# `swarm-metrics` on this agent's PATH, configured for this swarm's metrics
# store. The sibling of ./logs.nix, in the same shape for the same reasons:
# the binary defaults nothing (see `swarm-metrics/README.md`), so it is
# installed wrapped, and it is gated on the secret store's address as well as
# on the store URL, because the identity it presents is the agent's own queue
# secret read from that store.
{
  lib,
  pkgs,
  config,
  ...
}:
let
  cfg = config.services.hyperhive.agent.metrics;
  baoCfg = config.services.hyperhive.agent.bao;
  configured = cfg.url != null && baoCfg.addr != null;

  # The coordinates ./logs.nix gives `swarm-logs`. Paths and a name only: a
  # value in `--set` lands in the world-readable nix store.
  wrapperEnv = {
    HIVE_AGENT_METRICS_URL = cfg.url;
    HIVE_AGENT_NAME = config.services.hyperhive.agent.user.name;
    BAO_ADDR = baoCfg.addr;
    BAO_CLIENT_CERT = baoCfg.clientCertFile;
    BAO_CLIENT_KEY = baoCfg.clientKeyFile;
    BAO_CACERT = "/run/credentials/hive-agent.service/hive-agent-bao-server-ca";
  };

  swarmMetricsConfigured = pkgs.symlinkJoin {
    name = "swarm-metrics-configured";
    paths = [ config.services.hyperhive.agent.packages.swarm-metrics ];
    nativeBuildInputs = [ pkgs.makeWrapper ];
    postBuild = ''
      wrapProgram $out/bin/swarm-metrics ${
        lib.concatStringsSep " " (
          lib.mapAttrsToList (name: value: "--set ${name} ${lib.escapeShellArg value}") wrapperEnv
        )
      }
    '';
  };
in
{
  options.services.hyperhive.agent.metrics = {
    url = lib.mkOption {
      type = lib.types.nullOr lib.types.str;
      default = null;
      example = "https://metrics.example.com";
      description = ''
        The swarm metrics store's gateway origin, as this container reaches
        it. `swarm-metrics` appends the read API's paths (`/api/v1/query`,
        ...) to it.

        Set by the generated meta flake from the host's own
        {option}`services.hyperhive.swarm.victoriametrics.domain`.

        `null` means this hive has not been given the metrics store's address
        for its agents, and `swarm-metrics` is then not installed at all.
        Not defaulted: a guessed address resolves cleanly to the wrong place.
      '';
    };
  };

  config = lib.mkIf configured {
    environment.systemPackages = [ swarmMetricsConfigured ];
  };
}