From fbbd459e2646870da9a96ce65e77bc090c2b9930 Mon Sep 17 00:00:00 2001
From: Pacien TRAN-GIRARD
Date: Tue, 24 Nov 2015 16:18:19 +0100
Subject: Refactor Hamster A.I.

---
 .../stragegies/reducer/BlindCaseReducer.java       | 31 ++++++++
 src/ch/epfl/maze/physical/zoo/Hamster.java         | 87 +++++++++++++++++-----
 2 files changed, 100 insertions(+), 18 deletions(-)
 create mode 100644 src/ch/epfl/maze/physical/stragegies/reducer/BlindCaseReducer.java

diff --git a/src/ch/epfl/maze/physical/stragegies/reducer/BlindCaseReducer.java b/src/ch/epfl/maze/physical/stragegies/reducer/BlindCaseReducer.java
new file mode 100644
index 0000000..b359cc2
--- /dev/null
+++ b/src/ch/epfl/maze/physical/stragegies/reducer/BlindCaseReducer.java
@@ -0,0 +1,31 @@
+package ch.epfl.maze.physical.stragegies.reducer;
+
+import ch.epfl.maze.util.Direction;
+
+import java.util.Set;
+import java.util.stream.Collectors;
+
+/**
+ * A blind reducer filtering possibilities case by case.
+ *
+ * @author Pacien TRAN-GIRARD
+ */
+public interface BlindCaseReducer extends BlindChoiceReducer {
+
+    /**
+     * Checks if the given choice should be kept or excluded by the filter.
+     *
+     * @param choice A Direction
+     * @return T(The filter should keep the given choice)
+     */
+    boolean keepChoice(Direction choice);
+
+    @Override
+    default Set<Direction> reduce(Set<Direction> choices) {
+        return choices
+                .stream()
+                .filter(choice -> this.keepChoice(choice))
+                .collect(Collectors.toSet());
+    }
+
+}
diff --git a/src/ch/epfl/maze/physical/zoo/Hamster.java b/src/ch/epfl/maze/physical/zoo/Hamster.java
index 527e8ce..8586dee 100644
--- a/src/ch/epfl/maze/physical/zoo/Hamster.java
+++ b/src/ch/epfl/maze/physical/zoo/Hamster.java
@@ -1,14 +1,14 @@
 package ch.epfl.maze.physical.zoo;
 
 import ch.epfl.maze.physical.Animal;
-import ch.epfl.maze.physical.ProbabilisticAnimal;
+import ch.epfl.maze.physical.stragegies.picker.RandomPicker;
+import ch.epfl.maze.physical.stragegies.reducer.BackwardReducer;
+import ch.epfl.maze.physical.stragegies.reducer.BlindCaseReducer;
 import ch.epfl.maze.util.Direction;
 import ch.epfl.maze.util.Vector2D;
 
-import java.util.ArrayList;
-import java.util.List;
+import java.util.HashSet;
 import java.util.Set;
-import java.util.stream.Collectors;
 
 /**
  * Hamster A.I. that remembers the previous choice it has made and the dead ends
@@ -17,9 +17,9 @@ import java.util.stream.Collectors;
  * @author EPFL
  * @author Pacien TRAN-GIRARD
  */
-public class Hamster extends ProbabilisticAnimal {
+public class Hamster extends Animal implements BlindCaseReducer, BackwardReducer, RandomPicker {
 
-    private final List<Vector2D> deadPaths;
+    private final Set<Vector2D> positionBlacklist;
 
     /**
      * Constructs a hamster with a starting position.
@@ -28,20 +28,33 @@ public class Hamster extends ProbabilisticAnimal {
      */
     public Hamster(Vector2D position) {
         super(position);
-        this.deadPaths = new ArrayList<>();
+
+        this.positionBlacklist = new HashSet<>();
+    }
+
+    /**
+     * Checks is the choice leads to a known dead end.
+     *
+     * @param choice A Direction
+     * @return T(The given choice does not lead to a blacklisted path)
+     */
+    @Override
+    public boolean keepChoice(Direction choice) {
+        Vector2D choicePosition = this.getPosition().addDirectionTo(choice);
+        return !this.isPositionBlacklisted(choicePosition);
     }
 
     /**
-     * Discard directions known to lead to dead ends.
+     * Filters the Direction choices using the blacklist.
      *
-     * @param choices A set of choices
-     * @return A set of smart choices
+     * @param choices A set of Direction choices
+     * @return A subset of choices
      */
-    private Set<Direction> excludeDeadPaths(Set<Direction> choices) {
-        return choices
-                .stream()
-                .filter(dir -> !this.deadPaths.contains(this.getPosition().addDirectionTo(dir)))
-                .collect(Collectors.toSet());
+    @Override
+    public Set<Direction> reduce(Set<Direction> choices) {
+        Set<Direction> knownChoices = BlindCaseReducer.super.reduce(choices);
+        this.updateBlacklist(knownChoices);
+        return knownChoices.size() > 1 ? BackwardReducer.super.reduce(knownChoices) : knownChoices;
     }
 
     /**
@@ -50,9 +63,8 @@ public class Hamster extends ProbabilisticAnimal {
      */
     @Override
     public Direction move(Set<Direction> choices) {
-        Set<Direction> smartChoices = this.excludeDeadPaths(choices);
-        if (smartChoices.size() == 1) this.deadPaths.add(this.getPosition()); // dead end
-        return super.move(smartChoices);
+        Set<Direction> smartChoices = this.reduce(choices);
+        return this.pick(smartChoices);
     }
 
     @Override
@@ -60,4 +72,43 @@ public class Hamster extends ProbabilisticAnimal {
         return new Hamster(this.getPosition());
     }
 
+    /**
+     * Updates the position blacklist if needed.
+     *
+     * @param choices The choices currently available
+     */
+    private void updateBlacklist(Set<Direction> choices) {
+        if (this.inDeadEnd(choices))
+            this.blacklistPosition(this.getPosition());
+    }
+
+    /**
+     * Checks if the given choices set correspond to a dead end.
+     *
+     * @param choices The choices currently available
+     * @return T(The given choices set correspond to a dead end)
+     */
+    private boolean inDeadEnd(Set<Direction> choices) {
+        return choices.size() < 2;
+    }
+
+    /**
+     * Checks if the given position is known to lead to a dead end.
+     *
+     * @param position The position to check
+     * @return T(The given position is blacklisted)
+     */
+    private boolean isPositionBlacklisted(Vector2D position) {
+        return this.positionBlacklist.contains(position);
+    }
+
+    /**
+     * Regiters the given position in the blacklist.
+     *
+     * @param position The position to blacklist
+     */
+    private void blacklistPosition(Vector2D position) {
+        this.positionBlacklist.add(position);
+    }
+
 }
-- 
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