Add air quality history charts

esphome/components/air_quality_web/air_quality_web.h

@@ -5,6 +5,8 @@
 #include "esphome/components/sensor/sensor.h"
 #include "esphome/components/web_server_base/web_server_base.h"
 
+#include <cstddef>
+#include <cstdint>
 #include <string>
 
 namespace esphome::air_quality_web {
@@ -34,6 +36,23 @@ class AirQualityWeb : public PollingComponent {
  protected:
   static esp_err_t handle_request_(httpd_req_t *request);
   std::string snapshot_();
+  esp_err_t send_history_(httpd_req_t *request);
+
+  static constexpr uint32_t HISTORY_DURATION_MS = 36000000;
+  static constexpr uint32_t HISTORY_INTERVAL_MS = 60000;
+  static constexpr size_t HISTORY_CAPACITY = 601;
+  struct HistorySample {
+    uint32_t timestamp;
+    float co2;
+    float temperature;
+    float humidity;
+  };
+  static_assert(sizeof(HistorySample) == 16, "History samples must remain compact");
+  struct HistorySnapshot {
+    uint32_t timestamp;
+    size_t count;
+    HistorySample samples[HISTORY_CAPACITY];
+  };
 
   AirQualityServer server_;
   std::string mdns_hostname_;
@@ -41,6 +60,11 @@ class AirQualityWeb : public PollingComponent {
   sensor::Sensor *temperature_{nullptr};
   sensor::Sensor *humidity_{nullptr};
   Mutex snapshot_mutex_;
+  HistorySample history_[HISTORY_CAPACITY]{};
+  size_t history_head_{0};
+  size_t history_count_{0};
+  uint32_t last_sample_ms_{0};
+  bool has_sample_{false};
   std::string json_{"{\"co2\":null,\"temperature\":null,\"humidity\":null}"};
 };