move RW2 fields into RW1 proto for direct unmarshal

Add field to differentiate what we unmarshal and add basic
protection against unmarshal fields from the wrong verison.

Signed-off-by: György Krajcsovits <[email protected]>

Author: krajorama

pkg/mimirpb/compat_rw2.go

@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+package mimirpb
+
+import (
+	"errors"
+	"fmt"
+)
+
+// Remote Write 2.0 related variables and functions.
+var (
+	unexpectedRW1TimeseriesError = errors.New("proto: Remote Write 1.0 field Timeseries in non-Remote Write 1.0 message")
+	unexpectedRW1MetadataError   = errors.New("proto: Remote Write 1.0 field Metadata in non-Remote Write 1.0 message")
+	unexpectedRW2TimeseriesError = errors.New("proto: Remote Write 2.0 field Timeseries in non-Remote Write 2.0 message")
+	unexpectedRW2SymbolsError    = errors.New("proto: Remote Write 2.0 field Symbols in non-Remote Write 2.0 message")
+	oddNumberOfLabelRefsError    = errors.New("proto: Remote Write 2.0 odd number of label references")
+	invalidLabelRefError         = errors.New("proto: Remote Write 2.0 invalid label reference")
+	internalRW2Error             = errors.New("proto: Remote Write 2.0 internal error")
+)
+
+// getRW2Symbol resolves the symbol reference to a string.
+func getRW2Symbol(ref uint32, symbols []string) (string, error) {
+	if ref < uint32(len(symbols)) {
+		return symbols[ref], nil
+	}
+	return "", fmt.Errorf("symbol reference %d is out of bounds", ref)
+}