diff --git a/Gemfile b/Gemfile
--- a/Gemfile
+++ b/Gemfile
@@ -59,15 +59,16 @@
 #syntax highlighter
 gem 'rouge'
 
-#add bootstrap
+#bootstrap add-ons
 gem 'bootstrap-sass', '~> 3.2.0'
 gem 'bootstrap-switch-rails'
 gem 'bootstrap-toggle-rails'
 gem 'autoprefixer-rails'
-
-#bootstrap sortable
 gem 'momentjs-rails'
 gem 'rails_bootstrap_sortable'
+gem 'bootstrap-datepicker-rails'
+gem 'bootstrap3-datetimepicker-rails'
+gem 'jquery-datatables-rails'
 
 #----------- user interface -----------------
 #select 2
diff --git a/Gemfile.lock b/Gemfile.lock
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -61,10 +61,14 @@
     best_in_place (3.0.3)
       actionpack (>= 3.2)
       railties (>= 3.2)
+    bootstrap-datepicker-rails (1.7.1.1)
+      railties (>= 3.0)
     bootstrap-sass (3.2.0.2)
       sass (~> 3.2)
     bootstrap-switch-rails (3.3.3)
     bootstrap-toggle-rails (2.2.1.0)
+    bootstrap3-datetimepicker-rails (4.17.47)
+      momentjs-rails (>= 2.8.1)
     builder (3.2.2)
     coffee-rails (4.2.1)
       coffee-script (>= 2.2.0)
@@ -97,6 +101,11 @@
     i18n (0.7.0)
     in_place_editing (1.2.0)
     jquery-countdown-rails (2.0.2)
+    jquery-datatables-rails (3.4.0)
+      actionpack (>= 3.1)
+      jquery-rails
+      railties (>= 3.1)
+      sass-rails
     jquery-rails (4.2.1)
       rails-dom-testing (>= 1, < 3)
       railties (>= 4.2.0)
@@ -201,9 +210,11 @@
   activerecord-session_store
   autoprefixer-rails
   best_in_place (~> 3.0.1)
+  bootstrap-datepicker-rails
   bootstrap-sass (~> 3.2.0)
   bootstrap-switch-rails
   bootstrap-toggle-rails
+  bootstrap3-datetimepicker-rails
   coffee-rails
   dynamic_form
   fuzzy-string-match
@@ -211,6 +222,7 @@
   haml-rails
   in_place_editing
   jquery-countdown-rails
+  jquery-datatables-rails
   jquery-rails
   jquery-tablesorter
   jquery-timepicker-addon-rails
@@ -232,4 +244,4 @@
   yaml_db
 
 BUNDLED WITH
-   1.13.6
+   1.15.4
diff --git a/app/assets/javascripts/application.js b/app/assets/javascripts/application.js
--- a/app/assets/javascripts/application.js
+++ b/app/assets/javascripts/application.js
@@ -12,10 +12,14 @@
 //
 //= require jquery
 //= require jquery_ujs
+//= require dataTables/jquery.dataTables
+//= require dataTables/bootstrap/3/jquery.dataTables.bootstrap
 //= require jquery-ui
 //= require bootstrap-sprockets
 //= require moment
+//= require moment/th
 //= require bootstrap-sortable
+//= require bootstrap-datetimepicker
 //= require select2
 //= require ace-rails-ap
 //= require ace/mode-c_cpp
@@ -32,6 +36,8 @@
 //= require best_in_place
 //= require best_in_place.jquery-ui
 //= require brython
+//= require bootstrap-datepicker
+//= require bootstrap-datetimepicker
 
 // since this is after blank line, it is not downloaded
 //x= require prototype
diff --git a/app/assets/javascripts/groups.js.coffee b/app/assets/javascripts/groups.js.coffee
new file mode 100644
diff --git a/app/assets/javascripts/tags.coffee b/app/assets/javascripts/tags.coffee
new file mode 100644
--- /dev/null
+++ b/app/assets/javascripts/tags.coffee
@@ -0,0 +1,3 @@
+# Place all the behaviors and hooks related to the matching controller here.
+# All this logic will automatically be available in application.js.
+# You can use CoffeeScript in this file: http://coffeescript.org/
diff --git a/app/assets/javascripts/testcases.js.coffee b/app/assets/javascripts/testcases.js.coffee
new file mode 100644
diff --git a/app/assets/stylesheets/application.css.scss b/app/assets/stylesheets/application.css.scss
--- a/app/assets/stylesheets/application.css.scss
+++ b/app/assets/stylesheets/application.css.scss
@@ -33,6 +33,9 @@
 //@import bootstrap3-switch
 @import "bootstrap-toggle";
 @import "bootstrap-sortable";
+@import "bootstrap-datepicker3";
+@import "bootstrap-datetimepicker";
+@import "dataTables/bootstrap/3/jquery.dataTables.bootstrap";
 
 //bootstrap navbar color (from)
 $bgDefault: #19197b;
@@ -546,3 +549,9 @@
   margin-top: 5px;
   margin-bottom: 5px;
 }
+
+
+
+.grader-comment {
+  word-wrap: break-word;
+}
diff --git a/app/assets/stylesheets/groups.css.scss b/app/assets/stylesheets/groups.css.scss
new file mode 100644
diff --git a/app/assets/stylesheets/tags.scss b/app/assets/stylesheets/tags.scss
new file mode 100644
--- /dev/null
+++ b/app/assets/stylesheets/tags.scss
@@ -0,0 +1,3 @@
+// Place all the styles related to the tags controller here.
+// They will automatically be included in application.css.
+// You can use Sass (SCSS) here: http://sass-lang.com/
diff --git a/app/assets/stylesheets/testcases.css.scss b/app/assets/stylesheets/testcases.css.scss
new file mode 100644
diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -39,13 +39,10 @@
 
   def testcase_authorization
     #admin always has privileged
-    puts "haha"
     if @current_user.admin?
       return true
     end
 
-    puts "hehe"
-    puts GraderConfiguration["right.view_testcase"]
     unauthorized_redirect unless GraderConfiguration["right.view_testcase"]
   end
 
@@ -61,27 +58,28 @@
       return false
     end
 
+
     # check if run in single user mode
     if GraderConfiguration[SINGLE_USER_MODE_CONF_KEY]
-      user = User.find_by_id(session[:user_id])
-      if user==nil or (not user.admin?)
+      if @current_user==nil or (not @current_user.admin?)
         flash[:notice] = 'You cannot log in at this time'
         redirect_to :controller => 'main', :action => 'login'
         return false
       end
-      unless user.enabled?
-        flash[:notice] = 'Your account is disabled'
-        redirect_to :controller => 'main', :action => 'login'
-        return false
-      end
       return true
     end
 
+    # check if the user is enabled
+    unless @current_user.enabled? or @current_user.admin?
+      flash[:notice] = 'Your account is disabled'
+      redirect_to :controller => 'main', :action => 'login'
+      return false
+    end
+
     if GraderConfiguration.multicontests? 
-      user = User.find(session[:user_id])
-      return true if user.admin?
+      return true if @current_user.admin?
       begin
-        if user.contest_stat(true).forced_logout
+        if @current_user.contest_stat(true).forced_logout
           flash[:notice] = 'You have been automatically logged out.'
           redirect_to :controller => 'main', :action => 'index'
         end
diff --git a/app/controllers/graders_controller.rb b/app/controllers/graders_controller.rb
--- a/app/controllers/graders_controller.rb
+++ b/app/controllers/graders_controller.rb
@@ -1,22 +1,6 @@
 class GradersController < ApplicationController
 
-  before_filter :admin_authorization, except: [ :submission ]
-  before_filter(only: [:submission]) {
-    #check if authenticated
-    return false unless authenticate
-
-    #admin always has privileged
-    if @current_user.admin?
-      return true
-    end
-
-    if GraderConfiguration["right.user_view_submission"] and Submission.find(params[:id]).problem.available?
-      return true
-    else
-      unauthorized_redirect
-      return false
-    end
-  }
+  before_filter :admin_authorization
 
   verify :method => :post, :only => ['clear_all', 
                                      'start_exam',
@@ -77,25 +61,6 @@
     @task = Task.find(params[:id])
   end
 
-  def submission
-    @submission = Submission.find(params[:id])
-    formatter = Rouge::Formatters::HTML.new(css_class: 'highlight', line_numbers: true )
-    lexer = case @submission.language.name
-      when "c"      then Rouge::Lexers::C.new
-      when "cpp"    then Rouge::Lexers::Cpp.new
-      when "pas"    then Rouge::Lexers::Pas.new
-      when "ruby"   then Rouge::Lexers::Ruby.new
-      when "python" then Rouge::Lexers::Python.new
-      when "java"   then Rouge::Lexers::Java.new
-      when "php"    then Rouge::Lexers::PHP.new
-    end
-    @formatted_code = formatter.format(lexer.lex(@submission.source))
-    @css_style = Rouge::Themes::ThankfulEyes.render(scope: '.highlight')
-
-    user = User.find(session[:user_id])
-    SubmissionViewLog.create(user_id: session[:user_id],submission_id: @submission.id) unless user.admin?
-
-  end
 
   # various grader controls
 
diff --git a/app/controllers/groups_controller.rb b/app/controllers/groups_controller.rb
new file mode 100644
--- /dev/null
+++ b/app/controllers/groups_controller.rb
@@ -0,0 +1,104 @@
+class GroupsController < ApplicationController
+  before_action :set_group, only: [:show, :edit, :update, :destroy,
+                                   :add_user, :remove_user,:remove_all_user,
+                                   :add_problem, :remove_problem,:remove_all_problem,
+                                  ]
+  before_action :authenticate, :admin_authorization
+
+  # GET /groups
+  def index
+    @groups = Group.all
+  end
+
+  # GET /groups/1
+  def show
+  end
+
+  # GET /groups/new
+  def new
+    @group = Group.new
+  end
+
+  # GET /groups/1/edit
+  def edit
+  end
+
+  # POST /groups
+  def create
+    @group = Group.new(group_params)
+
+    if @group.save
+      redirect_to @group, notice: 'Group was successfully created.'
+    else
+      render :new
+    end
+  end
+
+  # PATCH/PUT /groups/1
+  def update
+    if @group.update(group_params)
+      redirect_to @group, notice: 'Group was successfully updated.'
+    else
+      render :edit
+    end
+  end
+
+  # DELETE /groups/1
+  def destroy
+    @group.destroy
+    redirect_to groups_url, notice: 'Group was successfully destroyed.'
+  end
+
+  def remove_user
+    user = User.find(params[:user_id])
+    @group.users.delete(user)
+    redirect_to group_path(@group), flash: {success: "User #{user.login} was removed from the group #{@group.name}"}
+  end
+
+  def remove_all_user
+    @group.users.clear
+    redirect_to group_path(@group), alert: 'All users removed'
+  end
+
+  def remove_all_problem
+    @group.problems.clear
+    redirect_to group_path(@group), alert: 'All problems removed'
+  end
+
+  def add_user
+    user = User.find(params[:user_id])
+    begin
+      @group.users << user
+      redirect_to group_path(@group), flash: { success: "User #{user.login} was add to the group #{@group.name}"}
+    rescue => e
+      redirect_to group_path(@group), alert: e.message
+    end
+  end
+
+  def remove_problem
+    problem = Problem.find(params[:problem_id])
+    @group.problems.delete(problem)
+    redirect_to group_path(@group), flash: {success: "Problem #{problem.name} was removed from the group #{@group.name}" }
+  end
+
+  def add_problem
+    problem = Problem.find(params[:problem_id])
+    begin
+      @group.problems << problem
+      redirect_to group_path(@group), flash: {success: "Problem #{problem.name} was add to the group #{@group.name}" }
+    rescue => e
+      redirect_to group_path(@group), alert: e.message
+    end
+  end
+
+  private
+    # Use callbacks to share common setup or constraints between actions.
+    def set_group
+      @group = Group.find(params[:id])
+    end
+
+    # Only allow a trusted parameter "white list" through.
+    def group_params
+      params.require(:group).permit(:name, :description)
+    end
+end
diff --git a/app/controllers/login_controller.rb b/app/controllers/login_controller.rb
--- a/app/controllers/login_controller.rb
+++ b/app/controllers/login_controller.rb
@@ -7,32 +7,38 @@
   end
 
   def login
-    if (!GraderConfiguration['right.bypass_agreement']) and (!params[:accept_agree])
+    user = User.authenticate(params[:login], params[:password])
+    unless user
+      flash[:notice] = 'Wrong password'
+      redirect_to :controller => 'main', :action => 'login'
+      return
+    end
+
+    if (!GraderConfiguration['right.bypass_agreement']) and (!params[:accept_agree]) and !user.admin?
       flash[:notice] = 'You must accept the agreement before logging in'
       redirect_to :controller => 'main', :action => 'login'
-    elsif user = User.authenticate(params[:login], params[:password])
-      session[:user_id] = user.id
-      session[:admin] = user.admin?
+      return
+    end
+
+    #process logging in
+    session[:user_id] = user.id
+    session[:admin] = user.admin?
 
