Merge pull request #23 from justCxx/exercise-17

Complete Exercise 17

app/controllers/reviews_controller.rb

@@ -5,7 +5,7 @@ def new
 
   def create
     @card = current_user.cards.find(review_params[:card_id])
-    review = @card.review(review_params[:answer])
+    review = @card.review(review_params[:answer], review_params[:quality].to_i)
 
     if review[:success]
       flash[:success] = t("review_success",
@@ -24,6 +24,6 @@ def create
   protected
 
   def review_params
-    params.require(:review).permit(:card_id, :answer)
+    params.require(:review).permit(:card_id, :answer, :quality)
   end
 end

app/models/card.rb

@@ -1,6 +1,4 @@
 class Card < ActiveRecord::Base
-  MAX_CORRECT_ANSWERS = 5
-  MAX_INCORRECT_ANSWERS = 3
   MAX_LEVENSHTEIN_DISTANCE = 1
 
   belongs_to :deck
@@ -9,7 +7,7 @@ class Card < ActiveRecord::Base
   validate :words_different
   validates_associated :deck
 
-  before_validation :set_review_date, if: :new_record?
+  after_initialize :set_default_date, if: :new_record?
 
   has_attached_file :image, styles: { medium: "360x360", thumb: "100x100" },
                             default_url: "cards/missing/:style/missing.png"
@@ -22,66 +20,38 @@ def self.for_review
     cards.offset(rand(cards.count))
   end
 
-  def review(translated)
+  def review(translated, quality)
     typos = words_distanse(translated, original_text)
-
-    if typos <= MAX_LEVENSHTEIN_DISTANCE
-      handle_correct_answer
-    else
-      handle_incorrect_answer
-    end
-
-    { success: typos <= MAX_LEVENSHTEIN_DISTANCE, typos: typos }
+    success = typos <= MAX_LEVENSHTEIN_DISTANCE
+    update_review_date(success ? quality : 0)
+    { success: success, typos: typos }
   end
 
   protected
 
-  def handle_correct_answer
-    increment(:correct_answers) if correct_answers < MAX_CORRECT_ANSWERS
-    update_attributes(incorrect_answers: 0)
-    update_review_date
+  def update_review_date(quality)
+    repetition = SuperMemo2.repetition(e_factor, interval, quality, repetitions)
+    repetition[:review_date] = DateTime.now + repetition[:interval]
+    update_attributes(repetition)
   end
 
-  def handle_incorrect_answer
-    decrement(:correct_answers) if correct_answers > 0
-    increment(:incorrect_answers) if incorrect_answers < MAX_INCORRECT_ANSWERS
-    save
+  def words_distanse(word1, word2)
+    DamerauLevenshtein.distance(normalize(word1), normalize(word2))
   end
 
+  private
+
   def normalize(str)
     str.squish.mb_chars.downcase.to_s
   end
 
-  def set_review_date
+  def set_default_date
     self.review_date = DateTime.now
   end
 
-  def update_review_date
-    case correct_answers
-    when 0
-      offset = 0
-    when 1
-      offset = 12.hour
-    when 2
-      offset = 3.day
-    when 3
-      offset = 1.week
-    when 4
-      offset = 2.week
-    else
-      offset = 1.month
-    end
-
-    update_attributes(review_date: review_date + offset)
-  end
-
   def words_different
     if normalize(original_text) == (translated_text)
       errors.add(:original_text, "can't equal translated text")
     end
   end
-
-  def words_distanse(word1, word2)
-    DamerauLevenshtein.distance(normalize(word1), normalize(word2))
-  end
 end

app/services/super_memo2.rb

@@ -0,0 +1,75 @@
+# This class implement a _SuperMemo2_ algorithm.
+# See more: http://www.supermemo.com/english/ol/sm2.htm
+#
+# Algorithm _SM-2_ used in the computer-based variant of the SuperMemo method
+# and involving the calculation of easiness factors for particular items:
+#
+# 1. Split the knowledge into smallest possible items.
+# 2. With all items associate an E-Factor equal to 2.5.
+# 3. Repeat items using the following intervals:
+#     I(1) = 1
+#     I(2) = 6
+#     for n > 2: I(n) = I(n-1) * EF
+#
+#    where:
+#    *I*(*n*) - inter-repetition interval after the n-th repetition (in days),
+#    *EF* - E-Factor of a given item
+#    If interval is a fraction, round it up to the nearest integer.
+# 4. After each repetition assess the quality of repetition response in 0-5
+#    grade scale:
+#     5 - perfect response
+#     4 - correct response after a hesitation
+#     3 - correct response recalled with serious difficulty
+#     2 - incorrect response; where the correct one seemed easy to recall
+#     1 - incorrect response; the correct one remembered
+#     0 - complete blackout.
+# 5. After each repetition modify the E-Factor of the recently repeated item
+#    according to the formula:
+#     E-Factror = EF + (0.1 - (5 - q) * (0.08 + (5 - q) * 0.02))
+#    where:
+#    *E-Factor* - new value of the E-Factor,
+#    *EF* - old value of the E-Factor,
+#    *q* - quality of the response in the 0-5 grade scale.
+#    If *EF* is less than 1.3 then let EF be 1.3.
+# 6. If the quality response was lower than 3 then start repetitions for the
+#    item from the beginning without changing the E-Factor (i.e. use intervals
+#    I(1), I(2) etc. as if the item was memorized anew).
+# 7. After each repetition session of a given day repeat again all items that
+#    scored below four in the quality assessment. Continue the repetitions until
+#    all of these items score at least fou
+class SuperMemo2
+  MIN_E_FACTOR = 1.3
+  MIN_QUALITY = 3
+
+  # Return repetition result
+  def self.repetition(e_factor, interval, quality, repetitions)
+    repetitions = reduce_repetitions(repetitions, quality)
+    {
+      e_factor: e_factor(e_factor, quality),
+      interval: interval(e_factor, interval, repetitions).days,
+      quality: quality,
+      repetitions: repetitions + 1
+    }
+  end
+
+  # Return interval unto the next repetition (see p.3 of class description).
+  def self.interval(e_factor, interval, repetitions)
+    case repetitions
+    when 0 then 1
+    when 1 then 6
+    else
+      (interval * e_factor).ceil
+    end
+  end
+
+  # Return E-Factor according to the formula (see p.5 of class description).
+  def self.e_factor(e_factor, quality)
+    ef = e_factor + (0.1 - (5 - quality) * (0.08 + (5 - quality) * 0.02))
+    [MIN_E_FACTOR, ef].max
+  end
+
+  # Return count of repetitions (see p.3 of class description).
+  def self.reduce_repetitions(repetitions, quality)
+    quality < MIN_QUALITY ? 0 : repetitions
+  end
+end

