acounts/abi: refactor abi, generalize abi pack/unpack to Arguments

accounts/abi/abi.go

@@ -50,25 +50,25 @@ func JSON(reader io.Reader) (ABI, error) {
 // methods string signature. (signature = baz(uint32,string32))
 func (abi ABI) Pack(name string, args ...interface{}) ([]byte, error) {
 	// Fetch the ABI of the requested method
-	var method Method
-
 	if name == "" {
-		method = abi.Constructor
-	} else {
-		m, exist := abi.Methods[name]
-		if !exist {
-			return nil, fmt.Errorf("method '%s' not found", name)
+		// constructor
+		arguments, err := abi.Constructor.Inputs.Pack(args...)
+		if err != nil {
+			return nil, err
 		}
-		method = m
+		return arguments, nil
+
 	}
-	arguments, err := method.pack(args...)
+	method, exist := abi.Methods[name]
+	if !exist {
+		return nil, fmt.Errorf("method '%s' not found", name)
+	}
+
+	arguments, err := method.Inputs.Pack(args...)
 	if err != nil {
 		return nil, err
 	}
 	// Pack up the method ID too if not a constructor and return
-	if name == "" {
-		return arguments, nil
-	}
 	return append(method.Id(), arguments...), nil
 }
 
@@ -77,26 +77,17 @@ func (abi ABI) Unpack(v interface{}, name string, output []byte) (err error) {
 	if len(output) == 0 {
 		return fmt.Errorf("abi: unmarshalling empty output")
 	}
-
 	// since there can't be naming collisions with contracts and events,
 	// we need to decide whether we're calling a method or an event
-	var unpack unpacker
 	if method, ok := abi.Methods[name]; ok {
 		if len(output)%32 != 0 {
 			return fmt.Errorf("abi: improperly formatted output")
 		}
-		unpack = method
+		return method.Outputs.Unpack(v, output)
 	} else if event, ok := abi.Events[name]; ok {
-		unpack = event
-	} else {
-		return fmt.Errorf("abi: could not locate named method or event")
+		return event.Inputs.Unpack(v, output)
 	}
-
-	// requires a struct to unpack into for a tuple return...
-	if unpack.isTupleReturn() {
-		return unpack.tupleUnpack(v, output)
-	}
-	return unpack.singleUnpack(v, output)
+	return fmt.Errorf("abi: could not locate named method or event")
 }
 
 // UnmarshalJSON implements json.Unmarshaler interface