# Mentorenwahl: A fullstack application for assigning mentors to students based on their whishes.
# Copyright (C) 2022  Dominic Grimm

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

module Backend
  module Api
    module Schema
      # Schema helper macros
      module Helpers
        # Object helpers
        module ObjectMacros
          # Defines field property and GraphQL specific getter
          macro field(type)
            property {{ type.var }} {% if type.value %} = {{ type.value }}{% end %}

            @[GraphQL::Field]
            def {{ type.var }} : {{ type.type }}
              @{{ type.var }}
            end
          end
        end

        # DB model leverage helpers
        module ObjectDbInit
          # Defines a DB model specific initializer
          macro db_init(type)
            def initialize(obj : {{ type }})
              initialize(obj.id.not_nil!)
            end
          end
        end

        # DB model finder helpers
        module ObjectFinders
          # Defines finder
          macro finders(type)
            # Finds object by ID
            def find : {{ type }}?
              {{ type }}.find(@id)
            end

            # :ditto:
            def find! : {{ type }}
              obj = find
              raise "#{{{ type }}} not found" unless obj

              obj
            end
          end
        end

        # DB model field helpers
        module DbObject
          # Defines DB model field helper functions
          macro db_object(type)
            {% space_name = type.names.last.underscore.gsub(/_/, " ").capitalize %}

            include ::Backend::Api::Schema::Helpers::ObjectDbInit
            include ::Backend::Api::Schema::Helpers::ObjectFinders

            db_init {{ type }}
            finders {{ type }}

            property id

            def initialize(@id : Int32)
            end

            def initialize(obj : {{ type }})
              @id = obj.id.not_nil!.to_i
            end

            @[GraphQL::Field]
            # {{ space_name }}'s ID
            def id : Int32
              @id
            end
          end
        end
      end
    end
  end
end