-      # clear forced logout flag for multicontests contest change
-      if GraderConfiguration.multicontests?
-        contest_stat = user.contest_stat
-        if contest_stat.respond_to? :forced_logout
-          if contest_stat.forced_logout
-            contest_stat.forced_logout = false
-            contest_stat.save
-          end
+    # clear forced logout flag for multicontests contest change
+    if GraderConfiguration.multicontests?
+      contest_stat = user.contest_stat
+      if contest_stat.respond_to? :forced_logout
+        if contest_stat.forced_logout
+          contest_stat.forced_logout = false
+          contest_stat.save
         end
       end
-
-      #save login information
-      Login.create(user_id: user.id, ip_address: request.remote_ip)
+    end
 
-      redirect_to :controller => 'main', :action => 'list'
-    else
-      flash[:notice] = 'Wrong password'
-      redirect_to :controller => 'main', :action => 'login'
-    end
+    #save login information
+    Login.create(user_id: user.id, ip_address: request.remote_ip)
+
+    redirect_to :controller => 'main', :action => 'list'
   end
 
   def site_login
diff --git a/app/controllers/main_controller.rb b/app/controllers/main_controller.rb
--- a/app/controllers/main_controller.rb
+++ b/app/controllers/main_controller.rb
@@ -86,7 +86,7 @@
       render :action => 'list' and return
     end
 
-    if @submission.valid?
+    if @submission.valid?(@current_user)
       if @submission.save == false
         flash[:notice] = 'Error saving your submission'
       elsif Task.create(:submission_id => @submission.id, 
@@ -97,7 +97,7 @@
       prepare_list_information
       render :action => 'list' and return
     end
-    redirect_to :action => 'list'
+    redirect_to edit_submission_path(@submission)
   end
 
   def source
diff --git a/app/controllers/problems_controller.rb b/app/controllers/problems_controller.rb
--- a/app/controllers/problems_controller.rb
+++ b/app/controllers/problems_controller.rb
@@ -165,7 +165,7 @@
       redirect_to :controller => 'main', :action => 'list'
       return
     end
-    @submissions = Submission.includes(:user).where(problem_id: params[:id]).order(:user_id,:id)
+    @submissions = Submission.includes(:user).includes(:language).where(problem_id: params[:id]).order(:user_id,:id)
 
     #stat summary
     range =65
@@ -195,7 +195,26 @@
       set_available(true)
     elsif params.has_key? 'disable_problem'
       set_available(false)
+    elsif params.has_key? 'add_group'
+      group = Group.find(params[:group_id])
+      ok = []
+      failed = []
+      get_problems_from_params.each do |p|
+        begin
+          group.problems << p
+          ok << p.full_name
+        rescue => e
+          failed << p.full_name
+        end
+      end
+      flash[:success] = "The following problems are added to the group #{group.name}: " + ok.join(', ') if ok.count > 0
+      flash[:alert] = "The following problems are already in the group #{group.name}: " + failed.join(', ') if failed.count > 0
+    elsif params.has_key? 'add_tags'
+      get_problems_from_params.each do |p|
+        p.tag_ids += params[:tag_ids]
+      end
     end
+
     redirect_to :action => 'manage'
   end
 
@@ -243,10 +262,7 @@
 
   def change_date_added
     problems = get_problems_from_params
-    year = params[:date_added][:year].to_i
-    month = params[:date_added][:month].to_i
-    day = params[:date_added][:day].to_i
-    date = Date.new(year,month,day)
+    date = Date.parse(params[:date_added])
     problems.each do |p|
       p.date_added = date
       p.save
@@ -288,7 +304,7 @@
   private
 
     def problem_params
-      params.require(:problem).permit(:name, :full_name, :full_score, :date_added, :available, :test_allowed,:output_only, :url, :description)
+      params.require(:problem).permit(:name, :full_name, :full_score, :date_added, :available, :test_allowed,:output_only, :url, :description, tag_ids:[])
     end
 
 end
diff --git a/app/controllers/report_controller.rb b/app/controllers/report_controller.rb
--- a/app/controllers/report_controller.rb
+++ b/app/controllers/report_controller.rb
@@ -52,6 +52,8 @@
     #set up range from param
     @since_id = params.fetch(:from_id, 0).to_i
     @until_id = params.fetch(:to_id, 0).to_i
+    @since_id = nil if @since_id == 0
+    @until_id = nil if @until_id == 0
 
     #calculate the routine
     @scorearray = calculate_max_score(@problems, @users, @since_id, @until_id)
diff --git a/app/controllers/submissions_controller.rb b/app/controllers/submissions_controller.rb
--- a/app/controllers/submissions_controller.rb
+++ b/app/controllers/submissions_controller.rb
@@ -1,6 +1,6 @@
 class SubmissionsController < ApplicationController
   before_action :authenticate
-  before_action :submission_authorization, only: [:show, :direct_edit_submission, :download, :edit]
+  before_action :submission_authorization, only: [:show, :download, :edit]
   before_action :admin_authorization, only: [:rejudge]
 
   # GET /submissions
@@ -51,7 +51,15 @@
   #on-site new submission on specific problem
   def direct_edit_problem
     @problem = Problem.find(params[:problem_id])
+    unless @current_user.can_view_problem?(@problem)
+      unauthorized_redirect
+      return
+    end
     @source = ''
+    if (params[:view_latest])
+      sub = Submission.find_last_by_user_and_problem(@current_user.id,@problem.id)
+      @source = @submission.source.to_s if @submission and @submission.source
+    end
     render 'edit'
   end
 
@@ -94,8 +102,7 @@
     end
 
     sub = Submission.find(params[:id])
-    if sub.problem.available?
-      puts "sub = #{sub.user.id}, current = #{@current_user.id}"
+    if @current_user.available_problems.include? sub.problem
       return true if GraderConfiguration["right.user_view_submission"] or sub.user == @current_user
     end
 
diff --git a/app/controllers/tags_controller.rb b/app/controllers/tags_controller.rb
new file mode 100644
--- /dev/null
+++ b/app/controllers/tags_controller.rb
@@ -0,0 +1,60 @@
+class TagsController < ApplicationController
+  before_action :set_tag, only: [:show, :edit, :update, :destroy]
+
+  # GET /tags
+  def index
+    @tags = Tag.all
+  end
+
+  # GET /tags/1
+  def show
+  end
+
+  # GET /tags/new
+  def new
+    @tag = Tag.new
+  end
+
+  # GET /tags/1/edit
+  def edit
+  end
+
+  # POST /tags
+  def create
+    @tag = Tag.new(tag_params)
+
+    if @tag.save
+      redirect_to @tag, notice: 'Tag was successfully created.'
+    else
+      render :new
+    end
+  end
+
+  # PATCH/PUT /tags/1
+  def update
+    if @tag.update(tag_params)
+      redirect_to @tag, notice: 'Tag was successfully updated.'
+    else
+      render :edit
+    end
+  end
+
+  # DELETE /tags/1
+  def destroy
+    #remove any association
+    ProblemTag.where(tag_id: @tag.id).destroy_all
+    @tag.destroy
+    redirect_to tags_url, notice: 'Tag was successfully destroyed.'
+  end
+
+  private
+    # Use callbacks to share common setup or constraints between actions.
+    def set_tag
+      @tag = Tag.find(params[:id])
+    end
+
+    # Only allow a trusted parameter "white list" through.
+    def tag_params
+      params.require(:tag).permit(:name, :description, :public)
+    end
+end
diff --git a/app/controllers/tasks_controller.rb b/app/controllers/tasks_controller.rb
--- a/app/controllers/tasks_controller.rb
+++ b/app/controllers/tasks_controller.rb
@@ -26,7 +26,7 @@
   # this has problem-level access control
   def download
     problem = Problem.find(params[:id])
-    if !problem or !problem.available or !@user.can_view_problem? problem
+    unless @current_user.can_view_problem? problem
       redirect_to :action => 'index' and return
     end
 
diff --git a/app/controllers/user_admin_controller.rb b/app/controllers/user_admin_controller.rb
--- a/app/controllers/user_admin_controller.rb
+++ b/app/controllers/user_admin_controller.rb
@@ -24,6 +24,7 @@
       @users = User.paginate :page => params[:page]
       @paginated = true
     end
+    @users = User.all
     @hidden_columns = ['hashed_password', 'salt', 'created_at', 'updated_at']
     @contests = Contest.enabled
   end
@@ -228,6 +229,7 @@
     end
   end
 
+
   # contest management
 
   def contests
@@ -411,7 +413,7 @@
   def bulk_manage
 
     begin 
-      @users = User.where('login REGEXP ?',params[:regex]) if params[:regex]
+      @users = User.where('(login REGEXP ?) OR (remark REGEXP ?)',params[:regex],params[:regex]) if params[:regex]
       @users.count if @users #i don't know why I have to call count, but if I won't exception is not raised
     rescue Exception
       flash[:error] = 'Regular Expression is malformed'
@@ -423,6 +425,8 @@
       @action[:set_enable] = params[:enabled]
       @action[:enabled] = params[:enable] == "1"
       @action[:gen_password] = params[:gen_password]
+      @action[:add_group] = params[:add_group]
+      @action[:group_name] = params[:group_name]
     end
 
     if params[:commit] == "Perform"
@@ -437,6 +441,21 @@
           u.save
         end
       end
+      if @action[:add_group] and @action[:group_name]
+        @group = Group.find(@action[:group_name])
+        ok = []
+        failed = []
+        @users.each do |user|  
+          begin
+            @group.users << user
+            ok << user.login
+          rescue => e
+            failed << user.login
+          end
+        end
+        flash[:success] = "The following users are added to the 'group #{@group.name}': " + ok.join(', ') if ok.count > 0
+        flash[:alert] = "The following users are already in the 'group #{@group.name}': " + failed.join(', ') if failed.count > 0
+      end
     end
   end
 
diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -85,11 +85,10 @@
   end
 
   def format_short_time(time)
-    now = Time.now.gmtime
+    now = Time.zone.now
     st = ''
-    if (time.yday != now.yday) or
-	(time.year != now.year)
-      st = time.strftime("%x ")
+    if (time.yday != now.yday) or (time.year != now.year)
+      st = time.strftime("%d/%m/%y ")
     end
     st + time.strftime("%X")
   end
@@ -100,6 +99,10 @@
     return Time.at(d).gmtime.strftime("%X")
   end
 
