Merge branch 'tasks' into 'master'

Add Todos

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/2425

Tasks:

-  Prepare database
 - [X] Create a new table (`todos`)
- Tasks Queue view
 - [X] Add a number icon showing the number of todos on the top right next to the new and logout button that will redirect the user to the todos page
 - [X] Add a chronological list of todos, with the 'Todos' tab active by default
 - [X] Add a 'Done' button to each todo
 - [x] Add filters (project, author, type, and action)
- Todos generation
 - [X] When user issue/mr is assgined to someone
 - [x] When user is mentioned on (issues/mr's/comments)
- Mark todo as `done`
 - [X] When clicks on the 'Done' button
 - [X] When edit issue/mr
 - [X] When left/edit a comment
 - [X] When reassign issue/mr
 - [X] When add/remove labels to issue/mr
 - [X] When issue/mr is closed
 - [X] When mr is merged
 - [X] When added an emoji
 - [X] When changed the issue/mr milestone

* Screenshot:

![Screenshot_2016-02-20_12.45.57](/uploads/4b2554b1bde25aed3347e1ae41e8e0c0/Screenshot_2016-02-20_12.45.57.png)

See merge request !2817

46 files changed, 1633 insertions, 20 deletions

diff --git a/CHANGELOG b/CHANGELOG
index b31e134918c..77a21e757c4 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -67,7 +67,7 @@ v 8.5.0 (unreleased)
   - Fix broken link to project in build notification emails
   - Ability to see and sort on vote count from Issues and MR lists
   - Fix builds scheduler when first build in stage was allowed to fail
-  - User project limit is reached notice is hidden if the projects limit is zero 
+  - User project limit is reached notice is hidden if the projects limit is zero
   - Add API support for managing runners and project's runners
   - Allow SAML users to login with no previous account without having to allow
     all Omniauth providers to do so.
@@ -77,6 +77,7 @@ v 8.5.0 (unreleased)
   - Emoji comment on diffs are not award emoji
   - Add label description (Nuttanart Pornprasitsakul)
   - Show label row when filtering issues or merge requests by label (Nuttanart Pornprasitsakul)
+  - Add Todos
 
 v 8.4.4
   - Update omniauth-saml gem to 1.4.2
diff --git a/app/assets/stylesheets/pages/todos.scss b/app/assets/stylesheets/pages/todos.scss
new file mode 100644
index 00000000000..2f57f21963d
--- /dev/null
+++ b/app/assets/stylesheets/pages/todos.scss
@@ -0,0 +1,124 @@
+/**
+ * Dashboard Todos
+ *
+ */
+
+.navbar-nav {
+  li {
+    .badge.todos-pending-count {
+      background-color: #7f8fa4;
+      margin-top: -5px;
+    }
+  }
+}
+
+.todos {
+  .panel {
+    border-top: none;
+    margin-bottom: 0;
+  }
+}
+
+.todo-item {
+  font-size: $gl-font-size;
+  padding: $gl-padding-top 0 $gl-padding-top ($gl-avatar-size + $gl-padding-top);
+  border-bottom: 1px solid $table-border-color;
+  color: #7f8fa4;
+
+  &.todo-inline {
+    .avatar {
+      position: relative;
+      top: -2px;
+    }
+
+    .todo-title {
+      line-height: 40px;
+    }
+  }
+
+  a {
+    color: #4c4e54;
+  }
+
+  .avatar {
+    margin-left: -($gl-avatar-size + $gl-padding-top);
+  }
+
+  .todo-title {
+    @include str-truncated(calc(100% - 174px));
+    font-weight: 600;
+
+    .author_name {
+      color: #333;
+    }
+  }
+
+  .todo-body {
+    margin-right: 174px;
+
+    .todo-note {
+      word-wrap: break-word;
+
+      .md {
+        color: #7f8fa4;
+        font-size: $gl-font-size;
+
+        p {
+          color: #5c5d5e;
+        }
+      }
+
+      pre {
+        border: none;
+        background: #f9f9f9;
+        border-radius: 0;
+        color: #777;
+        margin: 0 20px;
+        overflow: hidden;
+      }
+
+      .note-image-attach {
+        margin-top: 4px;
+        margin-left: 0px;
+        max-width: 200px;
+        float: none;
+      }
+
+      p:last-child {
+        margin-bottom: 0;
+      }
+    }
+
+    .todo-note-icon {
+      color: #777;
+      float: left;
+      font-size: $gl-font-size;
+      line-height: 16px;
+      margin-right: 5px;
+    }
+  }
+
+  &:last-child { border:none }
+}
+
+@media (max-width: $screen-xs-max) {
+  .todo-item {
+    padding-left: $gl-padding;
+
+    .todo-title {
+      white-space: normal;
+      overflow: visible;
+      max-width: 100%;
+    }
+
+    .avatar {
+      display: none;
+    }
+
+    .todo-body {
+      margin: 0;
+      border-left: 2px solid #DDD;
+      padding-left: 10px;
+    }
+  }
+}
diff --git a/app/controllers/dashboard/todos_controller.rb b/app/controllers/dashboard/todos_controller.rb
new file mode 100644
index 00000000000..9ee9039f004
--- /dev/null
+++ b/app/controllers/dashboard/todos_controller.rb
@@ -0,0 +1,35 @@
+class Dashboard::TodosController < Dashboard::ApplicationController
+  before_action :find_todos, only: [:index, :destroy_all]
+
+  def index
+    @todos = @todos.page(params[:page]).per(PER_PAGE)
+  end
+
+  def destroy
+    todo.done!
+
+    respond_to do |format|
+      format.html { redirect_to dashboard_todos_path, notice: 'Todo was successfully marked as done.' }
+      format.js { render nothing: true }
+    end
+  end
+
+  def destroy_all
+    @todos.each(&:done)
+
+    respond_to do |format|
+      format.html { redirect_to dashboard_todos_path, notice: 'All todos were marked as done.' }
+      format.js { render nothing: true }
+    end
+  end
+
+  private
+
+  def todo
+    @todo ||= current_user.todos.find(params[:id])
+  end
+
+  def find_todos
+    @todos = TodosFinder.new(current_user, params).execute
+  end
+end
diff --git a/app/controllers/projects/merge_requests_controller.rb b/app/controllers/projects/merge_requests_controller.rb
index 86b8e7bdf2e..5fe21694605 100644
--- a/app/controllers/projects/merge_requests_controller.rb
+++ b/app/controllers/projects/merge_requests_controller.rb
@@ -181,6 +181,8 @@ class Projects::MergeRequestsController < Projects::ApplicationController
       return
     end
 
+    TodoService.new.merge_merge_request(merge_request, current_user)
+
     @merge_request.update(merge_error: nil)
 
