socialforge/app/controllers/exercise_controller.rb

class ExerciseController < ApplicationController
  layout "base_courses"

  before_filter :find_exercise_and_course, :only => [:create_exercise_question, :edit, :update, :show, :destroy,
                                                        :commit_exercise, :commit_answer,:publish_exercise,:republish_exercise,
                                                        :show_student_result,:student_exercise_list]
  before_filter :find_course, :only => [:index,:new,:create]
  include ExerciseHelper

  def index
    publish_exercises = Exercise.where("publish_time is not null and exercise_status = 1 and publish_time <=?",Time.now)
    publish_exercises.each do |exercise|
      exercise.update_column('exercise_status', 2)
      course = exercise.course
      course.members.each do |m|
        exercise.course_messages << CourseMessage.new(:user_id => m.user_id, :course_id => course.id, :viewed => false, :status => 2)
      end
    end

    if @course.is_public == 0 && !(User.current.member_of_course?(@course)||User.current.admin?)
      render_403
      return
    end
    remove_invalid_exercise(@course)
    @is_teacher = User.current.allowed_to?(:as_teacher,@course)
    if @is_teacher || User.current.admin?
      exercises = @course.exercises.order("created_at asc")
    else
      exercises = @course.exercises.where("exercise_status <> 1").order("created_at asc")
    end
    @exercises = paginateHelper exercises,20 #分页
    respond_to do |format|
      format.html
    end
  end

  def show
    publish_exercises = Exercise.where("publish_time is not null and exercise_status = 1 and publish_time <=?",Time.now)
    publish_exercises.each do |exercise|
      exercise.update_column('exercise_status', 2)
      course = exercise.course
      course.members.each do |m|
        exercise.course_messages << CourseMessage.new(:user_id => m.user_id, :course_id => course.id, :viewed => false, :status => 2)
      end
    end

    unless User.current.member_of_course?(@course) || User.current.admin?
      render_403
      return
    end
    @exercise = Exercise.find params[:id]
    @exercise.course_messages.each do |message|
      if User.current.id == message.user_id && message.viewed == 0
        message.update_attributes(:viewed => true) if message.viewed == 0
      end
    end
    @is_teacher = User.current.allowed_to?(:as_teacher,@course) || User.current.admin?
    exercise_end = @exercise.end_time > Time.now
    if @exercise.time == -1
      @can_edit_excercise = exercise_end
    else
      @can_edit_excercise = !has_commit_exercise?(@exercise.id,User.current.id)&& exercise_end
    end
    unless @is_teacher
      @exercise_user = ExerciseUser.where("user_id=? and exercise_id=?", User.current.id, @exercise.id).first
      if @exercise_user.nil?
        eu = ExerciseUser.create(:user_id => User.current.id, :exercise_id => @exercise.id, :start_at => Time.now, :status => false)
        @exercise_user = ExerciseUser.where("user_id=? and exercise_id=?", User.current.id, @exercise.id).first
      end
      score = calculate_student_score(@exercise, User.current)
      @exercise_user.update_attributes(:score => score)
    end
    # @percent = get_percent(@exercise,User.current)
    @exercise_questions = @exercise.exercise_questions
    respond_to do |format|
      format.html {render :layout => 'base_courses'}
    end
    #end
  end

  def new
    option = {
        :exercise_name => "",
        :course_id => @course.id,
        :exercise_status => 1,
        :user_id => User.current.id,
        :time => "",
        :end_time => "",
        :publish_time => "",
        :exercise_description => "",
        :show_result => 1
    }
    @exercise = Exercise.create option
    if @exercise
      redirect_to edit_exercise_url @exercise.id
    end
  end