+  def format_full_time_ago(time)
+    st = time_ago_in_words(time) + ' ago (' + format_short_time(time) + ')'
+  end
+
   def read_textfile(fname,max_size=2048)
     begin
       File.open(fname).read(max_size)
@@ -200,7 +203,7 @@
   BOOTSTRAP_FLASH_MSG = {
     success: 'alert-success',
     error: 'alert-danger',
-    alert: 'alert-block',
+    alert: 'alert-danger',
     notice: 'alert-info'
   }
 
diff --git a/app/helpers/groups_helper.rb b/app/helpers/groups_helper.rb
new file mode 100644
--- /dev/null
+++ b/app/helpers/groups_helper.rb
@@ -0,0 +1,2 @@
+module GroupsHelper
+end
diff --git a/app/helpers/tags_helper.rb b/app/helpers/tags_helper.rb
new file mode 100644
--- /dev/null
+++ b/app/helpers/tags_helper.rb
@@ -0,0 +1,2 @@
+module TagsHelper
+end
diff --git a/app/models/grader_configuration.rb b/app/models/grader_configuration.rb
--- a/app/models/grader_configuration.rb
+++ b/app/models/grader_configuration.rb
@@ -12,6 +12,7 @@
   MULTIPLE_IP_LOGIN_KEY = 'right.multiple_ip_login'
   VIEW_TESTCASE = 'right.view_testcase'
   SINGLE_USER_KEY = 'system.single_user_mode'
+  SYSTEM_USE_PROBLEM_GROUP = 'system.use_problem_group'
 
   cattr_accessor :config_cache
   cattr_accessor :task_grading_info_cache
@@ -119,6 +120,10 @@
   def self.analysis_mode?
     return get(SYSTEM_MODE_CONF_KEY) == 'analysis'
   end
+
+  def self.use_problem_group?
+    return get(SYSTEM_USE_PROBLEM_GROUP)
+  end
   
   def self.contest_time_limit
     contest_time_str = GraderConfiguration[CONTEST_TIME_LIMIT_KEY]
diff --git a/app/models/group.rb b/app/models/group.rb
new file mode 100644
--- /dev/null
+++ b/app/models/group.rb
@@ -0,0 +1,13 @@
+class Group < ActiveRecord::Base
+  has_many :groups_problems, class_name: GroupProblem
+  has_many :problems, :through => :groups_problems
+
+  has_many :groups_users, class_name: GroupUser
+  has_many :users, :through => :groups_users
+
+  #has_and_belongs_to_many :problems
+  #has_and_belongs_to_many :users
+
+
+end
+
diff --git a/app/models/group_problem.rb b/app/models/group_problem.rb
new file mode 100644
--- /dev/null
+++ b/app/models/group_problem.rb
@@ -0,0 +1,7 @@
+class GroupProblem < ActiveRecord::Base
+  self.table_name = 'groups_problems'
+  
+  belongs_to :problem
+  belongs_to :group
+  validates_uniqueness_of :problem_id, scope: :group_id, message: ->(object, data) { "'#{Problem.find(data[:value]).full_name}' is already in the group" }
+end
diff --git a/app/models/group_user.rb b/app/models/group_user.rb
new file mode 100644
--- /dev/null
+++ b/app/models/group_user.rb
@@ -0,0 +1,7 @@
+class GroupUser < ActiveRecord::Base
+  self.table_name = 'groups_users'
+
+  belongs_to :user
+  belongs_to :group
+  validates_uniqueness_of :user_id, scope: :group_id, message: ->(object, data) { "'#{User.find(data[:value]).full_name}' is already in the group" }
+end
diff --git a/app/models/problem.rb b/app/models/problem.rb
--- a/app/models/problem.rb
+++ b/app/models/problem.rb
@@ -2,6 +2,14 @@
 
   belongs_to :description
   has_and_belongs_to_many :contests, :uniq => true
+
+  #has_and_belongs_to_many :groups
+  has_many :groups_problems, class_name: GroupProblem
+  has_many :groups, :through => :groups_problems
+
+  has_many :problems_tags, class_name: ProblemTag
+  has_many :tags, through: :problems_tags
+
   has_many :test_pairs, :dependent => :delete_all
   has_many :testcases, :dependent => :destroy
 
diff --git a/app/models/problem_tag.rb b/app/models/problem_tag.rb
new file mode 100644
--- /dev/null
+++ b/app/models/problem_tag.rb
@@ -0,0 +1,8 @@
+class ProblemTag < ActiveRecord::Base
+  self.table_name = 'problems_tags'
+
+  belongs_to :problem
+  belongs_to :tag
+
+  validates_uniqueness_of :problem_id, scope: :tag_id, message: ->(object, data) { "'#{Problem.find(data[:value]).full_name}' is already has this tag" }
+end
diff --git a/app/models/submission.rb b/app/models/submission.rb
--- a/app/models/submission.rb
+++ b/app/models/submission.rb
@@ -34,8 +34,8 @@
 
   def self.find_in_range_by_user_and_problem(user_id, problem_id,since_id,until_id)
     records = Submission.where(problem_id: problem_id,user_id: user_id)
-    records = records.where('id >= ?',since_id) if since_id > 0
-    records = records.where('id <= ?',until_id) if until_id > 0
+    records = records.where('id >= ?',since_id) if since_id and since_id > 0
+    records = records.where('id <= ?',until_id) if until_id and until_id > 0
     records.all
   end
 
@@ -137,7 +137,7 @@
 
     # for output_only tasks
     return if self.problem!=nil and self.problem.output_only
-    
+
     if self.language==nil
       errors.add('source',"Cannot detect language. Did you submit a correct source file?") unless self.language!=nil
     end
@@ -147,8 +147,12 @@
     return if self.source==nil
     if self.problem==nil
       errors.add('problem',"must be specified.")
-    elsif (!self.problem.available) and (self.new_record?)
-      errors.add('problem',"must be valid.")
+    else
+      #admin always have right
+      return if self.user.admin?
+
+      #check if user has the right to submit the problem
+      errors.add('problem',"must be valid.") if (!self.user.available_problems.include?(self.problem)) and (self.new_record?)
     end
   end
 
diff --git a/app/models/tag.rb b/app/models/tag.rb
new file mode 100644
--- /dev/null
+++ b/app/models/tag.rb
@@ -0,0 +1,4 @@
+class Tag < ActiveRecord::Base
+  has_many :problems_tags, class_name: ProblemTag
+  has_many :problems, through: :problems_tags
+end
diff --git a/app/models/user.rb b/app/models/user.rb
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -8,6 +8,10 @@
 
   has_and_belongs_to_many :roles
 
+  #has_and_belongs_to_many :groups
+  has_many :groups_users, class_name: GroupUser
+  has_many :groups, :through => :groups_users
+
   has_many :test_requests, -> {order(submitted_at: DESC)}
 
   has_many :messages, -> { order(created_at: DESC) },
@@ -240,9 +244,14 @@
     return true
   end
 
+  #get a list of available problem
   def available_problems
     if not GraderConfiguration.multicontests?
-      return Problem.available_problems
+      if GraderConfiguration.use_problem_group?
+        return available_problems_in_group
+      else
+        return Problem.available_problems
+      end
     else
       contest_problems = []
       pin = {}
@@ -259,12 +268,32 @@
     end
   end
 
+  def available_problems_in_group
+    problem = []
+    self.groups.each do |group|
+      group.problems.where(available: true).each { |p| problem << p }
+    end
+    problem.uniq!
+    if problem
+      problem.sort! do |a,b|
+        case
+        when a.date_added < b.date_added
+          1
+        when a.date_added > b.date_added
+          -1
+        else
+          a.name <=> b.name
+        end
+      end
+      return problem
+    else
+      return []
+    end
+  end
+
   def can_view_problem?(problem)
-    if not GraderConfiguration.multicontests?
-      return problem.available
-    else
-      return problem_in_user_contests? problem
-    end
+    return true if admin?
+    return available_problems.include? problem
   end
 
   def self.clear_last_login
diff --git a/app/views/announcements/show.html.erb b/app/views/announcements/show.html.erb
--- a/app/views/announcements/show.html.erb
+++ b/app/views/announcements/show.html.erb
@@ -15,7 +15,7 @@
 
 <p>
   <b>Body:</b>
-  <%=h @announcement.body %>
+  <%=h markdown(@announcement.body) %>
 </p>
 
 <p>
diff --git a/app/views/application/_submission_short.html.haml b/app/views/application/_submission_short.html.haml
--- a/app/views/application/_submission_short.html.haml
+++ b/app/views/application/_submission_short.html.haml
@@ -1,13 +1,15 @@
-
 - if submission.nil?
   = "-"
 - else
+  %strong= "Submission ID:"
+  = submission.id
+  %br
   - unless submission.graded_at
-    = t 'main.submitted_at'
-    = format_short_time(submission.submitted_at.localtime)
+    %strong= t 'main.submitted_at:'
+    = format_full_time_ago(submission.submitted_at.localtime)
   - else
-    %strong= t 'main.graded_at'
-    = "#{format_short_time(submission.graded_at.localtime)} "
+    %strong= t 'main.graded_at:'
+    = format_full_time_ago(submission.graded_at.localtime)
     %br
     - if GraderConfiguration['ui.show_score']
       %strong=t 'main.score'
@@ -17,10 +19,10 @@
       = submission.grader_comment
     = "]"
     %br
-    %strong View:
-    - if GraderConfiguration.show_grading_result
-      = link_to '[detailed result]', :action => 'result', :id => submission.id
-    = link_to "#{t 'main.cmp_msg'}", {:action => 'compiler_msg', :id => submission.id}, {popup: true,class: 'btn btn-xs btn-info'}
+  %strong View:
+  - if GraderConfiguration.show_grading_result
+    = link_to '[detailed result]', :action => 'result', :id => submission.id
+  = link_to "#{t 'main.cmp_msg'}", {:action => 'compiler_msg', :id => submission.id}, {popup: true,class: 'btn btn-xs btn-info'} if submission.graded_at
   = link_to "#{t 'main.src_link'}", download_submission_path(submission.id), class: 'btn btn-xs btn-info'
   = link_to "#{t 'main.submissions_link'}", problem_submissions_path(problem_id), class: 'btn btn-xs btn-info'
 
