Implement Suspend Dsl for Future, Function1, and TailRec

ThoughtWorksInc · Dec 24, 2021 · fa067f3 · fa067f3
1 parent a9a62fb
commit fa067f3
Showing 1 changed file with 40 additions and 9 deletions.
diff --git a/keywords-Suspend/src/main/scala/com/thoughtworks/dsl/keywords/Suspend.scala b/keywords-Suspend/src/main/scala/com/thoughtworks/dsl/keywords/Suspend.scala
@@ -2,18 +2,49 @@ package com.thoughtworks.dsl
 package keywords
 import Dsl.IsKeyword
 import Dsl.cpsApply
+import scala.concurrent.Future
+import scala.concurrent.ExecutionContext
+import scala.util.control.TailCalls.TailRec
+import scala.util.control.TailCalls
 
-opaque type Suspend[+Keyword] <: Dsl.Keyword.Opaque = Dsl.Keyword.Opaque.Of[() => Keyword]
-object Suspend {
-  @inline def apply[Keyword]: (() => Keyword) =:= Suspend[Keyword] = Dsl.Keyword.Opaque.Of.apply
+opaque type Suspend[+Keyword] <: Dsl.Keyword.Opaque =
+  Dsl.Keyword.Opaque.Of[() => Keyword]
+object Suspend extends Suspend.LowPriority0 {
+  @inline def apply[Keyword]: (() => Keyword) =:= Suspend[Keyword] =
+    Dsl.Keyword.Opaque.Of.apply
 
-  given[Upstream, UpstreamValue](using upstreamIsKeyword: => IsKeyword[Upstream, UpstreamValue]): IsKeyword[Suspend[Upstream], UpstreamValue] with {}
+  given [Upstream, UpstreamValue](using
+      upstreamIsKeyword: => IsKeyword[Upstream, UpstreamValue]
+  ): IsKeyword[Suspend[Upstream], UpstreamValue] with {}
 
-  given [Keyword, Domain, Value](using
-      Dsl.Searching[Keyword, Domain, Value]
-  ): Dsl.Composed[Suspend[Keyword], Domain, Value] = Dsl.Composed {
-    (keyword: Suspend[Keyword], handler: Value => Domain) =>
-      keyword().cpsApply(handler)
+  private[Suspend] trait LowPriority0:
+    given [Keyword, Domain, Value](using
+        Dsl.Searching[Keyword, Domain, Value]
+    ): Dsl.Composed[Suspend[Keyword], Domain, Value] = Dsl.Composed {
+      (keyword: Suspend[Keyword], handler: Value => Domain) =>
+        keyword().cpsApply(handler)
+    }
+
+  given [Keyword, State, Domain, Value](using
+      Dsl.Searching[Keyword, State => Domain, Value]
+  ): Dsl.Composed[Suspend[Keyword], State => Domain, Value] = Dsl.Composed {
+    (keyword: Suspend[Keyword], handler: Value => State => Domain) => value =>
+      keyword().cpsApply(handler)(value)
+  }
+
+  given [Keyword, Result, Value](using
+      Dsl.Searching[Keyword, Future[Result], Value],
+      ExecutionContext
+  ): Dsl.Composed[Suspend[Keyword], Future[Result], Value] = Dsl.Composed {
+    (keyword: Suspend[Keyword], handler: Value => Future[Result]) =>
+      Future.delegate(keyword().cpsApply(handler))
+  }
+
+  given [Keyword, Result, Value](using
+      Dsl.Searching[Keyword, TailRec[Result], Value]
+  ): Dsl.Composed[Suspend[Keyword], TailRec[Result], Value] = Dsl.Composed {
+    (keyword: Suspend[Keyword], handler: Value => TailRec[Result]) =>
+      TailCalls.tailcall { keyword().cpsApply(handler) }
   }
 
 }