     if params[:merge_when_build_succeeds].present? && @merge_request.ci_commit && @merge_request.ci_commit.active?
diff --git a/app/finders/todos_finder.rb b/app/finders/todos_finder.rb
new file mode 100644
index 00000000000..3ba27c40504
--- /dev/null
+++ b/app/finders/todos_finder.rb
@@ -0,0 +1,129 @@
+# TodosFinder
+#
+# Used to filter Todos by set of params
+#
+# Arguments:
+#   current_user - which user use
+#   params:
+#     action_id: integer
+#     author_id: integer
+#     project_id; integer
+#     state: 'pending' or 'done'
+#     type: 'Issue' or 'MergeRequest'
+#
+
+class TodosFinder
+  NONE = '0'
+
+  attr_accessor :current_user, :params
+
+  def initialize(current_user, params)
+    @current_user = current_user
+    @params = params
+  end
+
+  def execute
+    items = current_user.todos
+    items = by_action_id(items)
+    items = by_author(items)
+    items = by_project(items)
+    items = by_state(items)
+    items = by_type(items)
+
+    items
+  end
+
+  private
+
+  def action_id?
+    action_id.present? && [Todo::ASSIGNED, Todo::MENTIONED].include?(action_id.to_i)
+  end
+
+  def action_id
+    params[:action_id]
+  end
+
+  def author?
+    params[:author_id].present?
+  end
+
+  def author
+    return @author if defined?(@author)
+
+    @author =
+      if author? && params[:author_id] != NONE
+        User.find(params[:author_id])
+      else
+        nil
+      end
+  end
+
+  def project?
+    params[:project_id].present?
+  end
+
+  def project
+    return @project if defined?(@project)
+
+    if project?
+      @project = Project.find(params[:project_id])
+
+      unless Ability.abilities.allowed?(current_user, :read_project, @project)
+        @project = nil
+      end
+    else
+      @project = nil
+    end
+
+    @project
+  end
+
+  def type?
+    type.present? && ['Issue', 'MergeRequest'].include?(type)
+  end
+
+  def type
+    params[:type]
+  end
+
+  def by_action_id(items)
+    if action_id?
+      items = items.where(action: action_id)
+    end
+
+    items
+  end
+
+  def by_author(items)
+    if author?
+      items = items.where(author_id: author.try(:id))
+    end
+
+    items
+  end
+
+  def by_project(items)
+    if project?
+      items = items.where(project: project)
+    end
+
+    items
+  end
+
+  def by_state(items)
+    case params[:state]
+    when 'done'
+      items.done
+    else
+      items.pending
+    end
+  end
+
+  def by_type(items)
+    if type?
+      items = items.where(target_type: type)
+    end
+
+    items
+  end
+end
diff --git a/app/helpers/todos_helper.rb b/app/helpers/todos_helper.rb
new file mode 100644
index 00000000000..4b745a5b969
--- /dev/null
+++ b/app/helpers/todos_helper.rb
@@ -0,0 +1,87 @@
+module TodosHelper
+  def todos_pending_count
+    current_user.todos.pending.count
+  end
+
+  def todos_done_count
+    current_user.todos.done.count
+  end
+
+  def todo_action_name(todo)
+    case todo.action
+    when Todo::ASSIGNED then 'assigned you'
+    when Todo::MENTIONED then 'mentioned you on'
+    end
+  end
+
+  def todo_target_link(todo)
+    target = todo.target_type.titleize.downcase
+    link_to "#{target} #{todo.target.to_reference}", todo_target_path(todo)
+  end
+
+  def todo_target_path(todo)
+    anchor = dom_id(todo.note) if todo.note.present?
+
+    polymorphic_path([todo.project.namespace.becomes(Namespace),
+                      todo.project, todo.target], anchor: anchor)
+  end
+
+  def todos_filter_params
+    {
+      state:      params[:state],
+      project_id: params[:project_id],
+      author_id:  params[:author_id],
+      type:       params[:type],
+      action_id:  params[:action_id],
+    }
+  end
+
+  def todos_filter_path(options = {})
+    without = options.delete(:without)
+
+    options = todos_filter_params.merge(options)
+
+    if without.present?
+      without.each do |key|
+        options.delete(key)
+      end
+    end
+
+    path = request.path
+    path << "?#{options.to_param}"
+    path
+  end
+
+  def todo_actions_options
+    actions = [
+      OpenStruct.new(id: '', title: 'Any Action'),
+      OpenStruct.new(id: Todo::ASSIGNED, title: 'Assigned'),
+      OpenStruct.new(id: Todo::MENTIONED, title: 'Mentioned')
+    ]
+
+    options_from_collection_for_select(actions, 'id', 'title', params[:action_id])
+  end
+
+  def todo_projects_options
+    projects = current_user.authorized_projects.sorted_by_activity.non_archived
+    projects = projects.includes(:namespace)
+
+    projects = projects.map do |project|
+      OpenStruct.new(id: project.id, title: project.name_with_namespace)
+    end
+
+    projects.unshift(OpenStruct.new(id: '', title: 'Any Project'))
+
+    options_from_collection_for_select(projects, 'id', 'title', params[:project_id])
+  end
+
+  def todo_types_options
+    types = [
+      OpenStruct.new(title: 'Any Type', name: ''),
+      OpenStruct.new(title: 'Issue', name: 'Issue'),
+      OpenStruct.new(title: 'Merge Request', name: 'MergeRequest')
+    ]
+
+    options_from_collection_for_select(types, 'name', 'title', params[:type])
+  end
+end
diff --git a/app/models/note.rb b/app/models/note.rb
index b3809ad81e0..d287e0f3c6d 100644
--- a/app/models/note.rb
+++ b/app/models/note.rb
@@ -37,6 +37,8 @@ class Note < ActiveRecord::Base
   belongs_to :author, class_name: "User"
   belongs_to :updated_by, class_name: "User"
 
+  has_many :todos, dependent: :destroy
+
   delegate :name, to: :project, prefix: true
   delegate :name, :email, to: :author, prefix: true
 
diff --git a/app/models/todo.rb b/app/models/todo.rb
new file mode 100644
index 00000000000..34d71c1b0d3
--- /dev/null
+++ b/app/models/todo.rb
@@ -0,0 +1,53 @@
+# == Schema Information
+#
+# Table name: todos
+#
+#  id          :integer          not null, primary key
+#  user_id     :integer          not null
+#  project_id  :integer          not null
+#  target_id   :integer          not null
+#  target_type :string           not null
+#  author_id   :integer
+#  note_id     :integer
+#  action      :integer          not null
+#  state       :string           not null
+#  created_at  :datetime
+#  updated_at  :datetime
+#
+
+class Todo < ActiveRecord::Base
+  ASSIGNED  = 1
+  MENTIONED = 2
+
+  belongs_to :author, class_name: "User"
+  belongs_to :note
+  belongs_to :project
+  belongs_to :target, polymorphic: true, touch: true
+  belongs_to :user
+
+  delegate :name, :email, to: :author, prefix: true, allow_nil: true
+
+  validates :action, :project, :target, :user, presence: true
+
+  default_scope { reorder(id: :desc) }
+
+  scope :pending, -> { with_state(:pending) }
+  scope :done, -> { with_state(:done) }
+
+  state_machine :state, initial: :pending do
+    event :done do
+      transition pending: :done
+    end
+
+    state :pending
+    state :done
+  end
+
+  def body
+    if note.present?
+      note.note
+    else
+      target.title
+    end
+  end
+end
diff --git a/app/models/user.rb b/app/models/user.rb
index 9fe94b13e52..02ff2456f2b 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -140,7 +140,7 @@ class User < ActiveRecord::Base
   has_one  :abuse_report,             dependent: :destroy
   has_many :spam_logs,                dependent: :destroy
   has_many :builds,                   dependent: :nullify, class_name: 'Ci::Build'
-
+  has_many :todos,                    dependent: :destroy
 
   #
   # Validations
diff --git a/app/services/base_service.rb b/app/services/base_service.rb
index b48ca67d4d2..8563633816c 100644
--- a/app/services/base_service.rb
+++ b/app/services/base_service.rb
@@ -23,6 +23,10 @@ class BaseService
     EventCreateService.new
   end
 
+  def todo_service
+    TodoService.new
+  end
+
   def log_info(message)
     Gitlab::AppLogger.info message
   end
diff --git a/app/services/issuable_base_service.rb b/app/services/issuable_base_service.rb
index 2556f06e2d3..ca87dca4a70 100644
--- a/app/services/issuable_base_service.rb
+++ b/app/services/issuable_base_service.rb
@@ -54,7 +54,7 @@ class IssuableBaseService < BaseService
     if params.present? && issuable.update_attributes(params.merge(updated_by: current_user))
       issuable.reset_events_cache
       handle_common_system_notes(issuable, old_labels: old_labels)
-      handle_changes(issuable)
+      handle_changes(issuable, old_labels: old_labels)
       issuable.create_new_cross_references!(current_user)
       execute_hooks(issuable, 'update')
     end
@@ -71,6 +71,19 @@ class IssuableBaseService < BaseService
     end
   end
 
+  def has_changes?(issuable, options = {})
+    valid_attrs = [:title, :description, :assignee_id, :milestone_id, :target_branch]
+
+    attrs_changed = valid_attrs.any? do |attr|
+      issuable.previous_changes.include?(attr.to_s)
+    end
+
+    old_labels = options[:old_labels]
+    labels_changed = old_labels && issuable.labels != old_labels
+
+    attrs_changed || labels_changed
+  end
+
   def handle_common_system_notes(issuable, options = {})
     if issuable.previous_changes.include?('title')
       create_title_change_note(issuable, issuable.previous_changes['title'].first)
diff --git a/app/services/issues/close_service.rb b/app/services/issues/close_service.rb
index a1a20e47681..78254b49af3 100644
--- a/app/services/issues/close_service.rb
+++ b/app/services/issues/close_service.rb
@@ -3,6 +3,7 @@ module Issues
     def execute(issue, commit = nil)
       if project.jira_tracker? && project.jira_service.active
         project.jira_service.execute(commit, issue)
+        todo_service.close_issue(issue, current_user)
         return issue
       end
 
@@ -10,6 +11,7 @@ module Issues
         event_service.close_issue(issue, current_user)
         create_note(issue, commit)
         notification_service.close_issue(issue, current_user)
+        todo_service.close_issue(issue, current_user)
         execute_hooks(issue, 'close')
       end
 
diff --git a/app/services/issues/create_service.rb b/app/services/issues/create_service.rb
index bcb380d3215..10787e8873c 100644
--- a/app/services/issues/create_service.rb
+++ b/app/services/issues/create_service.rb
@@ -9,6 +9,7 @@ module Issues
       if issue.save
         issue.update_attributes(label_ids: label_params)
         notification_service.new_issue(issue, current_user)
+        todo_service.new_issue(issue, current_user)
         event_service.open_issue(issue, current_user)
         issue.create_cross_references!(current_user)
         execute_hooks(issue, 'open')
diff --git a/app/services/issues/update_service.rb b/app/services/issues/update_service.rb
index a55a04dd5e0..51ef9dfe610 100644
--- a/app/services/issues/update_service.rb
+++ b/app/services/issues/update_service.rb
@@ -4,7 +4,16 @@ module Issues
       update(issue)
     end
 
