class Subjects::DataStatisticService < ApplicationService
  attr_reader :subject, :user
  def initialize(subject, user)
    @subject = subject
    @user = user
    @shixun_ids = subject.shixuns.pluck(:id)
  end

  # 学习总人数
  def study_count
    @shixuns.includes(:myshixuns).map{|shixun| shixun.myshixuns.pluck(:user_id)}.uniq
  end

  # 课堂学习人数
  def course_study_count
    # 实训作业
    sw_user_ids = StudentWork.where.not(myshixun_id: nil).joins(homework_common: :homework_commons_shixuns)
                      .where(homework_commons_shixuns: {shixun_id: @shixun_ids}).pluck("student_works.user_id")
    # 试卷的实训题
    esa_user_ids = ExerciseShixunAnswer.joins(exercise_shixun_challenge: :shixun)
                       .where(shixuns: {id: @shixun_ids}).pluck("exercise_shixun_answers.user_id")
  end

end