Add label decorator

WORKSPACE

@@ -64,34 +64,64 @@ git_repository(
     tag = "v3.0.0",
     )
 
-new_git_repository(
-    name = "civetweb",
-    remote = "https://github.com/civetweb/civetweb.git",
-    tag = "v1.8",
-    build_file_content = """
+# new_git_repository(
+#     name = "civetweb",
+#     remote = "https://github.com/civetweb/civetweb.git",
+#     tag = "v1.8",
+#     build_file_content = """
+# cc_library(
+#     name = "civetweb",
+#     srcs = [
+#          "src/civetweb.c",
+#          "src/CivetServer.cpp",
+#     ],
+#     hdrs = [
+#          "include/civetweb.h",
+#          "include/CivetServer.h",
+#          "src/md5.inl",
+#          "src/handle_form.inl",
+#     ],
+#     includes = [
+#          "include",
+#     ],
+#     copts = [
+#           "-DNDEBUG",
+#           "-DNO_CGI",
+#           "-DNO_CACHING",
+#           "-DNO_SSL",
+#           "-DNO_FILES",
+#     ],
+#     visibility = ["//visibility:public"],
+# )
+# """
+# )
+new_local_repository(
+     name = "civetweb",
+     path = "../civetweb",
+     build_file_content = """
 cc_library(
-    name = "civetweb",
-    srcs = [
-         "src/civetweb.c",
-         "src/CivetServer.cpp",
-    ],
-    hdrs = [
-         "include/civetweb.h",
-         "include/CivetServer.h",
-         "src/md5.inl",
-         "src/handle_form.inl",
-    ],
-    includes = [
-         "include",
-    ],
-    copts = [
-          "-DNDEBUG",
-          "-DNO_CGI",
-          "-DNO_CACHING",
-          "-DNO_SSL",
-          "-DNO_FILES",
-    ],
-    visibility = ["//visibility:public"],
-)
-"""
-)
+     name = "civetweb",
+     srcs = [
+          "src/civetweb.c",
+          "src/CivetServer.cpp",
+     ],
+     hdrs = [
+          "include/civetweb.h",
+          "include/CivetServer.h",
+          "src/md5.inl",
+          "src/handle_form.inl",
+     ],
+     includes = [
+          "include",
+     ],
+     copts = [
+           "-DNDEBUG",
+           "-DNO_CGI",
+           "-DNO_CACHING",
+           "-DNO_SSL",
+           "-DNO_FILES",
+     ],
+     visibility = ["//visibility:public"],
+ )
+ """
+ )

lib/BUILD

@@ -2,10 +2,13 @@ cc_library(
     name = "prometheus-cpp",
     srcs = ["counter.cc",
             "gauge.cc",
-            "exposer.cc"],
+            "exposer.cc",
+            "label_decorator.cc"],
     hdrs = ["counter.h",
             "gauge.h",
-            "exposer.h"],
+            "exposer.h",
+            "label_decorator.h",
+            "metric.h"],
     visibility = ["//visibility:public"],
     deps = ["@protobuf//:protobuf",
             "@prometheus_client_model//:prometheus_client_model",

lib/counter.cc

@@ -1,4 +1,5 @@
 #include "counter.h"
+#include "cpp/metrics.pb.h"
 
 namespace prometheus {
 
@@ -7,4 +8,11 @@ void Counter::inc() { gauge_.inc(); }
 void Counter::inc(double val) { gauge_.inc(val); }
 
 double Counter::value() const { return gauge_.value(); }
+
+io::prometheus::client::Metric Counter::collect() {
+  io::prometheus::client::Metric metric;
+  auto counter = metric.mutable_counter();
+  counter->set_value(value());
+  return metric;
+}
 }

lib/counter.h

@@ -3,14 +3,17 @@
 #include <atomic>
 
 #include "gauge.h"
+#include "metric.h"
 
 namespace prometheus {
-class Counter {
+class Counter : Metric {
  public:
   void inc();
   void inc(double);
   double value() const;
 
