/**
 * @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_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,      /**< 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]; /**< 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;

/**
 * @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);