-    def handle_changes(issue)
+    def handle_changes(issue, options = {})
+      if has_changes?(issue, options)
+        todo_service.mark_pending_todos_as_done(issue, current_user)
+      end
+
+      if issue.previous_changes.include?('title') ||
+         issue.previous_changes.include?('description')
+        todo_service.update_issue(issue, current_user)
+      end
+
       if issue.previous_changes.include?('milestone_id')
         create_milestone_note(issue)
       end
@@ -12,6 +21,7 @@ module Issues
       if issue.previous_changes.include?('assignee_id')
         create_assignee_note(issue)
         notification_service.reassigned_issue(issue, current_user)
+        todo_service.reassigned_issue(issue, current_user)
       end
     end
 
diff --git a/app/services/merge_requests/close_service.rb b/app/services/merge_requests/close_service.rb
index 47454f9f0c2..27ee81fe3e7 100644
--- a/app/services/merge_requests/close_service.rb
+++ b/app/services/merge_requests/close_service.rb
@@ -9,6 +9,7 @@ module MergeRequests
         event_service.close_mr(merge_request, current_user)
         create_note(merge_request)
         notification_service.close_mr(merge_request, current_user)
+        todo_service.close_merge_request(merge_request, current_user)
         execute_hooks(merge_request, 'close')
       end
 
diff --git a/app/services/merge_requests/create_service.rb b/app/services/merge_requests/create_service.rb
index 009d5a6867e..33609d01f20 100644
--- a/app/services/merge_requests/create_service.rb
+++ b/app/services/merge_requests/create_service.rb
@@ -2,7 +2,7 @@ module MergeRequests
   class CreateService < MergeRequests::BaseService
     def execute
       # @project is used to determine whether the user can set the merge request's
-      # assignee, milestone and labels. Whether they can depends on their 
+      # assignee, milestone and labels. Whether they can depends on their
       # permissions on the target project.
       source_project = @project
       @project = Project.find(params[:target_project_id]) if params[:target_project_id]
@@ -18,6 +18,7 @@ module MergeRequests
         merge_request.update_attributes(label_ids: label_params)
         event_service.open_mr(merge_request, current_user)
         notification_service.new_merge_request(merge_request, current_user)
+        todo_service.new_merge_request(merge_request, current_user)
         merge_request.create_cross_references!(current_user)
         execute_hooks(merge_request)
       end
diff --git a/app/services/merge_requests/update_service.rb b/app/services/merge_requests/update_service.rb
index 5ff2cc03dda..6319ad805b6 100644
--- a/app/services/merge_requests/update_service.rb
+++ b/app/services/merge_requests/update_service.rb
@@ -14,7 +14,16 @@ module MergeRequests
       update(merge_request)
     end
 
-    def handle_changes(merge_request)
+    def handle_changes(merge_request, options = {})
+      if has_changes?(merge_request, options)
+        todo_service.mark_pending_todos_as_done(merge_request, current_user)
+      end
+
+      if merge_request.previous_changes.include?('title') ||
+         merge_request.previous_changes.include?('description')
+        todo_service.update_merge_request(merge_request, current_user)
+      end
+
       if merge_request.previous_changes.include?('target_branch')
         create_branch_change_note(merge_request, 'target',
                                   merge_request.previous_changes['target_branch'].first,
@@ -28,6 +37,7 @@ module MergeRequests
       if merge_request.previous_changes.include?('assignee_id')
         create_assignee_note(merge_request)
         notification_service.reassigned_merge_request(merge_request, current_user)
+        todo_service.reassigned_merge_request(merge_request, current_user)
       end
 
       if merge_request.previous_changes.include?('target_branch') ||
diff --git a/app/services/notes/create_service.rb b/app/services/notes/create_service.rb
index 8d9661167b5..b970439b921 100644
--- a/app/services/notes/create_service.rb
+++ b/app/services/notes/create_service.rb
@@ -8,6 +8,7 @@ module Notes
       if note.save
         # Finish the harder work in the background
         NewNoteWorker.perform_in(2.seconds, note.id, params)
+        TodoService.new.new_note(note, current_user)
       end
 
       note
diff --git a/app/services/notes/post_process_service.rb b/app/services/notes/post_process_service.rb
index f37d3c50cdd..e818f58d13c 100644
--- a/app/services/notes/post_process_service.rb
+++ b/app/services/notes/post_process_service.rb
@@ -1,6 +1,5 @@
 module Notes
   class PostProcessService
-
     attr_accessor :note
 
     def initialize(note)
@@ -25,6 +24,5 @@ module Notes
       @note.project.execute_hooks(note_data, :note_hooks)
       @note.project.execute_services(note_data, :note_hooks)
     end
-
   end
 end
diff --git a/app/services/notes/update_service.rb b/app/services/notes/update_service.rb
index 72e2f78008d..1361b1e0300 100644
--- a/app/services/notes/update_service.rb
+++ b/app/services/notes/update_service.rb
@@ -7,6 +7,10 @@ module Notes
       note.create_new_cross_references!(current_user)
       note.reset_events_cache
 
