complete rewrite to grpc

frames.go

@@ -0,0 +1,102 @@
+package main
+
+// Minimal frame abstractions retained after removal of the legacy TCP/frame
+// networking layer. These types remain only to avoid a wide cascading refactor
+// across existing grain / pool logic that still constructs and passes
+// FrameWithPayload objects internally.
+//
+// The original responsibilities this replaces:
+//   - Binary framing, checksums, network IO
+//   - Distinction between request / reply frame types
+//
+// What remains:
+//   - A light weight container (FrameWithPayload) used as an in‑process
+//     envelope for status code + typed marker + payload bytes (JSON or proto).
+//   - Message / status constants referenced in existing code paths.
+//
+// Recommended future cleanup (post‑migration):
+//   - Remove FrameType entirely and replace with enumerated semantic results
+//     or error values.
+//   - Replace FrameWithPayload with a struct { Status int; Data []byte }.
+//   - Remove remote_* reply type branching once all callers rely on gRPC
+//     status + strongly typed responses.
+//
+// For now we keep this minimal surface to keep the gRPC migration focused.
+
+type (
+	// FrameType is a symbolic identifier carried through existing code paths.
+	// No ordering or bit semantics are required anymore.
+	FrameType  uint32
+	StatusCode uint32
+)
+
+type Frame struct {
+	Type       FrameType
+	StatusCode StatusCode
+	Length     uint32
+	// Checksum retained for compatibility; no longer validated.
+	Checksum uint32
+}
+
+// FrameWithPayload wraps a Frame with an opaque payload.
+// Payload usually contains JSON encoded cart state or an error message.
+type FrameWithPayload struct {
+	Frame
+	Payload []byte
+}
+
+// -----------------------------------------------------------------------------
+// Legacy Frame Type Constants (minimal subset still referenced)
+// -----------------------------------------------------------------------------
+const (
+	RemoteGetState            = FrameType(0x01)
+	RemoteHandleMutation      = FrameType(0x02)
+	ResponseBody              = FrameType(0x03) // (rarely used; kept for completeness)
+	RemoteGetStateReply       = FrameType(0x04)
+	RemoteHandleMutationReply = FrameType(0x05)
+	RemoteCreateOrderReply    = FrameType(0x06)
+)
+
+// MakeFrameWithPayload constructs an in‑process frame wrapper.
+// Length & Checksum are filled for backward compatibility (no validation logic
+// depends on the checksum anymore).
+func MakeFrameWithPayload(msg FrameType, statusCode StatusCode, payload []byte) FrameWithPayload {
+	length := uint32(len(payload))
+	return FrameWithPayload{
+		Frame: Frame{
+			Type:       msg,
+			StatusCode: statusCode,
+			Length:     length,
+			Checksum:   (uint32(msg) + uint32(statusCode) + length) / 8, // simple legacy formula
+		},
+		Payload: payload,
+	}
+}
+
+// Clone creates a shallow copy of the frame, duplicating the payload slice.
+func (f *FrameWithPayload) Clone() *FrameWithPayload {
+	if f == nil {
+		return nil
+	}
+	cp := make([]byte, len(f.Payload))
+	copy(cp, f.Payload)
+	return &FrameWithPayload{
+		Frame:   f.Frame,
+		Payload: cp,
+	}
+}
+
+// NewErrorFrame helper for creating an error frame with a textual payload.
+func NewErrorFrame(msg FrameType, code StatusCode, err error) FrameWithPayload {
+	var b []byte
+	if err != nil {
+		b = []byte(err.Error())
+	}
+	return MakeFrameWithPayload(msg, code, b)
+}
+
+// IsSuccess returns true if the status code indicates success in the
+// conventional HTTP style range (200–299). This mirrors previous usage patterns.
+func (f *FrameWithPayload) IsSuccess() bool {
+	return f != nil && f.StatusCode >= 200 && f.StatusCode < 300
+}