Initial commit

src/main/java/com/github/nkzawa/emitter/Emitter.java

@@ -0,0 +1,93 @@
+package com.github.nkzawa.emitter;
+
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.ConcurrentMap;
+
+public class Emitter {
+
+    private ConcurrentMap<String, ConcurrentLinkedQueue<Listener>> callbacks
+            = new ConcurrentHashMap<String, ConcurrentLinkedQueue<Listener>>();
+
+    private ConcurrentMap<Listener, Listener> onceCallbacks = new ConcurrentHashMap<Listener, Listener>();
+
+
+    public Emitter on(String event, Listener fn) {
+        ConcurrentLinkedQueue<Listener> callbacks = this.callbacks.get(event);
+        if (callbacks == null) {
+            callbacks = new ConcurrentLinkedQueue <Listener>();
+            ConcurrentLinkedQueue<Listener> _callbacks = this.callbacks.putIfAbsent(event, callbacks);
+            if (_callbacks != null) {
+                callbacks = _callbacks;
+            }
+        }
+        callbacks.add(fn);
+        return this;
+    }
+
+    public Emitter once(final String event, final Listener fn) {
+        Listener on = new Listener() {
+            @Override
+            public void call(Object... args) {
+                Emitter.this.off(event, this);
+                fn.call(args);
+            }
+        };
+
+        this.onceCallbacks.put(fn, on);
+        this.on(event, on);
+        return this;
+    }
+
+    public Emitter off() {
+        this.callbacks.clear();
+        this.onceCallbacks.clear();
+        return this;
+    }
+
+    public Emitter off(String event) {
+        ConcurrentLinkedQueue<Listener> callbacks = this.callbacks.remove(event);
+        if (callbacks != null) {
+            for (Listener fn : callbacks) {
+                this.onceCallbacks.remove(fn);
+            }
+        }
+        return this;
+    }
+
+    public Emitter off(String event, Listener fn) {
+        ConcurrentLinkedQueue<Listener> callbacks = this.callbacks.get(event);
+        if (callbacks != null) {
+            Listener off = this.onceCallbacks.remove(fn);
+            callbacks.remove(off != null ? off : fn);
+        }
+        return this;
+    }
+
+    public Emitter emit(String event, Object... args) {
+        ConcurrentLinkedQueue<Listener> callbacks = this.callbacks.get(event);
+        if (callbacks != null) {
+            callbacks = new ConcurrentLinkedQueue<Listener>(callbacks);
+            for (Listener fn : callbacks) {
+                fn.call(args);
+            }
+        }
+        return this;
+    }
+
+    public List<Listener> listeners(String event) {
+        ConcurrentLinkedQueue<Listener> callbacks = this.callbacks.get(event);
+        return new ArrayList<Listener>(callbacks);
+    }
+
+    public boolean hasListeners(String event) {
+        return !this.listeners(event).isEmpty();
+    }
+
+    public static interface Listener {
+        public void call(Object... args);
+    }
+}