end

        # @api private
        def child_properties
          source_key.map { |property| property.name }
        end

        # @api private
        def source_key_different?(source)
          source_key.get!(source) != target_key.get!(get!(source))
        end

        # @api private
        def source_key_dirty?(source)
          source.dirty_attributes.keys.any? { |property| source_key.include?(property) }
        end
      end # class Relationship
    end # module ManyToOne
  end # module Associations
end # module DataMapper
