Merge pull request nusCS2113-AY1920S1#7 from saradj/B-statistics

Adding statis

src/main/java/duke/duke.plantuml

@@ -0,0 +1,26 @@
+@startuml
+
+title __DUKE's Class Diagram__\n
+
+  namespace duke {
+    class duke.Duke {
+        + Duke()
+        {static} + main()
+        + run()
+    }
+  }
+
+
+  duke.Duke o-- duke.storage.Storage : storage
+  duke.Duke o-- duke.task.TaskList : tasks
+  duke.Duke o-- duke.ui.Ui : ui
+
+
+right footer
+
+
+PlantUML diagram generated by SketchIt! (https://bitbucket.org/pmesmeur/sketch.it)
+For more information about this tool, please contact [email protected]
+endfooter
+
+@enduml

src/main/java/duke/stats/Statistics.java

@@ -0,0 +1,61 @@
+package duke.stats;
+
+import duke.task.Dish;
+import javafx.util.Pair;
+
+import java.nio.file.Path;
+import java.util.*;
+
+import static java.util.stream.Collectors.toMap;
+
+public class Statistics {
+    private Path path;
+    private Map<Dish, Pair<Double, Integer>> ratedDishes;
+
+    public Statistics(Path path, List<Dish> dishes) {
+        this.path = path;
+        this.ratedDishes = new HashMap<Dish, Pair<Double, Integer>>();
+    }
+
+    public void update(OrderList orderList) {
+        for (Order order : orderList.getAllOrders()) {
+            Dish dish = order.getDish();
+            ratedDishes.putIfAbsent(dish, new Pair(0, 0));
+            int newTotal = ratedDishes.get(dish).getValue() + dish.getAmount();
+            double newRating = (ratedDishes.get(dish).getKey() + dish.getRating() * dish.getAmount()) / newTotal;
+            ratedDishes.put(dish, new Pair<>(newRating, newTotal));
+        }
+    }
+
+    public Set<Dish> getTopRated() {
+        return ratedDishes
+                .entrySet()
+                .stream()
+                .sorted(new Comparator<Map.Entry<Dish, Pair<Double, Integer>>>() {
+                    @Override
+                    public int compare(Map.Entry<Dish, Pair<Double, Integer>> o1, Map.Entry<Dish, Pair<Double, Integer>> o2) {
+                        return o2.getValue().getKey().compareTo(o1.getValue().getKey());
+                    }
+                })
+                .collect(
+                        toMap(e -> e.getKey(), e -> e.getValue(), (e1, e2) -> e2,
+                                LinkedHashMap::new)).keySet();
+
+    }
+
+    public Set<Dish> getMostOrdered() {
+        return ratedDishes
+                .entrySet()
+                .stream()
+                .sorted(new Comparator<Map.Entry<Dish, Pair<Double, Integer>>>() {
+                    @Override
+                    public int compare(Map.Entry<Dish, Pair<Double, Integer>> o1, Map.Entry<Dish, Pair<Double, Integer>> o2) {
+                        return o2.getValue().getValue().compareTo(o1.getValue().getValue());
+                    }
+                })
+                .collect(
+                        toMap(e -> e.getKey(), e -> e.getValue(), (e1, e2) -> e2,
+                                LinkedHashMap::new)).keySet();
+    }
+
+}