  def create
    if params[:exercise]
      exercise = Exercise.find(params[:exercise_id]) if params[:exercise_id]
      exercise ||= Exercise.new
      exercise.exercise_name = params[:exercise][:exercise_name]
      exercise.exercise_description = params[:exercise][:exercise_description]
      exercise.end_time = Time.at(params[:exercise][:end_time].to_time.to_i + 16*60*60 -1)
      exercise.publish_time = params[:exercise][:publish_time]
      exercise.user_id = User.current.id
      exercise.time = params[:exercise][:time]
      exercise.course_id = params[:course_id]
      exercise.exercise_status = 1
      if exercise.save
        @exercise = exercise
        respond_to do |format|
          format.js
        end
      end
    end
  end

  def edit
    respond_to do |format|
      format.html{render :layout => 'base_courses'}
  end
  end

  def update
    @exercise.exercise_name = params[:exercise][:exercise_name]
    @exercise.exercise_description = params[:exercise][:exercise_description]
    @exercise.time =  params[:exercise][:time].blank? ? -1 : params[:exercise][:time]
    @exercise.end_time = Time.at(params[:exercise][:end_time].to_time.to_i + 16*60*60 -1)
    @exercise.publish_time = params[:exercise][:publish_time]
    @exercise.show_result = params[:exercise][:show_result].blank? ? 1 : params[:exercise][:show_result]
    if @exercise.save
      respond_to do |format|
        format.js
      end
    else
      render_404
      end
  end

  def destroy
    @is_teacher = User.current.allowed_to?(:as_teacher,@course) || User.current.admin?
    if @exercise && @exercise.destroy
      if @is_teacher
        exercises = Exercise.where("course_id =?", @course.id)
      else
        exercises = Exercise.where("course_id =? and exercise_status =?", @course.id, 2)
      end
      @exercises = paginateHelper exercises,20 #分页
      respond_to do |format|
        format.js
      end
    end
  end

  # 统计结果
  def statistics_result
    @exercise = Exercise.find(params[:id])
    exercise_questions = @exercise.exercise_questions
    @exercise_questions = paginateHelper exercise_questions, 5
    respond_to do |format|
      format.html{render :layout => 'base_courses'}
    end
  end

  # 添加题目
  # question_type 1：单选 2：多选 3：填空题
  def create_exercise_question
    question_title = params[:question_title].nil? || params[:question_title].empty? ? l(:label_enter_single_title) : params[:question_title]
    option = {
        :question_title => question_title,
        :question_type => params[:question_type] || 1,
        :question_number => params[:question_type] == "1"? @exercise.exercise_questions.where("question_type = 1").count + 1 :
                              (params[:question_type] == "2" ? (@exercise.exercise_questions.where("question_type = 2").count + 1) :
                              @exercise.exercise_questions.where("question_type = 3").count + 1),
        :question_score => params[:question_score]
    }
    @exercise_questions = @exercise.exercise_questions.new option
    # params[:question_answer] 题目选项
    if params[:question_answer]
      for i in 1..params[:question_answer].count
        answer = (params[:question_answer].values[i-1].nil? || params[:question_answer].values[i-1].empty?) ? l(:label_new_answer) : params[:question_answer].values[i-1]
        question_option = {
            :choice_position => i,
            :choice_text => answer
        }
        @exercise_questions.exercise_choices.new question_option
      end
    end
    # 如果是插入的话，那么从插入的这个id以后的question_num都将要+1
    if params[:quest_id]
      @is_insert = true
      if @exercise_questions.question_type == 1
        ExerciseQuestion.where("question_number>? and question_type=?",params[:quest_num].to_i, 1).update_all(" question_number = question_number + 1")
        #@exercise.exercise_questions.where("question_number > #{params[:quest_num].to_i} and question_type == 1").update_all(" question_number = question_number + 1")
      elsif @exercise_questions.question_type == 2
        ExerciseQuestion.where("question_number>? and question_type=?",params[:quest_num].to_i, 2).update_all(" question_number = question_number + 1")
      else
        ExerciseQuestion.where("question_number>? and question_type=?",params[:quest_num].to_i, 3).update_all(" question_number = question_number + 1")
      end
      # @exercise_question_num = params[:quest_num].to_i
      @exercise_questions.question_number = params[:quest_num].to_i + 1
    end
    if @exercise_questions.save
      # params[:exercise_choice] 标准答案参数
      # 问答题标准答案有三个，单独处理
      if @exercise_questions.question_type == 3
        for i in 1..params[:exercise_choice].count
          standart_answer = ExerciseStandardAnswer.new
          standart_answer.exercise_question_id =  @exercise_questions.id
          standart_answer.answer_text = params[:exercise_choice].values[i-1]
          standart_answer.save
        end
      else
        standart_answer = ExerciseStandardAnswer.new
        standart_answer.exercise_question_id =  @exercise_questions.id
        if  @exercise_questions.question_type == 1
          standart_answer.exercise_choice_id = sigle_selection_standard_answer(params[:exercise_choice])
        else
          standart_answer.exercise_choice_id = multiselect_standard_answer(params[:exercise_choice])
        end
        standart_answer.save
      end
      respond_to do |format|
        format.js
      end
    end

