1 files changed, 173 insertions, 0 deletions
diff --git a/core/src/main/scala/generic.scala~ b/core/src/main/scala/generic.scala~
new file mode 100644
index 0000000..4767435
--- /dev/null
+++ b/core/src/main/scala/generic.scala~
@@ -0,0 +1,173 @@
+package magnolia
+
+import scala.reflect._, macros._
+import macrocompat.bundle
+import scala.util.Try
+
+import scala.collection.immutable.ListMap
+
+object GlobalMutableState {
+  private[magnolia] var state: ListMap[AnyRef, AnyRef] = ListMap()
+  
+  private[magnolia] def push(key: AnyRef, value: AnyRef): Unit = {
+    state += ((key, value))
+  }
+  
+  private[magnolia] def pop(): Unit = {
+    state = state.init
+  }
+  
+  private[magnolia] def has(c: whitebox.Context)(key: AnyRef): Option[c.universe.Tree] =
+    state.get(key).asInstanceOf[Option[c.universe.Tree]]
+
+  private[magnolia] var searchType: AnyRef = null
+}
+
+@bundle
+class Macros(val context: whitebox.Context) extends GenericMacro(context) {
+  
+  
+  protected def classBody(context: whitebox.Context)(genericType: context.Type, implementation: context.Tree): context.Tree = {
+    import context.universe._
+    q"""def extract(src: _root_.magnolia.Thing): $genericType = $implementation"""
+  }
+
+  protected def dereferenceValue(context: whitebox.Context)(value: context.Tree, elem: String): context.Tree = {
+    import context.universe._
+    q"$value.access($elem)"
+  }
+  
+  protected def callDelegateMethod(context: whitebox.Context)(value: context.Tree, argument: context.Tree): context.Tree = {
+    import context.universe._
+    q"$value.extract($argument)"
+  }
+  
+  protected def coproductReduction(context: whitebox.Context)(left: context.Tree, right: context.Tree): context.Tree = {
+    import context.universe._
+    q"$left.orElse($right)"
+  }
+}
+
+abstract class GenericMacro(whiteboxContext: whitebox.Context) {
+
+  val c = whiteboxContext
+
+  def getImplicit(genericType: c.universe.Type,
+                  typeConstructor: c.universe.Type,
+                  myName: c.universe.TermName,
+                  count: Int): c.Tree = {
+    
+    import c.universe._
+    println(s"getImplicit($genericType, $count)")
+    val result = GlobalMutableState.has(c)(genericType).map { nm => q"$nm" }.orElse {
+      val searchType = appliedType(typeConstructor, genericType)
+      if(GlobalMutableState.has(c)(genericType).isEmpty) {
+        scala.util.Try {
+          GlobalMutableState.searchType = genericType
+          c.inferImplicitValue(searchType, false, false)
+        }.toOption.orElse {
+          println("Recursing")
+          directInferImplicit(genericType, typeConstructor, count + 1)
+        }
+      } else {
+        directInferImplicit(genericType, typeConstructor, count + 1)
+      }
+    }.getOrElse {
+      println("Failed 2.")
+      c.abort(c.enclosingPosition, "Could not find extractor for type "+genericType)
+    }
+
+
+    result
+  }
+  
+  def directInferImplicit(genericType: c.universe.Type,
+         typeConstructor: c.universe.Type,
+         count: Int): Option[c.Tree] = {
+    import c.universe._
+   
+    println(s"directInferImplicit($genericType, $count)")
+
+    val myName: TermName = TermName(c.freshName(genericType.typeSymbol.name.encodedName.toString.toLowerCase+"Extractor"))
+    val typeSymbol = genericType.typeSymbol
+    val classType = if(typeSymbol.isClass) Some(typeSymbol.asClass) else None
+    val isCaseClass = classType.map(_.isCaseClass).getOrElse(false)
+    val isSealedTrait = classType.map(_.isSealed).getOrElse(false)
+    val isAnyVal = genericType <:< typeOf[AnyVal]
+    
+    val resultType = appliedType(typeConstructor, genericType)
+
+    val construct = if(isCaseClass) {
+      val implicits = genericType.decls.collect {
+        case m: MethodSymbol if m.isCaseAccessor => m.asMethod
+      }.map { param =>
+        val returnType = param.returnType
+        GlobalMutableState.push(genericType, myName)
+        val imp = getImplicit(returnType, typeConstructor, myName, count)
+        GlobalMutableState.pop()
+        val dereferenced = dereferenceValue(c)(q"src", param.name.toString)
+        callDelegateMethod(c)(imp, dereferenced)
+      }
+
+      Some(q"new $genericType(..$implicits)")
+    } else if(isSealedTrait) {
+      val subtypes = classType.get.knownDirectSubclasses.to[List]
+      Some(subtypes.map(_.asType.toType).map { searchType =>
+        GlobalMutableState.push(genericType, myName)
+        val res = getImplicit(searchType, typeConstructor, myName, count)
+        GlobalMutableState.pop()
+        res
+      }.reduce(coproductReduction(c))).map { imp =>
+        callDelegateMethod(c)(imp, q"src")
+      }
+      
+    } else None
+
+    val result = construct.map { const =>
+      
+      val methodImplementation = classBody(c)(genericType, const)
+      q"""{
+        def $myName: $resultType = new $resultType {
+          $methodImplementation
+        }
+        $myName
+      }"""
+    }
+
+
+    result
+  }
+  
+  protected def classBody(c: whitebox.Context)(genericType: c.Type, implementation: c.Tree): c.Tree
+  protected def coproductReduction(c: whitebox.Context)(left: c.Tree, right: c.Tree): c.Tree
+  protected def dereferenceValue(c: whitebox.Context)(value: c.Tree, elem: String): c.Tree
+  protected def callDelegateMethod(c: whitebox.Context)(value: c.Tree, argument: c.Tree): c.Tree
+
+  def generic[T: c.WeakTypeTag, Tc: c.WeakTypeTag]: c.Tree = {
+    import c.universe._
+
+    val genericType: Type = weakTypeOf[T]
+    val reentrant = genericType == GlobalMutableState.searchType
+    if(reentrant) {
+      println("Reentrant.")
+      ???
+    }
+    val typeConstructor: Type = weakTypeOf[Tc].typeConstructor
+
+    val result = directInferImplicit(genericType, typeConstructor, 0)
+
+    println(result)
+    try result.map { tree => c.typecheck(tree) } catch {
+      case e: Exception =>
+        println(result)
+        println("Failed to typecheck because: "+e)
+    }
+
+    result.getOrElse {
+      println("Count not infer extractor...")
+      c.abort(c.enclosingPosition, "Could not infer extractor. Sorry.")
+    }
+  }
+
+}
+