+      if note.previous_changes.include?('note')
+        TodoService.new.update_note(note, current_user)
+      end
+
       note
     end
   end
diff --git a/app/services/todo_service.rb b/app/services/todo_service.rb
new file mode 100644
index 00000000000..dc270602ebc
--- /dev/null
+++ b/app/services/todo_service.rb
@@ -0,0 +1,170 @@
+# TodoService class
+#
+# Used for creating todos after certain user actions
+#
+# Ex.
+#   TodoService.new.new_issue(issue, current_user)
+#
+class TodoService
+  # When create an issue we should:
+  #
+  #  * create a todo for assignee if issue is assigned
+  #  * create a todo for each mentioned user on issue
+  #
+  def new_issue(issue, current_user)
+    new_issuable(issue, current_user)
+  end
+
+  # When update an issue we should:
+  #
+  #  * mark all pending todos related to the issue for the current user as done
+  #
+  def update_issue(issue, current_user)
+    create_mention_todos(issue.project, issue, current_user)
+  end
+
+  # When close an issue we should:
+  #
+  #  * mark all pending todos related to the target for the current user as done
+  #
+  def close_issue(issue, current_user)
+    mark_pending_todos_as_done(issue, current_user)
+  end
+
+  # When we reassign an issue we should:
+  #
+  #  * create a pending todo for new assignee if issue is assigned
+  #
+  def reassigned_issue(issue, current_user)
+    create_assignment_todo(issue, current_user)
+  end
+
+  # When create a merge request we should:
+  #
+  #  * creates a pending todo for assignee if merge request is assigned
+  #  * create a todo for each mentioned user on merge request
+  #
+  def new_merge_request(merge_request, current_user)
+    new_issuable(merge_request, current_user)
+  end
+
+  # When update a merge request we should:
+  #
+  #  * create a todo for each mentioned user on merge request
+  #
+  def update_merge_request(merge_request, current_user)
+    create_mention_todos(merge_request.project, merge_request, current_user)
+  end
+
+  # When close a merge request we should:
+  #
+  #  * mark all pending todos related to the target for the current user as done
+  #
+  def close_merge_request(merge_request, current_user)
+    mark_pending_todos_as_done(merge_request, current_user)
+  end
+
+  # When we reassign a merge request we should:
+  #
+  #  * creates a pending todo for new assignee if merge request is assigned
+  #
+  def reassigned_merge_request(merge_request, current_user)
+    create_assignment_todo(merge_request, current_user)
+  end
+
+  # When merge a merge request we should:
+  #
+  #  * mark all pending todos related to the target for the current user as done
+  #
+  def merge_merge_request(merge_request, current_user)
+    mark_pending_todos_as_done(merge_request, current_user)
+  end
+
+  # When create a note we should:
+  #
+  #  * mark all pending todos related to the noteable for the note author as done
+  #  * create a todo for each mentioned user on note
+  #
+  def new_note(note, current_user)
+    handle_note(note, current_user)
+  end
+
+  # When update a note we should:
+  #
+  #  * mark all pending todos related to the noteable for the current user as done
+  #  * create a todo for each new user mentioned on note
+  #
+  def update_note(note, current_user)
+    handle_note(note, current_user)
+  end
+
+  # When marking pending todos as done we should:
+  #
+  #  * mark all pending todos related to the target for the current user as done
+  #
+  def mark_pending_todos_as_done(target, user)
+    pending_todos(user, target.project, target).update_all(state: :done)
+  end
+
+  private
+
+  def create_todos(project, target, author, users, action, note = nil)
+    Array(users).each do |user|
+      next if pending_todos(user, project, target).exists?
+
+      Todo.create(
+        project: project,
+        user_id: user.id,
+        author_id: author.id,
+        target_id: target.id,
+        target_type: target.class.name,
+        action: action,
+        note: note
+      )
+    end
+  end
+
+  def new_issuable(issuable, author)
+    create_assignment_todo(issuable, author)
+    create_mention_todos(issuable.project, issuable, author)
+  end
+
+  def handle_note(note, author)
+    # Skip system notes, like status changes and cross-references
+    return if note.system
+
+    project = note.project
+    target  = note.noteable
+
+    mark_pending_todos_as_done(target, author)
+    create_mention_todos(project, target, author, note)
+  end
+
+  def create_assignment_todo(issuable, author)
+    if issuable.assignee && issuable.assignee != author
+      create_todos(issuable.project, issuable, author, issuable.assignee, Todo::ASSIGNED)
+    end
+  end
+
+  def create_mention_todos(project, issuable, author, note = nil)
+    mentioned_users = filter_mentioned_users(project, note || issuable, author)
+    create_todos(project, issuable, author, mentioned_users, Todo::MENTIONED, note)
+  end
+
+  def filter_mentioned_users(project, target, author)
+    mentioned_users = target.mentioned_users.select do |user|
+      user.can?(:read_project, project)
+    end
+
+    mentioned_users.delete(author)
+    mentioned_users.uniq
+  end
+
+  def pending_todos(user, project, target)
+    user.todos.pending.where(
+      project_id: project.id,
+      target_id: target.id,
+      target_type: target.class.name
+    )
+  end
+end
diff --git a/app/views/dashboard/todos/_todo.html.haml b/app/views/dashboard/todos/_todo.html.haml
new file mode 100644
index 00000000000..6975f6ed0db
--- /dev/null
+++ b/app/views/dashboard/todos/_todo.html.haml
@@ -0,0 +1,21 @@
+%li{class: "todo todo-#{todo.done? ? 'done' : 'pending'}", id: dom_id(todo) }
+  .todo-item{class: 'todo-block'}
+    = image_tag avatar_icon(todo.author_email, 40), class: 'avatar s40', alt:''
+
+    .todo-title
+      %span.author_name
+        = link_to_author todo
+      %span.todo_label
+        = todo_action_name(todo)
+        = todo_target_link(todo)
+
+      &middot; #{time_ago_with_tooltip(todo.created_at)}
+
+    - if todo.pending?
+      .todo-actions.pull-right
+        = link_to 'Done', [:dashboard, todo], method: :delete, class: 'btn'
+
+    .todo-body
+      .todo-note
+        .md
+          = event_note(todo.body, project: todo.project)
diff --git a/app/views/dashboard/todos/index.html.haml b/app/views/dashboard/todos/index.html.haml
new file mode 100644
index 00000000000..946d7df3933
--- /dev/null
+++ b/app/views/dashboard/todos/index.html.haml
@@ -0,0 +1,62 @@
+- page_title "Todos"
+- header_title "Todos", dashboard_todos_path
+
+.top-area
+  %ul.nav-links
+    %li{class: ('active' if params[:state].blank? || params[:state] == 'pending')}
+      = link_to todos_filter_path(state: 'pending') do
+        %span
+          To do
+        %span{class: 'badge'}
+          = todos_pending_count
+    %li{class: ('active' if params[:state] == 'done')}
+      = link_to todos_filter_path(state: 'done') do
+        %span
+          Done
+        %span{class: 'badge'}
+          = todos_done_count
+
+  .nav-controls
+    - if @todos.any?(&:pending?)
+      = link_to 'Mark all as done', destroy_all_dashboard_todos_path(todos_filter_params), class: 'btn', method: :delete
+
+.todos-filters
+  .gray-content-block.second-block
+    = form_tag todos_filter_path(without: [:project_id, :author_id, :type, :action_id]), method: :get, class: 'filter-form' do
+      .filter-item.inline
+        = select_tag('project_id', todo_projects_options,
+          class: 'select2 trigger-submit', include_blank: true,
+          data: {placeholder: 'Project'})
+      .filter-item.inline
+        = users_select_tag(:author_id, selected: params[:author_id],
+          placeholder: 'Author', class: 'trigger-submit', any_user: "Any Author", first_user: true, current_user: true)
+      .filter-item.inline
+        = select_tag('type', todo_types_options,
+          class: 'select2 trigger-submit', include_blank: true,
+          data: {placeholder: 'Type'})
+      .filter-item.inline.actions-filter
+        = select_tag('action_id', todo_actions_options,
+          class: 'select2 trigger-submit', include_blank: true,
+          data: {placeholder: 'Action'})
+
+.prepend-top-default
+  - if @todos.any?
+    - @todos.group_by(&:project).each do |group|
+      .panel.panel-default.panel-small
+        - project = group[0]
+        .panel-heading
+          = link_to project.name_with_namespace, namespace_project_path(project.namespace, project)
+
+        %ul.well-list.todos-list
+          = render group[1]
+    = paginate @todos, theme: "gitlab"
+  - else
+    .nothing-here-block You're all done!
+
+:javascript
+  new UsersSelect();
+
+  $('form.filter-form').on('submit', function (event) {
+    event.preventDefault();
+    Turbolinks.visit(this.action + '&' + $(this).serialize());
+  });
diff --git a/app/views/layouts/header/_default.html.haml b/app/views/layouts/header/_default.html.haml
index fcb6b835a7e..4781ff23507 100644
--- a/app/views/layouts/header/_default.html.haml
+++ b/app/views/layouts/header/_default.html.haml
@@ -21,6 +21,10 @@
             %li
               = link_to admin_root_path, title: 'Admin Area', data: {toggle: 'tooltip', placement: 'bottom', container: 'body'} do
                 = icon('wrench fw')
+          %li
+            = link_to dashboard_todos_path, title: 'Todos', data: {toggle: 'tooltip', placement: 'bottom', container: 'body'} do
+              %span.badge.todos-pending-count
+                = todos_pending_count
           - if current_user.can_create_project?
             %li
               = link_to new_project_path, title: 'New project', data: {toggle: 'tooltip', placement: 'bottom', container: 'body'} do
@@ -39,4 +43,4 @@
 = render 'shared/outdated_browser'
 - if @project && !@project.empty_repo?
   :javascript
-    var findFileURL = "#{namespace_project_find_file_path(@project.namespace, @project, @ref || @project.repository.root_ref)}";
\ No newline at end of file
+    var findFileURL = "#{namespace_project_find_file_path(@project.namespace, @project, @ref || @project.repository.root_ref)}";
diff --git a/app/views/layouts/nav/_dashboard.html.haml b/app/views/layouts/nav/_dashboard.html.haml
index 106abd24a56..db0cf393922 100644
--- a/app/views/layouts/nav/_dashboard.html.haml
+++ b/app/views/layouts/nav/_dashboard.html.haml
@@ -4,6 +4,12 @@
       = icon('home fw')
       %span
         Projects
+  = nav_link(controller: :todos) do
+    = link_to dashboard_todos_path, title: 'Todos' do
+      = icon('bell fw')
+      %span
+        Todos
+        %span.count= number_with_delimiter(todos_pending_count)
   = nav_link(path: 'dashboard#activity') do
     = link_to activity_dashboard_path, class: 'shortcuts-activity', title: 'Activity' do
       = icon('dashboard fw')
@@ -25,12 +31,12 @@
       %span
         Issues
         %span.count= number_with_delimiter(current_user.assigned_issues.opened.count)
-    = nav_link(path: 'dashboard#merge_requests') do
-      = link_to assigned_mrs_dashboard_path, title: 'Merge Requests', class: 'shortcuts-merge_requests' do
-        = icon('tasks fw')
-        %span
-          Merge Requests
-          %span.count= number_with_delimiter(current_user.assigned_merge_requests.opened.count)
+  = nav_link(path: 'dashboard#merge_requests') do
+    = link_to assigned_mrs_dashboard_path, title: 'Merge Requests', class: 'shortcuts-merge_requests' do
+      = icon('tasks fw')
+      %span
+        Merge Requests
+        %span.count= number_with_delimiter(current_user.assigned_merge_requests.opened.count)
   = nav_link(controller: :snippets) do
     = link_to dashboard_snippets_path, title: 'Snippets' do
       = icon('clipboard fw')
diff --git a/config/routes.rb b/config/routes.rb
index 0ed3f1731f8..30681356c5f 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -334,6 +334,12 @@ Rails.application.routes.draw do
       resources :groups, only: [:index]
       resources :snippets, only: [:index]
 
+      resources :todos, only: [:index, :destroy] do
+        collection do
+          delete :destroy_all
+        end
+      end
+
       resources :projects, only: [:index] do
         collection do
           get :starred
diff --git a/db/migrate/20160212123307_create_tasks.rb b/db/migrate/20160212123307_create_tasks.rb
new file mode 100644
index 00000000000..c3f6f3abc26
--- /dev/null
+++ b/db/migrate/20160212123307_create_tasks.rb
@@ -0,0 +1,14 @@
+class CreateTasks < ActiveRecord::Migration
+  def change
+    create_table :tasks do |t|
+      t.references :user, null: false, index: true
+      t.references :project, null: false, index: true
+      t.references :target, polymorphic: true, null: false, index: true
+      t.integer :author_id, index: true
+      t.integer :action, null: false
+      t.string :state, null: false, index: true
+
+      t.timestamps
+    end
+  end
+end
diff --git a/db/migrate/20160217174422_add_note_to_tasks.rb b/db/migrate/20160217174422_add_note_to_tasks.rb
new file mode 100644
index 00000000000..da5cb2e05db
--- /dev/null
+++ b/db/migrate/20160217174422_add_note_to_tasks.rb
@@ -0,0 +1,5 @@
+class AddNoteToTasks < ActiveRecord::Migration
+  def change
+    add_reference :tasks, :note, index: true
+  end
+end
diff --git a/db/migrate/20160220123949_rename_tasks_to_todos.rb b/db/migrate/20160220123949_rename_tasks_to_todos.rb
new file mode 100644
index 00000000000..30c10d27146
--- /dev/null
+++ b/db/migrate/20160220123949_rename_tasks_to_todos.rb
@@ -0,0 +1,5 @@
+class RenameTasksToTodos < ActiveRecord::Migration
+  def change
+    rename_table :tasks, :todos
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index af5bac63b42..4708c29d9ae 100644
--- 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: 20160217100506) do
+ActiveRecord::Schema.define(version: 20160220123949) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -824,6 +824,26 @@ ActiveRecord::Schema.define(version: 20160217100506) do
 
   add_index "tags", ["name"], name: "index_tags_on_name", unique: true, using: :btree
 