  end

  # 修改题目
  # params[:exercise_question]  The id of exercise_question
  # params[:question_answer]  eg:A、B、C选项
  def update_exercise_question
    @exercise_question = ExerciseQuestion.find params[:exercise_question]
    @exercise_question.question_title = params[:question_title].nil? || params[:question_title].empty? ? l(:label_enter_single_title) : params[:question_title]
    @exercise_question.question_score = params[:question_score]
    # 处理选项:如果选了某个选项，那么则要删除之前的选项
    if params[:question_answer]
      @exercise_question.exercise_choices.each do |answer|
        answer.destroy unless params[:question_answer].keys.include? answer.id.to_s
      end
      for i in 1..params[:question_answer].count
        question = @exercise_question.exercise_choices.find_by_id params[:question_answer].keys[i-1]
        answer = (params[:question_answer].values[i-1].nil? || params[:question_answer].values[i-1].empty?) ? l(:label_new_answer) : params[:question_answer].values[i-1]
        if question
          question.choice_position = i
          question.choice_text = answer
          question.save
        else
          question_option = {
              :choice_position => i,
              :choice_text => answer
          }
          @exercise_question.exercise_choices.new question_option
        end
      end
    end
    # 更新标准答案
    if params[:exercise_choice]
      if @exercise_question.question_type == 3
        # 删除不合理的选项
        @exercise_question.exercise_standard_answers.each do |answer|
          answer.destroy unless params[:exercise_choice].keys.include? answer.id.to_s
        end
        for i in 1..params[:exercise_choice].count
          # 找到对应的标准答案
          question_standart = @exercise_question.exercise_standard_answers.find_by_id params[:exercise_choice].keys[i-1]
          # 标准答案值
          answer_standart = (params[:exercise_choice].values[i-1].nil? || params[:exercise_choice].values[i-1].empty?) ? l(:label_new_answer) : params[:exercise_choice].values[i-1]
          if question_standart
            question_standart.answer_text = answer_standart
            question_standart.save
          else
            standart_answer_option = {
                :answer_text => answer_standart
            }
            @exercise_question.exercise_standard_answers.new standart_answer_option
          end
        end
      else
        answer_standart = @exercise_question.exercise_standard_answers.first
        answer_standart.exercise_choice_id = @exercise_question.question_type == 1 ? sigle_selection_standard_answer(params[:exercise_choice]) : multiselect_standard_answer(params[:exercise_choice])
        answer_standart.save
      end
      @exercise_question.save
      respond_to do |format|
        format.js
      end
    end
  end