+  io::prometheus::client::Metric collect();
+
  private:
   Gauge gauge_;
 };

lib/label_decorator.cc

@@ -0,0 +1,22 @@
+#include "label_decorator.h"
+
+#include "cpp/metrics.pb.h"
+#include "google/protobuf/repeated_field.h"
+
+namespace prometheus {
+
+LabelDecorator::LabelDecorator(
+    std::vector<std::pair<std::string, std::string>> labels,
+    std::unique_ptr<Metric> metric)
+    : labels_(std::move(labels)), metric_(std::move(metric)) {}
+
+io::prometheus::client::Metric LabelDecorator::collect() {
+  auto undecoratedMetric = metric_->collect();
+  for (auto&& labelPair : labels_) {
+    auto newLabelPair = undecoratedMetric.add_label();
+    newLabelPair->set_name(labelPair.first);
+    newLabelPair->set_value(labelPair.second);
+  }
+  return undecoratedMetric;
+}
+}

lib/label_decorator.h

@@ -0,0 +1,31 @@
+#pragma once
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "metric.h"
+
+namespace io {
+namespace prometheus {
+namespace client {
+class Metric;
+class LabelPair;
+}
+}
+}
+
+namespace prometheus {
+
+class LabelDecorator : Metric {
+public:
+  LabelDecorator(std::vector<std::pair<std::string, std::string>> labels,
+                 std::unique_ptr<Metric> metric);
+
+  io::prometheus::client::Metric collect();
+
+private:
+  const std::vector<std::pair<std::string, std::string>> labels_;
+  std::unique_ptr<Metric> metric_;
+};
+}

lib/metric.h

@@ -0,0 +1,18 @@
+#pragma once
+
+namespace io {
+namespace prometheus {
+namespace client {
+class Metric;
+}
+}
+}
+
+namespace prometheus {
+
+class Metric {
+  public:
+  virtual ~Metric() = default;
+  virtual io::prometheus::client::Metric collect() = 0;
+};
+}

tests/BUILD

@@ -1,6 +1,6 @@
 cc_test(
     name = "prometheus_test",
-    srcs = ["counter_test.cc", "gauge_test.cc"],
+    srcs = ["counter_test.cc", "gauge_test.cc", "label_decorator_test.cc", "mock_metric.h"],
     copts = ["-Iexternal/googletest/include"],
     deps = ["@googletest//:main",
             "//lib:prometheus-cpp"],

tests/label_decorator_test.cc

@@ -0,0 +1,44 @@
+#include <memory>
+
+#include <gmock/gmock.h>
+#include "cpp/metrics.pb.h"
+#include "lib/label_decorator.h"
+#include "mock_metric.h"
+
+using namespace testing;
+using namespace prometheus;
+
+class LabelDecoratorTest : public Test {};
+
+TEST_F(LabelDecoratorTest, initialize_without_labels) {
+  auto metricPtr = std::unique_ptr<MockMetric>(new NiceMock<MockMetric>());
+  auto metric = metricPtr.get();
+  ON_CALL(*metric, collect())
+      .WillByDefault(Return(io::prometheus::client::Metric{}));
+  auto labelDecorator = LabelDecorator{{}, std::move(metricPtr)};
+
+  auto collected = labelDecorator.collect();
+  EXPECT_THAT(collected.label_size(), Eq(0));
+}
+
+TEST_F(LabelDecoratorTest, initialize_with_labels) {
+  auto metric = std::unique_ptr<MockMetric>(new NiceMock<MockMetric>());
+  auto metricWithLabels = io::prometheus::client::Metric{};
+
+  auto firstLabel = metricWithLabels.add_label();
+  firstLabel->set_name("foo");
+  firstLabel->set_value("bar");
+  auto secondLabel = metricWithLabels.add_label();
+  secondLabel->set_name("boo");
+  secondLabel->set_value("baz");
+
+  ON_CALL(*metric, collect())
+      .WillByDefault(Return(io::prometheus::client::Metric{}));
+  auto labelDecorator =
+      LabelDecorator{{{firstLabel->name(), firstLabel->value()},
+                      {secondLabel->name(), secondLabel->value()}},
+                     std::move(metric)};
+
+  auto collected = labelDecorator.collect();
+  EXPECT_EQ(collected.DebugString(), metricWithLabels.DebugString());
+}

tests/mock_metric.h

@@ -0,0 +1,16 @@
+#include <gmock/gmock.h>
+
+#include "lib/metric.h"
+
+namespace io {
+namespace prometheus {
+namespace client {
+class Metric;
+}
+}
+}
+
+class MockMetric : public prometheus::Metric {
+ public:
+  MOCK_METHOD0(collect, io::prometheus::client::Metric());
+};