diff --git a/app/views/contests/edit.html.erb b/app/views/contests/edit.html.erb
deleted file mode 100644
--- a/app/views/contests/edit.html.erb
+++ /dev/null
@@ -1,29 +0,0 @@
-<h1>Editing contest</h1>
-
-<%= form_for(@contest) do |f| %>
-  <%= f.error_messages %>
-
-  <table>
-    <tr>
-      <td><%= f.label :name %></td>
-      <td><%= f.text_field :name %></td>
-    </tr>
-    <tr>
-      <td><%= f.label :title %></td>
-      <td><%= f.text_field :title %></td>
-    </tr>
-    <tr>
-      <td></td>
-      <td>
-	<%= f.check_box :enabled %>
-	<%= f.label :enabled %>
-      </td>
-    </tr>
-  </table>
-  <p>
-    <%= f.submit 'Update' %>
-  </p>
-<% end %>
-
-<%= link_to 'Show', @contest %> |
-<%= link_to 'Back', contests_path %>
diff --git a/app/views/contests/edit.html.haml b/app/views/contests/edit.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/contests/edit.html.haml
@@ -0,0 +1,20 @@
+%h1 Editing contest
+= form_for(@contest) do |f|
+  = f.error_messages
+  %table
+    %tr
+      %td= f.label :name
+      %td= f.text_field :name
+    %tr
+      %td= f.label :title
+      %td= f.text_field :title
+    %tr
+      %td
+      %td
+        = f.check_box :enabled
+        = f.label :enabled
+  %p
+    = f.submit 'Update'
+= link_to 'Show', @contest
+|
+= link_to 'Back', contests_path
diff --git a/app/views/contests/index.html.erb b/app/views/contests/index.html.erb
deleted file mode 100644
--- a/app/views/contests/index.html.erb
+++ /dev/null
@@ -1,29 +0,0 @@
-<h1>Listing contests</h1>
-
-<div class="infobox">
-  <b>Go back to:</b> [<%= link_to 'contest management', :controller => 'contest_management', :action => 'index' %>]
-</div>
-
-<table>
-  <tr>
-    <th>Name</th>
-    <th>Title</th>
-    <th>Enabled</th> 
-  </tr>
-
-<% @contests.each do |contest| %>
-  <% @contest = contest %>
-  <tr>
-    <td><%= in_place_editor_field :contest, :name, {}, :rows => 1 %></td>
-    <td><%= in_place_editor_field :contest, :title, {}, :rows => 1 %></td>
-    <td><%= in_place_editor_field :contest, :enabled, {}, :rows => 1 %></td>
-    <td><%= link_to 'Show', contest %></td>
-    <td><%= link_to 'Edit', edit_contest_path(contest) %></td>
-    <td><%= link_to 'Destroy', contest, :confirm => 'Are you sure?', :method => :delete %></td>
-  </tr>
-<% end %>
-</table>
-
-<br />
-
-<%= link_to 'New contest', new_contest_path %>
diff --git a/app/views/contests/index.html.haml b/app/views/contests/index.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/contests/index.html.haml
@@ -0,0 +1,27 @@
+%h1 Listing contests
+.infobox
+  %b Go back to:
+  [#{link_to 'contest management', :controller => 'contest_management', :action => 'index'}]
+%p= link_to 'New contest', new_contest_path, class: 'btn btn-success'
+%table.table.table-striped
+  %tr
+    %th Name
+    %th Title
+    %th Enabled
+    %th
+    %th
+    %th
+
+  - @contests.each do |contest|
+    - @contest = contest
+    %tr
+      -#%td= in_place_editor_field :contest, :name, {}, :rows => 1
+      -#%td= in_place_editor_field :contest, :title, {}, :rows => 1
+      -#%td= in_place_editor_field :contest, :enabled, {}, :rows => 1
+      %td= best_in_place @contest, :name
+      %td= best_in_place @contest, :title
+      %td= best_in_place @contest, :enabled
+      %td= link_to 'Show', contest
+      %td= link_to 'Edit', edit_contest_path(contest)
+      %td= link_to 'Destroy', contest, :confirm => 'Are you sure?', :method => :delete
+%br/
diff --git a/app/views/contests/new.html.erb b/app/views/contests/new.html.erb
deleted file mode 100644
--- a/app/views/contests/new.html.erb
+++ /dev/null
@@ -1,23 +0,0 @@
-<h1>New contest</h1>
-
-<%= form_for(@contest) do |f| %>
-  <%= f.error_messages %>
-
-  <p>
-    <%= f.label :name %><br />
-    <%= f.text_field :name %>
-  </p>
-  <p>
-    <%= f.label :title %><br />
-    <%= f.text_field :title %>
-  </p>
-  <p>
-    <%= f.label :enabled %><br />
-    <%= f.check_box :enabled %>
-  </p>
-  <p>
-    <%= f.submit 'Create' %>
-  </p>
-<% end %>
-
-<%= link_to 'Back', contests_path %>
diff --git a/app/views/contests/new.html.haml b/app/views/contests/new.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/contests/new.html.haml
@@ -0,0 +1,18 @@
+%h1 New contest
+= form_for(@contest) do |f|
+  = f.error_messages
+  %p
+    = f.label :name
+    %br/
+    = f.text_field :name
+  %p
+    = f.label :title
+    %br/
+    = f.text_field :title
+  %p
+    = f.label :enabled
+    %br/
+    = f.check_box :enabled
+  %p
+    = f.submit 'Create'
+= link_to 'Back', contests_path
diff --git a/app/views/contests/show.html.erb b/app/views/contests/show.html.erb
deleted file mode 100644
--- a/app/views/contests/show.html.erb
+++ /dev/null
@@ -1,14 +0,0 @@
-<h1>Contest: <%=h @contest.title %></h1>
-
-<div class="infobox">
-  <b>Go back to:</b> [<%= link_to 'contest management', :controller => 'contest_management', :action => 'index' %>]
-</div>
-
-<p>
-  <b>Enabled:</b>
-  <%=h @contest.enabled %>
-</p>
-
-
-<%= link_to 'Edit', edit_contest_path(@contest) %> |
-<%= link_to 'Back', contests_path %>
diff --git a/app/views/contests/show.html.haml b/app/views/contests/show.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/contests/show.html.haml
@@ -0,0 +1,11 @@
+%h1
+  Contest: #{h @contest.title}
+.infobox
+  %b Go back to:
+  [#{link_to 'contest management', :controller => 'contest_management', :action => 'index'}]
+%p
+  %b Enabled:
+  = h @contest.enabled
+= link_to 'Edit', edit_contest_path(@contest)
+|
+= link_to 'Back', contests_path
diff --git a/app/views/graders/submission.html.haml b/app/views/graders/submission.html.haml
deleted file mode 100644
--- a/app/views/graders/submission.html.haml
+++ /dev/null
@@ -1,87 +0,0 @@
-%h1= "Submission: #{@submission.id}"
-
-%textarea#data{style: "display:none;"}
-  :preserve
-    #{@submission.source}
-
-//%div.highlight{:style => "border: 1px solid black;"}
-//=@formatted_code.html_safe
-.containter
-  .row
-    .col-md-7
-      %h2 Source Code
-    .col-md-5
-      %h2 Stat
-  .row
-    .col-md-7
-      %div#editor{ style: "font-size: 14px; height: 400px; border-radius:5px;" }
-      :javascript
-        e = ace.edit("editor")
-        e.setOptions({ maxLines: Infinity })
-        e.setValue($("#data").text())
-        e.gotoLine(1)
-        e.getSession().setMode("#{get_ace_mode(@submission.language)}")
-        e.setReadOnly(true)
-    .col-md-5
-      %table.table.table-striped
-        %tr
-          %td.text-right
-            %strong User
-          %td
-            - if @submission.user 
-              = link_to "(#{@submission.user.login})", controller: "users", action: "profile", id: @submission.user
-              = @submission.user.full_name
-            - else
-              = "(n/a)"
-        %tr
-          %td.text-right
-            %strong Task
-          %td
-            - if @submission.problem!=nil
-              = link_to "(#{@submission.problem.name})", controller: "problems", action: "stat", id: @submission.problem
-              = @submission.problem.full_name
-            - else
-              = "(n/a)"
-        %tr
-          %td.text-right
-            %strong Tries
-          %td= @submission.number
-        %tr
-          %td.text-right
-            %strong Language
-          %td= @submission.language.pretty_name
-        %tr
-          %td.text-right
-            %strong Submitted
-          %td #{time_ago_in_words(@submission.submitted_at)} ago (at #{@submission.submitted_at.to_formatted_s(:long)})
-        %tr
-          %td.text-right
-            %strong Graded
-          - if @submission.graded_at
-            %td #{time_ago_in_words(@submission.graded_at)} ago (at #{@submission.graded_at.to_formatted_s(:long)})
-          - else
-            %td -
-        %tr
-          %td.text-right
-            %strong Points
-          %td #{@submission.points}/#{@submission.problem.full_score}
-        %tr
-          %td.text-right
-            %strong Comment
-          %td #{@submission.grader_comment}
-        %tr
-          %td.text-right
-            %strong Runtime (s)
-          %td #{@submission.max_runtime}
-        %tr
-          %td.text-right
-            %strong Memory (kb)
-          %td #{@submission.peak_memory}
-        - if session[:admin]
-          %tr
-            %td.text-right
-              %strong IP
-            %td #{@submission.ip_address}
-
-
-
diff --git a/app/views/graders/task.html.haml b/app/views/graders/task.html.haml
--- a/app/views/graders/task.html.haml
+++ b/app/views/graders/task.html.haml
@@ -9,7 +9,7 @@
   %br/
   = "Submission: #{@task.submission_id}"
   - if @task.submission !=nil
-    = link_to '[view submission]', :action => 'submission', :id => @task.submission.id
+    = link_to '[view submission]', submission_path( @task.submission.id )
   %br/
   = "Submitted at: #{format_short_time(@task.created_at)}"
   %br/
diff --git a/app/views/groups/_form.html.haml b/app/views/groups/_form.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/groups/_form.html.haml
@@ -0,0 +1,16 @@
+= form_for @group do |f|
+  - if @group.errors.any?
+    #error_explanation
+      %h2= "#{pluralize(@group.errors.count, "error")} prohibited this group from being saved:"
+      %ul
+        - @group.errors.full_messages.each do |msg|
+          %li= msg
+
+  .form-group.field
+    = f.label :name
+    = f.text_field :name, class: 'form-control'
+  .form-group.field
+    = f.label :description
+    = f.text_field :description, class: 'form-control'
+  .form-group.actions
+    = f.submit 'Save', class: 'btn btn-primary'
diff --git a/app/views/groups/edit.html.haml b/app/views/groups/edit.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/groups/edit.html.haml
@@ -0,0 +1,7 @@
+%h1 Editing group
+
+= render 'form'
+
+= link_to 'Show', @group
+\|
+= link_to 'Back', groups_path
diff --git a/app/views/groups/index.html.haml b/app/views/groups/index.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/groups/index.html.haml
@@ -0,0 +1,22 @@
+%h1 Groups
+
+%p
+  = link_to 'New Group', new_group_path, class: 'btn btn-primary'
+%table.table.table-hover
+  %thead
+    %tr
+      %th Name
+      %th Description
+      %th
+      %th
+
+  %tbody
+    - @groups.each do |group|
+      %tr
+        %td= group.name
+        %td= group.description
+        %td= link_to 'View', group, class: 'btn btn-default'
+        %td= link_to 'Destroy', group, :method => :delete, :data => { :confirm => 'Are you sure?' }, class: 'btn btn-danger'
+
+%br
+
diff --git a/app/views/groups/new.html.haml b/app/views/groups/new.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/groups/new.html.haml
@@ -0,0 +1,5 @@
+%h1 New group
+
+= render 'form'
+
+= link_to 'Back', groups_path
diff --git a/app/views/groups/show.html.haml b/app/views/groups/show.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/groups/show.html.haml
@@ -0,0 +1,73 @@
+%p
+  %b Name:
+  = @group.name
+%p
+  %b Description:
+  = @group.description
+
+%br
+= link_to 'Edit', edit_group_path(@group)
+\|
+= link_to 'Back', groups_path
+
+.row
+  .col-md-12
+    %h1 Group details
+.row
+  .col-md-6
+    .panel.panel-default
+      .panel-heading
+        .panel-title Users in this group
+      .panel-body
+        =form_tag add_user_group_path(@group), class: 'form-inline' do
+          .form-group
+            =label_tag :user_id, "User"
+            =select_tag :user_id, options_from_collection_for_select(User.all,'id','full_name'), class: 'select2'
+          =submit_tag "Add",class: 'btn btn-primary'
+
+
+        %table.table.table-hover
+          %thead
+            %tr
+              %th Login
+              %th Full name
+              %th Remark
+              %th= link_to 'Remove All', remove_all_user_group_path(@group), method: :delete, :data => { :confirm => "Remove ALL USERS from group?" }, class: 'btn btn-danger btn-sm'
+
+          %tbody
+            - @group.users.each do |user|
+              %tr
+                %td= user.login
+                %td= user.full_name
+                %td= user.remark
+                %td= link_to 'Remove', remove_user_group_path(@group,user), :method => :delete, :data => { :confirm => "Remove #{user.full_name}?" }, class: 'btn btn-danger btn-sm'
+  .col-md-6
+    .panel.panel-default
+      .panel-heading
+        .panel-title Problems
+      .panel-body
+
+        =form_tag add_problem_group_path(@group), class: 'form-inline' do
+          .form-group
+            =label_tag :problem_id, "Problem"
+            =select_tag :problem_id, options_from_collection_for_select(Problem.all,'id','full_name'), class: 'select2'
+          =submit_tag "Add",class: 'btn btn-primary'
+
+
+        %table.table.table-hover
+          %thead
+            %tr
+              %th name
+              %th Full name
+              %th Full score
+              %th= link_to 'Remove All', remove_all_problem_group_path(@group), method: :delete, :data => { :confirm => "Remove ALL PROBLEMS from group?" }, class: 'btn btn-danger btn-sm'
+
+          %tbody
+            - @group.problems.each do |problem|
+              %tr
+                %td= problem.name
+                %td= problem.full_name
+                %td= problem.full_score
+                %td= link_to 'Remove', remove_problem_group_path(@group,problem), :method => :delete, :data => { :confirm => "Remove #{problem.full_name}?" }, class: 'btn btn-danger btn-sm'
+
+
diff --git a/app/views/layouts/_header.html.haml b/app/views/layouts/_header.html.haml
--- a/app/views/layouts/_header.html.haml
+++ b/app/views/layouts/_header.html.haml
@@ -46,7 +46,9 @@
               %ul.dropdown-menu
                 = add_menu( 'Announcements', 'announcements', 'index')
                 = add_menu( 'Problems', 'problems', 'index')
+                = add_menu( 'Tags', 'tags', 'index')
                 = add_menu( 'Users', 'user_admin', 'index')
+                = add_menu( 'User Groups', 'groups', 'index')
                 = add_menu( 'Graders', 'graders', 'list')
                 = add_menu( 'Message ', 'messages', 'console')
                 %li.divider{role: 'separator'}
diff --git a/app/views/main/_login_box.html.haml b/app/views/main/_login_box.html.haml
--- a/app/views/main/_login_box.html.haml
+++ b/app/views/main/_login_box.html.haml
@@ -12,22 +12,26 @@
     %hr/
 
