Support files for the Publish/Subscriber mechan...

Support files for the Publish/Subscriber mechanism; this set of files
implements, in particular, a rollback mechanism for any collection type.
The mechanism is designed that it can consistently reset a whole set of
containers to a consistent state.

9 files changed, 181 insertions, 0 deletions

diff --git a/sources/scala/History.scala b/sources/scala/History.scala
new file mode 100644
index 0000000000..115fb850dc
--- /dev/null
+++ b/sources/scala/History.scala
@@ -0,0 +1,36 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2003, LAMP/EPFL                  **
+**  __\ \/ /__/ __ |/ /__/ __ |                                         **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+** $Id$
+\*                                                                      */
+
+package scala;
+
+
+/** <tt>History[A, B]</tt> objects may subscribe to events of
+ *  type <tt>A</tt> published by an object of type <tt>B</tt>.
+ *  The history subscriber object records all published events
+ *  up to maximum number of <tt>maxHistory</tt> events.
+ */
+class History[A, B] with Subscriber[A, B] {
+
+    protected val log: Queue[Pair[B, A]] = new Queue[Pair[B, A]];
+
+    val maxHistory: Int = 32000;
+
+    def update(pub: B, event: A): Unit = {
+        if (log.length >= maxHistory) {
+            val old = log.dequeue;
+        }
+        log.enqueue(Pair(pub, event));
+    }
+
+    def getHistory: Iterator[Pair[B, A]] = log.toList.elements;
+
+    def historySize: Int = log.length;
+
+    def clear: Unit = log.clear;
+}
diff --git a/sources/scala/Inclusion.scala b/sources/scala/Inclusion.scala
new file mode 100644
index 0000000000..52ee525d08
--- /dev/null
+++ b/sources/scala/Inclusion.scala
@@ -0,0 +1,13 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2003, LAMP/EPFL                  **
+**  __\ \/ /__/ __ |/ /__/ __ |                                         **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+** $Id$
+\*                                                                      */
+
+package scala;
+
+
+case class Inclusion[A](elem: A) extends ObservableUpdate[A];
diff --git a/sources/scala/Modification.scala b/sources/scala/Modification.scala
new file mode 100644
index 0000000000..4da13bd61a
--- /dev/null
+++ b/sources/scala/Modification.scala
@@ -0,0 +1,13 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2003, LAMP/EPFL                  **
+**  __\ \/ /__/ __ |/ /__/ __ |                                         **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+** $Id$
+\*                                                                      */
+
+package scala;
+
+
+case class Modification[A](old: A, nu: A) extends ObservableUpdate[A];
diff --git a/sources/scala/ObservableMap.scala b/sources/scala/ObservableMap.scala
new file mode 100644
index 0000000000..420a0feeaa
--- /dev/null
+++ b/sources/scala/ObservableMap.scala
@@ -0,0 +1,40 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2003, LAMP/EPFL                  **
+**  __\ \/ /__/ __ |/ /__/ __ |                                         **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+** $Id$
+\*                                                                      */
+
+package scala;
+
+
+abstract class ObservableMap[A, B, This <: ObservableMap[A, B, This]]: This
+                    extends MutableMap[A, B]
+                    with Publisher[ObservableUpdate[Pair[A, B]] with Undo, This] {
+
+    override def update(key: A, value: B): Unit = get(key) match {
+        case None => super.update(key, value);
+                     publish(new Inclusion(Pair(key, value)) with Undo {
+                                 def undo = remove(key);
+                             });
+        case Some(old) => super.update(key, value);
+                          publish(new Modification(Pair(key, old), Pair(key, value)) with Undo {
+                                      def undo = update(key, old._2);
+                                  });
+    }
+
+    override def remove(key: A): Unit = get(key) match {
+        case None =>
+        case Some(old) => super.remove(key);
+                          publish(new Removal(Pair(key, old)) with Undo {
+                                      def undo = update(key, old);
+                                  });
+    }
+
+    override def clear: Unit = {
+        super.clear;
+        publish(new Reset() with Undo { def undo = error("cannot undo"); });
+    }
+}
diff --git a/sources/scala/ObservableUpdate.scala b/sources/scala/ObservableUpdate.scala
new file mode 100644
index 0000000000..fabe049f40
--- /dev/null
+++ b/sources/scala/ObservableUpdate.scala
@@ -0,0 +1,13 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2003, LAMP/EPFL                  **
+**  __\ \/ /__/ __ |/ /__/ __ |                                         **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+** $Id$
+\*                                                                      */
+
+package scala;
+
+
+trait ObservableUpdate[+A];
diff --git a/sources/scala/Removal.scala b/sources/scala/Removal.scala
new file mode 100644
index 0000000000..37b062709e
--- /dev/null
+++ b/sources/scala/Removal.scala
@@ -0,0 +1,13 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2003, LAMP/EPFL                  **
+**  __\ \/ /__/ __ |/ /__/ __ |                                         **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+** $Id$
+\*                                                                      */
+
+package scala;
+
+
+case class Removal[A](elem: A) extends ObservableUpdate[A];
diff --git a/sources/scala/Reset.scala b/sources/scala/Reset.scala
new file mode 100644
index 0000000000..b458560251
--- /dev/null
+++ b/sources/scala/Reset.scala
@@ -0,0 +1,13 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2003, LAMP/EPFL                  **
+**  __\ \/ /__/ __ |/ /__/ __ |                                         **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+** $Id$
+\*                                                                      */
+
+package scala;
+
+
+case class Reset[A]() extends ObservableUpdate[A];
diff --git a/sources/scala/RevertableHistory.scala b/sources/scala/RevertableHistory.scala
new file mode 100644
index 0000000000..760f5dcea6
--- /dev/null
+++ b/sources/scala/RevertableHistory.scala
@@ -0,0 +1,25 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2003, LAMP/EPFL                  **
+**  __\ \/ /__/ __ |/ /__/ __ |                                         **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+** $Id$
+\*                                                                      */
+
+package scala;
+
+
+/** <tt>Subscriber[-A, -B]</tt> objects may subscribe to events of
+ *  type <tt>A</tt> published by an object of type <tt>B</tt>.
+ */
+class RevertableHistory[A <: Undo, B] extends History[A, B] with Undo {
+
+    def undo: Unit = {
+    	val old = log.toList.reverse;
+    	clear;
+    	old.foreach {
+    		case Pair(sub, event) => event.undo;
+    	}
+    }
+}
diff --git a/sources/scala/Undo.scala b/sources/scala/Undo.scala
new file mode 100644
index 0000000000..4349851e5a
--- /dev/null
+++ b/sources/scala/Undo.scala
@@ -0,0 +1,15 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2003, LAMP/EPFL                  **
+**  __\ \/ /__/ __ |/ /__/ __ |                                         **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+** $Id$
+\*                                                                      */
+
+package scala;
+
+
+trait Undo {
+    def undo: Unit;
+}