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

  def call
    return if subject.blank?
    homework_commons =
        HomeworkCommon.joins(:homework_commons_shixun)
            .where(homework_type: %i[practice])
            .where(homework_commons_shixuns: {shixun_id: @shixun_ids})
    course_ids = homework_commons.pluck(:course_id)
    homework_common_ids = homework_commons.pluck("homework_commons.id")
    schools = School.joins(courses: [:course_members, :homework_commons])

    # name：将该课程使用到课堂的单位
    # course_count: 将该课程使用到课堂的数量
    # student_count: 课堂的学生总数（去掉重复）
    # choice_shixun_num: 选用该课程实训的个数（去重）
    # choice_shixun_frequency: 选用该课程实训的次数
    course_info =
        schools.map do |school|
          name = school.name
          course_count = school.where(courses: {id: course_ids}).count
          student_count = school.where(course_members: {role: 4}).select("course_members.user_id").distinct.size
          homework_commons = school.where(homework_commons: {id: homework_common_ids})
                                 .select("homework_commons.id")
          choice_shixun_num = homework_commons.distinct.size
          choice_shixun_frequency = homework_commons.size
          {name: name, course_count: course_count, student_count: student_count, choice_shixun_num: choice_shixun_num,
           choice_shixun_frequency: choice_shixun_frequency}
        end
    # 默认按照选用实训的次数作为排序
    course_info.sort{|x,y| y['choice_shixun_frequency'] <=> x['choice_shixun_frequency']}
  end

end