   %div{ :style => "border: solid 1px gray; padding: 4px; background: #eeeeff;"}
-    = form_tag login_login_path do
-      %table
-        %tr
-          %td{:align => "right"} 
-            ="#{t 'login_label'}:"
-          %td= text_field_tag 'login'
-        %tr
-          %td{:align => "right"} 
-            ="#{t 'password_label'}:"
-          %td= password_field_tag
-        - unless GraderConfiguration['right.bypass_agreement']
-          %tr
-            %td{:align => "right"}= check_box_tag 'accept_agree'
-            %td ยอมรับข้อตกลงการใช้งาน
-        
-      = submit_tag t('login.login_submit')
+    = form_tag login_login_path, {class: 'form-horizontal'} do
+      .form-group
+        =label_tag :login, "Login",class: 'col-sm-3 control-label'
+        .col-sm-9
+          =text_field_tag :login, nil, class: 'form-control'
+      .form-group
+        =label_tag :password, "Password", class: 'col-sm-3 control-label'
+        .col-sm-9
+          =password_field_tag :password, nil, class: 'form-control'
+      - unless GraderConfiguration['right.bypass_agreement']
+        .form-group
+          .col-sm-offset-3.col-sm-9
+            .checkbox
+              %label
+                = check_box_tag 'accept_agree'
+                ยอมรับข้อตกลงการใช้งาน
+
+      .form-group
+        .col-sm-offset-3.col-sm-9
+          = submit_tag t('login.login_submit'), class: 'btn btn-primary'
 %br/
 
 - if GraderConfiguration['system.online_registration']
diff --git a/app/views/main/_problem.html.haml b/app/views/main/_problem.html.haml
--- a/app/views/main/_problem.html.haml
+++ b/app/views/main/_problem.html.haml
@@ -11,7 +11,7 @@
     = link_to_description_if_any "[#{t 'main.problem_desc'}] <span class='glyphicon glyphicon-file'></span>".html_safe, problem
   %td
     = @prob_submissions[problem.id][:count]
-    = link_to "[subs]", main_submission_path(problem.id)
+    -#= link_to "[subs]", main_submission_path(problem.id)
   %td
     = render :partial => 'submission_short',
       :locals => {:submission => @prob_submissions[problem.id][:submission], :problem_name => problem.name, :problem_id => problem.id }
diff --git a/app/views/main/_submission_short.html.haml b/app/views/main/_submission_short.html.haml
--- a/app/views/main/_submission_short.html.haml
+++ b/app/views/main/_submission_short.html.haml
@@ -13,7 +13,7 @@
       %strong=t 'main.score'
       = "#{(submission.points*100/submission.problem.full_score).to_i} "
     = " [" 
-    %tt
+    %tt.grader-comment
       = submission.grader_comment
     = "]"
     %br
diff --git a/app/views/main/login.html.haml b/app/views/main/login.html.haml
--- a/app/views/main/login.html.haml
+++ b/app/views/main/login.html.haml
@@ -1,12 +1,11 @@
 %h1= GraderConfiguration['ui.front.title']
 
-%table
-  %tr
-    %td
-      - if @announcements.length!=0
-        .announcementbox{:style => 'margin-top: 0px'}
-          %span{:class => 'title'}
-            Announcements
-          = render :partial => 'announcement', :collection => @announcements
-    %td{:style => 'vertical-align: top; width: 40%; padding-left: 20px;'}
-      = render :partial => 'login_box'
+.row
+  .col-md-6
+    - if @announcements.length!=0
+      .announcementbox{:style => 'margin-top: 0px'}
+        %span{:class => 'title'}
+          Announcements
+        = render :partial => 'announcement', :collection => @announcements
+  .col-md-4{style: "padding-left: 20px;"}
+    = render :partial => 'login_box'
diff --git a/app/views/problems/_form.html.haml b/app/views/problems/_form.html.haml
--- a/app/views/problems/_form.html.haml
+++ b/app/views/problems/_form.html.haml
@@ -12,6 +12,9 @@
   %label{:for => "problem_full_score"} Full score
   = text_field 'problem', 'full_score', class: 'form-control'
 .form-group
+  %label{:for => "problem_full_score"} Tags
+  = collection_select(:problem, :tag_ids, Tag.all, :id, :name,  {}, {multiple: true, class: 'form-control select2'})
+.form-group
   %label{:for => "problem_date_added"} Date added
   = date_select 'problem', 'date_added', class: 'form-control'
 - # TODO: these should be put in model Problem, but I can't think of
diff --git a/app/views/problems/index.html.haml b/app/views/problems/index.html.haml
--- a/app/views/problems/index.html.haml
+++ b/app/views/problems/index.html.haml
@@ -1,10 +1,10 @@
 - content_for :head do
   = stylesheet_link_tag 'problems'
-%h1 Listing problems
+%h1 Problems
 %p
-  = link_to 'New problem', new_problem_path, class: 'btn btn-default btn-sm'
-  = link_to 'Manage problems', { action: 'manage'}, class: 'btn btn-default btn-sm'
-  = link_to 'Import problems', {:action => 'import'}, class: 'btn btn-default btn-sm'
+  = link_to 'Import problems', {:action => 'import'}, class: 'btn btn-success btn-sm'
+  = link_to 'New problem', new_problem_path, class: 'btn btn-success btn-sm'
+  = link_to 'Bulk Manage', { action: 'manage'}, class: 'btn btn-info btn-sm'
   = link_to 'Turn off all problems', {:action => 'turn_all_off'}, class: 'btn btn-default btn-sm'
   = link_to 'Turn on all problems', {:action => 'turn_all_on'}, class: 'btn btn-default btn-sm'
 .submitbox
@@ -21,6 +21,10 @@
     %th Name
     %th Full name
     %th.text-right Full score
+    %th Tags
+    %th 
+      Submit
+      %sup{class: 'text-primary',data: {toggle: 'tooltip'}, title: 'Admin can always submit to any problem' } [?]
     %th Date added
     %th.text-center
       Avail?
@@ -37,8 +41,15 @@
     %tr{:class => "#{(problem.available) ? "success" : "danger"}", :id => "prob-#{problem.id}", :name => "prob-#{problem.id}"}
       - @problem=problem
       %td= problem.name #in_place_editor_field :problem, :name, {}, :rows=>1
-      %td= problem.full_name #in_place_editor_field :problem, :full_name, {}, :rows=>1
+      %td
+        = problem.full_name #in_place_editor_field :problem, :full_name, {}, :rows=>1
+        = link_to_description_if_any "[#{t 'main.problem_desc'}] <span class='glyphicon glyphicon-file'></span>".html_safe, problem
       %td.text-right= problem.full_score #in_place_editor_field :problem, :full_score, {}, :rows=>1
+      %td
+        - problem.tags.each do |t|
+          - #%button.btn.btn-default.btn-xs= t.name
+          %span.label.label-default= t.name
+      %td= link_to "Submit", direct_edit_problem_submissions_path(problem,@current_user.id), class: 'btn btn-xs btn-primary'
       %td= problem.date_added
       %td= toggle_button(@problem.available?, toggle_problem_path(@problem), "problem-avail-#{@problem.id}")
       %td= toggle_button(@problem.view_testcase?, toggle_view_testcase_problem_path(@problem), "problem-view-testcase-#{@problem.id}")
diff --git a/app/views/problems/manage.html.haml b/app/views/problems/manage.html.haml
--- a/app/views/problems/manage.html.haml
+++ b/app/views/problems/manage.html.haml
@@ -36,50 +36,83 @@
 
 %h1 Manage problems
 
-%p= link_to '[Back to problem list]', :action => 'list'
+%p= link_to '[Back to problem list]', problems_path
 
 = form_tag :action=>'do_manage' do
-  .submitbox
-    What do you want to do to the selected problem?
-    %br/
-    (You can shift-click to select a range of problems)
-    %ul
-      %li
-        Change date added to
-        = select_date Date.current, :prefix => 'date_added'
-        &nbsp;&nbsp;&nbsp;
-        = submit_tag 'Change', :name => 'change_date_added'
-      %li
-        Set available to
-        = submit_tag 'True', :name => 'enable_problem'
-        = submit_tag 'False', :name => 'disable_problem'
+  .panel.panel-primary
+    .panel-heading
+      Action
+    .panel-body
+      .submit-box
+        What do you want to do to the selected problem?
+        %br/
+        (You can shift-click to select a range of problems)
+        %ul.form-inline
+          %li
+            Change "Date added" to
+            .input-group.date
+              = text_field_tag :date_added, class: 'form-control'
+              %span.input-group-addon
+                %span.glyphicon.glyphicon-calendar
+            -# = select_date Date.current, :prefix => 'date_added'
+            &nbsp;&nbsp;&nbsp;
+            = submit_tag 'Change', :name => 'change_date_added', class: 'btn btn-primary btn-sm'
+          %li
+            Set "Available" to
+            = submit_tag 'True', :name => 'enable_problem', class: 'btn btn-primary btn-sm'
+            = submit_tag 'False', :name => 'disable_problem', class: 'btn btn-primary btn-sm'
 
-      - if GraderConfiguration.multicontests?
-        %li
-          Add to 
-          = select("contest","id",Contest.all.collect {|c| [c.title, c.id]})
-          = submit_tag 'Add', :name => 'add_to_contest'
+          - if GraderConfiguration.multicontests?
+            %li
+              Add selected problems to contest
+              = select("contest","id",Contest.all.collect {|c| [c.title, c.id]})
+              = submit_tag 'Add', :name => 'add_to_contest', class: 'btn btn-primary btn-sm'
+          %li
+            Add selected problems to user group
+            = select_tag "group_id", options_from_collection_for_select( Group.all, 'id','name',params[:group_name]), id: 'group_name',class: 'select2'
+            = submit_tag 'Add', name: 'add_group', class: 'btn btn-primary'
+          %li
+            Add the following tags to the selected problems
+            = select_tag "tag_ids", options_from_collection_for_select( Tag.all, 'id','name'), id: 'tags_name',class: 'select2', multiple: true, data: {placeholder: 'Select tags by clicking', width: "200px"}
+            = submit_tag 'Add', name: 'add_tags', class: 'btn btn-primary'
 
-  %table
-    %tr{style: "text-align: left;"}
-      %th= check_box_tag 'select_all'
-      %th Name
-      %th Full name
-      %th Available
-      %th Date added
-      - if GraderConfiguration.multicontests?
-        %th Contests
+  %table.table.table-hover.datatable
+    %thead
+      %tr{style: "text-align: left;"}
+        %th= check_box_tag 'select_all'
+        %th Name
+        %th Full name
+        %th Tags
+        %th Available
+        %th Date added
+        - if GraderConfiguration.multicontests?
+          %th Contests
 
