# 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/>.

require "ldap"

module Backend
  module Api
    module Schema
      @[GraphQL::Object]
      class Mutation < GraphQL::BaseMutation
        @[GraphQL::Field]
        # Logs in as *username* with credential *password*
        def login(username : String, password : String) : LoginPayload
          raise "Auth failed" if username.empty? || password.empty?

          user = Db::User.find_by(username: username)
          raise "Auth failed" unless user && Ldap.authenticate?(Ldap.uid(username), password)

          LoginPayload.new(
            user: User.new(user),
            token: Auth.create_user_jwt(
              user.id.not_nil!.to_i,
              (Time.utc + (user.admin ? Time::Span.new(hours: 6) : Time::Span.new(days: 1))).to_unix
            ),
          )
        end

        @[GraphQL::Field]
        # Creates user
        def create_user(context : Context, input : UserCreateInput, check_ldap : Bool = true) : User
          context.admin!

          raise "LDAP user does not exist" if check_ldap && begin
                                                !Ldap.user(Ldap.uid(input.username))
                                              rescue LDAP::Client::AuthError
                                                true
                                              end
          user = Db::User.create!(username: input.username, role: input.role.to_s)

          User.new(user)
        end

        @[GraphQL::Field]
        # Deletes user by ID
        def delete_user(context : Context, id : Int32) : Int32
          context.admin!

          user = Db::User.find!(id)
          user.destroy!

          id
        end

        @[GraphQL::Field]
        # Sends all unregistered teachers a registration email
        def send_teachers_registration_email(context : Context) : Bool
          context.admin!

          Worker::Jobs::SendTeachersRegistrationEmailJob.new.enqueue

          true
        end

        @[GraphQL::Field]
        # Creates teacher
        def create_teacher(context : Context, input : TeacherCreateInput) : Teacher
          context.admin!

          teacher = Db::Teacher.create!(user_id: input.user_id, max_students: input.max_students)
          Teacher.new(teacher)
        end

        @[GraphQL::Field]
        # Deletes teacher by ID
        def delete_teacher(context : Context, id : Int32) : Int32
          context.admin!

          teacher = Db::Teacher.find!(id)
          teacher.destroy!

          id
        end

        @[GraphQL::Field]
        # Self register as teacher
        def register_teacher(context : Context, input : TeacherInput) : Teacher
          context.teacher? external: false

          Teacher.new(
            Db::Teacher.create!(user_id: context.user.not_nil!.id, max_students: input.max_students, skif: input.skif)
          )
        end

        @[GraphQL::Field]
        # Creates student
        def create_student(context : Context, input : StudentCreateInput) : Student
          context.admin!

          user = Db::User.find!(input.user_id)
          raise "User not a student" unless Db::UserRole.parse(user.role).student?

          student = Db::Student.create!(user_id: user.id)
          Student.new(student)
        end

        @[GraphQL::Field]
        # Deletes student by ID
        def delete_student(context : Context, id : Int32) : Int32
          context.admin!

          student = Db::Student.find!(id)
          student.destroy!

          id
        end

        @[GraphQL::Field]
        # Creates vote for authenticated user's student
        def create_vote(context : Context, input : VoteCreateInput) : Vote
          context.student!

          skif = context.external.as(Db::Student).skif
          input.teacher_ids.each do |id|
            teacher = Db::Teacher.find(id)

            if teacher.nil?
              raise "Teachers not found"
            elsif teacher.skif != skif
              if teacher.skif
                raise "Teacher is SKIF, student is not"
              else
                raise "Teacher is not SKIF, student is"
              end
            end
          end

          student = context.external.not_nil!.as(Db::Student)
          vote = Db::Vote.create!(student_id: student.id)
          Db::TeacherVote.import(input.teacher_ids.map_with_index { |id, i| Db::TeacherVote.new(vote_id: vote.id, teacher_id: id.to_i64, priority: i) })

          Vote.new(vote)
        end
      end
    end
  end
end