Go: Add helpers for defined enum types

Adds basic string conversion / lookup helpers for compiled enums

Signed-off-by: Kendall Goto <kendall@level.co>

Author: kendallgoto

shared/src/main/scala/io/kaitai/struct/languages/GoCompiler.scala

@@ -536,15 +536,59 @@ class GoCompiler(typeProvider: ClassTypeProvider, config: RuntimeConfig)
 
     out.dec
     out.puts(")")
+
     // Inspired by https://gist.github.com/bgadrian/cb8b9344d9c66571ef331a14eb7a2e80
-    val mapEntriesStr = enumColl.map { case (id, _) => s"$id: {}" }.mkString(", ")
-    out.puts(s"var values_$fullEnumNameStr = map[$fullEnumNameStr]struct{}{$mapEntriesStr}")
+    val mapEntriesStr = enumColl.map { case (id, label) => s"$id: \"${type2class(label.name)}\"" }.mkString(", ")
+    out.puts(s"var valueNames_$fullEnumNameStr = map[$fullEnumNameStr]string{$mapEntriesStr}")
+
     out.puts(s"func (v $fullEnumNameStr) isDefined() bool {")
     out.inc
-    out.puts(s"_, ok := values_$fullEnumNameStr[v]")
+    out.puts(s"_, ok := valueNames_$fullEnumNameStr[v]")
     out.puts("return ok")
     out.dec
     out.puts("}")
+
+    out.puts(s"func (v $fullEnumNameStr) IsA$fullEnumNameStr() bool {")
+    out.inc
+    out.puts(s"return v.isDefined()")
+    out.dec
+    out.puts("}")
+
+    out.puts(s"func (v $fullEnumNameStr) String() string {")
+    out.inc
+    out.puts(s"name, ok := valueNames_$fullEnumNameStr[v]")
+    out.puts("if ok {")
+    out.inc
+    out.puts("return name")
+    out.dec
+    out.puts("}")
+    out.puts(s"return \"${fullEnumNameStr}(\" + string(v) + \")\"")
+    out.dec
+    out.puts("}")
+
+    out.puts(s"func ${fullEnumNameStr}Strings() []string {")
+    out.inc
+    out.puts(s"strings := make([]string, 0, len(valueNames_$fullEnumNameStr))")
+    out.puts(s"for _, name := range valueNames_$fullEnumNameStr {")
+    out.inc
+    out.puts("strings = append(strings, name)")
+    out.dec
+    out.puts("}")
+    out.puts("return strings")
+    out.dec
+    out.puts("}")
+
+    out.puts(s"func ${fullEnumNameStr}Values() []${fullEnumNameStr} {")
+    out.inc
+    out.puts(s"values := make([]${fullEnumNameStr}, 0, len(valueNames_$fullEnumNameStr))")
+    out.puts(s"for value := range valueNames_$fullEnumNameStr {")
+    out.inc
+    out.puts("values = append(values, value)")
+    out.dec
+    out.puts("}")
+    out.puts("return values")
+    out.dec
+    out.puts("}")
   }
 
   override def classToString(toStringExpr: Ast.expr): Unit = {