-    - num = 0
-    - for problem in @problems
-      - num += 1
-      %tr{:id => "row-prob-#{problem.id}", :name=> "prob-#{problem.id}"}
-        %td= check_box_tag "prob-#{problem.id}-#{num}"
-        %td= problem.name
-        %td= problem.full_name
-        %td= problem.available
-        %td= problem.date_added
-        - if GraderConfiguration.multicontests?
+    %tbody
+      - num = 0
+      - for problem in @problems
+        - num += 1
+        %tr{:id => "row-prob-#{problem.id}", :name=> "prob-#{problem.id}"}
+          %td= check_box_tag "prob-#{problem.id}-#{num}"
+          %td= problem.name
+          %td= problem.full_name
           %td
-            - problem.contests.each do |contest|
-              = "(#{contest.name} [#{link_to 'x', :action => 'remove_contest', :id => problem.id, :contest_id => contest.id }])"
+            - problem.tags.each do |t|
+              %span.label.label-default= t.name
+          %td= problem.available
+          %td= problem.date_added
+          - if GraderConfiguration.multicontests?
+            %td
+              - problem.contests.each do |contest|
+                = "(#{contest.name} [#{link_to 'x', :action => 'remove_contest', :id => problem.id, :contest_id => contest.id }])"
+
+:javascript
+  $('.input-group.date').datetimepicker({
+    format: 'DD/MMM/YYYY',
+    showTodayButton: true,
+    widgetPositioning: {horizontal: 'auto', vertical: 'bottom'},
+
+  });
+  $('.datatable').DataTable({
+    paging: false
+  });
diff --git a/app/views/problems/stat.html.haml b/app/views/problems/stat.html.haml
--- a/app/views/problems/stat.html.haml
+++ b/app/views/problems/stat.html.haml
@@ -25,13 +25,14 @@
 
 %h2 Submissions
 - if @submissions and @submissions.count > 0
-  %table.info#main_table
+  %table#main_table.table.table-condensed.table-striped
     %thead
-      %tr.info-head
+      %tr
         %th ID
         %th Login
         %th Name
         %th Submitted_at
+        %th language
         %th Points
         %th comment
         %th IP
@@ -40,14 +41,19 @@
       - @submissions.each do |sub|
         - next unless sub.user
         - row_odd,curr = !row_odd, sub.user if curr != sub.user
-        %tr{class: row_odd ? "info-odd" : "info-even"}
+        %tr
           %td= link_to sub.id, submission_path(sub)
           %td= link_to sub.user.login, stat_user_path(sub.user)
           %td= sub.user.full_name
-          %td= time_ago_in_words(sub.submitted_at) + " ago"
+          %td{data: {order: sub.submitted_at}}= time_ago_in_words(sub.submitted_at) + " ago"
+          %td= sub.language.name
           %td= sub.points
           %td.fix-width= sub.grader_comment
           %td= sub.ip_address
 - else
   No submission
 
+:javascript
+  $("#main_table").DataTable({
+    paging: false
+  });
diff --git a/app/views/report/_score_table.html.haml b/app/views/report/_score_table.html.haml
--- a/app/views/report/_score_table.html.haml
+++ b/app/views/report/_score_table.html.haml
@@ -12,6 +12,9 @@
       %th.text-right Total
       %th.text-right Passed
   %tbody
+    - sum = Array.new(@scorearray[0].count,0)
+    - nonzero = Array.new(@scorearray[0].count,0)
+    - full = Array.new(@scorearray[0].count,0)
     - @scorearray.each do |sc|
       %tr
         - total,num_passed = 0,0
@@ -27,8 +30,40 @@
             %td.text-right= sc[i][0]
             - total += sc[i][0]
             - num_passed += 1 if sc[i][1]
+            - sum[i] += sc[i][0]
+            - nonzero[i] += 1 if sc[i][0] > 0
+            - full[i] += 1 if sc[i][1]
         %td.text-right= total 
         %td.text-right= num_passed
+    %tfoot
+      %tr
+        %td Summation
+        %td
+        %td
+        - sum.each.with_index do |s,i|
+          - next if i == 0
+          %td.text-right= number_with_delimiter(s)
+        %td
+        %td
+      %tr
+        %td partial solver
+        %td
+        %td
+        - nonzero.each.with_index do |s,i|
+          - next if i == 0
+          %td.text-right= number_with_delimiter(s)
+        %td
+        %td
+      %tr
+        %td Full solver
+        %td
+        %td
+        - full.each.with_index do |s,i|
+          - next if i == 0
+          %td.text-right= number_with_delimiter(s)
+        %td
+        %td
+
 
 :javascript
   $.bootstrapSortable(true,'reversed')
diff --git a/app/views/report/max_score.html.haml b/app/views/report/max_score.html.haml
--- a/app/views/report/max_score.html.haml
+++ b/app/views/report/max_score.html.haml
@@ -33,11 +33,11 @@
       .panel-body
         .radio
           %label
-            = radio_button_tag 'users', 'all', true
+            = radio_button_tag 'users', 'all', (params[:users] == "all")
             All users
         .radio
           %label
-            = radio_button_tag 'users', 'enabled'
+            = radio_button_tag 'users', 'enabled', (params[:users] == "enabled")
             Only enabled users
 .row
   .col-md-12
diff --git a/app/views/sites/edit.html.haml b/app/views/sites/edit.html.haml
--- a/app/views/sites/edit.html.haml
+++ b/app/views/sites/edit.html.haml
@@ -1,24 +1,36 @@
 %h1 Editing site
 = error_messages_for :site
 = form_for(@site) do |f|
-  %p
-    %b Name
-    %br/
-    = f.text_field :name
-  %p
-    %b Password
-    %br/
-    = f.text_field :password
-  %p
-    %b Started
-    %br/
-    = f.check_box :started
-  %p
-    %b Start time
-    %br/
-    = f.datetime_select :start_time, :include_blank => true
-  %p
-    = f.submit "Update"
+  .row
+    .col-md-4
+      .form-group.field
+        = f.label :name, "Name"
+        = f.text_field :name, class: 'form-control'
+      .form-group.field
+        = f.label :password, "Password"
+        = f.text_field :password, class: 'form-control'
+      .form-group.field
+        = f.label :started, "Started"
+        = f.check_box :started, class: 'form-control'
+      .form-group.field
+        = f.label :start_time, "Start time"
+        -# = f.datetime_select :start_time, :include_blank => true
+        .input-group.date
+          = f.text_field :start_time, class:'form-control' , value: (@site.start_time ? @site.start_time.strftime('%d/%b/%Y %H:%M') : '')
+          %span.input-group-addon
+            %span.glyphicon.glyphicon-calendar
+      .actions
+        = f.submit "Update", class: 'btn btn-primary'
+    .col-md-8
+
 = link_to 'Show', @site
 |
 = link_to 'Back', sites_path
+
+
+:javascript
+  $('.input-group.date').datetimepicker({
+    format: 'DD/MMM/YYYY HH:mm',
+    showTodayButton: true,
+  });
+
diff --git a/app/views/submissions/edit.html.haml b/app/views/submissions/edit.html.haml
--- a/app/views/submissions/edit.html.haml
+++ b/app/views/submissions/edit.html.haml
@@ -11,6 +11,7 @@
     .col-md-8
       %div#editor{style: 'height: 500px; border-radius: 7px; font-size: 14px;'}
     .col-md-4
+      - # submission form
       = form_tag({controller: :main, :action => 'submit'}, :multipart => true, class: 'form') do
 
         = hidden_field_tag 'editor_text', @source
@@ -25,14 +26,16 @@
         .form-group
           = submit_tag 'Submit', class: 'btn btn-success', id: 'live_submit', 
             data: {confirm: "Submitting this source code for task #{@problem.long_name}?"}
-      .panel.panel-info
+      - # latest submission status
+      .panel{class: (@submission && @submission.graded_at) ? "panel-info" : "panel-warning"}
         .panel-heading
           Latest Submission Status
           = link_to "Refresh",get_latest_submission_status_submissions_path(@submission.user,@problem), class: "btn btn-default btn-sm", remote: true if @submission
         .panel-body
-          - if @submission
-            = render :partial => 'submission_short',
-              :locals => {submission: @submission, problem_name: @problem.name, problem_id: @problem.id }
+          %div#latest_status
+            - if @submission
+              = render :partial => 'submission_short',
+                :locals => {submission: @submission, problem_name: @problem.name, problem_id: @problem.id }
   .row
     .col-md-12
       %h2 Console
diff --git a/app/views/submissions/get_latest_submission_status.js.haml b/app/views/submissions/get_latest_submission_status.js.haml
--- a/app/views/submissions/get_latest_submission_status.js.haml
+++ b/app/views/submissions/get_latest_submission_status.js.haml
@@ -1,2 +1,2 @@
 :plain
-  $("#latest_status").html("#{j render({partial: 'submission_short', locals: {submission: @submission, problem_name: @problem.name}})}")
+  $("#latest_status").html("#{j render({partial: 'submission_short', locals: {submission: @submission, problem_name: @problem.name, problem_id: @problem.id}})}")
diff --git a/app/views/tags/_form.html.haml b/app/views/tags/_form.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/tags/_form.html.haml
@@ -0,0 +1,22 @@
+= form_for @tag do |f|
+  - if @tag.errors.any?
+    #error_explanation
+      %h2= "#{pluralize(@tag.errors.count, "error")} prohibited this tag from being saved:"
+      %ul
+        - @tag.errors.full_messages.each do |msg|
+          %li= msg
+
+  .row
+    .col-md-6
+      .form-group.field
+        = f.label :name
+        = f.text_field :name, class: 'form-control'
+      .form-group.field
+        = f.label :description
+        = f.text_area :description, class: 'form-control'
+      .form-group.field
+        = f.label :public
+        = f.text_field :public, class: 'form-control'
+      .actions
+        = f.submit 'Save', class: 'btn btn-primary'
+    .col-md-6
diff --git a/app/views/tags/edit.html.haml b/app/views/tags/edit.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/tags/edit.html.haml
@@ -0,0 +1,7 @@
+%h1 Editing tag
+
+= render 'form'
+
+= link_to 'Show', @tag
+\|
+= link_to 'Back', tags_path
diff --git a/app/views/tags/index.html.haml b/app/views/tags/index.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/tags/index.html.haml
@@ -0,0 +1,26 @@
+%h1 Tags
+
+= link_to 'New Tag', new_tag_path, class: 'btn btn-success'
+
+%table.table.table-hover
+  %thead
+    %tr
+      %th Name
+      %th Description
+      %th Public
+      %th
+      %th
+      %th
+
+  %tbody
+    - @tags.each do |tag|
+      %tr
+        %td= tag.name
+        %td= tag.description
+        %td= tag.public
+        %td= link_to 'Show', tag
+        %td= link_to 'Edit', edit_tag_path(tag)
+        %td= link_to 'Destroy', tag, :method => :delete, :data => { :confirm => 'Are you sure?' }
+
+%br
+
diff --git a/app/views/tags/new.html.haml b/app/views/tags/new.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/tags/new.html.haml
@@ -0,0 +1,5 @@
+%h1 New tag
+
+= render 'form'
+
+= link_to 'Back', tags_path
diff --git a/app/views/tags/show.html.haml b/app/views/tags/show.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/tags/show.html.haml
@@ -0,0 +1,15 @@
+%p#notice= notice
+
+%p
+  %b Name:
+  = @tag.name
+%p
+  %b Description:
+  = @tag.description
+%p
+  %b Public:
+  = @tag.public
+
+= link_to 'Edit', edit_tag_path(@tag)
+\|
+= link_to 'Back', tags_path
diff --git a/app/views/user_admin/_form.html.erb b/app/views/user_admin/_form.html.erb
deleted file mode 100644
--- a/app/views/user_admin/_form.html.erb
+++ /dev/null
@@ -1,25 +0,0 @@
-<%= error_messages_for 'user' %>
-
-<!--[form:user]-->
-<p><label for="user_name">Login</label><br/>
-<%= text_field 'user', 'login'  %></p>
-
-<p><label for="user_name">Full name</label><br/>
-<%= text_field 'user', 'full_name'  %></p>
-
-<p><label for="password">Password</label><br/>
-<%= password_field 'user', 'password'  %></p>
-
-<p><label for="password_confirmation">Password (confirm)</label><br/>
-<%= password_field 'user', 'password_confirmation'  %></p>
-
-<p><label for="user_email">E-mail</label><br/>
-<%= email_field 'user', 'email'  %></p>
-
-<p><label for="user_alias">Alias</label><br/>
-<%= text_field 'user', 'alias'  %></p>
-
-<p><label for="user_remark">Remark</label><br/>
-<%= text_field 'user', 'remark'  %></p>
-<!--[eoform:user]-->
-
diff --git a/app/views/user_admin/_form.html.haml b/app/views/user_admin/_form.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/user_admin/_form.html.haml
@@ -0,0 +1,38 @@
+= error_messages_for 'user'
+/ [form:user]
+.form-group
+  %label.col-md-2.control-label{for: :login} Login
+  .col-md-4
+    = text_field 'user', 'login', class: 'form-control'
+  .col-md-6
+.form-group
+  %label.col-md-2.control-label{for: :full_name} Full name
+  .col-md-4
+    = text_field 'user', 'full_name', class: 'form-control'
+  .col-md-6
+.form-group
+  %label.col-md-2.control-label{for: :password} Password
+  .col-md-4
+    = password_field 'user', 'password', class: 'form-control'
+  .col-md-6
+.form-group
+  %label.col-md-2.control-label{for: :password_confirmation} Password (confirm)
+  .col-md-4
+    = password_field 'user', 'password_confirmation', class: 'form-control'
+  .col-md-6
+.form-group
+  %label.col-md-2.control-label{for: :email} E-mail
+  .col-md-4
+    = email_field 'user', 'email', class: 'form-control'
+  .col-md-6
+.form-group
+  %label.col-md-2.control-label{for: :alias} Alias
+  .col-md-4
+    = text_field 'user', 'alias', class: 'form-control'
+  .col-md-6
+.form-group
+  %label.col-md-2.control-label{for: :remark} Remark
+  .col-md-4
+    = text_field 'user', 'remark', class: 'form-control'
+  .col-md-6
+/ [eoform:user]
diff --git a/app/views/user_admin/bulk_manage.html.haml b/app/views/user_admin/bulk_manage.html.haml
--- a/app/views/user_admin/bulk_manage.html.haml
+++ b/app/views/user_admin/bulk_manage.html.haml
@@ -46,6 +46,15 @@
             %label.checkbox-inline
               = check_box_tag "gen_password", true, params[:gen_password]
               Generate new random password
+        .row.form-group
+          .col-md-4
+            %label.checkbox-inline
+              = check_box_tag "add_group", true, params[:add_group]
+              Add users to group
+          %label.col-md-3.control-label.text-right Group name
+          .col-md-5
+            = select_tag "group_name", options_from_collection_for_select( Group.all, 'id','name',params[:group_name]), id: 'group_name',class: 'form-control select2'
+
 
