Add connection context that will serve us as an interface between command handler and the service

server/reply_builder.h

@@ -0,0 +1,63 @@
+// Copyright 2021, Beeri 15.  All rights reserved.
+// Author: Roman Gershman (romange@gmail.com)
+//
+#include <string_view>
+#include <optional>
+
+#include "io/sync_stream_interface.h"
+
+#include "server/op_status.h"
+
+namespace dfly {
+
+class RespSerializer {
+ public:
+  explicit RespSerializer(::io::Sink* sink);
+
+  std::error_code ec() const {
+    return ec_;
+  }
+
+  void CloseConnection() {
+    if (!ec_)
+      ec_ = std::make_error_code(std::errc::connection_aborted);
+  }
+
+  //! Sends a string as is without any formatting. raw should be RESP-encoded.
+  void SendDirect(std::string_view str);
+
+  ::io::Sink* sink() { return sink_; }
+
+ protected:
+  void Send(const iovec* v, uint32_t len);
+
+  ::io::Sink* sink_;
+
+ private:
+  std::error_code ec_;
+};
+
+class ReplyBuilder : public RespSerializer {
+ public:
+  explicit ReplyBuilder(::io::Sink* stream) : RespSerializer(stream) {
+  }
+
+  /// aka "$6\r\nfoobar\r\n"
+  void SendBulkString(std::string_view str);
+
+  void SendNull();
+
+  void SendOk() {
+    return SendSimpleString("OK");
+  }
+
+  void SendError(std::string_view str);
+  void SendError(OpStatus status);
+
+  //! See https://redis.io/topics/protocol
+  void SendSimpleString(std::string_view str);
+
+private:
+};
+
+}  // namespace dfly