/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */

/*  Fluent Bit

 *  ==========

 *  Copyright (C) 2015-2026 The Fluent Bit Authors

 *

 *  Licensed under the Apache License, Version 2.0 (the "License");

 *  you may not use this file except in compliance with the License.

 *  You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 *  Unless required by applicable law or agreed to in writing, software

 *  distributed under the License is distributed on an "AS IS" BASIS,

 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 *  See the License for the specific language governing permissions and

 *  limitations under the License.

 */

#include <fluent-bit/flb_output_plugin.h>

#include <fluent-bit/flb_kv.h>

#include <fluent-bit/flb_metrics.h>

#include "prom.h"

#include "prom_http.h"

static int config_add_labels(struct flb_output_instance *ins,

                             struct prom_exporter *ctx)

{

    struct mk_list *head;

    struct flb_config_map_val *mv;

    struct flb_slist_entry *k = NULL;

    struct flb_slist_entry *v = NULL;

    struct flb_kv *kv;

    if (!ctx->add_labels || mk_list_size(ctx->add_labels) == 0) {

        return 0;

    }

    /* iterate all 'add_label' definitions */

    flb_config_map_foreach(head, mv, ctx->add_labels) {

        if (mk_list_size(mv->val.list) != 2) {

            flb_plg_error(ins, "'add_label' expects a key and a value, "

                          "e.g: 'add_label version 1.8.0'");

            return -1;

        }

        k = mk_list_entry_first(mv->val.list, struct flb_slist_entry, _head);

        v = mk_list_entry_last(mv->val.list, struct flb_slist_entry, _head);

        kv = flb_kv_item_create(&ctx->kv_labels, k->str, v->str);

        if (!kv) {

            flb_plg_error(ins, "could not append label %s=%s\n", k->str, v->str);

            return -1;

        }

    }

    return 0;

}

static int cb_prom_init(struct flb_output_instance *ins,

                        struct flb_config *config,

                        void *data)

{

    int ret;

    struct prom_exporter *ctx;

    flb_output_net_default("0.0.0.0", 2021 , ins);

    ctx = flb_calloc(1, sizeof(struct prom_exporter));

    if (!ctx) {

        flb_errno();

        return -1;

    }

    ctx->ins = ins;

    flb_kv_init(&ctx->kv_labels);

    flb_output_set_context(ins, ctx);

    /* Load config map */

    ret = flb_output_config_map_set(ins, (void *) ctx);

    if (ret == -1) {

        return -1;

    }

    /* Parse 'add_label' */

    ret = config_add_labels(ins, ctx);

    if (ret == -1) {

        return -1;

    }

    /* HTTP Server context */

    ctx->http = prom_http_server_create(ctx, config);

    if (!ctx->http) {

        flb_plg_error(ctx->ins, "could not initialize HTTP server, aborting");

        return -1;

    }

    /* Hash table for metrics */

    ctx->ht_metrics = flb_hash_table_create(FLB_HASH_TABLE_EVICT_NONE, 32, 0);

    if (!ctx->ht_metrics) {

        flb_plg_error(ctx->ins, "could not initialize hash table for metrics");

        return -1;

    }

    /* Start HTTP Server */

    ret = prom_http_server_start(ctx->http);

    if (ret == -1) {

        return -1;

    }

    flb_plg_info(ctx->ins, "listening iface=%s tcp_port=%d",

                 ins->host.name, ins->host.port);

    return 0;

}

static void append_labels(struct prom_exporter *ctx, struct cmt *cmt)

{

    struct flb_kv *kv;

    struct mk_list *head;

    mk_list_foreach(head, &ctx->kv_labels) {

        kv = mk_list_entry(head, struct flb_kv, _head);

        cmt_label_add(cmt, kv->key, kv->val);

    }

}

static int hash_store(struct prom_exporter *ctx, struct flb_input_instance *ins,

                      cfl_sds_t buf)

{

    int ret;

    int len;

    len = strlen(ins->name);

    /* store/override the content into the hash table */

    ret = flb_hash_table_add(ctx->ht_metrics, ins->name, len,

                             buf, cfl_sds_len(buf));

    if (ret < 0) {

        return -1;

    }

    return 0;

}

static flb_sds_t hash_format_metrics(struct prom_exporter *ctx)

{

    int size = 2048;

    flb_sds_t buf;

    struct mk_list *head;

    struct flb_hash_table_entry *entry;

    buf = flb_sds_create_size(size);

    if (!buf) {

        return NULL;

    }

    /* Take every hash entry and compose one buffer with the whole content */

    mk_list_foreach(head, &ctx->ht_metrics->entries) {

        entry = mk_list_entry(head, struct flb_hash_table_entry, _head_parent);

        flb_sds_cat_safe(&buf, entry->val, entry->val_size);

    }

    return buf;

}

static void cb_prom_flush(struct flb_event_chunk *event_chunk,

                          struct flb_output_flush *out_flush,

                          struct flb_input_instance *ins, void *out_context,

                          struct flb_config *config)