app/views/cards/index.html.erb

@@ -6,8 +6,7 @@
     <th><%= Card.human_attribute_name(:translated_text) %></th>
     <th><%= Card.human_attribute_name(:image) %></th>
     <th><%= Card.human_attribute_name(:review_date) %></th>
-    <th><%= Card.human_attribute_name(:correct_answers) %></th>
-    <th><%= Card.human_attribute_name(:incorrect_answers) %></th>
+    <th><%= Card.human_attribute_name(:repetitions) %></th>
     <th><%= Deck.human_attribute_name(:title) %></th>
   </tr>
 
@@ -16,9 +15,8 @@
       <td><%= card.original_text %></td>
       <td><%= card.translated_text %></td>
       <td><%= image_tag card.image.url(:thumb) %></td>
-      <td><%= card.review_date.strftime("%d/%m/%Y %H:%M") %></td>
-      <td><%= card.correct_answers %></td>
-      <td><%= card.incorrect_answers %></td>
+      <td><%= card.review_date.localtime.strftime("%d/%m/%Y %H:%M") %></td>
+      <td><%= card.repetitions %></td>
       <td><%= card.deck.title %></td>
       <td><%= link_to t(:edit), edit_card_path(card) %></td>
       <td><%= link_to t(:destroy), card_path(card), method: :delete %></td>

app/views/reviews/_form.html.erb

@@ -5,5 +5,6 @@
     <p><%= card.translated_text %></p>
   </div>
   <%= f.input :answer, label: (t :review_answer) %>
+  <%= f.input :quality, label: (t :review_quality), collection: 1..5 %>
   <%= f.button :submit, (t :review_check) %>
 <% end %>

app/views/reviews/new.html.erb

@@ -1,5 +1,5 @@
 <% if @card %>
-  <%= render 'form', card: @card %>
+  <%= render "form", card: @card %>
 <% else %>
   <p> Нет карточек для просмотра. </p>
 <% end %>

config/locales/en.yml

@@ -52,6 +52,7 @@ en:
   review_answer: "Answer"
   review_check: "Check"
   review_wrong: "Wrong! Next review: %{next_review}"
+  review_quality: "Answer quality"
   review_success: >
     Right! Original: %{original},
     translated: %{translated}.

config/locales/ru.yml

@@ -14,10 +14,9 @@ ru:
       deck:
         title: "Название"
       card:
-        correct_answers: "Правильные ответы"
-        incorrect_answers: "Неправильные ответы"
         image: "Изображение"
         original_text: "Оригинал"
+        repetitions: "Повторения"
         review_date: "Дата просмотра"
         translated_text: "Перевод"
       user:
@@ -56,6 +55,7 @@ ru:
   review_answer: "Ответ"
   review_check: "Проверить"
   review_wrong: "Неверно! Следующий просмотр: %{next_review}"
+  review_quality: "Оценка ответа"
   review_success: >
     Правильно! Оригинал: %{original}, перевод: %{translated}.
     Ваш ответ: %{user_answer}. Ошибок: %{typos}.

db/migrate/20150824141658_add_super_memo_to_card.rb

@@ -0,0 +1,8 @@
+class AddSuperMemoToCard < ActiveRecord::Migration
+  def change
+    add_column :cards, :e_factor, :float, default: 2.5
+    add_column :cards, :interval, :integer, default: 0
+    add_column :cards, :quality, :integer, default: 0
+    add_column :cards, :repetitions, :integer, default: 0
+  end
+end

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: 20150822114606) do
+ActiveRecord::Schema.define(version: 20150824141658) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -30,15 +30,19 @@
     t.text     "original_text"
     t.text     "translated_text"
     t.datetime "review_date"
-    t.datetime "created_at",                     null: false
-    t.datetime "updated_at",                     null: false
+    t.datetime "created_at",                       null: false
+    t.datetime "updated_at",                       null: false
     t.string   "image_file_name"
     t.string   "image_content_type"
     t.integer  "image_file_size"
     t.datetime "image_updated_at"
-    t.integer  "deck_id",                        null: false
+    t.integer  "deck_id",                          null: false
     t.integer  "correct_answers",    default: 0
     t.integer  "incorrect_answers",  default: 0
+    t.float    "e_factor",           default: 2.5
+    t.integer  "interval",           default: 0
+    t.integer  "quality",            default: 0
+    t.integer  "repetitions",        default: 0
   end
 
   add_index "cards", ["deck_id"], name: "index_cards_on_deck_id", using: :btree