Accept initializer_list, span, and string_view in api

src/metric.hpp

@@ -36,8 +36,8 @@
 //   histogram.observe(0.25);  // ONLY call from creating thread
 
 #include <functional>
+#include <initializer_list>
 #include <span>
-#include <string>
 #include <type_traits>
 #include <vector>
 
@@ -127,20 +127,36 @@ template <class T> struct Family {
   // Labels are sorted by key for Prometheus compatibility
   // ERROR: Will abort if labels already registered via register_callback()
   // OK: Multiple calls with same labels return same instance (idempotent)
-  T create(std::vector<std::pair<std::string, std::string>> labels);
+  T create(std::initializer_list<std::pair<std::string_view, std::string_view>>
+               labels) {
+    return create(
+        std::span<const std::pair<std::string_view, std::string_view>>(
+            labels.begin(), labels.end()));
+  }
+  T create(
+      std::span<const std::pair<std::string_view, std::string_view>> labels);
 
   // Register callback-based metric (Counter and Gauge only)
   // Validates that label set isn't already taken
-  void
-  register_callback(std::vector<std::pair<std::string, std::string>> labels,
-                    MetricCallback<T> callback);
+  void register_callback(
+      std::initializer_list<std::pair<std::string_view, std::string_view>>
+          labels,
+      MetricCallback<T> callback) {
+    register_callback(
+        std::span<const std::pair<std::string_view, std::string_view>>(
+            labels.begin(), labels.end()),
+        callback);
+  }
+  void register_callback(
+      std::span<const std::pair<std::string_view, std::string_view>> labels,
+      MetricCallback<T> callback);
 
 private:
   Family();
   friend struct Metric;
-  friend Family<Counter> create_counter(std::string, std::string);
-  friend Family<Gauge> create_gauge(std::string, std::string);
-  friend Family<Histogram> create_histogram(std::string, std::string,
+  friend Family<Counter> create_counter(std::string_view, std::string_view);
+  friend Family<Gauge> create_gauge(std::string_view, std::string_view);
+  friend Family<Histogram> create_histogram(std::string_view, std::string_view,
                                             std::span<const double>);
 
   struct State;
@@ -153,19 +169,25 @@ private:
 // Create counter family (monotonically increasing values)
 // ERROR: Aborts if family with same name is registered with different help
 // text.
-Family<Counter> create_counter(std::string name, std::string help);
+Family<Counter> create_counter(std::string_view name, std::string_view help);
 
 // Create gauge family (can increase/decrease)
 // ERROR: Aborts if family with same name is registered with different help
 // text.
-Family<Gauge> create_gauge(std::string name, std::string help);
+Family<Gauge> create_gauge(std::string_view name, std::string_view help);
 
 // Create histogram family with custom buckets
 // Buckets will be sorted, deduplicated, and +Inf will be added automatically
 // ERROR: Aborts if family with same name is registered with different help text
 // or buckets.
-Family<Histogram> create_histogram(std::string name, std::string help,
+Family<Histogram> create_histogram(std::string_view name, std::string_view help,
                                    std::span<const double> buckets);
+inline Family<Histogram>
+create_histogram(std::string_view name, std::string_view help,
+                 std::initializer_list<double> buckets) {
+  return create_histogram(
+      name, help, std::span<const double>(buckets.begin(), buckets.end()));
+}
 
 // Helper functions for generating standard histogram buckets
 // Following Prometheus client library conventions
@@ -189,9 +211,9 @@ std::vector<double> exponential_buckets(double start, double factor, int count);
 std::span<std::string_view> render(ArenaAllocator &arena);
 
 // Validation functions for Prometheus compatibility
-bool is_valid_metric_name(const std::string &name);
-bool is_valid_label_key(const std::string &key);
-bool is_valid_label_value(const std::string &value);
+bool is_valid_metric_name(std::string_view name);
+bool is_valid_label_key(std::string_view key);
+bool is_valid_label_value(std::string_view value);
 
 // Note: Histograms do not support callbacks due to their multi-value nature
 // (buckets + sum + count). Use static histogram metrics only.