begin refactor of proxy engine

proxychain/rsm/modify_response_header.go

@@ -0,0 +1,26 @@
+package rsm // ReSponseModifers
+
+import (
+	"ladder/proxychain"
+)
+
+// ModifyResponseHeader modifies response headers from the upstream server
+// if value is "", then the response header is deleted.
+func ModifyResponseHeader(key string, value string) proxychain.ResponseModification {
+	return func(px *proxychain.ProxyChain) error {
+		if value == "" {
+			px.Context.Response().Header.Del(key)
+			return nil
+		}
+		px.Context.Response().Header.Set(key, value)
+		return nil
+	}
+}
+
+// DeleteResponseHeader removes response headers from the upstream server
+func DeleteResponseHeader(key string) proxychain.ResponseModification {
+	return func(px *proxychain.ProxyChain) error {
+		px.Context.Response().Header.Del(key)
+		return nil
+	}
+}