From 6906ad4ad5f5b018e3493af8d3d4d9df8ac1e6e7 Mon Sep 17 00:00:00 2001
From: Christopher Vogt <oss.nsp@cvogt.org>
Date: Tue, 8 Nov 2016 00:49:25 +0000
Subject: add context based task result cache

---
 compatibility/Context.java         |  1 +
 stage1/ContextImplementation.scala |  1 +
 stage1/cbt.scala                   |  1 +
 stage2/BasicBuild.scala            | 17 +++++++++++++++++
 stage2/Stage2.scala                |  1 +
 test/test.scala                    |  1 +
 6 files changed, 22 insertions(+)

diff --git a/compatibility/Context.java b/compatibility/Context.java
index 921087f..0e2fff5 100644
--- a/compatibility/Context.java
+++ b/compatibility/Context.java
@@ -14,6 +14,7 @@ public abstract class Context{
   public abstract String scalaVersionOrNull(); // needed to propagate scalaVersion to dependendee builds
   public abstract ConcurrentHashMap<String,Object> permanentKeys();
   public abstract ConcurrentHashMap<Object,ClassLoader> permanentClassLoaders();
+  public abstract ConcurrentHashMap<Object,Object> taskCache();
   public abstract File cache();
   public abstract File cbtHome();
   public abstract File cbtRootHome();
diff --git a/stage1/ContextImplementation.scala b/stage1/ContextImplementation.scala
index 91c54f4..c3f25fd 100644
--- a/stage1/ContextImplementation.scala
+++ b/stage1/ContextImplementation.scala
@@ -14,6 +14,7 @@ case class ContextImplementation(
   scalaVersionOrNull: String,
   permanentKeys: ConcurrentHashMap[String,AnyRef],
   permanentClassLoaders: ConcurrentHashMap[AnyRef,ClassLoader],
+  taskCache: ConcurrentHashMap[AnyRef,AnyRef],
   cache: File,
   cbtHome: File,
   cbtRootHome: File,
diff --git a/stage1/cbt.scala b/stage1/cbt.scala
index 7a239a1..08394f0 100644
--- a/stage1/cbt.scala
+++ b/stage1/cbt.scala
@@ -88,6 +88,7 @@ object `package`{
       scalaVersion.getOrElse(null),
       permanentKeys,
       permanentClassLoaders,
+      taskCache,
       cache,
       cbtHome,
       cbtRootHome,
diff --git a/stage2/BasicBuild.scala b/stage2/BasicBuild.scala
index 128d2f8..ef4757e 100644
--- a/stage2/BasicBuild.scala
+++ b/stage2/BasicBuild.scala
@@ -244,4 +244,21 @@ trait BaseBuild extends BuildInterface with DependencyImplementation with Trigge
   // ========== cbt internals ==========
   def finalBuild: BuildInterface = this
   override def show = this.getClass.getSimpleName ++ "(" ++ projectDirectory.string ++ ")"
+
+  // TODO: allow people not provide the method name, maybe via macro
+  /**
+  caches given value in context keyed with given key and projectDirectory
+  the context is fresh on every complete run of cbt
+  */
+  def cached[T <: AnyRef](name: String)(task: => T): T = {
+    val cache = context.taskCache
+    val key = (projectDirectory,name)
+    if( cache.containsKey(key) ){
+      cache.get(key).asInstanceOf[T]
+    } else{
+      val value = task
+      cache.put( key, value )
+      value
+    }
+  }
 }
diff --git a/stage2/Stage2.scala b/stage2/Stage2.scala
index b1539bf..d585cd0 100644
--- a/stage2/Stage2.scala
+++ b/stage2/Stage2.scala
@@ -39,6 +39,7 @@ object Stage2 extends Stage2Base{
       null,
       args.permanentKeys,
       args.permanentClassLoaders,
+      new java.util.concurrent.ConcurrentHashMap,
       args.cache,
       args.cbtHome,
       args.cbtHome,
diff --git a/test/test.scala b/test/test.scala
index 039ee6a..72360d0 100644
--- a/test/test.scala
+++ b/test/test.scala
@@ -118,6 +118,7 @@ object Main{
         null,
         new ConcurrentHashMap[String,AnyRef],
         new ConcurrentHashMap[AnyRef,ClassLoader],
+        new java.util.concurrent.ConcurrentHashMap[AnyRef,AnyRef],
         cache,
         cbtHome,
         cbtHome,
-- 
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