require 'dry/core/inflector'
require 'rom/sql/association'

module ROM
  module SQL
    class Schema < ROM::Schema
      # Additional schema DSL for definition SQL associations
      #
      # This DSL is exposed in `associations do .. end` blocks in schema defintions.
      #
      # @api public
      class AssociationsDSL < BasicObject
        # @!attribute [r] source
        #   @return [Relation::Name] The source relation
        attr_reader :source

        # @!attribute [r] registry
        #   @return [RelationRegistry] Relations registry from a rom container
        attr_reader :registry

        # @api private
        def initialize(source, &block)
          @source = source
          @registry = {}
          instance_exec(&block)
        end

        # Establish a one-to-many association
        #
        # @example using relation identifier
        #   has_many :tasks
        #
        # @example with a :through option
        #   # this establishes many-to-many association
        #   has_many :tasks, through: :users_tasks
        #
        # @example using aliased association with a custom view
        #   has_many :posts, as: :published_posts, view: :published
        #
        # @example using custom target relation
        #   has_many :user_posts, relation: :posts
        #
        # @param [Symbol] target The target relation identifier
        # @param [Hash] options A hash with additional options
        #
        # @return [Associations::OneToMany]
        #
        # @see #many_to_many
        #
        # @api public
        def one_to_many(target, options = {})
          if options[:through]
            many_to_many(target, options)
          else
            add(Association::OneToMany.new(source, target, options))
          end
        end
        alias_method :has_many, :one_to_many

        # Establish a one-to-one association
        #
        # @example using relation identifier
        #   one_to_one :addresses, as: :address
        #
        # @example with an intermediate join relation
        #   one_to_one :tasks, as: :priority_task, through: :assignments
        #
        # @param [Symbol] target The target relation identifier
        # @param [Hash] options A hash with additional options
        #
        # @return [Associations::OneToOne]
        #
        # @see #belongs_to
        #
        # @api public
        def one_to_one(target, options = {})
          if options[:through]
            one_to_one_through(target, options)
          else
            add(Association::OneToOne.new(source, target, options))
          end
        end

        # Establish a one-to-one association with a :through option
        #
        # @example
        #   one_to_one_through :users, as: :author, through: :users_posts
        #
        # @return [Associations::OneToOneThrough]
        #
        # @api public
        def one_to_one_through(target, options = {})
          add(Association::OneToOneThrough.new(source, target, options))
        end

        # Establish a many-to-many association
        #
        # @example using relation identifier
        #   many_to_many :tasks, through: :users_tasks
        #
        # @param [Symbol] target The target relation identifier
        # @param [Hash] options A hash with additional options
        #
        # @return [Associations::OneToOne]
        #
        # @see #one_to_many
        #
        # @api public
        def many_to_many(target, options = {})
          add(Association::ManyToMany.new(source, target, options))
        end

        # Establish a many-to-one association
        #
        # @example using relation identifier
        #   many_to_one :users, as: :author
        #
        # @param [Symbol] target The target relation identifier
        # @param [Hash] options A hash with additional options
        #
        # @return [Associations::OneToOne]
        #
        # @see #one_to_many
        #
        # @api public
        def many_to_one(target, options = {})
          add(Association::ManyToOne.new(source, target, options))
        end

        # Shortcut for many_to_one which sets alias automatically
        #
        # @example with an alias (relation identifier is inferred via pluralization)
        #   belongs_to :user
        #
        # @example with an explicit alias
        #   belongs_to :users, as: :author
        #
        # @see #many_to_one
        #
        # @return [Associations::ManyToOne]
        #
        # @api public
        def belongs_to(name, options = {})
          many_to_one(dataset_name(name), {as: name}.merge(options))
        end

        # Shortcut for one_to_one which sets alias automatically
        #
        # @example with an alias (relation identifier is inferred via pluralization)
        #   one_to_one :address
        #
        # @example with an explicit alias and a custom view
        #   one_to_one :posts, as: :priority_post, view: :prioritized
        #
        # @see #one_to_one
        #
        # @return [Associations::ManyToOne]
        #
        # @api public
        def has_one(name, options = {})
          one_to_one(dataset_name(name), {as: name}.merge(options))
        end

        # Return an association set for a schema
        #
        # @return [AssociationSet]
        #
        # @api private
        def call
          AssociationSet.new(registry)
        end

        private

        # @api private
        def add(association)
          registry[association.name] = association
        end

        # @api private
        def dataset_name(name)
          ::Dry::Core::Inflector.pluralize(name).to_sym
        end
      end
    end
  end
end