import Boo.Lang.Compiler
import Boo.Lang.Compiler.Ast
import Boo.Lang.Compiler.TypeSystem
import Boo.Lang.Compiler.TypeSystem.Services
import Boo.Lang.Compiler.MetaProgramming
import Boo.Lang.Environments

macro delegate:
    case [| delegate $field as $fieldType |]:
        enclosingType = delegate.GetAncestor of TypeDefinition()
        Context.Parameters.Pipeline.AfterStep += do (sender, args):
            if args.Step isa Boo.Lang.Compiler.Steps.MacroAndAttributeExpansion:
                implementDelegationOf field, fieldType, enclosingType

def implementDelegationOf(field as ReferenceExpression, fieldType as TypeReference, typeDef as TypeDefinition):

    for member in membersOf(fieldType):
        match member:
            case IMethod(Name: methodName, ReturnType: returnType):
                newMethod = [|
                    def $methodName() as $returnType:
                        $(field.CloneNode()).$methodName()
                |]
                typeDef.Members.Add(newMethod)

def membersOf(typeRef as TypeReference):
    my(NameResolutionService).ResolveTypeReference(typeRef)
    return (typeRef.Entity cast INamespace).GetMembers()

[extension] def op_Implicit(type as IType) as TypeReference:
    return my(BooCodeBuilder).CreateTypeReference(type)

code = [|
    class Foo:
        def Bar():
            print "Foo.Bar"
        def Baz():
            print "Foo.Baz"

    class Gazonk:
        delegate foo as Foo
        foo = Foo()
|]

result = compile_(code, System.Reflection.Assembly.GetExecutingAssembly())
print result.CompileUnit.ToCodeString()
assert len(result.Errors) == 0, result.Errors.ToString(true)

gazonk as duck = result.GeneratedAssembly.GetType("Gazonk")()
gazonk.Bar()
gazonk.Baz()