Add Webserver Prometheus support for sensor, binary sensor, fan, light, cover and switch (#1032)

esphome/components/web_server/web_server_prometheus.h

@@ -0,0 +1,61 @@
+#pragma once
+
+#include "esphome/core/component.h"
+#include "esphome/core/controller.h"
+#include "esphome/components/web_server_base/web_server_base.h"
+
+namespace esphome {
+namespace web_server {
+
+class WebServerPrometheus {
+ public:
+  WebServerPrometheus(){};
+  /// Handle an prometheus metrics request under '/metrics'.
+  void handle_request(AsyncWebServerRequest *request);
+
+ protected:
+#ifdef USE_SENSOR
+  /// Return the type for prometheus
+  void sensor_type_(AsyncResponseStream *stream);
+  /// Return the sensor state as prometheus data point
+  void sensor_row_(AsyncResponseStream *stream, sensor::Sensor *obj);
+#endif
+
+#ifdef USE_BINARY_SENSOR
+  /// Return the type for prometheus
+  void binary_sensor_type_(AsyncResponseStream *stream);
+  /// Return the sensor state as prometheus data point
+  void binary_sensor_row_(AsyncResponseStream *stream, binary_sensor::BinarySensor *obj);
+#endif
+
+#ifdef USE_FAN
+  /// Return the type for prometheus
+  void fan_type_(AsyncResponseStream *stream);
+  /// Return the sensor state as prometheus data point
+  void fan_row_(AsyncResponseStream *stream, fan::FanState *obj);
+#endif
+
+#ifdef USE_LIGHT
+  /// Return the type for prometheus
+  void light_type_(AsyncResponseStream *stream);
+  /// Return the Light Values state as prometheus data point
+  void light_row_(AsyncResponseStream *stream, light::LightState *obj);
+#endif
+
+#ifdef USE_COVER
+  /// Return the type for prometheus
+  void cover_type_(AsyncResponseStream *stream);
+  /// Return the switch Values state as prometheus data point
+  void cover_row_(AsyncResponseStream *stream, cover::Cover *obj);
+#endif
+
+#ifdef USE_SWITCH
+  /// Return the type for prometheus
+  void switch_type_(AsyncResponseStream *stream);
+  /// Return the switch Values state as prometheus data point
+  void switch_row_(AsyncResponseStream *stream, switch_::Switch *obj);
+#endif
+};
+
+}  // namespace web_server
+}  // namespace esphome