added mapping support

src/main/scala/com/htmlism/mos6502/dsl/package.scala

@@ -65,6 +65,26 @@ package object dsl {
       .push(grp)
   }
 
+  def mapping[A](implicit ctx: AsmDocumentContext, ev: Mapping[A]): Unit = {
+    val xs =
+      ev.all
+        .map(x => ev.label(x) -> ev.value(x))
+        .toList
+
+    val grp =
+      DefinitionGroup(
+        ev.comment,
+        xs
+          .map {
+            case (s, n) =>
+              Definition(s, n)
+          }
+      )
+
+    ctx
+      .push(grp)
+  }
+
   def define[A <: Address: Operand](name: String, x: A)(implicit ctx: DefinitionGroupContext): Definition[A] = {
     val definition =
       Definition(name, x)

src/test/scala/com/htmlism/mos6502/dsl/DslSpec.scala

@@ -105,6 +105,27 @@ class DslSpec extends AnyFlatSpec with should.Matchers {
       )
     )
   }
+
+  "mapping" should "compile" in {
+    val doc =
+      asmDoc { implicit ctx =>
+        mapping[Direction]
+      }
+
+    doc shouldEqual AsmDocument(
+      List(
+        DefinitionGroup(
+          "foo as a mapping",
+          List(
+            Definition("up", 0x77),
+            Definition("down", 0x61),
+            Definition("left", 0x73),
+            Definition("right", 0x64)
+          )
+        )
+      )
+    )
+  }
 }
 
 sealed trait Triforce
@@ -152,4 +173,27 @@ object Direction {
       def comment(x: Direction): String =
         x.toString
     }
+
+  implicit val mappingDirection: Mapping[Direction] =
+    new Mapping[Direction] {
+      def comment: String =
+        "foo as a mapping"
+
+      def all: NonEmptyList[Direction] =
+        NonEmptyList.of(Up, Down, Left, Right)
+
+      def value(x: Direction): Int =
+        x match {
+          case Up => 0x77
+          case Down => 0x61
+          case Left => 0x73
+          case Right => 0x64
+        }
+
+      def label(x: Direction): String =
+        x.toString.toLowerCase
+
+      def comment(x: Direction): String =
+        x.toString
+    }
 }