  # 删除题目
  def delete_exercise_question
    @exercise_question = ExerciseQuestion.find params[:exercise_question]
    @exercise = @exercise_question.exercise

    if @exercise_question.question_type == 1
      ExerciseQuestion.where("question_number>? and question_type=?",params[:quest_num].to_i, 1).update_all(" question_number = question_number - 1")
      #@exercise.exercise_questions.where("question_number > #{params[:quest_num].to_i} and question_type == 1").update_all(" question_number = question_number + 1")
    elsif @exercise_question.question_type == 2
      ExerciseQuestion.where("question_number>? and question_type=?",params[:quest_num].to_i, 2).update_all(" question_number = question_number - 1")
    else
      ExerciseQuestion.where("question_number>? and question_type=?",params[:quest_num].to_i, 3).update_all(" question_number = question_number - 1")
    end
    # @exercise_question_num = params[:quest_num].to_i
    # @exercise_questions.question_number = params[:quest_num].to_i - 1
    #
    # exercise_questions = @exercise.exercise_questions.where("question_number > #{@exercise_question.question_number}")
    # exercise_questions.each do |question|
    #   question.question_number -= 1
    #   question.save
    # end
    if @exercise_question && @exercise_question.destroy
      respond_to do |format|
        format.js
      end
    end
  end

  # 发布试卷
  def publish_exercise
    @is_teacher = User.current.allowed_to?(:as_teacher,@course)
    @index = params[:index]
    @exercise.exercise_status = 2
    @exercise.publish_time = Time.now
    if @exercise.save
      @exercise.course.members.each do |m|
         @exercise.course_messages << CourseMessage.create(:user_id =>m.user_id, :course_id => @exercise.course.id, :viewed => false,:status=>2)
      end
      #redirect_to exercise_index_url(:course_id=> @course.id)
      respond_to do |format|
        format.js
      end
    end
  end

  # 重新发布试卷
  # 重新发布的时候会删除所有的答题
  def republish_exercise
    @is_teacher = User.current.allowed_to?(:as_teacher,@course)
    @index = params[:index]
    @exercise.exercise_questions.each do |exercise_question|
      exercise_question.exercise_answers.destroy_all
    end
    @exercise.course_messages.destroy_all
    @exercise.exercise_users.destroy_all
    @exercise.exercise_status = 1
    @exercise.publish_time = nil
    @exercise.save
    respond_to do |format|
      format.js
    end
  end

  def student_exercise_list
=begin
    if @exercise.end_time <= Time.now
      @course.student.each do |student|
        if ExerciseUser.where("user_id = ? && exercise_id = ?",student.student_id,@exercise.id).empty?
          ExerciseUser.create(:user_id => student.student_id, :exercise_id => @exercise.id, :start_at => @exercise.end_time, :status => true,:score=>0)
        end

        s_score = calculate_student_score(@exercise, student.student)
        exercise_user = ExerciseUser.where("user_id =? and exercise_id=?", student.student_id, @exercise.id).first
        exercise_user.update_attributes(:score => s_score)
      end
    end
=end
    @is_teacher = User.current.allowed_to?(:as_teacher,@course) || User.current.admin?
    @all_exercises = @course.exercises.where("exercise_status > 1").order("created_at desc")
    @exercise_count = @exercise.exercise_users.where('score is not NULL').count
    if @is_teacher || (!@exercise.exercise_users.where(:user_id => User.current.id).empty? && @exercise.end_time <= Time.now)
      @exercise_users_list = @exercise.exercise_users.where('score is not NULL')
      @show_all = true;
    elsif !@exercise.exercise_users.where(:user_id => User.current.id).empty? && @exercise.end_time > Time.now
      @exercise_users_list = @exercise.exercise_users.where("user_id = ? and score is not NULL",User.current.id)
    else
      @exercise_users_list = []
    end
    respond_to do |format|
      format.html
      format.xls {
        filename = "#{@course.teacher.lastname.to_s + @course.teacher.firstname}_#{@course.name}_#{@course.time.to_s + @course.term}_#{@exercise.exercise_name}#{l(:excel_exercise_list)}.xls"
        send_data(exercise_to_xls(@exercise_users_list), :type => "text/excel;charset=utf-8; header=present",
                  :filename => filename_for_content_disposition(filename))
      }
    end
  end

