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       1            1 : /*
       2              :  * Copyright (c) 2024 Mustafa Abdullah Kus, Sparse Technology
       3              :  * Copyright (c) 2024 Nordic Semiconductor
       4              :  *
       5              :  * SPDX-License-Identifier: Apache-2.0
       6              :  */
       7              : 
       8              : #ifndef ZEPHYR_INCLUDE_PROMETHEUS_HISTOGRAM_H_
       9              : #define ZEPHYR_INCLUDE_PROMETHEUS_HISTOGRAM_H_
      10              : 
      11              : /**
      12              :  * @file
      13              :  *
      14              :  * @brief Prometheus histogram APIs.
      15              :  *
      16              :  * @addtogroup prometheus
      17              :  * @{
      18              :  */
      19              : 
      20              : #include <zephyr/sys/iterable_sections.h>
      21              : #include <zephyr/net/prometheus/metric.h>
      22              : 
      23              : #include <stddef.h>
      24              : 
      25              : /**
      26              :  * @brief Prometheus histogram bucket definition.
      27              :  *
      28              :  * This structure defines a Prometheus histogram bucket.
      29              :  */
      30            1 : struct prometheus_histogram_bucket {
      31              :         /** Upper bound value of bucket */
      32            1 :         double upper_bound;
      33              :         /** Cumulative count of observations in the bucket */
      34            1 :         unsigned long count;
      35              : };
      36              : 
      37              : /**
      38              :  * @brief Type used to represent a Prometheus histogram metric.
      39              :  *
      40              :  * * References
      41              :  * * See https://prometheus.io/docs/concepts/metric_types/#histogram
      42              :  */
      43            1 : struct prometheus_histogram {
      44              :         /** Base of the Prometheus histogram metric */
      45            1 :         struct prometheus_metric base;
      46              :         /** Array of buckets in the histogram */
      47            1 :         struct prometheus_histogram_bucket *buckets;
      48              :         /** Number of buckets in the histogram */
      49            1 :         size_t num_buckets;
      50              :         /** Sum of all observed values in the histogram */
      51            1 :         double sum;
      52              :         /** Total count of observations in the histogram */
      53            1 :         unsigned long count;
      54              :         /** User data */
      55            1 :         void *user_data;
      56              : };
      57              : 
      58              : /**
      59              :  * @brief Prometheus Histogram definition.
      60              :  *
      61              :  * This macro defines a Histogram metric. If you want to make the histogram static,
      62              :  * then add "static" keyword before the PROMETHEUS_HISTOGRAM_DEFINE.
      63              :  *
      64              :  * @param _name The histogram metric name.
      65              :  * @param _desc Histogram description
      66              :  * @param _label Label for the metric. Additional labels can be added at runtime.
      67              :  * @param _collector Collector to map this metric. Can be set to NULL if it not yet known.
      68              :  * @param ... Optional user data specific to this metric instance.
      69              :  *
      70              :  * Example usage:
      71              :  * @code{.c}
      72              :  *
      73              :  * PROMETHEUS_HISTOGRAM_DEFINE(http_request_histogram, "HTTP request histogram",
      74              :  *                         ({ .key = "request_latency", .value = "request_latency_seconds" }),
      75              :  *                         NULL);
      76              :  *
      77              :  * @endcode
      78              :  */
      79            1 : #define PROMETHEUS_HISTOGRAM_DEFINE(_name, _desc, _label, _collector, ...) \
      80              :         STRUCT_SECTION_ITERABLE(prometheus_histogram, _name) = {        \
      81              :                 .base.name = STRINGIFY(_name),                          \
      82              :                 .base.type = PROMETHEUS_HISTOGRAM,                      \
      83              :                 .base.description = _desc,                              \
      84              :                 .base.labels[0] = __DEBRACKET _label,                   \
      85              :                 .base.num_labels = 1,                                   \
      86              :                 .base.collector = _collector,                           \
      87              :                 .buckets = NULL,                                        \
      88              :                 .num_buckets = 0,                                       \
      89              :                 .sum = 0.0,                                             \
      90              :                 .count = 0U,                                            \
      91              :                 .user_data = COND_CODE_0(                               \
      92              :                         NUM_VA_ARGS_LESS_1(LIST_DROP_EMPTY(__VA_ARGS__, _)), \
      93              :                         (NULL),                                         \
      94              :                         (GET_ARG_N(1, __VA_ARGS__))),                   \
      95              :         }
      96              : 
      97              : /**
      98              :  * @brief Observe a value in a Prometheus histogram metric
      99              :  *
     100              :  * Observes the specified value in the given histogram metric.
     101              :  *
     102              :  * @param histogram Pointer to the histogram metric to observe.
     103              :  * @param value Value to observe in the histogram metric.
     104              :  * @return 0 on success, -EINVAL if the value is negative.
     105              :  */
     106            1 : int prometheus_histogram_observe(struct prometheus_histogram *histogram, double value);
     107              : 
     108              : /**
     109              :  * @}
     110              :  */
     111              : 
     112              : #endif /* ZEPHYR_INCLUDE_PROMETHEUS_HISTOGRAM_H_ */