+  create_table "todos", force: :cascade do |t|
+    t.integer  "user_id",     null: false
+    t.integer  "project_id",  null: false
+    t.integer  "target_id",   null: false
+    t.string   "target_type", null: false
+    t.integer  "author_id"
+    t.integer  "action",      null: false
+    t.string   "state",       null: false
+    t.datetime "created_at"
+    t.datetime "updated_at"
+    t.integer  "note_id"
+  end
+
+  add_index "todos", ["author_id"], name: "index_todos_on_author_id", using: :btree
+  add_index "todos", ["note_id"], name: "index_todos_on_note_id", using: :btree
+  add_index "todos", ["project_id"], name: "index_todos_on_project_id", using: :btree
+  add_index "todos", ["state"], name: "index_todos_on_state", using: :btree
+  add_index "todos", ["target_type", "target_id"], name: "index_todos_on_target_type_and_target_id", using: :btree
+  add_index "todos", ["user_id"], name: "index_todos_on_user_id", using: :btree
+
   create_table "users", force: :cascade do |t|
     t.string   "email",                       default: "",    null: false
     t.string   "encrypted_password",          default: "",    null: false
diff --git a/features/dashboard/todos.feature b/features/dashboard/todos.feature
new file mode 100644
index 00000000000..1e7b1b50d64
--- /dev/null
+++ b/features/dashboard/todos.feature
@@ -0,0 +1,38 @@
+@dashboard
+Feature: Dashboard Todos
+  Background:
+    Given I sign in as a user
+    And I own project "Shop"
+    And "John Doe" is a developer of project "Shop"
+    And "Mary Jane" is a developer of project "Shop"
+    And "Mary Jane" owns private project "Enterprise"
+    And I am a developer of project "Enterprise"
+    And I have todos
+    And I visit dashboard todos page
+
+  @javascript
+  Scenario: I mark todos as done
+    Then I should see todos assigned to me
+    And I mark the todo as done
+    And I click on the "Done" tab
+    Then I should see all todos marked as done
+
+  @javascript
+    Scenario: I filter by project
+      Given I filter by "Enterprise"
+      Then I should not see todos
+
+  @javascript
+    Scenario: I filter by author
+      Given I filter by "John Doe"
+      Then I should not see todos related to "Mary Jane" in the list
+
+  @javascript
+    Scenario: I filter by type
+      Given I filter by "Issue"
+      Then I should not see todos related to "Merge Requests" in the list
+
+  @javascript
+    Scenario: I filter by action
+      Given I filter by "Mentioned"
+      Then I should not see todos related to "Assignments" in the list
diff --git a/features/steps/dashboard/todos.rb b/features/steps/dashboard/todos.rb
new file mode 100644
index 00000000000..9722a5a848c
--- /dev/null
+++ b/features/steps/dashboard/todos.rb
@@ -0,0 +1,128 @@
+class Spinach::Features::DashboardTodos < Spinach::FeatureSteps
+  include SharedAuthentication
+  include SharedPaths
+  include SharedProject
+  include SharedUser
+  include Select2Helper
+
+  step '"John Doe" is a developer of project "Shop"' do
+    project.team << [john_doe, :developer]
+  end
+
+  step 'I am a developer of project "Enterprise"' do
+    enterprise.team << [current_user, :developer]
+  end
+
+  step '"Mary Jane" is a developer of project "Shop"' do
+    project.team << [john_doe, :developer]
+  end
+
+  step 'I have todos' do
+    create(:todo, user: current_user, project: project, author: mary_jane, target: issue, action: Todo::MENTIONED)
+    create(:todo, user: current_user, project: project, author: john_doe, target: issue, action: Todo::ASSIGNED)
+    note = create(:note, author: john_doe, noteable: issue, note: "#{current_user.to_reference} Wdyt?")
+    create(:todo, user: current_user, project: project, author: john_doe, target: issue, action: Todo::MENTIONED, note: note)
+    create(:todo, user: current_user, project: project, author: john_doe, target: merge_request, action: Todo::ASSIGNED)
+  end
+
+  step 'I should see todos assigned to me' do
+    expect(page).to have_content 'To do 4'
+    expect(page).to have_content 'Done 0'
+
+    expect(page).to have_link project.name_with_namespace
+    should_see_todo(1, "John Doe assigned you merge request !#{merge_request.iid}", merge_request.title)
+    should_see_todo(2, "John Doe mentioned you on issue ##{issue.iid}", "#{current_user.to_reference} Wdyt?")
+    should_see_todo(3, "John Doe assigned you issue ##{issue.iid}", issue.title)
+    should_see_todo(4, "Mary Jane mentioned you on issue ##{issue.iid}", issue.title)
+  end
+
+  step 'I mark the todo as done' do
+    page.within('.todo:nth-child(1)') do
+      click_link 'Done'
+    end
+
+    expect(page).to have_content 'Todo was successfully marked as done.'
+    expect(page).to have_content 'To do 3'
+    expect(page).to have_content 'Done 1'
+    should_not_see_todo "John Doe assigned you merge request !#{merge_request.iid}"
+  end
+
+  step 'I click on the "Done" tab' do
+    click_link 'Done 1'
+  end
+
+  step 'I should see all todos marked as done' do
+    expect(page).to have_link project.name_with_namespace
+    should_see_todo(1, "John Doe assigned you merge request !#{merge_request.iid}", merge_request.title, false)
+  end
+
+  step 'I filter by "Enterprise"' do
+    select2(enterprise.id, from: "#project_id")
+  end
+
+  step 'I filter by "John Doe"' do
+    select2(john_doe.id, from: "#author_id")
+  end
+
+  step 'I filter by "Issue"' do
+    select2('Issue', from: "#type")
+  end
+
+  step 'I filter by "Mentioned"' do
+    select2("#{Todo::MENTIONED}", from: '#action_id')
+  end
+
+  step 'I should not see todos' do
+    expect(page).to have_content "You're all done!"
+  end
+
+  step 'I should not see todos related to "Mary Jane" in the list' do
+    should_not_see_todo "Mary Jane mentioned you on issue ##{issue.iid}"
+  end
+
+  step 'I should not see todos related to "Merge Requests" in the list' do
+    should_not_see_todo "John Doe assigned you merge request !#{merge_request.iid}"
+  end
+
+  step 'I should not see todos related to "Assignments" in the list' do
+    should_not_see_todo "John Doe assigned you merge request !#{merge_request.iid}"
+    should_not_see_todo "John Doe assigned you issue ##{issue.iid}"
+  end
+
+  def should_see_todo(position, title, body, pending = true)
+    page.within(".todo:nth-child(#{position})") do
+      expect(page).to have_content title
+      expect(page).to have_content body
+
+      if pending
+        expect(page).to have_link 'Done'
+      else
+        expect(page).to_not have_link 'Done'
+      end
+    end
+  end
+
+  def should_not_see_todo(title)
+    expect(page).not_to have_content title
+  end
+
+  def john_doe
+    @john_doe ||= user_exists("John Doe", { username: "john_doe" })
+  end
+
+  def mary_jane
+    @mary_jane ||= user_exists("Mary Jane", { username: "mary_jane" })
+  end
+
+  def enterprise
+    @enterprise ||= Project.find_by(name: 'Enterprise')
+  end
+
+  def issue
+    @issue ||= create(:issue, assignee: current_user, project: project)
+  end
+
+  def merge_request
+    @merge_request ||= create(:merge_request, assignee: current_user, source_project: project)
+  end
+end
diff --git a/features/steps/shared/paths.rb b/features/steps/shared/paths.rb
index 2c854ac7bf9..f4df4874d2f 100644
--- a/features/steps/shared/paths.rb
+++ b/features/steps/shared/paths.rb
@@ -103,6 +103,10 @@ module SharedPaths
     visit dashboard_groups_path
   end
 