  # 学生提交答卷，选中答案的过程中提交
  def commit_answer
    eq = ExerciseQuestion.find(params[:exercise_question_id])
    # 已提交过的且是限时的则不允许答题
    if (has_commit_exercise?(@exercise.id,User.current.id) && (!User.current.admin?) && @exercise.time != -1) || @exercise.end_time < Time.now
      render :json => {:text => "failure"}
      return
    end
    if eq.question_type == 1
      # 单选题
      ea = ExerciseAnswer.find_by_exercise_question_id_and_user_id(params[:exercise_question_id],User.current.id)
      if ea.nil?
        # 尚未答该题，添加答案
        ea = ExerciseAnswer.new
        ea.user_id = User.current.id
        ea.exercise_question_id = params[:exercise_question_id]
      end
      #修改该题对应答案
      ea.exercise_choice_id = params[:exercise_choice_id]
      if ea.save
        # 保存成功返回成功信息及当前以答题百分比
        uncomplete_question = get_uncomplete_question(@exercise, User.current)
        if uncomplete_question.count < 1
          complete = 1;
        else
          complete = 0;
        end
        @percent = get_percent(@exercise,User.current)
        render :json => {:text => "ok" ,:complete => complete,:percent => format("%.2f" ,@percent)}
      else
        #返回失败信息
        render :json => {:text => "failure"}
      end
    elsif eq.question_type == 2
      #多选题
      ea = ExerciseAnswer.find_by_exercise_choice_id_and_user_id(params[:exercise_choice_id],User.current.id)
      if ea.nil?
        #尚未答该题，添加答案
        ea = ExerciseAnswer.new
        ea.user_id = User.current.id
        ea.exercise_question_id = params[:exercise_question_id]
        ea.exercise_choice_id = params[:exercise_choice_id]
        if ea.save
          uncomplete_question = get_uncomplete_question(@exercise, User.current)
          if uncomplete_question.count < 1
            complete = 1;
          else
            complete = 0;
          end
          @percent = get_percent(@exercise,User.current)
          render :json => {:text => "ok",:complete => complete,:percent => format("%.2f" ,@percent)}
        else
          render :json => {:text => "failure"}
        end
      else
        #pv不为空，则当前选项之前已被选择，再次点击则是不再选择该项，故删除该答案
        if ea.delete
          @percent = get_percent(@exercise, User.current)
          render :json => {:text => "false" ,:percent => format("%.2f" , @percent)}
        else
          render :json => {:text => "failure"}
        end
      end
    elsif eq.question_type == 3
      #单行文本，多行文本题
      ea = ExerciseAnswer.find_by_exercise_question_id_and_user_id(params[:exercise_question_id], User.current.id)
      if ea.nil?
        # ea为空之前尚未答题，添加答案
        if params[:answer_text].nil? || params[:answer_text].blank?
          #用户提交空答案，视作不作答
          @percent = get_percent(@exercise,User.current)
          render :json => {:text => "",:percent => format("%.2f", @percent)}
        else
          #添加答案
          ea = ExerciseAnswer.new
          ea.user_id = User.current.id
          ea.exercise_question_id = params[:exercise_question_id]
          ea.answer_text = params[:answer_text]
          if ea.save
            uncomplete_question = get_uncomplete_question(@exercise, User.current)
            if uncomplete_question.count < 1
              complete = 1;
            else
              complete = 0;
            end
            @percent = get_percent(@exercise,User.current)
            render :json => {:text => ea.answer_text,:complete => complete,:percent => format("%.2f",@percent)}
          else
            render :json => {:text => "failure"}
          end
        end
      else
        # ea不为空说明用户之前已作答
        if params[:answer_text].nil? || params[:answer_text].blank?
          # 用户提交空答案，视为删除答案
          if ea.delete
            @percent = get_percent(@exercise,User.current)
            render :json => {:text => "",:percent => format("%.2f", @percent)}
          else
            render :json => {:text => "failure"}
          end
        else
          #用户修改答案
          ea.answer_text = params[:answer_text]
          if ea.save
            @percent = get_percent(@exercise,User.current)
            render :json => {:text => ea.answer_text,:percent => format("%.2f", @percent)}
          else
            render :json => {:text => "failure"}
          end
        end
      end

