{
  config,
  lib,
  pkgs,
  ...
}:
with lib; let
  cfg = config.nixfiles.modules.monitoring;
in {
  options.nixfiles.modules.monitoring.enable = mkEnableOption ''
    a glue to provision a monitoring stack
  '';

  config = mkIf cfg.enable {
    nixfiles.modules = {
      alertmanager.enable = true;
      grafana.enable = true;
      loki.enable = true;
      prometheus.enable = true;
    };

    services = {
      grafana = {
        declarativePlugins = with pkgs.grafanaPlugins; [
          redis-app
          redis-datasource
          redis-explorer-app
        ];

        provision = {
          enable = true;

          # https://grafana.com/docs/grafana/latest/administration/provisioning/#data-sources
          datasources.settings.datasources = with config.nixfiles.modules; [
            {
              name = "Alertmanager";
              type = "alertmanager";
              access = "proxy";
              jsonData.implementation = "prometheus";
              url = "https://${alertmanager.domain}";
            }
            {
              name = "Loki";
              type = "loki";
              access = "proxy";
              url = "https://${loki.domain}";
              isDefault = true;
            }
            {
              name = "Prometheus";
              type = "prometheus";
              access = "proxy";
              url = "https://${prometheus.domain}";
            }
            (mkIf config.nixfiles.modules.redis.enable {
              name = "Redis";
              type = "redis-datasource";
              access = "proxy";
              url = with config.services.redis.servers.default; "redis://${bind}:${toString port}";
              jsonData.client = "standalone";
            })
          ];

          # https://grafana.com/docs/grafana/latest/administration/provisioning/#dashboards
          dashboards.settings.providers = [
            # The System dashboard is imported manually from here[1]. Too bad
            # provisioned dashboards cannot properly integrate dynamic datasources
            # yet.
            #
            # [1]: https://grafana.com/grafana/dashboards/1860-node-exporter-full
            {
              name = "endlessh";
              options.path = ./dashboards/endlessh.json;
            }
            {
              name = "unbound";
              options.path = ./dashboards/unbound.json;
            }
            {
              name = "nginx";
              options.path = ./dashboards/nginx.json;
            }
            {
              name = "postgersql";
              options.path = ./dashboards/postgresql.json;
            }
          ];

          # https://grafana.com/docs/grafana/latest/administration/provisioning/#alerting
          alerting.contactPoints.settings.contactPoints = [
            {
              name = "Alertmanager";
              receivers = [
                {
                  uid = 1;
                  type = "prometheus-alertmanager";
                  settings.url = "https://${config.nixfiles.modules.alertmanager.domain}";
                }
              ];
            }
          ];
        };
      };

      loki.configuration.ruler.alertmanager_url = "https://${config.nixfiles.modules.alertmanager.domain}";

      prometheus = {
        # It would be nice if these could be generated dynamically. That would
        # require a complete rework of how configurations are defined, though.
        scrapeConfigs = let
          mkTargets = hosts: port: map (host: "${host.hostname}:${toString port}") hosts;
        in
          with my.configurations;
          with config.services.prometheus.exporters; [
            {
              job_name = "endlessh-go";
              static_configs = [
                {
                  targets =
                    mkTargets
                    [
                      manwe
                      varda
                      yavanna
                    ]
                    config.services.endlessh-go.prometheus.port;
                }
              ];
            }
            {
              job_name = "nginx";
              static_configs = [
                {
                  targets =
                    mkTargets
                    [
                      manwe
                      yavanna
                    ]
                    nginx.port;
                }
              ];
            }
            {
              job_name = "node";
              static_configs = [
                {
                  targets =
                    mkTargets
                    [
                      manwe
                      varda
                      yavanna
                    ]
                    node.port;
                }
              ];
            }
            {
              job_name = "postgres";
              static_configs = [
                {
                  targets =
                    mkTargets
                    [
                      manwe
                    ]
                    postgres.port;
                }
              ];
            }
            {
              job_name = "redis";
              static_configs = [
                {
                  targets =
                    mkTargets
                    [
                      manwe
                    ]
                    redis.port;
                }
              ];
            }
            {
              job_name = "unbound";
              static_configs = [
                {
                  targets =
                    mkTargets
                    [
                      manwe
                    ]
                    unbound.port;
                }
              ];
            }
            {
              job_name = "wireguard";
              static_configs = [
                {
                  targets =
                    mkTargets
                    [
                      manwe
                    ]
                    wireguard.port;
                }
              ];
            }
          ];

        alertmanagers = [
          {
            scheme = "https";
            static_configs = [
              {targets = [config.nixfiles.modules.alertmanager.domain];}
            ];
          }
        ];
      };
    };
  };
}