 .row
   .col-md-12
diff --git a/app/views/user_admin/edit.html.haml b/app/views/user_admin/edit.html.haml
--- a/app/views/user_admin/edit.html.haml
+++ b/app/views/user_admin/edit.html.haml
@@ -1,9 +1,11 @@
 %h1 Editing user
 
-= form_tag :action => 'update', :id => @user do
+= form_tag( {:action => 'update', :id => @user}, {class: 'form-horizontal'}) do
   = error_messages_for 'user'
   = render partial: "form"
-  = submit_tag "Edit"
+  .form-group
+    .col-md-offset-2.col-md-4
+      = submit_tag "Edit", class: 'btn btn-primary'
 
 
 = link_to 'Show', :action => 'show', :id => @user 
diff --git a/app/views/user_admin/index.html.haml b/app/views/user_admin/index.html.haml
--- a/app/views/user_admin/index.html.haml
+++ b/app/views/user_admin/index.html.haml
@@ -1,4 +1,4 @@
-%h1 Listing users
+%h1 Users
 
 .panel.panel-primary
   .panel-title.panel-heading
@@ -41,8 +41,8 @@
 %p
   = link_to '+ New user', { :action => 'new' }, { class: 'btn btn-success '}
   = link_to '+ New list of users', { :action => 'new_list' }, { class: 'btn btn-success '}
+  = link_to 'Bulk Manage', bulk_manage_user_admin_path , { class: 'btn btn-default btn-info'}
   = link_to 'View administrators',{ :action => 'admin'}, { class: 'btn btn-default '}
-  = link_to 'Bulk Manage', bulk_manage_user_admin_path , { class: 'btn btn-default '}
   = link_to 'Random passwords',{ :action => 'random_all_passwords'}, { class: 'btn btn-default '}
   = link_to 'View active users',{ :action => 'active'}, { class: 'btn btn-default '}
   = link_to 'Mass mailing',{ :action => 'mass_mailing'}, { class: 'btn btn-default '}
@@ -56,17 +56,17 @@
     = link_to "[#{contest.name}]", :action => 'contests', :id => contest.id
   = link_to "[no contest]", :action => 'contests', :id => 'none'
 
-Total #{@user_count} users |
-- if !@paginated
-  Display all users.
-  \#{link_to '[show in pages]', :action => 'index', :page => '1'}
-- else
-  Display in pages.
-  \#{link_to '[display all]', :action => 'index', :page => 'all'} |
-  \#{will_paginate @users, :container => false}
+-# Total #{@user_count} users |
+-# - if !@paginated
+-#   Display all users.
+-#   \#{link_to '[show in pages]', :action => 'index', :page => '1'}
+-# - else
+-#   Display in pages.
+-#   \#{link_to '[display all]', :action => 'index', :page => 'all'} |
+-#   \#{will_paginate @users, :container => false}
 
 
-%table.table.table-hover.table-condense
+%table.table.table-hover.table-condense.datatable
   %thead
     %th Login
     %th Full name
@@ -95,7 +95,12 @@
       %td= link_to 'Clear IP', {:action => 'clear_last_ip', :id => user, :page=>params[:page]}, :confirm => 'This will reset last logging in ip of the user, are you sure?', class: 'btn btn-default btn-xs btn-block'
       %td= link_to 'Show', {:action => 'show', :id => user}, class: 'btn btn-default btn-xs btn-block'
       %td= link_to 'Edit', {:action => 'edit', :id => user}, class: 'btn btn-default btn-xs btn-block'
-      %td= link_to 'Destroy', { :action => 'destroy', :id => user }, :confirm => 'Are you sure?', :method => :delete, class: 'btn btn-danger btn-xs btn-block'
+      %td= link_to 'Destroy', user_admin_destroy_path(user), data: {confirm: 'Are you sure?'}, method: :delete, class: 'btn btn-danger btn-xs btn-block'
 %br/
 = link_to '+ New user', { :action => 'new' }, { class: 'btn btn-success '}
 = link_to '+ New list of users', { :action => 'new_list' }, { class: 'btn btn-success '}
+
+:javascript
+  $('.datatable').DataTable({
+    'pageLength': 50
+  });
diff --git a/app/views/user_admin/new.html.erb b/app/views/user_admin/new.html.erb
deleted file mode 100644
--- a/app/views/user_admin/new.html.erb
+++ /dev/null
@@ -1,8 +0,0 @@
-<h1>New user</h1>
-
-<%= form_tag :action => 'create' do %>
-  <%= render :partial => 'form' %>
-  <%= submit_tag "Create" %>
-<% end %>
-
-<%= link_to 'Back', :action => 'list' %>
diff --git a/app/views/user_admin/new.html.haml b/app/views/user_admin/new.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/user_admin/new.html.haml
@@ -0,0 +1,7 @@
+%h1 New user
+= form_tag( {action: 'create'}, { class: 'form-horizontal'}) do
+  = render :partial => 'form'
+  .form-group
+    .col-md-offset-2.col-md-10
+      = submit_tag "Create", class: 'btn btn-primary'
+= link_to 'Back', :action => 'index'
diff --git a/app/views/user_admin/show.html.erb b/app/views/user_admin/show.html.erb
deleted file mode 100644
--- a/app/views/user_admin/show.html.erb
+++ /dev/null
@@ -1,10 +0,0 @@
-<h1>User information</h1>
-
-<% for column in User.content_columns %>
-<p>
-  <b><%= column.human_name %>:</b> <%=h @user.send(column.name) %>
-</p>
-<% end %>
-
-<%= link_to 'Edit', :action => 'edit', :id => @user %> |
-<%= link_to 'Back', :action => 'list' %>
diff --git a/app/views/user_admin/show.html.haml b/app/views/user_admin/show.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/user_admin/show.html.haml
@@ -0,0 +1,14 @@
+%h1 User information
+- for column in User.content_columns
+  %p
+    %b
+      = column.human_name
+      \:
+    = h @user.send(column.name)
+%p
+  %strong Group
+  \:
+  = @user.groups.map{ |x| link_to(x.name,group_path(x)).html_safe}.join(', ').html_safe
+= link_to 'Edit', :action => 'edit', :id => @user
+|
+= link_to 'Back', :action => 'index'
diff --git a/app/views/users/stat.html.haml b/app/views/users/stat.html.haml
--- a/app/views/users/stat.html.haml
+++ b/app/views/users/stat.html.haml
@@ -36,7 +36,7 @@
 =render partial: 'application/bar_graph', locals: {histogram: @histogram, param: {bar_width: 7}}
 
 
-%table.tablesorter-cafe#submission_table
+%table#submission_table.table.table-striped
   %thead
     %tr
       %th ID
@@ -64,3 +64,7 @@
 
 
 
+:javascript
+  $("#submission_table").DataTable({
+    paging: false
+  });
diff --git a/config/application.rb.SAMPLE b/config/application.rb.SAMPLE
--- a/config/application.rb.SAMPLE
+++ b/config/application.rb.SAMPLE
@@ -65,7 +65,7 @@
     config.assets.precompile += ['local_jquery.js','tablesorter-theme.cafe.css']
     %w( announcements submissions configurations contests contest_management graders heartbeat 
         login main messages problems report site sites sources tasks 
-        test user_admin users ).each do |controller|
+        test user_admin users testcases).each do |controller|
       config.assets.precompile += ["#{controller}.js", "#{controller}.css"]
     end
   end
diff --git a/config/initializers/assets.rb b/config/initializers/assets.rb
new file mode 100644
--- /dev/null
+++ b/config/initializers/assets.rb
@@ -0,0 +1,23 @@
+# Be sure to restart your server when you modify this file.
+
+# Version of your assets, change this if you want to expire all your assets.
+Rails.application.config.assets.version = '1.0'
+
+# Add additional assets to the asset load path.
+# Rails.application.config.assets.paths << Emoji.images_path
+# Add Yarn node_modules folder to the asset load path.
+Rails.application.config.assets.paths << Rails.root.join('node_modules')
+Rails.application.config.assets.paths << Rails.root.join('vendor/assets/fonts')
+
+# Precompile additional assets.
+# application.js, application.css, and all non-JS/CSS in the app/assets
+# folder are already added.
+# Rails.application.config.assets.precompile += %w( admin.js admin.css )
+
+Rails.application.config.assets.precompile += ['announcement_refresh.js','effects.js','site_update.js']
+Rails.application.config.assets.precompile += ['local_jquery.js','tablesorter-theme.cafe.css']
+%w( announcements submissions configurations contests contest_management graders heartbeat 
+    login main messages problems report site sites sources tasks groups
+    test user_admin users tags testcases).each do |controller|
+  Rails.application.config.assets.precompile += ["#{controller}.js", "#{controller}.css"]
+end
diff --git a/config/routes.rb b/config/routes.rb
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -1,4 +1,5 @@
 CafeGrader::Application.routes.draw do
+  resources :tags
   get "sources/direct_edit"
 
   root :to => 'main#login'
@@ -29,7 +30,20 @@
       get 'import'
       get 'manage'
     end
+  end
 
+  resources :groups do
+    member do
+      post 'add_user', to: 'groups#add_user', as: 'add_user'
+      delete 'remove_user/:user_id', to: 'groups#remove_user', as: 'remove_user'
+      delete 'remove_all_user', to: 'groups#remove_all_user', as: 'remove_all_user'
+      post 'add_problem', to: 'groups#add_problem', as: 'add_problem'
+      delete 'remove_problem/:problem_id', to: 'groups#remove_problem', as: 'remove_problem'
+      delete 'remove_all_problem', to: 'groups#remove_all_problem', as: 'remove_all_problem'
+    end
+    collection do
+
+    end
   end
 
   resources :testcases, only: [] do
@@ -59,7 +73,7 @@
     end
     collection do
       get 'prob/:problem_id', to: 'submissions#index', as: 'problem'
-      get 'direct_edit_problem/:problem_id', to: 'submissions#direct_edit_problem', as: 'direct_edit_problem'
+      get 'direct_edit_problem/:problem_id(/:user_id)', to: 'submissions#direct_edit_problem', as: 'direct_edit_problem'
       get 'get_latest_submission_status/:uid/:pid', to: 'submissions#get_latest_submission_status', as: 'get_latest_submission_status'
     end
   end
@@ -72,6 +86,8 @@
 