    else
      render :json => {:text => "failure"}
    end
  end

  # 提交问卷
  def commit_exercise
    # 老师不需要提交
    if User.current.allowed_to?(:as_teacher,@course)
      if @exercise.publish_time.nil?
        @exercise.update_attributes(:show_result => params[:show_result])
        @exercise.update_attributes(:exercise_status => 2)
        @exercise.update_attributes(:publish_time => Time.now)
        course = @exercise.course
        course.members.each do |m|
          @exercise.course_messages << CourseMessage.new(:user_id => m.user_id, :course_id => course.id, :viewed => false, :status => 2)
        end
        redirect_to exercise_url(@exercise)
        return
      elsif @exercise.publish_time > Time.now
        @exercise.update_attributes(:show_result => params[:show_result])
        redirect_to exercise_url(@exercise)
        return
      end
      @exercise.update_attributes(:show_result => params[:show_result])
      redirect_to exercise_url(@exercise)
      # REDO: 提示提交成功
    else
      # 更新提交状态
      cur_exercise_user = ExerciseUser.where("user_id =? and exercise_id=?", User.current, @exercise.id).first
      cur_exercise_user.update_attributes(:status => 1)
      # 答题过程中需要统计完成量
      @uncomplete_question = get_uncomplete_question(@exercise, User.current)
      # 获取改学生的考试得分
      @score = calculate_student_score(@exercise, User.current)
      # @score = 100
      if @uncomplete_question.count < 1
        # 查看是否有已提交记录
        cur_exercise_user.score = @score
        if cur_exercise_user.save
        #redirect_to poll_index_path(:polls_group_id => @course.id,:polls_type => 'Course')
          @status = 0 #提交成功
        else
          @status = 2 #未知错误
        end
      else
        @status = 1 #有未做得必答题
      end
      @save = params[:save].to_i if params[:save]
      respond_to do |format|
        format.js
      end
    end
  end

  #查看学生的答卷情况
  def show_student_result
    @user = User.find params[:user_id]
    @can_edit_excercise = false
    @exercise_questions = @exercise.exercise_questions
    score = calculate_student_score(@exercise, @user)
    eu = get_exercise_user(@exercise.id, @user.id)
    eu.update_attributes(:score => score)
    @exercise_user = ExerciseUser.where("user_id =? and exercise_id=?", @user.id, @exercise.id).first
    respond_to do |format|
      format.html {render :layout => 'base_courses'}
    end
  end

  # 计算学生得分
  def calculate_student_score(exercise, user)
    score = 0
    score1 = 0
    score2 = 0
    score3 = 0
    exercise_qustions = exercise.exercise_questions
    exercise_qustions.each do |question|
      answer = get_user_answer(question, user)
      standard_answer = get_user_standard_answer(question, user)
      unless answer.empty?
        # 问答题有多个答案
        if question.question_type == 3 && !standard_answer.empty?
          if standard_answer.include?(answer.first.answer_text)
            score1 = score1+ question.question_score unless question.question_score.nil?
          end
        elsif question.question_type == 1 && !standard_answer.nil?
          if answer.first.exercise_choice.choice_position == standard_answer.exercise_choice_id
            score2 = score2 + question.question_score unless question.question_score.nil?
          end
        elsif question.question_type == 2 && !standard_answer.nil?
          arr = get_mulscore(question, user)
          if arr.to_i == standard_answer.exercise_choice_id
            score3 = score3 + question.question_score unless question.question_score.nil?
          end
          # ecs = ExerciseAnswer.where("user_id =? and exercise_question_id =?", user.id, question.id)
          # arr = []
          # ecs.each do |ec|
          #   arr << ec.exercise_choice.choice_position
          # end
          # arr.sort
          # arr = arr.join("")
          # if arr.to_i == standard_answer.exercise_choice_id
          #   score3 = score + question.question_score unless question.question_score.nil?
          # end
        end
      end
    end
    score = score1 + score2 + score3
  end

