Remove `cortex/pkg/util/extract` dependency from Loki (#5049)

Copy only `extract.MetricNameMatcherFromMatchers`.

Signed-off-by: Kaviraj <kavirajkanagaraj@gmail.com>

pkg/storage/chunk/chunk_store.go

@@ -17,14 +17,13 @@ import (
 	"github.com/prometheus/prometheus/model/labels"
 
 	"github.com/cortexproject/cortex/pkg/util"
-	"github.com/cortexproject/cortex/pkg/util/extract"
 	util_log "github.com/cortexproject/cortex/pkg/util/log"
 	"github.com/cortexproject/cortex/pkg/util/validation"
 
-	"github.com/grafana/loki/pkg/util/spanlogger"
-
 	"github.com/grafana/loki/pkg/storage/chunk/cache"
 	"github.com/grafana/loki/pkg/storage/chunk/encoding"
+	"github.com/grafana/loki/pkg/util/extract"
+	"github.com/grafana/loki/pkg/util/spanlogger"
 )
 
 var (

pkg/util/extract/extract.go

@@ -0,0 +1,29 @@
+package extract
+
+import (
+	"github.com/prometheus/common/model"
+	"github.com/prometheus/prometheus/model/labels"
+)
+
+// MetricNameMatcherFromMatchers extracts the metric name from a set of matchers
+func MetricNameMatcherFromMatchers(matchers []*labels.Matcher) (*labels.Matcher, []*labels.Matcher, bool) {
+	// Handle the case where there is no metric name and all matchers have been
+	// filtered out e.g. {foo=""}.
+	if len(matchers) == 0 {
+		return nil, matchers, false
+	}
+
+	outMatchers := make([]*labels.Matcher, len(matchers)-1)
+	for i, matcher := range matchers {
+		if matcher.Name != model.MetricNameLabel {
+			continue
+		}
+
+		// Copy other matchers, excluding the found metric name matcher
+		copy(outMatchers, matchers[:i])
+		copy(outMatchers[i:], matchers[i+1:])
+		return matcher, outMatchers, true
+	}
+	// Return all matchers if none are metric name matchers
+	return nil, matchers, false
+}