   #user admin
   get 'user_admin/bulk_manage', to: 'user_admin#bulk_manage', as: 'bulk_manage_user_admin'
+  post 'user_admin', to: 'user_admin#create'
+  delete 'user_admin/:id', to: 'user_admin#destroy', as: 'user_admin_destroy'
 
   #report
   get 'report/current_score', to: 'report#current_score', as: 'report_current_score'
diff --git a/db/migrate/20170911091143_create_groups.rb b/db/migrate/20170911091143_create_groups.rb
new file mode 100644
--- /dev/null
+++ b/db/migrate/20170911091143_create_groups.rb
@@ -0,0 +1,30 @@
+class CreateGroups < ActiveRecord::Migration
+
+  def change
+    create_table :groups do |t|
+      t.string :name
+      t.string :description
+    end
+
+    create_join_table :groups, :users do |t|
+      # t.index [:group_id, :user_id]
+      t.index [:user_id, :group_id]
+    end
+
+    create_join_table :problems, :groups do |t|
+      # t.index [:problem_id, :group_id]
+      t.index [:group_id, :problem_id]
+    end
+
+    reversible do |change|
+      change.up do
+        GraderConfiguration.where(key: 'system.use_problem_group').first_or_create(value_type: 'boolean', value: 'false',
+                                                                                   description: 'If true, available problem to the user will be only ones associated with the group of the user');
+      end
+
+      change.down do
+        GraderConfiguration.where(key: 'system.use_problem_group').destroy_all
+      end
+    end
+  end
+end
diff --git a/db/migrate/20170914150545_create_tags.rb b/db/migrate/20170914150545_create_tags.rb
new file mode 100644
--- /dev/null
+++ b/db/migrate/20170914150545_create_tags.rb
@@ -0,0 +1,11 @@
+class CreateTags < ActiveRecord::Migration
+  def change
+    create_table :tags do |t|
+      t.string :name, null: false
+      t.text :description
+      t.boolean :public
+
+      t.timestamps null: false
+    end
+  end
+end
diff --git a/db/migrate/20170914150742_create_problem_tags.rb b/db/migrate/20170914150742_create_problem_tags.rb
new file mode 100644
--- /dev/null
+++ b/db/migrate/20170914150742_create_problem_tags.rb
@@ -0,0 +1,10 @@
+class CreateProblemTags < ActiveRecord::Migration
+  def change
+    create_table :problems_tags do |t|
+      t.references :problem, index: true, foreign_key: true
+      t.references :tag, index: true, foreign_key: true
+
+      t.index [:problem_id,:tag_id], unique: true
+    end
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20170427070345) do
+ActiveRecord::Schema.define(version: 20170914150742) do
 
   create_table "announcements", force: :cascade do |t|
     t.string   "author",       limit: 255
@@ -79,6 +79,25 @@
 
   add_index "grader_processes", ["host", "pid"], name: "index_grader_processes_on_ip_and_pid", using: :btree
 
+  create_table "groups", force: :cascade do |t|
+    t.string "name",        limit: 255
+    t.string "description", limit: 255
+  end
+
+  create_table "groups_problems", id: false, force: :cascade do |t|
+    t.integer "problem_id", limit: 4, null: false
+    t.integer "group_id",   limit: 4, null: false
+  end
+
+  add_index "groups_problems", ["group_id", "problem_id"], name: "index_groups_problems_on_group_id_and_problem_id", using: :btree
+
+  create_table "groups_users", id: false, force: :cascade do |t|
+    t.integer "group_id", limit: 4, null: false
+    t.integer "user_id",  limit: 4, null: false
+  end
+
+  add_index "groups_users", ["user_id", "group_id"], name: "index_groups_users_on_user_id_and_group_id", using: :btree
+
   create_table "heart_beats", force: :cascade do |t|
     t.integer  "user_id",    limit: 4
     t.string   "ip_address", limit: 255
@@ -127,6 +146,15 @@
     t.boolean "view_testcase"
   end
 
+  create_table "problems_tags", force: :cascade do |t|
+    t.integer "problem_id", limit: 4
+    t.integer "tag_id",     limit: 4
+  end
+
+  add_index "problems_tags", ["problem_id", "tag_id"], name: "index_problems_tags_on_problem_id_and_tag_id", unique: true, using: :btree
+  add_index "problems_tags", ["problem_id"], name: "index_problems_tags_on_problem_id", using: :btree
+  add_index "problems_tags", ["tag_id"], name: "index_problems_tags_on_tag_id", using: :btree
+
   create_table "rights", force: :cascade do |t|
     t.string "name",       limit: 255
     t.string "controller", limit: 255
@@ -200,6 +228,14 @@
   add_index "submissions", ["user_id", "problem_id", "number"], name: "index_submissions_on_user_id_and_problem_id_and_number", unique: true, using: :btree
   add_index "submissions", ["user_id", "problem_id"], name: "index_submissions_on_user_id_and_problem_id", using: :btree
 
+  create_table "tags", force: :cascade do |t|
+    t.string   "name",        limit: 255,   null: false
+    t.text     "description", limit: 65535
+    t.boolean  "public"
+    t.datetime "created_at",                null: false
+    t.datetime "updated_at",                null: false
+  end
+
   create_table "tasks", force: :cascade do |t|
     t.integer  "submission_id", limit: 4
     t.datetime "created_at"
@@ -280,4 +316,6 @@
 
   add_index "users", ["login"], name: "index_users_on_login", unique: true, using: :btree
 
+  add_foreign_key "problems_tags", "problems"
+  add_foreign_key "problems_tags", "tags"
 end
diff --git a/db/seeds.rb b/db/seeds.rb
--- a/db/seeds.rb
+++ b/db/seeds.rb
@@ -163,7 +163,16 @@
      :value_type => 'string',
      :default_value => 'none',
      :description => "New user will be assigned to this contest automatically, if it exists.  Set to 'none' if there is no default contest."
-   }
+   },
+
+   {
+     :key => 'system.use_problem_group',
+     :value_type => 'boolean',
+     :default_value => 'false',
+     :description => "If true, available problem to the user will be only ones associated with the group of the user."
+   },
+
+
 
   ]
 
diff --git a/lib/grader_script.rb b/lib/grader_script.rb
--- a/lib/grader_script.rb
+++ b/lib/grader_script.rb
@@ -33,6 +33,7 @@
     GraderScript.call_grader "#{env} test_request -err-log &"
   end
 
+  #call the import problem script
   def self.call_import_problem(problem_name, 
                                problem_dir,
                                time_limit=1,
diff --git a/lib/testdata_importer.rb b/lib/testdata_importer.rb
--- a/lib/testdata_importer.rb
+++ b/lib/testdata_importer.rb
@@ -8,8 +8,9 @@
     @problem = problem
   end
 
-  def import_from_file(tempfile, 
-                       time_limit, 
+  #Create or update problem according to the parameter
+  def import_from_file(tempfile,
+                       time_limit,
                        memory_limit,
                        checker_name='text',
                        import_to_db=false)
@@ -52,6 +53,7 @@
     return filename.slice(i..len)
   end
 
+  # extract an archive file located at +tempfile+ to the +raw_dir+
   def extract(tempfile)
     testdata_filename = save_testdata_file(tempfile)
     ext = TestdataImporter.long_ext(tempfile.original_filename)
diff --git a/test/controllers/groups_controller_test.rb b/test/controllers/groups_controller_test.rb
new file mode 100644
--- /dev/null
+++ b/test/controllers/groups_controller_test.rb
@@ -0,0 +1,49 @@
+require 'test_helper'
+
+class GroupsControllerTest < ActionController::TestCase
+  setup do
+    @group = groups(:one)
+  end
+
+  test "should get index" do
+    get :index
+    assert_response :success
+    assert_not_nil assigns(:groups)
+  end
+
+  test "should get new" do
+    get :new
+    assert_response :success
+  end
+
+  test "should create group" do
+    assert_difference('Group.count') do
+      post :create, group: { description: @group.description, name: @group.name }
+    end
+
+    assert_redirected_to group_path(assigns(:group))
+  end
+
+  test "should show group" do
+    get :show, id: @group
+    assert_response :success
+  end
+
+  test "should get edit" do
+    get :edit, id: @group
+    assert_response :success
+  end
+
+  test "should update group" do
+    patch :update, id: @group, group: { description: @group.description, name: @group.name }
+    assert_redirected_to group_path(assigns(:group))
+  end
+
+  test "should destroy group" do
+    assert_difference('Group.count', -1) do
+      delete :destroy, id: @group
+    end
+
+    assert_redirected_to groups_path
+  end
+end
diff --git a/test/controllers/tags_controller_test.rb b/test/controllers/tags_controller_test.rb
new file mode 100644
--- /dev/null
+++ b/test/controllers/tags_controller_test.rb
@@ -0,0 +1,49 @@
+require 'test_helper'
+
+class TagsControllerTest < ActionController::TestCase
+  setup do
+    @tag = tags(:one)
+  end
+
+  test "should get index" do
+    get :index
+    assert_response :success
+    assert_not_nil assigns(:tags)
+  end
+
+  test "should get new" do
+    get :new
+    assert_response :success
+  end
+
+  test "should create tag" do
+    assert_difference('Tag.count') do
+      post :create, tag: { description: @tag.description, name: @tag.name, public: @tag.public }
+    end
+
+    assert_redirected_to tag_path(assigns(:tag))
+  end
+
+  test "should show tag" do
+    get :show, id: @tag
+    assert_response :success
+  end
+
+  test "should get edit" do
+    get :edit, id: @tag
+    assert_response :success
+  end
+
+  test "should update tag" do
+    patch :update, id: @tag, tag: { description: @tag.description, name: @tag.name, public: @tag.public }
+    assert_redirected_to tag_path(assigns(:tag))
+  end
+
+  test "should destroy tag" do
+    assert_difference('Tag.count', -1) do
+      delete :destroy, id: @tag
+    end
+
+    assert_redirected_to tags_path
+  end
+end
diff --git a/test/fixtures/problem_tags.yml b/test/fixtures/problem_tags.yml
new file mode 100644
--- /dev/null
+++ b/test/fixtures/problem_tags.yml
@@ -0,0 +1,9 @@
+# Read about fixtures at http://api.rubyonrails.org/classes/ActiveRecord/FixtureSet.html
+
+one:
+  problem_id: 
+  tag_id: 
+
+two:
+  problem_id: 
+  tag_id: 
diff --git a/test/fixtures/tags.yml b/test/fixtures/tags.yml
new file mode 100644
--- /dev/null
+++ b/test/fixtures/tags.yml
@@ -0,0 +1,11 @@
+# Read about fixtures at http://api.rubyonrails.org/classes/ActiveRecord/FixtureSet.html
+
+one:
+  name: MyString
+  description: MyString
+  public: 
+
+two:
+  name: MyString
+  description: MyString
+  public: 
diff --git a/test/models/problem_tag_test.rb b/test/models/problem_tag_test.rb
new file mode 100644
--- /dev/null
+++ b/test/models/problem_tag_test.rb
@@ -0,0 +1,7 @@
+require 'test_helper'
+
+class ProblemTagTest < ActiveSupport::TestCase
+  # test "the truth" do
+  #   assert true
+  # end
+end
diff --git a/test/models/tag_test.rb b/test/models/tag_test.rb
new file mode 100644
--- /dev/null
+++ b/test/models/tag_test.rb
@@ -0,0 +1,7 @@
+require 'test_helper'
+
+class TagTest < ActiveSupport::TestCase
+  # test "the truth" do
+  #   assert true
+  # end
+end