Error handling on system boot (#30)

Implements #3

Reviewed-on: #30
Co-authored-by: localhorst <localhorst@mosad.xyz>
Co-committed-by: localhorst <localhorst@mosad.xyz>

main/metrics.h

@@ -1,26 +1,61 @@
+/**
+ * @file metrics.h
+ * @brief Prometheus metrics HTTP endpoint.
+ *
+ * This module provides a HTTP server on port 9100 that exposes
+ * system metrics in Prometheus format at /metrics endpoint.
+ */
+
 #pragma once
 
-#include <esp_http_server.h>
+#include "esp_err.h"
+#include "esp_http_server.h"
 
+#include <stdint.h>
+
+/** @brief Maximum size of HTTP response buffer. */
 #define HTML_RESPONSE_SIZE 4096U
+
+/** @brief Maximum length of metric name. */
 #define METRIC_NAME_MAX_SIZE 64U
+
+/** @brief Maximum number of metrics. */
 #define METRIC_MAX_COUNT 38U
 
+/**
+ * @brief Metric value type enumeration.
+ */
 typedef enum _MetricValueType
 {
-    FLOAT,
-    INTEGER_U8,
-    INTEGER_64,
+    FLOAT,      /**< Floating point value. */
+    INTEGER_U8, /**< 8-bit unsigned integer. */
+    INTEGER_64, /**< 64-bit signed integer. */
 } eMetricValueType;
 
+/**
+ * @brief Metric data structure.
+ */
 typedef struct _metric
 {
-    char caMetricName[METRIC_NAME_MAX_SIZE];
-    eMetricValueType type;
-    float fMetricValue;
-    uint8_t u8MetricValue;
-    int64_t i64MetricValue;
+    char caMetricName[METRIC_NAME_MAX_SIZE]; /**< Metric name. */
+    eMetricValueType type;                   /**< Value type. */
+    float fMetricValue;                      /**< Float value (if type is FLOAT). */
+    uint8_t u8MetricValue;                   /**< U8 value (if type is INTEGER_U8). */
+    int64_t i64MetricValue;                  /**< I64 value (if type is INTEGER_64). */
 } sMetric;
 
-void initMetrics(void);
-void vSetMetrics(sMetric *paMetrics, uint16_t u16Size);
+/**
+ * @brief Initialize the metrics module.
+ *
+ * Starts the HTTP server and creates the metrics collection task.
+ *
+ * @return ESP_OK on success, ESP_FAIL on error.
+ */
+esp_err_t initMetrics(void);
+
+/**
+ * @brief Update the metrics buffer.
+ * @param paMetrics Array of metrics to publish.
+ * @param u16Size Number of metrics in array.
+ */
+void vSetMetrics(sMetric *paMetrics, uint16_t u16Size);