module Eco
  module API
    class UseCases
      class UseCase < BaseCase
        @types = BaseCase.types

        attr_reader :name, :type, :times_launched
        attr_reader :options

        def initialize(name, type:, root:, &block)
          raise InvalidType.new("Invalid type for '#{name}'.", type: type, types: self.class.types) unless self.class.valid_type?(type)

          self.root = root
          @callback = block
          @name     = name
          @type     = type
          @times_launched = 0
        end

        def source_object
          return nil unless callback_from_loader?
          callback_self
        end

        def chainer
          # TODO: root is a Eco::API::UseCases that will not point to this new case.
          # => Moreover, the name and type will be the same as self
          Eco::API::UseCases::UseCaseChain.new(usecase: self, root: @root)
        end

        def root=(value)
          raise "Root should be a Eco::API::UseCases. Given: #{value.class}" if !value.is_a?(Eco::API::UseCases)
          @root = value
        end

        # Actual launch of the usecase
        # @param io [Eco::API::UseCases::BaseIO] an input/output helper with the necessary parameters.
        # @param kargs [Hash] hash with symbol keys.
        # @option kargs [Eco::API::Common::People::Entries, Eco::API::Organization::People] :input the input data of reference.
        # @option kargs [Eco::API::Organization::People] :people object.
        # @option kargs [Eco::API:Session] :session
        # @option kargs [Hash] :options hash with symbol keys (i.e. behaviour modifiers, cli trackers, filters, etc.)
        def launch(io: nil, **kargs)
          params = io&.params(keyed: true, all: true) || {}
          kargs  = params.merge(kargs).merge(usecase: self)

          UseCaseIO.new(**kargs).tap do |uio|
            @options   = uio.options
            uio.session.logger.debug("#{self.class}: going to process '#{name}'")
            set_session_n_options(session: uio.session, options: uio.options) if callback_from_loader?
            uio.output = @callback.call(*uio.params)
            @times_launched += 1
          end
        end

        protected

        def callback
          @callback
        end

        def callback_self
          eval("self", @callback.binding)
        end

        def callback_from_loader?
          callback_self.is_a?(Eco::API::Common::Loaders::Base)
        end

        # Set the instance variables `@session` and `@options`
        # in the use case definition
        # @note this only works when the use case was defined
        #   via an children class of `Eco::API::Common::Loaders::Base`
        def set_session_n_options(session:, options: @options)
          return false unless callback_from_loader?
          use_case_self = self
          callback_self.instance_eval do
            next unless self.is_a?(Eco::API::Common::Loaders::CaseBase)
            # `self` is the use case itself (when used the Loader)
            @session = session
            @options = options
            @usecase = use_case_self
          end
          true
        end
      end
    end
  end
end