From 65ea6c17a0c1348aa9ef4e158102ddf173936882 Mon Sep 17 00:00:00 2001
From: Yuuta Liang <yuutaw@student.cs.ubc.ca>
Date: Thu, 23 Nov 2023 08:09:01 +0800
Subject: Add GUI

Signed-off-by: Yuuta Liang <yuutaw@student.cs.ubc.ca>
---
 src/main/model/GroupObserver.java | 48 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 src/main/model/GroupObserver.java

(limited to 'src/main/model/GroupObserver.java')

diff --git a/src/main/model/GroupObserver.java b/src/main/model/GroupObserver.java
new file mode 100644
index 0000000..41a9aac
--- /dev/null
+++ b/src/main/model/GroupObserver.java
@@ -0,0 +1,48 @@
+package model;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * A group of observers with different types registered.
+ */
+public class GroupObserver implements Observer {
+    /**
+     * The map. Because Java doesn't have dependent maps, they are left here as unchecked.
+     */
+    private final Map<Class, Observer> map = new HashMap<>();
+
+    /**
+     * EFFECTS: Register a data type with an observer. Override existing registrations with the same type.
+     * REQUIRES: cls != null, obs != null.
+     */
+    public <T> void register(Class<T> cls, Observer<T> obs) {
+        map.put(cls, obs);
+    }
+
+    /**
+     * EFFECTS: Notify the registered observer based on the type of 'o' with given arguments.
+     * Does nothing if no registration found. Subclasses are supported as long as a parent class observer is registered.
+     * Specific type match takes priority. Non-specific type match is not guaranteed to be the closest.
+     * REQUIRES: o != null, direction be DIRECTION_*, index >= 0 or == INDEX_NOT_IN_LIST.
+     */
+    @Override
+    public void accept(Object o, int direction, int i) {
+        Observer obs = map.get(o.getClass());
+        if (obs == null) {
+            Class supertype = map.keySet().stream().filter(clz -> clz.isInstance(o)).findFirst().orElse(null);
+            if (supertype == null) {
+                return;
+            }
+            obs = map.get(supertype);
+        }
+        obs.accept(o, direction, i);
+    }
+
+    /**
+     * EFFECTS: Count the observers.
+     */
+    public int getRegisteredObserverCount() {
+        return map.size();
+    }
+}
-- 
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