+  step 'I visit dashboard todos page' do
+    visit dashboard_todos_path
+  end
+
   step 'I should be redirected to the dashboard groups page' do
     expect(current_path).to eq dashboard_groups_path
   end
diff --git a/spec/factories/todos.rb b/spec/factories/todos.rb
new file mode 100644
index 00000000000..bd85b1d798a
--- /dev/null
+++ b/spec/factories/todos.rb
@@ -0,0 +1,34 @@
+# == Schema Information
+#
+# Table name: todos
+#
+#  id          :integer          not null, primary key
+#  user_id     :integer          not null
+#  project_id  :integer          not null
+#  target_id   :integer          not null
+#  target_type :string           not null
+#  author_id   :integer
+#  note_id     :integer
+#  action      :integer          not null
+#  state       :string           not null
+#  created_at  :datetime
+#  updated_at  :datetime
+#
+
+FactoryGirl.define do
+  factory :todo do
+    project
+    author
+    user
+    target factory: :issue
+    action { Todo::ASSIGNED }
+
+    trait :assigned do
+      action { Todo::ASSIGNED }
+    end
+
+    trait :mentioned do
+      action { Todo::MENTIONED }
+    end
+  end
+end
diff --git a/spec/models/note_spec.rb b/spec/models/note_spec.rb
index e6da3724d33..583937ca748 100644
--- a/spec/models/note_spec.rb
+++ b/spec/models/note_spec.rb
@@ -26,6 +26,8 @@ describe Note, models: true do
     it { is_expected.to belong_to(:project) }
     it { is_expected.to belong_to(:noteable) }
     it { is_expected.to belong_to(:author).class_name('User') }
+
+    it { is_expected.to have_many(:todos).dependent(:destroy) }
   end
 
   describe 'validation' do
diff --git a/spec/models/todo_spec.rb.rb b/spec/models/todo_spec.rb.rb
new file mode 100644
index 00000000000..ac481bf9fbd
--- /dev/null
+++ b/spec/models/todo_spec.rb.rb
@@ -0,0 +1,89 @@
+# == Schema Information
+#
+# Table name: todos
+#
+#  id          :integer          not null, primary key
+#  user_id     :integer          not null
+#  project_id  :integer          not null
+#  target_id   :integer          not null
+#  target_type :string           not null
+#  author_id   :integer
+#  note_id     :integer
+#  action      :integer          not null
+#  state       :string           not null
+#  created_at  :datetime
+#  updated_at  :datetime
+#
+
+require 'spec_helper'
+
+describe Todo, models: true do
+  describe 'relationships' do
+    it { is_expected.to belong_to(:author).class_name("User") }
+    it { is_expected.to belong_to(:note) }
+    it { is_expected.to belong_to(:project) }
+    it { is_expected.to belong_to(:target).touch(true) }
+    it { is_expected.to belong_to(:user) }
+  end
+
+  describe 'respond to' do
+    it { is_expected.to respond_to(:author_name) }
+    it { is_expected.to respond_to(:author_email) }
+  end
+
+  describe 'validations' do
+    it { is_expected.to validate_presence_of(:action) }
+    it { is_expected.to validate_presence_of(:target) }
+    it { is_expected.to validate_presence_of(:user) }
+  end
+
+  describe '#action_name' do
+    it 'returns proper message when action is an assigment' do
+      subject.action = Todo::ASSIGNED
+
+      expect(subject.action_name).to eq 'assigned'
+    end
+
+    it 'returns proper message when action is a mention' do
+      subject.action = Todo::MENTIONED
+
+      expect(subject.action_name).to eq 'mentioned you on'
+    end
+  end
+
+  describe '#body' do
+    before do
+      subject.target = build(:issue, title: 'Bugfix')
+    end
+
+    it 'returns target title when note is blank' do
+      subject.note = nil
+
+      expect(subject.body).to eq 'Bugfix'
+    end
+
+    it 'returns note when note is present' do
+      subject.note = build(:note, note: 'quick fix')
+
+      expect(subject.body).to eq 'quick fix'
+    end
+  end
+
+  describe '#target_iid' do
+    let(:issue) { build(:issue, id: 1, iid: 5) }
+
+    before do
+      subject.target = issue
+    end
+
+    it 'returns target.iid when target respond to iid' do
+      expect(subject.target_iid).to eq 5
+    end
+
+    it 'returns target_id when target does not respond to iid' do
+      allow(issue).to receive(:respond_to?).with(:iid).and_return(false)
+
+      expect(subject.target_iid).to eq 1
+    end
+  end
+end
diff --git a/spec/models/user_spec.rb b/spec/models/user_spec.rb
index 47ce409fe4b..32d4f39b04a 100644
--- a/spec/models/user_spec.rb
+++ b/spec/models/user_spec.rb
@@ -92,6 +92,7 @@ describe User, models: true do
     it { is_expected.to have_many(:identities).dependent(:destroy) }
     it { is_expected.to have_one(:abuse_report) }
     it { is_expected.to have_many(:spam_logs).dependent(:destroy) }
+    it { is_expected.to have_many(:todos).dependent(:destroy) }
   end
 
   describe 'validations' do
diff --git a/spec/services/issues/close_service_spec.rb b/spec/services/issues/close_service_spec.rb
index 3a8daf28f5e..62b25709a5d 100644
--- a/spec/services/issues/close_service_spec.rb
+++ b/spec/services/issues/close_service_spec.rb
@@ -5,6 +5,7 @@ describe Issues::CloseService, services: true do
   let(:user2) { create(:user) }
   let(:issue) { create(:issue, assignee: user2) }
   let(:project) { issue.project }
+  let!(:todo) { create(:todo, :assigned, user: user, project: project, target: issue, author: user2) }
 
   before do
     project.team << [user, :master]
@@ -32,6 +33,10 @@ describe Issues::CloseService, services: true do
         note = @issue.notes.last
         expect(note.note).to include "Status changed to closed"
       end
+
+      it 'marks todos as done' do
+        expect(todo.reload).to be_done
+      end
     end
 
     context "external issue tracker" do
@@ -42,6 +47,7 @@ describe Issues::CloseService, services: true do
 
       it { expect(@issue).to be_valid }
       it { expect(@issue).to be_opened }
+      it { expect(todo.reload).to be_pending }
     end
   end
 end
diff --git a/spec/services/issues/create_service_spec.rb b/spec/services/issues/create_service_spec.rb
index 2148d091a57..5e7915db7e1 100644
--- a/spec/services/issues/create_service_spec.rb
+++ b/spec/services/issues/create_service_spec.rb
@@ -3,14 +3,18 @@ require 'spec_helper'
 describe Issues::CreateService, services: true do
   let(:project) { create(:empty_project) }
   let(:user) { create(:user) }
+  let(:assignee) { create(:user) }
 
   describe :execute do
-    context "valid params" do
+    context 'valid params' do
       before do
         project.team << [user, :master]
+        project.team << [assignee, :master]
+
         opts = {
           title: 'Awesome issue',
-          description: 'please fix'
+          description: 'please fix',
+          assignee: assignee
         }
 
         @issue = Issues::CreateService.new(project, user, opts).execute
@@ -18,6 +22,21 @@ describe Issues::CreateService, services: true do
 
       it { expect(@issue).to be_valid }
       it { expect(@issue.title).to eq('Awesome issue') }
+      it { expect(@issue.assignee).to eq assignee }
+
+      it 'creates a pending todo for new assignee' do
+        attributes = {
+          project: project,
+          author: user,
+          user: assignee,
+          target_id: @issue.id,
+          target_type: @issue.class.name,
+          action: Todo::ASSIGNED,
+          state: :pending
+        }
+
+        expect(Todo.where(attributes).count).to eq 1
+      end
     end
   end
 end
diff --git a/spec/services/issues/update_service_spec.rb b/spec/services/issues/update_service_spec.rb
index 87da0e9618b..e579e49dfa7 100644
--- a/spec/services/issues/update_service_spec.rb
+++ b/spec/services/issues/update_service_spec.rb
@@ -80,6 +80,74 @@ describe Issues::UpdateService, services: true do
       end
     end
 
+    context 'todos' do
+      let!(:todo) { create(:todo, :assigned, user: user, project: project, target: issue, author: user2) }
+
+      context 'when the title change' do
+        before do
+          update_issue({ title: 'New title' })
+        end
+
+        it 'marks pending todos as done' do
+          expect(todo.reload.done?).to eq true
+        end
+      end
+
+      context 'when the description change' do
+        before do
+          update_issue({ description: 'Also please fix' })
+        end
+
+        it 'marks todos as done' do
+          expect(todo.reload.done?).to eq true
+        end
+      end
+
+      context 'when is reassigned' do
+        before do
+          update_issue({ assignee: user2 })
+        end
+
+        it 'marks previous assignee todos as done' do
+          expect(todo.reload.done?).to eq true
+        end
+
+        it 'creates a todo for new assignee' do
+          attributes = {
+            project: project,
+            author: user,
+            user: user2,
+            target_id: issue.id,
+            target_type: issue.class.name,
+            action: Todo::ASSIGNED,
+            state: :pending
+          }
+
+          expect(Todo.where(attributes).count).to eq 1
+        end
+      end
+
+      context 'when the milestone change' do
+        before do
+          update_issue({ milestone: create(:milestone) })
+        end
+
+        it 'marks todos as done' do
+          expect(todo.reload.done?).to eq true
+        end
+      end
+
+      context 'when the labels change' do
+        before do
+          update_issue({ label_ids: [label.id] })
+        end
+
+        it 'marks todos as done' do
+          expect(todo.reload.done?).to eq true
+        end
+      end
+    end
+
     context 'when Issue has tasks' do
       before { update_issue({ description: "- [ ] Task 1\n- [ ] Task 2" }) }
 
