{ config, pkgs, lib, ... }:

{
  services.prometheus = {
    enable = true;
    retentionTime = "14d";
    listenAddress = "[::1]";
    exporters = {
      node = {
        enable = true;
        listenAddress = config.services.prometheus.listenAddress;
      };
      #nginx = {};
      #postgres = {};
    };
    scrapeConfigs = [
      {
        job_name = "synapse";
        scrape_interval = "15s";
        static_configs = [
          {
            targets = lib.pipe config.services.matrix-synapse.settings.listeners [
              (lib.filter (l: l.type == "metrics"))
              builtins.head
              (l: "[${builtins.head l.bind_addresses}]:${l.port}")
            ];
          }
        ];
      }
      {
        job_name = "node";
        scrape_interval = "15s";
        static_configs = [
          { targets = [ "${config.services.prometheus.exporters.node.listenAddress}:${toString config.services.prometheus.exporters.node.port}" ]; }
        ];
      }
    ];
    ruleFiles = [
      # https://github.com/element-hq/synapse/tree/master/contrib/prometheus
      (pkgs.writeText "prom-synapse-rules.yaml" ''
        groups:
        - name: synapse
          rules:
          - record: 'synapse_federation_client_sent'
            labels:
              type: "EDU"
            expr: 'synapse_federation_client_sent_edus_total + 0'
          - record: 'synapse_federation_client_sent'
            labels:
              type: "PDU"
            expr: 'synapse_federation_client_sent_pdu_destinations_count_total + 0'
          - record: 'synapse_federation_client_sent'
            labels:
              type: "Query"
            expr: 'sum(synapse_federation_client_sent_queries) by (job)'
          - record: 'synapse_federation_server_received'
            labels:
              type: "EDU"
            expr: 'synapse_federation_server_received_edus_total + 0'
          - record: 'synapse_federation_server_received'
            labels:
              type: "PDU"
            expr: 'synapse_federation_server_received_pdus_total + 0'
          - record: 'synapse_federation_server_received'
            labels:
              type: "Query"
            expr: 'sum(synapse_federation_server_received_queries) by (job)'
          - record: 'synapse_federation_transaction_queue_pending'
            labels:
              type: "EDU"
            expr: 'synapse_federation_transaction_queue_pending_edus + 0'
          - record: 'synapse_federation_transaction_queue_pending'
            labels:
              type: "PDU"
            expr: 'synapse_federation_transaction_queue_pending_pdus + 0'
      '')
    ];
  };
}