Revert "Implement notifies for transfer plugin (#3972)" (#3995)

This reverts commit 68f1dd5ddf.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

plugin/pkg/parse/parse.go

@@ -9,31 +9,41 @@ import (
 	"github.com/caddyserver/caddy"
 )
 
-// TransferIn parses transfer statements: 'transfer from [address...]'.
-func TransferIn(c *caddy.Controller) (froms []string, err error) {
+// Transfer parses transfer statements: 'transfer [to|from] [address...]'.
+func Transfer(c *caddy.Controller, secondary bool) (tos, froms []string, err error) {
 	if !c.NextArg() {
-		return nil, c.ArgErr()
+		return nil, nil, c.ArgErr()
 	}
 	value := c.Val()
 	switch value {
-	default:
-		return nil, c.Errf("unknown property %s", value)
-	case "from":
-		froms = c.RemainingArgs()
-		if len(froms) == 0 {
-			return nil, c.ArgErr()
+	case "to":
+		tos = c.RemainingArgs()
+		for i := range tos {
+			if tos[i] != "*" {
+				normalized, err := HostPort(tos[i], transport.Port)
+				if err != nil {
+					return nil, nil, err
+				}
+				tos[i] = normalized
+			}
 		}
+
+	case "from":
+		if !secondary {
+			return nil, nil, fmt.Errorf("can't use `transfer from` when not being a secondary")
+		}
+		froms = c.RemainingArgs()
 		for i := range froms {
 			if froms[i] != "*" {
 				normalized, err := HostPort(froms[i], transport.Port)
 				if err != nil {
-					return nil, err
+					return nil, nil, err
 				}
 				froms[i] = normalized
 			} else {
-				return nil, fmt.Errorf("can't use '*' in transfer from")
+				return nil, nil, fmt.Errorf("can't use '*' in transfer from")
 			}
 		}
 	}
-	return froms, nil
+	return
 }