{

    int ret;

    int add_ts;

    size_t off = 0;

    flb_sds_t metrics;

    cfl_sds_t text = NULL;

    cfl_sds_t tmp = NULL;

    struct cmt *cmt;

    struct prom_exporter *ctx = out_context;

    int ok = CMT_DECODE_MSGPACK_SUCCESS;

    text = flb_sds_create_size(128);

    if (text == NULL) {

        flb_plg_debug(ctx->ins, "failed to allocate buffer for text representation of metrics");

        FLB_OUTPUT_RETURN(FLB_ERROR);

    }

    /*

     * A new set of metrics has arrived, perform decoding, apply labels,

     * convert to Prometheus text format and store the output in the

     * hash table for metrics.

     * Note that metrics might be concatenated. So, we need to consume

     * until the end of event_chunk.

     */

    while ((ret = cmt_decode_msgpack_create(&cmt,

                                            (char *) event_chunk->data,

                                            event_chunk->size, &off)) == ok) {

        /* append labels set by config */

        append_labels(ctx, cmt);

        /* add timestamp in the output format ? */

        if (ctx->add_timestamp) {

            add_ts = CMT_TRUE;

        }

        else {

            add_ts = CMT_FALSE;

        }

        /* convert to text representation */

        tmp = cmt_encode_prometheus_create(cmt, add_ts);

        if (!tmp) {

            cmt_destroy(cmt);

            flb_sds_destroy(text);

            FLB_OUTPUT_RETURN(FLB_ERROR);

        }

        ret = flb_sds_cat_safe(&text, tmp, flb_sds_len(tmp));

        if (ret != 0) {

            flb_plg_error(ctx->ins, "could not concatenate text representant coming from: %s",

                          flb_input_name(ins));

            cmt_encode_prometheus_destroy(tmp);

            flb_sds_destroy(text);

            cmt_destroy(cmt);

            FLB_OUTPUT_RETURN(FLB_ERROR);

        }

        cmt_encode_prometheus_destroy(tmp);

        cmt_destroy(cmt);

    }

    if (cfl_sds_len(text) == 0) {

        flb_plg_debug(ctx->ins, "context without metrics (empty)");

        flb_sds_destroy(text);

        FLB_OUTPUT_RETURN(FLB_OK);

    }

    /* register payload of metrics / override previous one */

    ret = hash_store(ctx, ins, text);

    if (ret == -1) {

        flb_plg_error(ctx->ins, "could not store metrics coming from: %s",

                      flb_input_name(ins));

        flb_sds_destroy(text);

        cmt_destroy(cmt);

        FLB_OUTPUT_RETURN(FLB_ERROR);

    }

    flb_sds_destroy(text);

    /* retrieve a full copy of all metrics */

    metrics = hash_format_metrics(ctx);

    if (!metrics) {

        flb_plg_error(ctx->ins, "could not retrieve metrics");

        FLB_OUTPUT_RETURN(FLB_ERROR);

    }

    /* push new (full) metrics payload */

    ret = prom_http_server_mq_push_metrics(ctx->http,

                                           (char *) metrics,

                                           flb_sds_len(metrics));

    flb_sds_destroy(metrics);

    if (ret != 0) {

        FLB_OUTPUT_RETURN(FLB_ERROR);

    }

    FLB_OUTPUT_RETURN(FLB_OK);

}

static int cb_prom_exit(void *data, struct flb_config *config)

{

    struct prom_exporter *ctx = data;

    if (!ctx) {

        return 0;

    }

    if (ctx->ht_metrics) {

        flb_hash_table_destroy(ctx->ht_metrics);

    }

    flb_kv_release(&ctx->kv_labels);

    prom_http_server_stop(ctx->http);

    prom_http_server_destroy(ctx->http);

    flb_free(ctx);

    return 0;

}

/* Configuration properties map */

static struct flb_config_map config_map[] = {

    {

     FLB_CONFIG_MAP_BOOL, "add_timestamp", "false",

     0, FLB_TRUE, offsetof(struct prom_exporter, add_timestamp),

     "Add timestamp to every metric honoring collection time."

    },

    {

     FLB_CONFIG_MAP_SLIST_1, "add_label", NULL,

     FLB_CONFIG_MAP_MULT, FLB_TRUE, offsetof(struct prom_exporter, add_labels),

     "TCP port for listening for HTTP connections."

    },

    /* EOF */

    {0}

};

/* Plugin reference */

struct flb_output_plugin out_prometheus_exporter_plugin = {

    .name        = "prometheus_exporter",

    .description = "Prometheus Exporter",

    .cb_init     = cb_prom_init,

    .cb_flush    = cb_prom_flush,

    .cb_exit     = cb_prom_exit,

    .flags       = FLB_OUTPUT_NET | FLB_OUTPUT_HTTP_SERVER,

    .event_type  = FLB_OUTPUT_METRICS,

    .config_map  = config_map,

};