  private
  #测验列表转换为excel
  def exercise_to_xls items
    xls_report = StringIO.new
    book = Spreadsheet::Workbook.new
    sheet1 = book.create_worksheet :name => "exercise"
    blue = Spreadsheet::Format.new :color => :blue, :weight => :bold, :size => 10
    sheet1.row(0).default_format = blue
    sheet1.row(0).concat([l(:excel_user_id),l(:excel_user_name),l(:excel_nickname),l(:excel_student_id),l(:excel_mail),l(:excel_class),l(:excel_f_score),l(:excel_commit_time)])
    count_row = 1
    items.each do |exercise|
      sheet1[count_row,0]=exercise.user.id
      sheet1[count_row,1] = exercise.user.lastname.to_s + exercise.user.firstname.to_s
      sheet1[count_row,2] = exercise.user.login
      sheet1[count_row,3] = exercise.user.user_extensions.student_id
      sheet1[count_row,4] = exercise.user.mail
      sheet1[count_row,5] = ""
      sheet1[count_row,6] = exercise.score
      sheet1[count_row,7] = format_time(exercise.created_at)
      count_row += 1
    end
    book.write xls_report
    xls_report.string
  end

  # ExerciseUser记录用户是否已提交问卷有对应的记录则已提交，没有则新建一个
  def get_exercise_user exercise_id,user_id
    eu = ExerciseUser.find_by_exercise_id_and_user_id(exercise_id,user_id)
    if eu.nil?
      eu = ExerciseUser.new
    end
    eu
  end

  # 获取当前学生回答问题的答案
  def get_user_answer(question,user)
    # user_answer = ExerciseAnswer.where("user_id=? and exercise_question_id=?", user.id, question.id).first
    user_answer = question.exercise_answers.where("#{ExerciseAnswer.table_name}.user_id = #{user.id}")
    user_answer
  end

  # 获取问题的标准答案
  def get_user_standard_answer(question,user)
    if question.question_type == 3
      standard_answer =[]
      question.exercise_standard_answers.each do |answer|
        standard_answer << answer.answer_text
      end
    else
      standard_answer = question.exercise_standard_answers.first
    end
    standard_answer
  end
  # 是否完成了答题
  def get_complete_question(exercise,user)
    questions = exercise.exercise_questions
    complete_question = []
    questions.each do |question|
      answers = get_user_answer(question,user)
      if !(answers.nil? || answers.count < 1)
        complete_question << question
      end
    end
    complete_question
  end

  # 获取答题百分比
  def get_percent exercise,user
    complete_count = get_complete_question(exercise,user).count
    if exercise.exercise_questions.count == 0
      return 0
    else
      return (complete_count.to_f / exercise.exercise_questions.count.to_f)*100
    end
  end

  def remove_invalid_exercise(course)
    exercises = course.exercises.where("exercise_name=?","")
    unless exercises.empty?
      exercises.each do |exercise|
        if exercise.exercise_questions.empty?
          exercise.destroy
        end
      end
    end
  end

  def find_exercise_and_course
    @exercise = Exercise.find params[:id]
    @course = Course.find @exercise.course_id
  rescue Exception => e
    render_404
  end

  def find_course
    @course = Course.find params[:course_id]
  rescue Exception => e
    render_404
  end
end