@@ -144,6 +212,5 @@ describe Issues::UpdateService, services: true do
         end
       end
     end
-
   end
 end
diff --git a/spec/services/merge_requests/close_service_spec.rb b/spec/services/merge_requests/close_service_spec.rb
index 50d0c288790..8443a00e70c 100644
--- a/spec/services/merge_requests/close_service_spec.rb
+++ b/spec/services/merge_requests/close_service_spec.rb
@@ -5,6 +5,7 @@ describe MergeRequests::CloseService, services: true do
   let(:user2) { create(:user) }
   let(:merge_request) { create(:merge_request, assignee: user2) }
   let(:project) { merge_request.project }
+  let!(:todo) { create(:todo, :assigned, user: user, project: project, target: merge_request, author: user2) }
 
   before do
     project.team << [user, :master]
@@ -41,6 +42,10 @@ describe MergeRequests::CloseService, services: true do
         note = @merge_request.notes.last
         expect(note.note).to include 'Status changed to closed'
       end
+
+      it 'marks todos as done' do
+        expect(todo.reload).to be_done
+      end
     end
   end
 end
diff --git a/spec/services/merge_requests/create_service_spec.rb b/spec/services/merge_requests/create_service_spec.rb
index be8f1676eeb..120f4d6a669 100644
--- a/spec/services/merge_requests/create_service_spec.rb
+++ b/spec/services/merge_requests/create_service_spec.rb
@@ -3,6 +3,7 @@ require 'spec_helper'
 describe MergeRequests::CreateService, services: true do
   let(:project) { create(:project) }
   let(:user) { create(:user) }
+  let(:assignee) { create(:user) }
 
   describe :execute do
     context 'valid params' do
@@ -14,10 +15,12 @@ describe MergeRequests::CreateService, services: true do
           target_branch: 'master'
         }
       end
+
       let(:service) { MergeRequests::CreateService.new(project, user, opts) }
 
       before do
         project.team << [user, :master]
+        project.team << [assignee, :developer]
         allow(service).to receive(:execute_hooks)
 
         @merge_request = service.execute
@@ -25,10 +28,49 @@ describe MergeRequests::CreateService, services: true do
 
       it { expect(@merge_request).to be_valid }
       it { expect(@merge_request.title).to eq('Awesome merge_request') }
+      it { expect(@merge_request.assignee).to be_nil }
 
       it 'should execute hooks with default action' do
         expect(service).to have_received(:execute_hooks).with(@merge_request)
       end
+
+      it 'does not creates todos' do
+        attributes = {
+          project: project,
+          target_id: @merge_request.id,
+          target_type: @merge_request.class.name
+        }
+
+        expect(Todo.where(attributes).count).to be_zero
+      end
+
+      context 'when merge request is assigned to someone' do
+        let(:opts) do
+          {
+            title: 'Awesome merge_request',
+            description: 'please fix',
+            source_branch: 'feature',
+            target_branch: 'master',
+            assignee: assignee
+          }
+        end
+
+        it { expect(@merge_request.assignee).to eq assignee }
+
+        it 'creates a todo for new assignee' do
+          attributes = {
+            project: project,
+            author: user,
+            user: assignee,
+            target_id: @merge_request.id,
+            target_type: @merge_request.class.name,
+            action: Todo::ASSIGNED,
+            state: :pending
+          }
+
+          expect(Todo.where(attributes).count).to eq 1
+        end
+      end
     end
   end
 end
diff --git a/spec/services/merge_requests/update_service_spec.rb b/spec/services/merge_requests/update_service_spec.rb
index 2e9e6e0870d..99703c7a8ec 100644
--- a/spec/services/merge_requests/update_service_spec.rb
+++ b/spec/services/merge_requests/update_service_spec.rb
@@ -98,6 +98,84 @@ describe MergeRequests::UpdateService, services: true do
       end
     end
 
+    context 'todos' do
+      let!(:pending_todo) { create(:todo, :assigned, user: user, project: project, target: merge_request, author: user2) }
+
+      context 'when the title change' do
+        before do
+          update_merge_request({ title: 'New title' })
+        end
+
+        it 'marks pending todos as done' do
+          expect(pending_todo.reload).to be_done
+        end
+      end
+
+      context 'when the description change' do
+        before do
+          update_merge_request({ description: 'Also please fix' })
+        end
+
+        it 'marks pending todos as done' do
+          expect(pending_todo.reload).to be_done
+        end
+      end
+
+      context 'when is reassigned' do
+        before do
+          update_merge_request({ assignee: user2 })
+        end
+
+        it 'marks previous assignee pending todos as done' do
+          expect(pending_todo.reload).to be_done
+        end
+
+        it 'creates a pending todo for new assignee' do
+          attributes = {
+            project: project,
+            author: user,
+            user: user2,
+            target_id: merge_request.id,
+            target_type: merge_request.class.name,
+            action: Todo::ASSIGNED,
+            state: :pending
+          }
+
+          expect(Todo.where(attributes).count).to eq 1
+        end
+      end
+
+      context 'when the milestone change' do
+        before do
+          update_merge_request({ milestone: create(:milestone) })
+        end
+
+        it 'marks pending todos as done' do
+          expect(pending_todo.reload).to be_done
+        end
+      end
+
+      context 'when the labels change' do
+        before do
+          update_merge_request({ label_ids: [label.id] })
+        end
+
+        it 'marks pending todos as done' do
+          expect(pending_todo.reload).to be_done
+        end
+      end
+
+      context 'when the target branch change' do
+        before do
+          update_merge_request({ target_branch: 'target' })
+        end
+
+        it 'marks pending todos as done' do
+          expect(pending_todo.reload).to be_done
+        end
+      end
+    end
+
     context 'when MergeRequest has tasks' do
       before { update_merge_request({ description: "- [ ] Task 1\n- [ ] Task 2" }) }
 
