Clean up

src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusMetric.cs

@@ -63,12 +63,15 @@ public PrometheusMetric(string name, string unit, PrometheusType type)
 
         this.Name = sanitizedName;
         this.Unit = sanitizedUnit;
+        this.Type = type;
     }
 
     public string Name { get; }
 
     public string Unit { get; }
 
+    public PrometheusType Type { get; }
+
     internal static string SanitizeMetricName(string metricName)
     {
         StringBuilder sb = null;

src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializer.cs

@@ -231,6 +231,7 @@ public static int WriteLabel(byte[] buffer, int cursor, string labelKey, object
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static int WriteMetricName(byte[] buffer, int cursor, PrometheusMetric metric)
     {
+        // Metric name has already been escaped.
         for (int i = 0; i < metric.Name.Length; i++)
         {
             var ordinal = (ushort)metric.Name[i];
@@ -272,8 +273,10 @@ public static int WriteHelpMetadata(byte[] buffer, int cursor, PrometheusMetric
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public static int WriteTypeMetadata(byte[] buffer, int cursor, PrometheusMetric metric, string metricType)
+    public static int WriteTypeMetadata(byte[] buffer, int cursor, PrometheusMetric metric)
     {
+        var metricType = MapPrometheusType(metric.Type);
+
         Debug.Assert(!string.IsNullOrEmpty(metricType), $"{nameof(metricType)} should not be null or empty.");
 
         cursor = WriteAsciiStringNoEscape(buffer, cursor, "# TYPE ");
@@ -299,6 +302,7 @@ public static int WriteUnitMetadata(byte[] buffer, int cursor, PrometheusMetric
 
         buffer[cursor++] = unchecked((byte)' ');
 
+        // Unit name has already been escaped.
         for (int i = 0; i < metric.Unit.Length; i++)
         {
             var ordinal = (ushort)metric.Unit[i];

src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializerExt.cs

@@ -37,24 +37,6 @@ UpDownCounter becomes gauge
         PrometheusType.Untyped, PrometheusType.Counter, PrometheusType.Gauge, PrometheusType.Summary, PrometheusType.Histogram, PrometheusType.Histogram, PrometheusType.Histogram, PrometheusType.Histogram, PrometheusType.Gauge,
     };
 
-    private static string MapPrometheusType(PrometheusType type)
-    {
-        return type switch
-        {
-            PrometheusType.Gauge => "gauge",
-            PrometheusType.Counter => "counter",
-            PrometheusType.Summary => "summary",
-            PrometheusType.Histogram => "histogram",
-            _ => "untyped",
-        };
-    }
-
-    private static PrometheusType GetPrometheusType(Metric metric)
-    {
-        int metricType = (int)metric.MetricType >> 4;
-        return MetricTypes[metricType];
-    }
-
     private static readonly ConcurrentDictionary<Metric, PrometheusMetric> MetricsCache = new ConcurrentDictionary<Metric, PrometheusMetric>();
     private static int metricsCacheCount;
 
@@ -67,10 +49,9 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric)
             return cursor;
         }
 
-        PrometheusType prometheusType = GetPrometheusType(metric);
         var prometheusMetric = GetPrometheusMetric(metric);
 
-        cursor = WriteTypeMetadata(buffer, cursor, prometheusMetric, MapPrometheusType(prometheusType));
+        cursor = WriteTypeMetadata(buffer, cursor, prometheusMetric);
         cursor = WriteUnitMetadata(buffer, cursor, prometheusMetric);
         cursor = WriteHelpMetadata(buffer, cursor, prometheusMetric, metric.Description);
 
@@ -253,4 +234,22 @@ private static PrometheusMetric GetPrometheusMetric(Metric metric)
             });
         }
     }
+
+    private static string MapPrometheusType(PrometheusType type)
+    {
+        return type switch
+        {
+            PrometheusType.Gauge => "gauge",
+            PrometheusType.Counter => "counter",
+            PrometheusType.Summary => "summary",
+            PrometheusType.Histogram => "histogram",
+            _ => "untyped",
+        };
+    }
+
+    private static PrometheusType GetPrometheusType(Metric metric)
+    {
+        int metricType = (int)metric.MetricType >> 4;
+        return MetricTypes[metricType];
+    }
 }