mentorenwahl/backend/src/backend/worker/jobs/assignment_job.cr

# 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 Worker
    module Jobs
      # Assigns students to teachers when all students voted
      class AssignStudentsJob < Mosquito::QueuedJob
        # run_every 1.minute

        def rescheduleable? : Bool
          false
        end

        alias TeacherVote = {student: Int32, priority: Int32}
        alias Assignment = {teacher: Int32, priority: Int32}

        # :ditto:
        def perform : Nil
          teacher_count = Db::Teacher.query.count
          student_count = Db::Student.query.count
          vote_count = Db::Vote.query.count

          if teacher_count == 0
            log "No teachers found, skipping assignment"
            fail
          elsif student_count == 0
            log "No students found, skipping assignment"
            fail
          elsif student_count != Db::User.query.where(role: Db::UserRole::Student).count
            log "Not all students registered, skipping assignment"
            fail
          elsif vote_count < student_count
            log "Not all students voted, skipping assignment"
            fail
          elsif Db::Assignment.query.count > 0
            log "Assignment has already run, skipping another assignment"
            fail
          end

          teachers = Db::Teacher.query
            .where do
              raw("EXISTS (SELECT 1 FROM teacher_votes WHERE teacher_id = teachers.id)") &
                max_students > 0
            end
        end
      end
    end
  end
end