@@ -130,6 +208,5 @@ describe MergeRequests::UpdateService, services: true do
         end
       end
     end
-
   end
 end
diff --git a/spec/services/notes/post_process_service_spec.rb b/spec/services/notes/post_process_service_spec.rb
index 1a3f339bd64..d4c50f824c1 100644
--- a/spec/services/notes/post_process_service_spec.rb
+++ b/spec/services/notes/post_process_service_spec.rb
@@ -20,6 +20,7 @@ describe Notes::PostProcessService, services: true do
     it do
       expect(project).to receive(:execute_hooks)
       expect(project).to receive(:execute_services)
+
       Notes::PostProcessService.new(@note).execute
     end
   end
diff --git a/spec/services/notes/update_service_spec.rb b/spec/services/notes/update_service_spec.rb
new file mode 100644
index 00000000000..dde4bde7dc2
--- /dev/null
+++ b/spec/services/notes/update_service_spec.rb
@@ -0,0 +1,45 @@
+require 'spec_helper'
+
+describe Notes::UpdateService, services: true do
+  let(:project) { create(:empty_project) }
+  let(:user) { create(:user) }
+  let(:user2) { create(:user) }
+  let(:issue) { create(:issue, project: project) }
+  let(:note) { create(:note, project: project, noteable: issue, author: user, note: 'Old note') }
+
+  before do
+    project.team << [user, :master]
+    project.team << [user2, :developer]
+  end
+
+  describe '#execute' do
+    def update_note(opts)
+      @note = Notes::UpdateService.new(project, user, opts).execute(note)
+      @note.reload
+    end
+
+    context 'todos' do
+      let!(:todo) { create(:todo, :assigned, user: user, project: project, target: issue, author: user2) }
+
+      context 'when the note change' do
+        before do
+          update_note({ note: 'New note' })
+        end
+
+        it 'marks todos as done' do
+          expect(todo.reload).to be_done
+        end
+      end
+
+      context 'when the note does not change' do
+        before do
+          update_note({ note: 'Old note' })
+        end
+
+        it 'keep todos' do
+          expect(todo.reload).to be_pending
+        end
+      end
+    end
+  end
+end
diff --git a/spec/services/todo_service_spec.rb b/spec/services/todo_service_spec.rb
new file mode 100644
index 00000000000..df3aa955f24
--- /dev/null
+++ b/spec/services/todo_service_spec.rb
@@ -0,0 +1,264 @@
+require 'spec_helper'
+
+describe TodoService, services: true do
+  let(:author) { create(:user) }
+  let(:john_doe) { create(:user, username: 'john_doe') }
+  let(:michael) { create(:user, username: 'michael') }
+  let(:stranger) { create(:user, username: 'stranger') }
+  let(:project) { create(:project) }
+  let(:mentions) { [author.to_reference, john_doe.to_reference, michael.to_reference, stranger.to_reference].join(' ') }
+  let(:service) { described_class.new }
+
+  before do
+    project.team << [author, :developer]
+    project.team << [john_doe, :developer]
+    project.team << [michael, :developer]
+  end
+
+  describe 'Issues' do
+    let(:issue) { create(:issue, project: project, assignee: john_doe, author: author, description: mentions) }
+    let(:unassigned_issue) { create(:issue, project: project, assignee: nil) }
+
+    describe '#new_issue' do
+      it 'creates a todo if assigned' do
+        service.new_issue(issue, author)
+
+        should_create_todo(user: john_doe, target: issue, action: Todo::ASSIGNED)
+      end
+
+      it 'does not create a todo if unassigned' do
+        should_not_create_any_todo { service.new_issue(unassigned_issue, author) }
+      end
+
+      it 'does not create a todo if assignee is the current user' do
+        should_not_create_any_todo { service.new_issue(unassigned_issue, john_doe) }
+      end
+
+      it 'creates a todo for each valid mentioned user' do
+        service.new_issue(issue, author)
+
+        should_create_todo(user: michael, target: issue, action: Todo::MENTIONED)
+        should_not_create_todo(user: author, target: issue, action: Todo::MENTIONED)
+        should_not_create_todo(user: john_doe, target: issue, action: Todo::MENTIONED)
+        should_not_create_todo(user: stranger, target: issue, action: Todo::MENTIONED)
+      end
+    end
+
+    describe '#update_issue' do
+      it 'creates a todo for each valid mentioned user' do
+        service.update_issue(issue, author)
+
+        should_create_todo(user: michael, target: issue, action: Todo::MENTIONED)
+        should_create_todo(user: john_doe, target: issue, action: Todo::MENTIONED)
+        should_not_create_todo(user: author, target: issue, action: Todo::MENTIONED)
+        should_not_create_todo(user: stranger, target: issue, action: Todo::MENTIONED)
+      end
+
+      it 'does not create a todo if user was already mentioned' do
+        create(:todo, :mentioned, user: michael, project: project, target: issue, author: author)
+
+        expect { service.update_issue(issue, author) }.not_to change(michael.todos, :count)
+      end
+    end
+
+    describe '#close_issue' do
+      it 'marks related pending todos to the target for the user as done' do
+        first_todo = create(:todo, :assigned, user: john_doe, project: project, target: issue, author: author)
+        second_todo = create(:todo, :assigned, user: john_doe, project: project, target: issue, author: author)
+
+        service.close_issue(issue, john_doe)
+
+        expect(first_todo.reload).to be_done
+        expect(second_todo.reload).to be_done
+      end
+    end
+
+    describe '#reassigned_issue' do
+      it 'creates a pending todo for new assignee' do
+        unassigned_issue.update_attribute(:assignee, john_doe)
+        service.reassigned_issue(unassigned_issue, author)
+
+        should_create_todo(user: john_doe, target: unassigned_issue, action: Todo::ASSIGNED)
+      end
+
+      it 'does not create a todo if unassigned' do
+        issue.update_attribute(:assignee, nil)
+
+        should_not_create_any_todo { service.reassigned_issue(issue, author) }
+      end
+
+      it 'does not create a todo if new assignee is the current user' do
+        unassigned_issue.update_attribute(:assignee, john_doe)
+
+        should_not_create_any_todo { service.reassigned_issue(unassigned_issue, john_doe) }
+      end
+    end
+
+    describe '#mark_pending_todos_as_done' do
+      it 'marks related pending todos to the target for the user as done' do
+        first_todo = create(:todo, :assigned, user: john_doe, project: project, target: issue, author: author)
+        second_todo = create(:todo, :assigned, user: john_doe, project: project, target: issue, author: author)
+
+        service.mark_pending_todos_as_done(issue, john_doe)
+
+        expect(first_todo.reload).to be_done
+        expect(second_todo.reload).to be_done
+      end
+    end
+
+    describe '#new_note' do
+      let!(:first_todo) { create(:todo, :assigned, user: john_doe, project: project, target: issue, author: author) }
+      let!(:second_todo) { create(:todo, :assigned, user: john_doe, project: project, target: issue, author: author) }
+      let(:note) { create(:note, project: project, noteable: issue, author: john_doe, note: mentions) }
+      let(:award_note) { create(:note, :award, project: project, noteable: issue, author: john_doe, note: 'thumbsup') }
+      let(:system_note) { create(:system_note, project: project, noteable: issue) }
+
+      it 'mark related pending todos to the noteable for the note author as done' do
+        first_todo = create(:todo, :assigned, user: john_doe, project: project, target: issue, author: author)
+        second_todo = create(:todo, :assigned, user: john_doe, project: project, target: issue, author: author)
+
+        service.new_note(note, john_doe)
+
+        expect(first_todo.reload).to be_done
+        expect(second_todo.reload).to be_done
+      end
+
+      it 'mark related pending todos to the noteable for the award note author as done' do
+        service.new_note(award_note, john_doe)
+
+        expect(first_todo.reload).to be_done
+        expect(second_todo.reload).to be_done
+      end
+
+      it 'does not mark related pending todos it is a system note' do
+        service.new_note(system_note, john_doe)
+
+        expect(first_todo.reload).to be_pending
+        expect(second_todo.reload).to be_pending
+      end
+
+      it 'creates a todo for each valid mentioned user' do
+        service.new_note(note, john_doe)
+
+        should_create_todo(user: michael, target: issue, author: john_doe, action: Todo::MENTIONED, note: note)
+        should_create_todo(user: author, target: issue, author: john_doe, action: Todo::MENTIONED, note: note)
+        should_not_create_todo(user: john_doe, target: issue, author: john_doe, action: Todo::MENTIONED, note: note)
+        should_not_create_todo(user: stranger, target: issue, author: john_doe, action: Todo::MENTIONED, note: note)
+      end
+    end
+  end
+
+  describe 'Merge Requests' do
+    let(:mr_assigned) { create(:merge_request, source_project: project, author: author, assignee: john_doe, description: mentions) }
+    let(:mr_unassigned) { create(:merge_request, source_project: project, author: author, assignee: nil) }
+
+    describe '#new_merge_request' do
+      it 'creates a pending todo if assigned' do
+        service.new_merge_request(mr_assigned, author)
+
+        should_create_todo(user: john_doe, target: mr_assigned, action: Todo::ASSIGNED)
+      end
+
+      it 'does not create a todo if unassigned' do
+        should_not_create_any_todo { service.new_merge_request(mr_unassigned, author) }
+      end
+
+      it 'does not create a todo if assignee is the current user' do
+        should_not_create_any_todo { service.new_merge_request(mr_unassigned, john_doe) }
+      end
+
+      it 'creates a todo for each valid mentioned user' do
+        service.new_merge_request(mr_assigned, author)
+
+        should_create_todo(user: michael, target: mr_assigned, action: Todo::MENTIONED)
+        should_not_create_todo(user: author, target: mr_assigned, action: Todo::MENTIONED)
+        should_not_create_todo(user: john_doe, target: mr_assigned, action: Todo::MENTIONED)
+        should_not_create_todo(user: stranger, target: mr_assigned, action: Todo::MENTIONED)
+      end
+    end
+
+    describe '#update_merge_request' do
+      it 'creates a todo for each valid mentioned user' do
+        service.update_merge_request(mr_assigned, author)
+
+        should_create_todo(user: michael, target: mr_assigned, action: Todo::MENTIONED)
+        should_create_todo(user: john_doe, target: mr_assigned, action: Todo::MENTIONED)
+        should_not_create_todo(user: author, target: mr_assigned, action: Todo::MENTIONED)
+        should_not_create_todo(user: stranger, target: mr_assigned, action: Todo::MENTIONED)
+      end
+
+      it 'does not create a todo if user was already mentioned' do
+        create(:todo, :mentioned, user: michael, project: project, target: mr_assigned, author: author)
+
+        expect { service.update_merge_request(mr_assigned, author) }.not_to change(michael.todos, :count)
+      end
+    end
+
+    describe '#close_merge_request' do
+      it 'marks related pending todos to the target for the user as done' do
+        first_todo = create(:todo, :assigned, user: john_doe, project: project, target: mr_assigned, author: author)
+        second_todo = create(:todo, :assigned, user: john_doe, project: project, target: mr_assigned, author: author)
+        service.close_merge_request(mr_assigned, john_doe)
+
+        expect(first_todo.reload).to be_done
+        expect(second_todo.reload).to be_done
+      end
+    end
+
+    describe '#reassigned_merge_request' do
+      it 'creates a pending todo for new assignee' do
+        mr_unassigned.update_attribute(:assignee, john_doe)
+        service.reassigned_merge_request(mr_unassigned, author)
+
+        should_create_todo(user: john_doe, target: mr_unassigned, action: Todo::ASSIGNED)
+      end
+
+      it 'does not create a todo if unassigned' do
+        mr_assigned.update_attribute(:assignee, nil)
+
+        should_not_create_any_todo { service.reassigned_merge_request(mr_assigned, author) }
+      end
+
+      it 'does not create a todo if new assignee is the current user' do
+        mr_assigned.update_attribute(:assignee, john_doe)
+
+        should_not_create_any_todo { service.reassigned_merge_request(mr_assigned, john_doe) }
+      end
+    end
+
+    describe '#merge_merge_request' do
+      it 'marks related pending todos to the target for the user as done' do
+        first_todo = create(:todo, :assigned, user: john_doe, project: project, target: mr_assigned, author: author)
+        second_todo = create(:todo, :assigned, user: john_doe, project: project, target: mr_assigned, author: author)
+        service.merge_merge_request(mr_assigned, john_doe)
+
+        expect(first_todo.reload).to be_done
+        expect(second_todo.reload).to be_done
+      end
+    end
+  end
+
+  def should_create_todo(attributes = {})
+    attributes.reverse_merge!(
+      project: project,
+      author: author,
+      state: :pending
+    )
+
+    expect(Todo.where(attributes).count).to eq 1
+  end
+
+  def should_not_create_todo(attributes = {})
+    attributes.reverse_merge!(
+      project: project,
+      author: author,
+      state: :pending
+    )
+
+    expect(Todo.where(attributes).count).to eq 0
+  end
+
+  def should_not_create_any_todo
+    expect { yield }.not_to change(Todo, :count)
+  end
+end